Kyaw linn oo et al ajes 2015 copy

Journal of Asian Earth Sciences xxx (2015) xxx–xxx

Provenance of the Eocene sandstones in the southern Chindwin Basin,Myanmar: Implications for the unroofing history of the Cretaceous– Eocene magmatic arc

Kyaw Linn Oo a,⇑, Khin Zaw b, Sebastien Meffre b, Myitta c, Day Wa Aung c, Chun-Kit Lai b,d

a PETRONAS Carigali Myanmar Inc. (PCMI), Myanmarb ARC Centre of Excellence in Ore Deposits (CODES), University of Tasmania, Hobart, Tasmania, Australiac Department of Geology, University of Yangon, Yangon, Myanmard Chinalco Rio Tinto Exploration (CRTX) Co. Ltd., Beijing, China

a r t i c l e i n f o a b s t r a c t

Article history:

Received 12 June 2014

Received in revised form 31 March 2015

Accepted 14 April 2015

Available online xxxx

The Eocene sedimentary rocks, exposed in the southern Chindwin Basin, northern part of Myanmar, are characterized by a thick sequence of continental clastic units consisting of sandstones with abundant volcaniclastic materials, and a subordinate amount of metamorphic lithic fragments. Detrital information preserved in these Eocene clastic sequences has shed light on the erosional unroofing history of a Cretaceous to Eocene Andean-type continental magmatic arc related to the India–Asia collision.

An integrated study of the petrography, geochemistry and LA-ICP-MS (Laser Ablation Inductively Couple Plasma Mass Spectrometer) U–Pb zircon geochronology of the late Middle Eocene, volcaniclastic Pondaung sandstones, combined with the WSW-directed regional mean palaeocurrent direction ( 254 azimuth), has revealed an older, calc-alkaline, andesitic volcanic arc (detrital U–Pb zircon age: 101–43 Ma), situated to the NE of the southern Chindwin Basin, possibly related to the Neo-Tethys seafloor subduction beneath the Eurasia continental margin, i.e., the West Burma Block or Burma (Myanmar) Plate. We suggest that this arc may have been eroded during the late Middle Eocene (Bartonian) with volcaniclastic detritus deposited in the fore-arc basin of the Central Myanmar Basin, forming the Pondaung Formation.

2015 Elsevier Ltd. All rights reserved.

Keywords:

Central Myanmar Basin

Chindwin Sub-Basin

Erosional unroofing

Andean-type continental magmatic arc

Pondaung sandstones

1. Introduction suggested that no such palaeo-river connection existed duringthe Paleogene. A significant proportion of volcaniclastic materials in the Eocene sandstones of the Indo-Burman Ranges (IBR) and the Central Myanmar Basin (CMB) are considered to have been derived from the unroofing of a local magmatic arc, which formed along the eastern Myanmar rather than derived from the Trans-Himalayan batholiths of Tibet (Allen et al., 2008; Licht et al., 2013). Wang et al. (2014) have recently proposed, based on U–Pb and Hf isotope analyses of detrital zircons from the Upper Cretaceous to Eocene stratigraphic units of the Chindwin Basin, that the Cretaceous to Eocene Western Myanmar Arc (WMA) was the southeastern extension of the Trans-Himalayan magmatic arc in Tibet (Kohistan-Ladakh-Gangdese arc), which was formed along the southern Asian margin during the Neo-Tethyan subduction.

Eocene sedimentary rocks constitute 50% of the Cenozoic stratigraphic units in the Central Myanmar Basin, with a total thickness of about 13 km (Aung Khin and Kyaw Win, 1969). Among this sequence, the late Middle Eocene–Upper Eocene, fluvio-deltaic Pondaung and Yaw formations represent 25% of the entire Eocene succession. The rest of the Lower- to Middle Eocene units (i.e.,

Since 2008, Myanmar has become a center of attention formany geoscientists who are investigating sedimentary provenances, tectono-magmatic evolution and palaeo-river reconstruction in Myanmar by using detrital U–Pb zircon geochronology and isotopic fingerprinting methods (Allen et al., 2008; Liang et al., 2008; Mitchell et al., 2012; Licht et al., 2013; Robinson et al., 2014; Wang et al., 2014). However, advanced technology alone may not help to reach a complete understanding without justification from a sound knowledge of regional and local geology of Myanmar.

Liang et al. (2008) considered that the Yarlung-Tsangpo River in Tibet was connected to the Irrawaddy River in the late Miocene, whereas Robinson et al. (2014) suggested that the river system was disconnected in the early Miocene. Licht et al. (2013)

⇑ Corresponding author at: Petronas Carigali Myanmar Inc. (PCMI), 16, Shwe

Taung Kyar, Bahan 11201, Yangon, Myanmar.

E-mail address: [email protected] (Kyaw Linn Oo).

http://dx.doi.org/10.1016/j.jseaes.2015.04.029

1367-9120/ 2015 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Kyaw Linn Oo, , et al. Provenance of the Eocene sandstones in the southern Chindwin Basin, Myanmar: Implications for

the unroofing history of the Cretaceous–Eocene magmatic arc. Journal of Asian Earth Sciences (2015), http://dx.doi.org/10.1016/j.jseaes.2015.04.029

Contents lists available at ScienceDirect

Journal of Asian Earth Sciences

j o u rn a l h o mep ag e : www.e l se v i e r. co m/ l oc a t e / j seaes

















mailto:[email protected]














http://www.sciencedirect.com/science/journal/13679120



http://www.elsevier.com/locate/jseaes







2 Kyaw Linn Oo et al. / Journal of Asian Earth Sciences xxx (2015) xxx–xxx

Fig. 1. (A) Simplified geological map of Myanmar and the eastern Himalayan region showing major geotectonic belts, volcanic centers and plutonic rocks of the Western

Myanmar Arc (WMA) in the Central Myanmar Basin (CMB) and granitoid rocks along the Mogok Metamorphic Belt (MMB) (modified after Mitchell et al., 2012). Location of

the studied area in the southern part of Chindwin Sub-Basin (CSB) is shown (Fig. 1B). ITSZ, Indus-Tsangpo Suture Zone; MBT, Main Boundary Thrust; EHS, East Himalayan

Syntaxis; GB, Gaoligong Belt; CTFB, Chittagong-Tripura Fold Belt; HSB, Hukaung Sub-Basin; MSB, Minbu Sub-Basin (Salin); PSB, Pyay Sub-Basin; IRSB, Irrawaddy Sub-Basin;

SF, Sagaing Fault; JMB, Jade Mine Belt; SG, Salingyi diorites; MSKD, Mokpalin–Sit-Kinsin Diorites. (B) Geological map of the studied area in the southern Chindwin Basin

(location is shown in Fig. 1A) showing the Middle–Upper Eocene lithostratigraphic units and the sample locations for the current study (after Kyaw Linn Oo, 2008).

Laungshe, Tilin and Tabyin formations in descending stratigraphicorder) are of shallow marine origin and are made up predominantly of thick shale and mudstone (Aung Khin and Kyaw Win, 1969; Bender, 1983). The Pondaung Formation is the thickest continental deposit in the Central Myanmar Basin ( 2300 m thick in the Chindwin Sub-Basin), composed of more than 70% sandstones with minor conglomerates in the lower part. The Pondaung sandstones contain abundant volcaniclastic materials and subordinate amount of low- to medium-grade metamorphic rock fragments (Kyaw Linn Oo et al., 2009; Licht et al., 2013; Khin Zaw et al., 2014a).

Licht et al. (2013) have recently conducted a provenance study on the upper member of the Pondaung Formation ( 500 m thick) in the northeastern Minbu Basin and the Yaw Formation in the northwest- ern Chindwin Basin, using petrography and bulk-sediment Nd–Sr isotopic analysis. However, about 1500 m thick section of the fluvial-dominated, lower member of the Pondaung Formation has not been investigated. In this study, we investigated the provenance

characteristics of the sandstones from the lower member of thePondaung Formation and the Yaw Formation in the southern Chindwin Basin, based on integrated analyses of detrital modes, XRF trace element geochemistry, regional mean palaeo-current data, and detrital U–Pb zircon ages. Our study also discusses the tectonic significance of the volcaniclastic Pondaung sandstones in the context of India–Asia collision in Myanmar, and provides key chronological and palaeogeographical constraints on the erosional unroofing history of an older volcanic arc in Myanmar.

2. Geological background

2.1. Tectonic framework of the Central Myanmar Basin

Myanmar lies in a tectonically active region, south of theHimalayan orogenic belt, and east of the Sumatra–Andaman–Ara












Kyaw Linn Oo et al. / Journal of Asian Earth Sciences xxx (2015) xxx–xxx 3

Table 1

Stratigraphy of the southern Chindwin Sub-Basin in the Central Myanmar Basin, and the stratigraphic intervals of the analyzed samples (modified after Aung Khin and Kyaw Win,

1969; Bender, 1983).

Stratigraphic

age

Stratigraphic units,

depositional

setting, thickness

Stratigraphic age determinations (fauna, flora,

magnetostratigraphy, radiometric dating)

Stratigraphic intervals of the collected sandstone

samples for this study and the previous studies

Lower

Miocene

Letkat Formation

Fluvial (285 m)

Fossil rare, a palynological assemblage zone indicates the –

early Miocene (Reimann and Aye Thaung, 1981; Engelhardt,

1993)

Oligocene Hiatus: Uplifting of the Chindwin Sub-Basin separated from the Minbu Sub-Basin to the south

Upper

Eocene

Priabonian Yaw Formation Nummulites yawensis, Orthophragmina (Discocyclina) 5 samples for petrographic data in this study;

petrographic data of the western part of

Chindwin Basin (Licht et al., 2013)

Deltaic–shallow

marine (337 m)

Sella, Operculina sp.cf. canalifera, Velates perversus

Two distinct plynological assemblage zones indicate late

Eocene (Reimann and Aye Thaung, 1981)

Unconformity/Sequence boundary between the Late Bartonian & Early Priabonian (Bar2/Pri 1) at 37.2 Ma

Late Middle Bartonian

EoceneUpper member of

Pondaung Fm.

Fluvio-deltaic

(300 m)

Abundant vertebrate fauna, Anthropoid primate fossil (e.g.,

Pondaungia cotteri), Mammalian fossil correlation = late

Middle Eocene (Bartonian Stage)

Magnetostratigraphic age of the upper member of

Pondaung Fm. in the NE of Minbu Basin = 37.4 Ma (Benammi

et al., 2002)

Fission-tract zircon dating from a tuffaceous bed of the

Basin = 37.2 ± 1.3 Ma (Tsubamoto et al., 2002)

LA ICP-MS U–Pb zircon dating from the same tuffaceous

Petrographic and Nd, Sr bulk-rock isotopic data of

the NE of Minbu Basin (Licht et al., 2013)

upper member of Pondaung Fm. in the NE of Minbu

bed = 40.31 ± 0.65 Ma (Khin Zaw et al., 2014a)

Fossil rare, silicified woods

Youngest detrital LA ICP-MS U–Pb zircon age of this

study = 43.3 ± 4.4 Ma (middle Eocene)

Nummulites acutus

Early Middle Lutetian

EoceneLower member of

Pondaung Fm.

Fluvial (2000 m)

Tabyin Fm.

Shallow marine

(760 m)

7 samples for petrographic data in this study

5 samples for U–Pb zircon geochronology and

XRF whole-rock geochemistry in this study

–

kan Trench (Morley, 2009), i.e., Myanmar portion of the India–Sunda convergence zone, which forms a transition from oceanic lithosphere subduction to the continent–continent collision (Le Dain et al., 1984; Win Swe, 2012). The Indo-Burman Ranges (IBR), immediate to the east of the Arakan Trench, has been recog- nized as an accretionary wedge, resulted from oblique subduction of the India oceanic lithosphere beneath the Burma Plate (Maurin and Rangin, 2009), and as an India–Asia (Myanmar) collision front during the Cretaceous and Eocene (Ni et al., 1989; Khin Zaw, 1990; Mitchell, 1993; Hall, 2012).

The Central Myanmar Basin (CMB) lies between the IBR in the west and the Shan Plateau in the east, i.e., a part of the Sibumasu Terrane of Metcalfe (2002, 2011, 2013), located in the eastern Myanmar. The CMB is divided into the eastern (backarc) and the western (forearc) troughs particularly after the late Miocene when the Central Volcanic Line (CVL) became well established (Bender,

1983; Pivnik et al., 1998). The western trough of the CMB is further subdivided into a few sub-basins, namely (from north to south) the Hukaung, Chindwin, Minbu/Salin, Pyay and Irrawaddy sub-basins (Fig. 1A). The CMB contains a thick succession of the Upper Cretaceous to Cenozoic sedimentary rocks ( 25 km thick), deposited in fluvio-deltaic systems and prograded southwards over shallow marine depositional environments (Aung Khin and Kyaw Win,1969; Bender, 1983), in a forearc location (Pivnik et al., 1998). These sub-basins may have developed as a series of pull-apart basins since the early Eocene as the Burma Plate moved northwards during the motion of India to the north with respect to Asia (Pivnik et al., 1998; Rangin et al., 1999).

At the eastern edge of the CMB, the N-trending active dextral Sagaing Fault (Win Swe, 1972; Curray et al., 1979) extends for about 1500 km along the western margin of the Shan Plateau, immediately to the west of the Mogok Metamorphic Belt (MMB), representing a present-day plate boundary between the Burma Plate (Curray et al., 1979; Curray, 2005) and the Sibumasu

Terrane. The subduction zone, to the west of the IBR (i.e.,Andaman-Arakan Trench), forms the western margin of theBurma Plate (e.g., Steckler et al., 2008; Mitchell et al., 2012).

2.2. Western Myanmar subduction zone: Andaman-Arakan Trench

Tomography and earthquake hypocenters delineated an east-ward dipping subducted slab beneath the Burma Plate, which is presumed to be a slice of Neo-Tethys oceanic crust from the earlier phase of subduction (Nielsen et al., 2004; Hall, 2009; Maurin and Rangin, 2009). Except under southernmost Myanmar, the geometry of the subducting slab is well established from earthquake focal depths (hypocenters) of an east-dipping Wadati-Benioff zone, gradually deepen eastwards following the trajectory of the subducted oceanic slab up to 200 km beneath the Central Myanmar Basin (e.g., Ni et al., 1989; Richards et al., 2007; Wang Yu et al.,2014).

P-wave tomographic depth slices of the Asia region (Bijwaard and Spakman, 2000) of the upper mantle (at 300 km) indicated the significant high velocity anomalies, parallel to the present Sumatra–Andaman-Arakan trenches, interpreted as the principal lithospheric slabs subducted during the late Cenozoic (Hall,2009). At depths below 700 km in the lower mantle also showed the linear high velocity anomalies in the south, north and the eastern end of India (i.e., beneath the Burma Plate), interpreted as a series of subduction zones active during India’s northward movement before collision with Asia (van der Voo et al., 1999; Aitchison et al., 2007; Hall, 2009). The velocity anomalies of both the upper and lower mantle characterize the evidence of long-term subduction at the Indonesian margins (Hall, 2009).The earlier seismologic studies suggested the cessation of subduction beneath the Burma Plate in the western Myanmar (e.g., Rao and Kumar, 1999) and no evidence of present-day active subduction to the north of the Andaman Islands, as it is shown by













Thrust belt (Radha Krishna and Sanu, 2000; Satyabala, 2003;Curray, 2005; Nielsen et al., 2004). Than Tin Aung et al. (2008) described the marine terraces along the Rakhine coast of Myanmar as evidence for three great earthquakes in the past3400 years. Radiocarbon dating of coral remains suggests that the oldest terrace emerged three times, during 1395–740 BC, AD805–1220 and AD 1585–1810 (Than Tin Aung et al., 2008).

In any case, the western Myanmar subduction zone is still active and accommodated a minor part (ca. 10–15%) of the

total India/Sundaland motion (Pubellier et al., 2003), as indicated

by the infrequent occurrence of moderate to strong historic earthquakes along the Rakhine (Arakan) coast (Chhibber, 1934;

Sahu et al., 2006) and the existence of a flight of marine terraces

(Than Tin Aung et al., 2006, 2008). It is implied that the

western Myanmar subduction zone has been active seismically, but

less active than the Sumatran region (Win Swe and Soe Thura

Tun,200

8).

2.3. The southern Chindwin Basin

The study area, in the southern part of the Chindwin Sub-Basin,is located about 48 km to the west of Monywa, and about 10 km to the north of Minbu Sub-Basin (also called Salin Sub-Basin) in the Central Myanmar Basin (Fig. 1A). The area is covered with fluvial to deltaic sedimentary units in descending stratigraphic order: the Tabyin Formation (early Middle Eocene, Lutetian Stage), Pondaung Formation (late Middle Eocene, Bartonian Stage), the Yaw Formation (Upper Eocene, Priabonian Stage), and the Letkat Formation (Lower Miocene?), which are exposed in a regional north-plunging syncline (Fig. 1B). The Tabyin Formation is poorly exposed only in the crestal part of the Pondaung Range in the studied area (Fig. 1B). Detailed stratigraphic age determination of the rock units are shown in Table 1.

The Pondaung Formation (Cotter, 1914) is the thickest and best exposed fluvial sedimentary sequence in the northern Minbu Sub-Basin and the southern Chindwin Sub-Basin. It was deposited in a braided to meandering river system in the southern Chindwin Sub-Basin (Kyaw Linn Oo, 2008) (Fig. 2C), and a fluvio-deltaic system in the northeastern Minbu Sub-Basin (Aung Naing Soe et al.,2002). The upper member of the Pondaung Formation (Aye Ko Aung, 1999) in the northeast of the Minbu Sub-Basin is well-known for hosting important Asian anthropoid primates and vertebrate mammalian fossils (e.g., Tsubamoto et al., 2002, 2009; Aung Naing Soe et al., 2002; Khin Zaw et al., 2014a). It is characterized by the widespread occurrence of reddish-colored or variegated clay/mudstones of fluvial floodplain palaeosol facies (Aung Naing Soe et al., 2002; Kyaw Linn Oo and Myitta, 2007; Kyaw Linn Oo, 2008; Licht et al., 2014b), interbedded with thin to medium-bedded, fine-grained sandstones. The lower member of the Pondaung Formation (Aye Ko Aung, 1999) in the studied area is composed of medium- to thick-bedded, cross-stratified, medium- to coarse-grained sandstones, gritty to pebbly sandstones and conglomerates, interbedded with silty mudstones.In the southern Chindwin Basin, there is a widespread, traceable, highly ferruginous horizon (Stamp, 1922; Kyaw Linn Oo and Myitta, 2007), i.e., a stratigraphic break or a sequence boundary, between the late Middle Eocene Pondaung Formation and the overlying Upper Eocene Yaw Formation (Fig. 2B). The Yaw Formation (Cotter, 1914) in the southern Chindwin Basin is interpreted to have been deposited in a tide-dominated marginal marine to deltaic environment, characterized by a thick, prograding sequence of bluish gray mudstones to dark-colored carbonaceous to coaly shale units, interbedded with thin- to medium-bedded sandstones (Kyaw Linn Oo, 2008) (Fig. 2A). The Lower Miocene (?) fluvial deposit of the Letkat Formation overlies disconformably on the Yaw Formation.

Fig. 2. (A) A field outcrop of the Upper Eocene Yaw Formation (a section of prodelta mud facies); (B) A region-wide traceable, highly ferruginous horizon between the

Yaw Formation and the underlying Pondaung Formation (Location: 22 070 5700 N,

94 320 2200 E, SE of Sityin village). Note: It is a lithostratigraphic break or a sequenceboundary between the end of Bartonian and the early Priabonian stages, correlative

to the major sequence boundary (Bar 2/Pr 1, at 37.10 Ma) of Hardenbol et al. (1998),

and also consistent with the petrofacies boundary between the Pondaung

sandstones and the Yaw sandstones. (C) A field outcrop of the late Middle Eocene

Pondaung Formation (a section of fluvial channel and overbank floodplain facies,

the reddish-colored variegated clay or palaeosol).

marine seismic studies to be an active dextral strike-slip margin(Nielsen et al., 2004). The recent structural and kinematic analysis of the IBR, based on seismic reflection, geodetic and geological field data, has indicated that the IBR is having right-lateral shearing in the innermost part and E–W shortening in the outermost part due to the diffuse strain partitioning, related to the oblique convergence of the India/Sunda plates (Maurin and Rangin, 2009).

However, the still active subduction in the western Myanmar is confirmed by a number of studies (e.g., Dasgupta et al., 2003; Satyabala, 2003; Nielsen et al., 2004; Khan, 2005; Socquet et al.,2006). The Indian plate subducts at a rate of 35–50 mm/yr. beneath the Burma micro-plate along the western coast of Myanmar, between the Rakhine (Arakan) trench and Chittagong Fold and













the Supplementary material. Cathodoluminescence (CL) imagesof the zircons were also obtained to help with the interpretation of the U–Pb age data. The images were obtained using a FEI Quanta 600 SEM housed at the University of Tasmania.

Analyses were performed two hours after ignition of the mass spectrometer to enable the machine to stabilize. Four primary (Temora standard of Black et al., 2004) and two secondary standards (91500 standard of Wiedenbeck et al., 1995) were analyzed at the beginning of the session and after every 12 unknown zircons (roughly every hour). The data reduction method used was based on that outlined in detail by Meffre et al. (2007). The standard errors quoted were based on the standard error of the measurements within the integration intervals, and the errors on the measurement of the standards using similar techniques to that outlined in Paton et al. (2010). Element abundances were calculated using the method outlined by Kosler (2001), using Zr as the internal standard element, assuming stoichiometric proportions and using the secondary standard 91500 to correct for mass bias, using trace element values from the GeoREM database (Jochum and Nohl, 2008).The data were not collected to give detailed quantitative or sta- tistical provenance information, but rather to investigate the age range for the main magmatic events associated with the volcanic components observed in the thin sections. The strategy employed was to combine all the zircon analyses from all of the samples and focus on the euhedral oscillatory zoned zircons with Th/U values > 0.1 (hereby interpreted as magmatic).

3. Analytical methods

3.1. Sampling method

Seventy fresh sandstone samples were collected from sevenstratigraphic measured sections in stream outcrops of the lower member of the Pondaung Formation and the Yaw Formation, exposed in both limbs of the regional north-plunging synclinal structure in the southern Chindwin Basin. Locations of the measured stratigraphic sections for the analyzed samples are shown in Fig. 1B. The stratigraphic intervals of the selected samples and type of analyses performed are also described in Table 1.

3.2. Petrographic analysis

Standard petrographic thin sections were prepared from the 50medium-grained sandstones and examined under a polarizing microscope with an attached mechanical stage, out of which 12 representative thin-sections were selected and analyzed by the modified Gazzi-Dickinson method of point counting (e.g., Ingersoll et al., 1984; Dickinson, 1970, 1985). A total of 400 framework grains were identified per thin section for QFL mode and lithic population, at a spacing of 0.33 mm. Cement, matrix, heavy minerals, carbonate, mica and miscellaneous grains were included in this count. Petrographic counting parameters are presented in Table 2. The Q–F–L plots of McBride (1963) and Dickinson (1985) are used for classification and provenance study. In addition, the triangular plots of Dickinson (1985), including Qm–P–K, Qm–F–Lt, and Lm–Lv–Ls plots are used for discriminating probable detrital provenances. 4. Results and interpretations

4.1. Petrography of the sandstones3.3. XRF-whole rock geochemical analysis

Recalculated detrital modes and lithic percentages are shown inTable 3. The sandstone modal compositions plotted on ternaryFive volcaniclastic sandstone samples, collected from the Lower

Member of Pondaung Formation, were used for XRF-whole rock geochemical analysis and LA ICP-MS U–Pb zircon dating. Sample locations are shown in Fig. 1B. The X-ray Fluorescence (XRF) method used a PANalytical (Philips) PW 1480 XRF spectrometer at the ARC Centre of Excellence in Ore Deposits (CODES), University of Tasmania, Australia. Major elements were measured from fusion discs, which were prepared at 1100 C in 5%Au/95%Pt crucibles using 0.500 g of sample, 4.500 g of 12–22 Flux (lithium tetraborate–metaborate mix) and 0.0606 g of LiNO3, following

the techniques described by Watson (1996) and Robinson (2003).Powdered samples were analyzed for 10 major oxides (SiO2, TiO2,

Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5 and loss on ignition)

and 10 trace elements (Y, U, Rb, Th, Pb, As, Bi, Zn, Cu, Ni) using a ScMo X-ray tube, and another 10 trace elements (Sn, Nb, Zr, Sr, Ba, Sc, V, La, Ce and Nd) using an Au X-ray tube.

Table 2

Petrographic point-counting parameters for the Pondaung and Yaw sandstones

(modified from Dickinson, 1970; Ingersoll et al., 1984).

Grain categories Recalculated

parameters

Qm

Qp

Cht

Q

Monocrystalline quartz

Polycrystalline quartz

Chert

Total quartzose grains (Qm + Qp + Cht)

Q–F–L:

Q = Qm + Qp + Cht

F = P + K

L = Lv + Lm + Ls

(excluding Qp and

Cht)

Qm–F–Lt:

Qm = Qm F = P + K

Lt = Qp + Lv + Lm + Ls

P Plagioclase feldspar grains (mainly of

polysynthetic twinned feldspars)

K Potassium feldspar grains (mainly of

untwinned feldspars, simple-twinned

feldspars, microcline and perthitic feldspars)

Total feldspar grains (P + K)

3.4. LA ICP-MS U–Pb zircon dating

U–Pb zircon dating using LA-ICP-MS (Laser Ablation InductivelyCouple Plasma Mass Spectrometer) is currently the most common method for analyzing detrital zircons because it achieves the same precision and accuracy as an ion probe (e.g., Kosler et al., 2013) but is considerably more efficient and cost effective. Detrital U–Pb zircon ages can be used to constrain the age of deposition of the host sediment, reconstruct provenance, characterize a sedimentary unit, and characterize many different aspects of source regions (Gehrels, 2014).

In this study, we used an Agilent quadrupole ICPMS with a193 nm New Wave Laser at CODES, the University of Tasmania, for zircon age dating. The zircons were separated using standard gravity and magnetic techniques, picked and mounted onto double sided tape, mounted in epoxy and polished. They were analyzed using the equipment and techniques described more details in

F Qm–P–K:

Qm = Qm P = P

K = K

Lm–Lv–Ls:

Lm = Lml + Lmh

Lv = Lvl + Lvm + Lvv

Ls = Ls

Lvl

Lvm

Lvv

Volcanic lithic grain with lathwork texture

Volcanic lithic grain with microlitic texture

Volcanic grain with vitric texture (including

different types of devitrified volcanic glass)

Total volcanic grains (lvl + lvm + lvv)

Total metamorphic lithic grains

Total sedimentary lithic grains

Total unstable aphanitic lithic grains

(Lm + Lv + Ls), excluding the quartz-related

grains (Qp + Cht)

Total lithic grains (Qp + Lm + Lv + Ls),

Lv

Lm

Ls

L

Lt

including quartz-related grains

Total grain parameters and the major plot names are in bold.













Table 3

Recalculated modal point-count data of the Pondaung and Yaw sandstones in the southern Chindwin Basin.

Samples Q–F–L % Qm–F–Lt % Qm–P–K % Lm–Lv–Ls % Ratios

Q F L Qm F Lt Qm P K Lm Lv Ls P/F Lv/L Lm/L

Yaw-37

Yaw-35

Yaw-34

Yaw-33

Yaw-39

Average

60

65

51

62

75

63

25

12

32

20

20

22

15

23

17

18

5

15

37

45

38

47

61

46

24

12

32

20

20

22

39

43

30

23

19

32

60

81

54

71

75

68

13

7

10

6

4

8

27

12

36

23

21

24

59

49

80

76

23

57

33

42

20

18

77

38

8

9

0

6

0

5

0.3

0.4

0.2

0.2

0.1

0.2

0.3

0.4

0.2

0.2

0.8

0.4

0.6

0.5

0.8

0.8

0.2

0.6

Pond-9

Pond-3

Pond-30

Pond-29

Pond-26

Pond-25

Pond-15

Average

44

46

24

29

29

49

36

37

29

20

11

14

20

26

32

22

27

34

65

57

51

25

32

41

31

26

6

11

15

30

20

20

30

20

11

10

20

27

32

21

38

54

83

79

65

43

48

59

52

57

36

51

43

52

39

47

38

39

37

22

53

34

54

40

10

4

27

27

4

14

7

13

30

64

6

5

52

16

2

25

65

36

87

94

44

80

98

72

5

0

7

1

4

4

0

3

0.8

0.9

0.6

0.6

0.9

0.7

0.9

0.8

0.7

0.4

0.9

0.9

0.4

0.8

1.0

0.8

0.3

0.6

0.1

0.0

0.5

0.2

0.0

0.2

The average values are in bold and italic.

diagrams of McBride (1963) show typical Q–F–L (Quartz–Feldspar–Lithic) percentages in the Pondaung sandstone samples (37–22–41) and the Yaw sandstone samples (63–22–15) (Fig. 3A). The Pondaung sandstones are feldspathic lithic arenite or feldspathic volcanic arenite in composition (Fig. 4A–G), whereas the Yaw sandstones are sub-lithic arenite to sub-arkose, containing abundant monocrystalline quartz and altered K-feldspar grains (Fig. 5G and H).

The Pondaung sandstones contain abundant volcanic lithic fragments (Lvl, Lvm) and volcanic glass with varying degree of devitri- fication (Lvv). Volcanic lithic fragments with lathwork texture (Lvl) and microlitic texture (Lvm) show similar characters to basaltic and andesitic fragments (Fig. 4A–D). The andesitic grains are composed of plagioclase phenocrysts set in an aphanitic groundmass (Fig. 4E–G). Large euhedral zoned plagioclase feldspars are commonly found in association with feldspar-phyric, microlitic, volcanic grains (Fig. 4H). Low- to high grade metamorphic lithic fragments of slate, phyllite and schist (Lm) occur in subordinate amounts in the Pondaung sandstones (Fig. 5D–F), but become a dominant lithic type in the Yaw sandstones.

volume of volcanic rocks in the source terrane, during depositionof the Pondaung Formation in the middle Eocene. The occurrence of plutonic igneous lithic grains composed of quartz–feldspar–mi ca aggregates, quartz–mica aggregates, and microcline, perthite and myrmekite fragments also indicate a plutonic source (Fig. 5A and B).

4.3. Petrofacies of the Yaw sandstones

The increasing Lm/L ratio, together with significant decreasingtrend of P/F ratio throughout the sandstones of Yaw Formation, suggests a marked change in source rock composition (Fig. 3B). Lower value of P/F is typical for detrital sediments derived from mixed plutonic and metamorphic terranes (Dickinson, 1970; Ingersoll, 1978). During the deposition of the Yaw Formation, the associated metamorphic and granitic source inputs were likely to become more substantial, possibly due to the rapid erosion of a volcanic arc down to the deeper granitoids, with associated uplift. In addition, the abundance of micas suggests an uplifted crystalline basement terrane composed mainly of micaceous granite or granodiorite, as well as low- to high grade metasedimentary rocks.

4.2. Petrofacies of the Pondaung sandstones4.4. Provenance of the Pondaung and Yaw sandstones

The Pondaung sandstones and the Yaw sandstones demonstratetwo different types of petrofacies, which are observed clearly when the compositional variations of the sandstones are plotted on an area graph (Fig. 3B). The ratios of plagioclase to total feldspar (P/F) and volcanic lithic to total lithic fragments (Lv/L) are appar- ently higher in the Pondaung sandstones than in the Yaw sandstones (Fig. 3B). The mean value of P/F in the Pondaung sandstones is more than 0.8. This value is common for most detrital sediments derived from volcanic terranes (Dickinson, 1970; Ingersoll, 1978). The mean value of Lv/L is 0.8, higher than that of metamorphic lithic to total lithic fragments (Mean value of Lm/L = 0.2), also a characteristic for volcanic arc derived materials (Dickinson, 1970; Ingersoll, 1978). The abundant compositionally zoned plagioclase and volcanic lithic fragments were derived possibly from andesitic rocks, and unaltered euhedral feldspar crystals

Point-count data of the sandstones plotted on QFL, QmPK,QmFLt and LmLvLs triangular diagrams (Dickinson and Suczek,1979; Dickinson, 1985), clearly demonstrate that the Pondaung sandstones fall within the suite of transitional to dissected magmatic arc provenances, whereas the Yaw sandstones may have come from a recycled orogenic provenance (Figs. 6 and 7). The Q–F–L plots also suggested that provenance of the sandstones moved from a dissected magmatic arc to recycled orogen or uplifted basement terrane (Fig. 6).

4.5. XRF major-element geochemistry: sandstone maturity, degree ofchemical weathering and climate condition in source area

The results of XRF major elements for each Pondaung sandstonesample are reported in Table 4. For evaluating sandstone maturity, the Index of Compositional Variability [ICV = (Fe2O3 + K2O + Na2O + CaO + MgO + MnO)/Al2O3] is commonly used (Cox et al.,

1995). The ICV values of the Pondaung sandstones range from1.0 to 1.9 (Average = 1.4), indicating that the sandstones are

(Fig. 4H) representCavazza, 1991).

Throughout the

fresh pyroclastic influxes (Ingersoll and

stratigraphic section of the PondaungFormation, the amount and character of plagioclase sand fluctu-ates, but persists up to several meters, suggesting a substantial













Fig. 3. (A) Ternary classification diagrams (McBride, 1963) of Pondaung and Yaw sandstones, showing an apparent shift in Q–F–L composition from feldspathic lithic arenite

(Pondaung sandstones) to lithic arkose–sub-arkose (Yaw sandstones). (B) Schematic diagram showing the percentages of Quartz, Feldspar and Lithic grains (Q–F–L) of the

sandstone samples taken in stratigraphic positions, together with the ratios of Plagioclase to Total Feldspar (P/F), volcanic lithic to total lithic (Lv/L) and metamorphic lithic to total lithic fragments (Lm/L), indicating a two distinct petrofacies boundary between them. (C) Major-element geochemical plots (SiO2 vs. Al2O3 + K2O + Na2O; after Suttner

and Dutta, 1986) of the Pondaung sandstones to recognize the chemical maturity as a function of palaeoclimate condition.













Fig. 4. Photomicrographs of the Pondaung sandstones in the southern Chindwin Basin. (A–D) volcanic vitric (Lvv) and volcanic lithic fragments with a characteristic texture of

andesitic basalt to basaltic andesite; feldsparphyric, microlitic volcanic lithic (Lvm) and plagioclase phenocrysts set in a groundmass of plagioclase microlites (Lvl). Figures A

and C are taken under PPL; Figs. B and D are taken under XPL. (E–H) Large, euhedral phenocrysts of zoned plagioclase feldspars (F) are embedded in microlitic volcanic lithic

fragments (Lvl) or vitric groundmass (Lvv) (under XPL).

compositionally immature. A good measure of the degree ofchemical weathering on source rocks can be obtained from the Chemical Index of Alteration (CIA; Nesbitt and Young, 1982), i.e., CIA (%) = Al2O3/(Al2O3 + CaO⁄ + Na2O + K2O) 100. The CIA of the

Pondaung sandstones ranges 44–65% (Average = 57%), indicating that chemical weathering in the source rock terrane was moderate. A moderate degree of plagioclase feldspar alteration in the source rock is also indicated by the Plagioclase Index of Alteration (PIA; Harnois, 1988), i.e., PIA (%) = (Al2 O3 K2O)/(Al2O3 + C aO⁄ + Na2O) 100. The PIA of the PO sandstones ranges from

42% to 64% (Average = 55%). The values of ICV, CIA and PIA areshown in Table 4. The SiO2 vs. (Al2O3 + K2O + Na2O) plot is used

to recognize the chemical maturity of the Pondaung sandstones as a function of climate (Suttner and Dutta, 1986). The plot reveals

that the Pondaung sandstones are chemically less mature andformed under semi-arid to arid climate conditions (Fig. 3C).

4.6. XRF trace-element geochemistry

Results of the XRF trace-element geochemical analyses for thePondaung sandstone samples are presented in Table 4. If the detrital grains were transported without much density sorting and con- sist essentially of volcaniclastic sediments, then it is possible that they would retain their original volcanic chemical signatures. Relatively mild chemical weathering in the source area should not strongly alter the immobile element geochemistry; highly weathered materials such as laterites and bauxites would lose all source rock chemical traits (Larue and Sampayo, 1990). Major













Fig. 5. Photomicrographs of the Pondaung sandstones in the southern Chindwin Basin. (A–B) Fresh plutonic fragments; aggregates of polycrystalline quartz with plagioclase

feldspar (Qp–F), hornblende (Hb) and mica (mica), associated with volcanic fragments (Lvv), suggesting a ‘‘volcano-plutonic’’ source (under XPL). (C–D) Elongated fragments

of polycrystalline quartz (Qp) having sutured inter-crystalline boundaries and undulose extinction, suggesting a metamorphic recrystallization (possibly from gneiss);

monocrystalline quartz (Qm) with chains of vacuoles inclusions and tourmaline grain (To) indicating a hydrothermal or vein quartz associated with felsic plutonic source

(under XPL). (D–F) Metamorphic lithic fragments (Lm) of quartz–mica schist are associated with Lvv and Lvm grains (Fig. E is taken under PPL, Figure F is taken under XPL). (G,

H) Photomicrographs of the Yaw sandstones showing abundant quartz grains, algae-coated grains (Alg) of monocrystalline quartz (Qm) and altered feldspar grain (F); a

feldspar grain (F) is coated by irregular, crinkle and concentric cortices of algae followed by siderite (Sid) cement, a glaucony grain (Glau), and bioclast fragment suggesting

slow sediment supply, deposited in low energy brackish water in semi-restricted ponds or bay in lower delta plain environment.

element compositions are routinely used to classify volcanic rocksin terms of petrogenesis and tectonic setting (e.g., Pearce and Norry, 1979; Pearce et al., 1984). However, this method is not applicable to altered volcanic rocks or the volcaniclastic sandstones in this study because many of the major elements, espe- cially Si, Fe, Mg, Ca, Na and K are relatively mobile during weathering and diagenetic alteration.

The high-field-strength elements (HFSE) such as Ti, Zr, Nb, andY are relatively immobile during hydrothermal alteration,

diagenesis and weathering, and during regional metamorphismup to the amphibolite facies. Ratios of these immobile elements are the basis of many tectono-magmatic discrimination diagrams (e.g., Pearce and Norry, 1979; Winchester and Floyd, 1977). Using the relatively immobile-element plots of Winchester and Floyd (1977) and Pearce and Norry (1979), there is a clear assignment for the composition and tectonic setting of the Pondaung sandstones (Fig. 8A and B). Results are also plotted on the two tectonic discrimination diagrams of Pearce et al. (1984) (Fig. 8C and D). The













Fig. 6. Triangular plots of QFL and QmFLt showing the sandstone suites derived from different provenances (Dickinson, 1985). The Pondaung sandstones fall in the

transitional- to dissected magmatic arc and the Yaw sandstones are distributed toward the recycled orogenic provenances.

Fig. 7. Triangular plots of the polycrystalline aphanitic lithic fragments Lm–Lv–Ls, and monocrystalline components Qm–P–K (Dickinson, 1985) to characterize source rock

composition. The Yaw sandstones are distributed toward more stable trend as they become more quartzose and mature and contain lower plagioclase content.

present study reveals that the volcaniclastic sandstones of thePondaung Formation were derived from calc-alkaline andesitic volcanic rocks, emplaced in a continental arc setting (Fig. 8A–D).

grains (n = 6) gave older U–Pb ages, e.g., from Proterozoic (n = 3)to Triassic–Jurassic (n = 3) that are chronologically similar to those of Sibumasu origin (e.g., Sevastjanova et al., 2011), suggesting possible derivation from the Shan Plateau to the east, or the western part of the Sibumasu Terrane.

Although more zircon grains may be warranted to explain the unroofing history of the Cretaceous–Eocene magmatic arc formed along the Myanmar continental margin, our finding is further supported by Wang et al. (2014) as they documented the isotopic signatures of the late Cretaceous to Eocene zircons, found in the stratigraphic units of the western Chindwin Basin, which are correlative to the Gangdese arc in Tibet.

4.7. LA ICP-MS U–Pb zircon geochronology

The total of 60 detrital-zircon grains were separated from thefive volcaniclastic sandstone samples of Pondaung Formation and analyzed by using a Laser Ablation Inductively Couple Plasma Mass Spectrometer (LA ICP-MS). Analytical results are summarized in Table 5, with each sample analysis illustrated in Concordia diagrams (Fig. 9A–F). Comparisons of our results with those of Wang et al. (2014) are shown in Fig. 10. Most of the zircon grains are euhedral to subhedral, with distinct oscillatory zones and having Th/U values > 0.1, the characteristics of magmatic zircons (e.g., Hoskin and Schaltegger, 2003) derived from the volcanic lithic grains (Fig. 10D).

There are two major clusters of the U–Pb zircon ages, observed in the relative probability plot of all analyses (i.e., two major detrital peaks at 100 Ma and 47 Ma) (Fig. 10C), as well as on each sample’s Concordia plots, where the major detrital peaks of each sample are around middle to late Cretaceous (101.7–80.4 Ma), and the youngest zircon ages are between early Palaeocene to middle Eocene (65.1–43.0 Ma). The Concordia plot for all the samples has yielded 47.75 ± 0.87 Ma, which falls in the Lutetian stage of the middle Eocene (Fig. 9F). In our study, a few detrital zircon

5. Discussion

5.1. Myanmar Magmatic-Arc

Geochronology and tectonic evolution of the magmatic arcs inMyanmar (Mitchell et al., 2012) with detrital zircon U–Pb age data of the present and previous studies are shown in Fig. 11. The late Neogene–Quaternary volcanic arc of Myanmar is indicated by the presence of calc-alkaline, Central Volcanic Line (CVL) (Chhibber,1934; Bender, 1983; Stephenson and Marshall, 1984), running north–south along the medial part of the Central Myanmar Basin. The CVL comprises a few isolated, late Miocene–Pleistocene, extinct volcanoes of Mt. Loimye, Taungthonlon, Monywa and













Table 4

XRF whole-rock geochemical data and values of ICV (Index of Compositional Variability, Cox et al., 1995), CIA (Chemical Index of Alteration, Nesbitt and Young, 1982) and PIA

(Plagioclase Index of Alteration, Harnois, 1988) for the Pondaung sandstones.

1-(PD-21/6) 2-(PD-24/2) 3-(PD-1/5) 4-(PD-28/3) 5-(PD-28/9) Average

Major elements (wt%)

SiO2

TiO2

Al2O3

Fe2O3

MnO MgO CaO Na2O K2O P2O5

LOI

Total

ICV

CIA%

PIA%

62.42

0.54

15.33

4.92

0.08

2.44

4.18

3.12

0.75

0.09

5.63

99.5

1.0

66

64

50.95

0.53

12.35

4.34

0.32

2.88

11.69

2.51

1.12

0.16

12.49

99.34

1.9

45

42

53.65

0.61

11.59

4.57

0.93

1.67

11.67

1.83

0.84

0.1

12.11

99.57

1.9

45

43

66.68

0.43

13.05

4.68

0.07

3

2.75

2.63

1.4

0.1

4.81

99.6

1.1

66

63

65.66

0.52

12.98

4.96

0.07

3.29

3.02

2.72

1.19

0.11

5.13

99.65

1.2

65

63

59.9

0.5

13.1

4.7

0.3

2.7

6.7

2.6

1.1

0.1

8.0

1.4

57.4

55.0

Trace elements (ppm)

Y

U

Rb

Th

Pb

As

Bi

Zn

Cu

Ni

Sn

Nb

Zr

Sr

Cr

Ba

Sc

V

La

Ce

Nd

Zr/Y

Zr/Nb

Nb/Y

10

<1.5

14

2

9

4

<2

59

19

22

<1.5

3

95

582

59

667

15

98

8

19

8

9.5

31.7

0.3

21

<1.5

31

3

16

<3

<2

63

15

58

2

3

79

466

188

394

18

116

19

43

19

3.8

26.3

0.14

24

<1.5

25

2

7

6

<2

54

17

33

<1.5

5

86

300

97

505

18

122

12

30

14

3.6

17.2

0.21

16

2

37

4

13

<3

<2

52

14

85

<1.5

4

79

377

155

422

11

83

14

31

14

4.9

19.8

0.3

16

2

33

3

11

<3

<2

57

15

91

2

4

96

330

247

316

14

114

13

30

17

6

24

0.3

17.4

0.8

28.0

2.8

11.2

2.0

0.0

57.0

16.0

57.8

0.8

3.8

87.0

411.0

149.2

460.8

15.2

106.6

13.2

30.6

14.4

5.6

23.8

0.3

The total values are in bold and italic.

Mt. Popa, from north to south (Fig. 1A). It is continuing southwardsinto the recently active volcanoes (Narcondam and Barren Islands) of the Andaman arc and the late Neogene volcanic line of Sumatra, a part of the active Sunda arc-trench system (Mitchell, 1993; Win Swe, 2012).

The CVL, together with the granitoids of Wuntho-Saligyi segment in the north, are named as the Inner Volcanic-magmatic Arc (Bender, 1983; Khin Zaw, 1990) or Western Granitoid Belt of Myanmar (Khin Zaw, 1990; Khin Zaw et al., 2014b). It is now commonly referred to as the Western Myanmar Arc (WMA) or Wuntho-Popa Arc (Mitchell, 1993; Mitchell et al., 2012; Wang et al., 2014). It has long been considered as a Mesozoic to Cenozoic subduction-related magmatic arc formed by prolonged east-verging plate convergence (Mitchell, 1977, 1993; Bender,1983; Khin Zaw, 1990; Mitchell et al., 2012; Win Swe, 2012; Khin Zaw et al., 2014b; Wang et al., 2014). The magmatic rocks of the WMA are superimposed on a basement of gneiss, mica schist, phyllite, amphibolite and ophiolitic ultramafic rocks (Mitchell, 1993; Pivnik et al., 1998). Similarities in age of the WMA and Sumatra magmatic arcs, and their absence from the

intervening Andaman Sea, suggest that the two arcs were continu-ous in the late Cretaceous (Mitchell, 1993).

However, the emplacement history of the late Neogene– Quaternary volcanic arc of Myanmar is still not clearly understood (e.g., Hall, 2002). It is generally accepted that the recently active, northeastward subduction of the India oceanic lithosphere has resulted in development of a well-defined Wadati-Benioff zone located at 100–140 km beneath Mt. Popa and Monywa (Guzman-Speziale and Ni, 1996; Satyabala, 1998; Maury et al.,2004). The depth of the Wadati-Benioff zone below the calc-alkalic and shoshonitic volcanoes of Mt. Popa and Monywa is within the typical range for modern arcs and the magmas show typical subduction-related geochemical signatures (Maury et al.,2004). The CVL is characterized by high-level intrusions associated with high-sulfidation Cu (Au) related younger volcanics, e.g.,

Monywa (Khin Zaw et al., 2014b). Recent 39Ar–40Ar dating of alunite from Lepadaung at Monywa Cu deposit yielded 19.7 Ma (Khin Zaw et al., 2014b), and of Mt. Popa yielded K–Ar ages of0.96–0.80 Ma (Maury et al., 2004) and 4.30 Ma (Cumming et al.,200

9).













Fig. 8. Geochemical discrimination diagrams for the volcaniclastic Pondaung sandstones. (A) Zr/TiO2 vs. Nb/Y (Winchester and Floyd, 1977) (B) Zr/Y vs. Zr (Pearce and Norry,

1979) (C) Rb vs. Y + Nb (Pearce et al., 1984). (D) Nb vs. Y (Pearce et al., 1984), suggesting that the volcaniclastic materials in the Pondaung sandstones were derived from calc-

alkaline, continental arc andesitic rocks.

However, depth-to-magnetic basement map and seismicprofiles of the Salin Sub-Basin in central Myanmar has identified the NE–SW striking, basement-involved normal faults and tension gashes that are coincided with the Mt. Popa and Monywa volcanics, formed during the Miocene extensional deformation period (Pivnik et al., 1998; Vigny et al., 2003; Bertrand and Rangin, 2003). The late Miocene–Pleistocene regional uplift in the eastern side of the Salin Sub-Basin, during the tectonic inversion period, may have controlled the extrusion of volcanics along the reactivated basement-involved normal faults perpendicular to the NW–SE trending basin-center thrust faults (Pivnik et al., 1998). It is probably related to the hyper-oblique convergence of India along the western Myanmar; the northward motion of India coupled with the Burma Plate and collided with Asia during Miocene–Quaternary, resulted in extensional to transpressional deformations in Myanmar (Pivnik et al., 1998; Rangin et al., 1999).

The northern segment of the arc, the Wuntho Massif and the Salingyi area (Fig. 1A), contains Cretaceous to Eocene, calc-alkaline, granodioritic plutons and andesitic volcanics (United Nations, 1978a; Mitchell, 1993; Barley et al., 2003), which is located at about 100 km northeast of the studied area. Mitchell (1993) reported that the Middle Cretaceous to early Palaeogene granodioritic batholiths intruded a thick, folded sequence of basaltic andesites and basalt pillow lavas (i.e., known as Mawgyi Andesites) in the Banmauk area of the Wuntho Massif. K–Ar and SHRIMP zircon dating on the granitoids in the Kanzachaung and

Shangalon areas have yielded 94 Ma and 38 Ma, respectively(Mitchell, 1993; Barley et al., 1996, 2003), representing the Cenomanian and Lutetian stages of the middle Cretaceous and middle Eocene, respectively. It is also suggested that the early- to middle Eocene subduction in Myanmar is indicated by K–Ar ages of 50.1 Ma on andesite and 52.9 Ma on quartz diorite from the Shangalon Cu–Mo deposit, located to the south of Banmauk in the Wuntho Massif area (United Nations, 1978a; Mitchell, 1993).40K–40Ar dating on the granitoids of the Salingyi area gave 106–91 Ma (United Nations, 1978b; Mitchell, 1993), corresponding to the Albian to Cenomanian stages of the middle Cretaceous.

The Wuntho-Salingyi segment is also considered to have been translated northward about 1100 km, from its original position in the Andaman Sea, along the right-lateral movement of Sagaing Fault since the middle Miocene (Mitchell, 1977, 1993; Mitchell et al., 2012). Results of isotopic dating of the granitoids and volcanic rocks of the Western Granitoid Belt of Khin Zaw (1990) or the Western Myanmar Arc (WMA) of Mitchell et al. (2012) are summarized in Table 6.I-type granitoids found along the western margin of the Shan-Thai (Sibumasu) Terrane, i.e., along the Mogok Metamorphic Belt (MMB) and the Myeik (Mergui) Archipelago (Tenasserim granitoids) in southern Myanmar, are part of the eco- nomically important W–Sn related Central Granitoid Belt of Myanmar (Khin Zaw, 1990; Barley et al., 2003), which also belongs to the Western Granite Province (Peninsular–Thailand–Myanmar) of Cobbing et al. (1992). The granitoids of this belt are of middle













Table 5

Detrital zircon U–Pb ages for the Pondaung sandstones.

206Pb/238U age(Ma)

206Pb/238U 208Pb/232Th 207Pb/206Pb 207Pb/235USample no. Ti Hf Pb Th U Th/U

207PbcorAnalysis no. ±1SE Ratio %rse Ratio %rse Ratio %rse Ratio %rse Ppm Ppm Ppm Ppm Ppm

1-(PD-21/6)

Fe01l6

Fe01l8

Fe01l12

Fe01l1

Fe01l10

Fe01l11

Fe01l9

Fe01l4

Fe01l7

Fe01l3

Fe01l5

Fe01l2

2-(PD-24/2)

Fe01j6

Fe01j5

Fe01j11

Fe01j10

Fe01j1

Fe01j9

Fe01j7

Fe01j12

Fe01j3

Fe01j2

Fe01j8

Fe01j4

3-(PD-1/5)

Fe01k11

Fe01k1

Fe01k3

Fe01k8

Fe01k10

Fe01k4

Fe01k6

Fe01k7

Fe01k9

Fe01k2

Fe01k12

Fe01k5

4-(PD-28/3)

Fe01m7

Fe01m3

Fe01m11

Fe01m9

Fe01m4

Fe01m8

Fe01m2

Fe01m12

Fe01m5

Fe01m1

Fe01m6

Fe01m10

5-(PD-28/9)

Fe01n10

Fe01n9

Fe01n3

Fe01n8

Fe01n6

Fe01n12

Fe01n11

Fe01n4

Fe01n5

Fe01n7

Fe01n1

Fe01n2

43.3

96.9

97.4

99.4

99.5

99.7

100.4

101.1

103.8

106.2

108.6

203.7

2.2

1.6

1.8

1.5

1.4

1.6

1.5

1.3

1.4

1.8

1.4

2.7

0.0068

0.0152

0.0153

0.0156

0.0156

0.0156

0.0157

0.0158

0.0162

0.0166

0.0170

0.0324

4.8

1.7

1.8

1.5

1.4

1.6

1.5

1.3

1.3

1.6

1.3

1.3

0.0020

0.0047

0.0042

0.0052

0.0047

0.0052

0.0049

0.0048

0.0055

0.0055

0.0063

0.0170

10.0

5.3

7.7

4.8

3.0

4.6

3.8

2.6

3.3

6.7

4.0

4.2

0.054

0.050

0.049

0.050

0.049

0.049

0.049

0.047

0.047

0.047

0.050

0.057

18.6

6.2

7.4

5.5

4.0

5.6

5.1

3.9

4.1

6.3

4.1

3.6

0.038

0.099

0.103

0.102

0.102

0.101

0.102

0.101

0.103

0.102

0.113

0.248

17.5

6.0

7.2

5.3

3.9

5.6

4.7

3.9

3.9

6.0

4.0

3.7

7.9

2.7

3.9

4.1

5.3

4.5

6.7

6.4

3.3

6.3

10.8

14.1

8803

12,468

11,318

11,075

10,553

11,673

10,614

11,798

11,300

11,383

12,274

12,337

1

3

2

3

7

3

5

9

7

3

7

13

110

76

51

90

330

93

148

314

206

43

116

86

107

218

139

218

427

221

304

528

451

168

389

385

1.0

0.3

0.4

0.4

0.8

0.4

0.5

0.6

0.5

0.3

0.3

0.2

46.9

74.1

81.7

83.8

87.7

88.5

89.0

92.3

99.8

107.0

117.5

842.6

1.2

1.2

1.2

1.4

1.9

1.7

1.1

1.5

2.3

2.3

1.5

8.8

0.0074

0.0116

0.0141

0.0131

0.0137

0.0139

0.0140

0.0144

0.0156

0.0166

0.0185

0.1398

2.5

1.6

1.3

1.6

2.1

1.8

1.2

1.6

2.2

2.2

1.3

1.1

0.0025

0.0035

0.0079

0.0044

0.0037

0.0044

0.0045

0.0039

0.0042

0.0055

0.0059

0.0476

7.0

4.4

2.5

3.9

6.4

3.5

3.0

4.3

6.2

6.7

2.9

2.4

0.053

0.051

0.125

0.050

0.049

0.051

0.053

0.049

0.050

0.043

0.052

0.068

9.2

5.8

2.9

6.6

8.4

6.5

3.7

5.7

9.6

8.6

3.9

2.1

0.048

0.077

0.236

0.090

0.087

0.090

0.096

0.095

0.099

0.090

0.125

1.285

8.3

5.7

2.9

6.5

8.3

6.2

3.6

5.4

9.1

8.3

3.9

2.1

6.4

7.7

54.5

10.7

5.1

15.4

4.9

7.1

9.6

7.8

7.0

7.8

11,242

10,898

11,076

10,658

11,417

10,811

12,003

11,001

10,104

8966

10,855

9941

1

3

7

3

2

3

8

4

1

1

6

22

73

137

283

146

45

148

291

174

46

35

190

54

174

272

395

162

111

172

512

238

73

86

308

153

0.4

0.5

0.7

0.9

0.4

0.9

0.6

0.7

0.6

0.4

0.6

0.4

47.2

47.2

48.3

49.5

98.2

98.6

99.1

99.5

100.5

100.7

102.4

503.0

1.0

1.1

0.8

1.1

2.1

1.4

1.5

1.9

1.7

1.9

1.5

4.5

0.0074

0.0075

0.0076

0.0077

0.0156

0.0154

0.0155

0.0156

0.0157

0.0159

0.0160

0.0817

2.0

2.3

1.7

2.2

2.1

1.4

1.4

1.9

1.7

1.9

1.4

0.9

0.0024

0.0020

0.0023

0.0020

0.0053

0.0049

0.0052

0.0048

0.0050

0.0043

0.0052

0.0236

7.2

8.9

3.9

6.8

5.5

3.7

5.6

7.1

6.0

5.9

4.7

2.6

0.053

0.060

0.051

0.049

0.062

0.047

0.051

0.050

0.048

0.054

0.048

0.062

7.4

9.7

5.5

8.6

6.0

5.0

5.2

8.8

6.0

6.0

4.7

1.6

0.052

0.059

0.050

0.048

0.125

0.093

0.102

0.100

0.097

0.112

0.102

0.682

7.6

9.1

5.1

8.3

6.4

5.0

4.9

8.1

6.0

5.9

4.5

1.6

7.7

3.2

8.6

7.4

17.0

6.3

5.8

9.5

5.4

5.7

5.9

11.3

11,030

10,520

9637

10,738

12,737

10,577

12,677

10,932

12,757

9481

13,236

14,549

2

1

3

2

6

5

4

2

3

2

5

58

102

57

289

123

220

152

65

48

70

53

102

88

237

130

402

202

408

347

284

127

222

135

324

745

0.4

0.4

0.7

0.6

0.5

0.4

0.2

0.4

0.3

0.4

0.3

0.1

51.6

66.9

67.6

99.7

101.2

101.4

101.5

101.6

103.1

103.5

173.4

628.1

1.0

1.1

0.9

1.4

1.6

1.2

1.8

1.5

1.4

1.7

3.9

6.4

0.0081

0.0105

0.0106

0.0156

0.0159

0.0159

0.0158

0.0159

0.0161

0.0163

0.0273

0.1023

1.8

1.6

1.3

1.4

1.6

1.2

1.8

1.5

1.3

1.6

2.2

1.0

0.0026

0.0036

0.0033

0.0048

0.0052

0.0052

0.0049

0.0048

0.0053

0.0048

0.0095

0.0309

3.8

4.9

2.6

4.1

3.8

2.8

6.4

5.1

2.5

4.4

6.8

2.1

0.052

0.056

0.050

0.049

0.049

0.049

0.045

0.048

0.049

0.053

0.051

0.060

7.1

5.8

3.6

4.4

5.5

3.1

7.0

5.2

4.6

5.7

7.5

2.0

0.055

0.077

0.071

0.101

0.104

0.104

0.090

0.101

0.103

0.116

0.188

0.821

6.7

5.6

3.6

4.5

5.4

3.2

6.6

5.1

4.4

5.6

7.5

1.9

9.5

14.9

2.8

4.6

7.1

4.7

5.0

3.8

5.6

5.8

5.2

7.7

9378

9950

10,713

12,630

9391

12,118

11,522

12,943

10,717

10,854

10,202

10,740

2

3

9

4

3

8

2

4

6

3

2

23

279

95

604

113

132

218

43

81

321

60

21

82

260

241

754

250

193

521

140

249

335

168

61

229

1.1

0.4

0.8

0.5

0.7

0.4

0.3

0.3

1.0

0.4

0.4

0.4

65.1

78.9

80.9

81.8

97.7

99.1

100.7

132.1

218.4

436.0

487.3

1062.2

1.6

1.4

2.0

1.6

1.4

1.3

1.5

5.4

2.2

4.1

4.3

10.9

0.0103

0.0123

0.0128

0.0128

0.0152

0.0154

0.0158

0.0208

0.0344

0.0700

0.0787

0.1797

2.4

1.8

2.3

1.9

1.4

1.3

1.5

4.1

1.0

1.0

0.9

1.0

0.0032

0.0038

0.0041

0.0035

0.0048

0.0050

0.0047

0.0066

0.0107

0.0216

0.0228

0.0526

6.4

5.7

5.9

6.8

4.1

3.3

4.5

5.9

1.6

2.5

1.5

1.8

0.055

0.046

0.056

0.047

0.046

0.046

0.052

0.052

0.050

0.055

0.059

0.077

8.6

6.1

9.3

7.9

4.9

4.2

5.4

4.6

2.3

1.8

1.6

1.7

0.069

0.077

0.091

0.078

0.092

0.096

0.107

0.152

0.229

0.513

0.613

1.852

8.5

6.2

8.8

7.7

4.9

4.1

5.5

7.5

2.3

1.8

1.6

1.8

4.5

33.3

8.8

4.9

7.9

6.1

3.8

6.5

4.9

0.6

8.8

10.3

9526

10,526

10,647

12,851

11,319

11,851

11,113

10,488

12,472

13,897

9990

10,525

1

2

1

2

5

6

3

5

23

35

45

29

61

77

59

69

124

161

102

130

518

80

423

95

110

198

85

147

317

360

222

268

614

538

535

149

0.6

0.4

0.7

0.5

0.4

0.4

0.5

0.5

0.8

0.1

0.8

0.6

Numbers in bold were used for age calculations.

SE: Standard Error.207Pbcor: 207Pb corrected 206Pb/238U age.













Fig. 9. Concordia diagrams (238U/206Pb–207Pb/206Pb) of the detrital zircons from Pondaung sandstones, southern Chindwin Basin (sample locations are shown in Fig. 1B). (A)

Sample no. 1-(PD-21/6) collected from the uppermost horizon of the lower member of Pondaung Formation (22 030 29.000 N, 94 340 1.200 E). (B) Sample no. 2-(PD-24/2) collected

from the uppermost part of the lower member of the Pondaung Formation (22 020 11.000 N, 94 280 27.000 E). (C) Sample no. 3-(PD-1/5) collected from the middle part of the lower

member of the Pondaung Formation (22 050 24.200 N, 94 270 22.700 E). (D) Sample no. 4-(PD-28/3) collected from the lower part of the lower member of the Pondaung Formation

(22 050 28.100 N, 94 270 14.500 E). (E) Sample no. 5-(PD-28/9) collected from the lowermost part of the lower member of the Pondaung Formation (22 050 24.200 N, 94 260 59.700 E). (F) Concordia diagram for all zircon grains from the five samples gives 47.75 ± 0.87 Ma, the early Eocene (Lutetian).

Cretaceous to the earliest Eocene age (120–50 Ma). LA ICP-MSU–Pb dating of zircon inclusions in a Mogok ruby gave ages of31–32 Ma (Khin Zaw et al., 2015). Larue Kyaw Thu (2007) also dated leucocratic granite intrusions at Mogok using U–Pb zircon method and yielded ages of 45 and 25 Ma. It is suggested that prior to the India–Asia collision, an up to 200 km wide

subduction-related magmatic belt (i.e., Trans-Himalayan Arc andLhasa Terrane) was extending along the southern Eurasian continental margin from Pakistan, India, Tibet and Nepal through Myanmar to Sumatra (Mitchell, 1993; Barley et al., 2003; Searle et al., 2007, 2012; Mitchell et al., 2012). In fact, Khin Zaw (1990) first speculated the subduction-related arc and back arc basin to













Fig. 10. (A and B) Detrital zircon U–Pb and Hf isotope study of the late Cretaceous–Eocene samples from the western part of Chindwin Basin (after Wang et al., 2014). (C)

Detrital zircon U–Pb analysis of the late Middle Eocene samples from the southern Chindwin (this study). (D) Cathodoluminescence (CL) images of the Pondaung zircons. Note

that the unroofing history of the late Cretaceous to Middle Eocene local magmatic arc is supported by similar characteristic peaks of U–Pb zircon ages in Wang et al. (2014)

and the present study.

collisional setting along the western margin of MMB as early asJurassic based on the distribution and geochemistry of volcanic and magmatic rocks. This interpretation is later supported by170 Ma SHRIMP U–Pb age of zircon in orthogneisses near Mandalay (Barley et al., 2003) suggesting an Andean type convergent pate margin. Isotopic dating results of the MMB granitoids are summarized in Table 7.

In the southern part of the studied area, volcanic tuffs and tuffaceous beds are found in the upper member of the Pondaung Formation, exposed mainly in the Asian anthropoid primate-bearing locations (i.e., Paukkaung and Bahin villages located in the northeastern Minbu Basin). Zircon fission-track dating obtained from a tuffaceous bed gave 37.2 Ma and 38.8 Ma, representing the Bartonian Stage of the late Middle Eocene (Tsubamoto et al., 2002, 2009). Khin Zaw et al. (2014a) recently reported new LA-ICP-MS U–Pb ages of zircons from the same tuffaceous bed, which yielded 40.31 Ma and 40.22 Ma. Published and our new radiometric data are compiled and summarized in Table 8.However, published data of the geochemistry and geochronology of the granitoids and volcanic rocks in the Wuntho-Massif area are too limited to provide a complete history of the subduction-related, older magmatic arc of Myanmar. The geodynamics of the India–Asia Collision project (GIAC, 1999) suggested that the Shan volcanic arc may have been built on the Shan Plateau before 53 Ma, as a result of subduction of the Neo-Tethys seafloor along the Sundaland active margin (Fig. 12). The arc may have been destroyed during the early- to middle Eocene (53–43 Ma) when the western depocenter of the Central Myanmar

Basin was initiated, and the Shan Plateau deformed by crustalthickening, followed by crustal relaxation due to a change in convergence direction of the Indian Plate from NE to N with respect to Sundaland (GIAC, 1999). This deformation is also recorded in the Jurassic zircons that have been partly recrystallized with metamorphic overgrowths in the orthogneisses from near Mandalay, which recorded a period of high-grade metamorphism in the middle Eocene (i.e., U–Pb zircon age: 43 Ma) (Barley et al., 2003; Searle et al., 2007; Mitchell et al., 2012).

5.2. Composition, erosion and weathering condition in source area

Significant changes in sandstone petrofacies and gradual transi-tion of provenances between the Pondaung sandstones and the Yaw sandstones have clearly demonstrated either a volcanic to plutonic change in source area or unroofing of a volcanic arc down to deeper plutons (e.g., Dickinson and Suczek, 1979). The apparent increase in the relative amount of K-feldspar and a significant decrease in the amount of arc-derived components in the Yaw sandstones, also indicate that erosion had depleted the volcanics in the source area. The observed petrofacies changes from the Pondaung sandstones to the Yaw sandstones are also consistent with a major sequence boundary between the underlying Pondaung Formation and the overlying Yaw Formation (Fig. 2B, Table 1). This supports a break in sedimentation that may have attributed to change in source rock composition.

The inferred magmatic arc can be correlated with granitoids and volcanic rocks found around the Wuntho-Massif and Salingyi













PO, MSB: Pondaung sandstone, Minbu Sub-Basin(tuffaceous sandstones)

(a) (b) (c) (d) (e)(f)

United Na ons (1978) Khin Zaw (1990)Tsubamoto et al. (2002, 2009) Shi et al. (2012)Mitchell et al. (2012)Khin Zaw et al. (2014a)

HSB: CSB: WTM: SLG:MPL:

Hukaung Sub-Basin (volcaniclas c sandstones) Chindwin Sub-Basin (volcaniclas c sandstones) Wuntho-Massif (andesite, granodiorite, diorite) Salingyi dioritesMokpalin diorites

Fig. 11. Geochronology and tectonic evolution of the magmatic arcs in Myanmar (modified after Mitchell et al., 2012) with U–Pb detrital zircon age data of the present study.

area (Table 6), and the I-type granitoids in the MMB (e.g., theMokpalin and Sit-Kinsin diorites, Table 7) having a similar isotopic fingerprints of the Gangdese batholiths in Tibet (Fig. 11). In addition, low- to medium-grade metamorphic lithic fragments of continental margin source are commonly found in the Myanmar basement terrane (i.e., MMB and JMB shown in Fig. 1A), but are rarely exposed in the Tibetan Lhasa Terrane (Licht et al., 2013). Licht et al. (2015a) reject any dramatic provenance shift during the Middle Eocene and Pleistocene period in the CMB, but support a gradual decreasing trend of the volcanic input and its replace- ment by a dominant supply from the Myanmar basement terrane. The trend is consistent with the local unroofing of an Andean-type cordillera (Garzanti and Ando, 2007) that extended onto the

Myanmar continental margin along the flank of the Shan Plateau(i.e., the MMB at the western foothills of the Shan-Thai or Sibumasu Terrane) where most of the post-collisional deformation of the CMB is located (Licht et al., 2015a). The arc may have been progressively eroded during the middle Eocene, and experienced an episode of uplift (e.g., Morley, 2004; Barley et al., 2003; Allen et al., 2008).

The Pondaung sandstones were likely to have derived from a tectonically active provenance, such as an active continental arc, where high relief of uplifted volcano-plutonic and metamorphic rocks produce fresh or less altered first cycled sediments. During the middle- to late Eocene, rates of deposition were high (Metivier et al., 1999; Licht et al., 2013), and the thick sequences













Table 6

Summary of age data of the volcanic and granitoid rocks of Western Myanmar Arc (WMA).

Areas or provinces Sample Method Age (Ma) Geochemistry/tectonic environment References

Jade Mine Belt

(JMB)

Jadeitite U–Pb zircon 122.2 ± 4.8

146.5 ± 3.4

163 ± 3.3

Quaternary

– Shi et al. (2009)

Taungthonlon Andesite (hypersthene–

augite–hornblende

Andesite)

Biotite–hornblende,

Granodiorite, Hornblende–

biotite granodiorite

Leucocratic biotite–

hornblende granite

Leucocratic biotite–

hornblende granite

Tonalite porphyry

Vesicular plagiophyric

epidotised Andesite,

Altered quartz diorite

Granodiorite

Granodiorite

Feldsparphyric andesite;

flow/dyke

Basalt

– Shoshonitic Stephenson and Marshall

(1984), Maury et al. (2004),

Mitchell et al. (2007)

United Nations (1978a)Wuntho-Massif

Banmauk

K/Ar

Biotite

93.7 ± 3.4

97.8 ± 3.6

–

87Rb–86SrKanzachaung

Batholith

90 ± 78 Low Rb/Sr, I-type Darbyshire and Swainbank

(1988)

Barley et al. (1996, 2003)SHRIMP U–Pb zircon 94.3 ± 1 –

Shangalon Cu–Mo

deposit

K/Ar, Biotite

K/Ar, whole rock

K/Ar, Muscovite

37.9 ± 1.4

50.1 ± 2.5

52.9 ± 2

- United Nations (1978a)

Darbyshire and Swainbank

(1988)

Barley et al. (1996, 2003)87Rb-86SrSHRIMP U–Pb

K/Ar, whole rock

110 ± 63

38.5 ± 0.6

70.7 ± 4.2

Low Rb/Sr, I-type

–Mawgyi Andesite United Nations (1978a)

40K/40ArMonywa

Twin Taung

Sabetaung

0.44 ± 0.12 Shoshonitic lavas, low degree melting of

a subduction modified mantle

–

–

Maury et al. (2004)

Andesite porphyry

Andesite, quartz andesite

and dacitic porphyry

Alunite

Granites

Diorites

Gabbros

Diorite

K/Ar

U–Pb zircon

5.8

13.6 ± 0.1Kyaw Win and Kirwin (1998)


Lepadaung

Salingyi

Ar/Ar

K/Ar

19.7

103 ± 4

106 ± 7

91 ± 8

105 ± 1.7

–

I-type, Magmatic–volcanic arc,

subduction related

Khin Zaw et al. (2014b)

United Nations (1978b)

Low 87Sr/86Sr, High eNd(T) value; Juvenile

mantle origin

High K calc-alkaline, mantle-derived,

continental margin orogenic

environment, subduction related

–

U–Pb zircon Mitchell et al. (2012)

40K/40ArMt. Popa Basaltic andesite

Basalt

0.96 ± 0.17

0.80 ± 0.03

Stephenson and Marshall

(1984), Maury et al. (2004)

Hornblende-phyric basaltic

andesite

K/Ar 4.30 ± 0.5 Cumming et al. (2009)

of the Pondaung and Yaw formations represent a significant pro-portion of the Palaeogene sediments deposited in the Central Myanmar Basin (United Nations, 1978c; Licht et al., 2013). A thick sequence of fluvial sediments implies rapid uplift and denudation in the source area, and also suggests a rapid sedimentation rate in a subsiding basin. Source areas undergoing rapid uplift may gen- erate large volumes of coarse-grained clastic sediments, with the development of high-gradient braided or low-sinuosity channel systems, within the upstream portion of the drainage basin (Cant and Walker, 1978).

We also take into account the significant effect of tropical weathering on sandstone composition in provenance study of the Southeast Asian region, which had attributed to the compositional maturity in the Eocene sandstones of northern Borneo (van Hattum et al., 2013). However, geochemical characteristics of the Pondaung sandstones reflected that there was no evidence of intense tropical weathering in either of their original source rocks, during transportation or before deposition. The low maturity index of the sandstones (ICV), moderate degree of chemical weathering (CIA), moderate alteration of plagioclase feldspar in the source rocks (PIA) and the plot of chemical maturity as a function of climate all

suggest that the Pondaung sandstones were formed undersemi-arid to arid palaeoclimate condition. A seasonal tropical climate with a significant dry season, prevailed in the late middle Eocene of Myanmar (Licht et al., 2015b), is further corroborated by the evidence of faunal and floral assemblages (Ramdarshan et al., 2010; Licht et al., 2014a), growth arrest lines in lower jaws of mammalian fossils (Jaeger et al., 2004) and palaeosoils with carbonate nodules, together with shrinking and swelling pedogenic features observed in the upper member of the Pondaung Formation (Licht et al., 2014b).

5.3. Detrital zircon U–Pb geochronology

As the detrital zircons were separated from sedimentary rocks,deposition age of the host sediment can be no older than the youngest U–Pb age of the detrital zircons in this study (i.e.,43.3 ± 4.4 Ma) (Dickinson and Gehrels, 2009). Several complexities can result in measured U–Pb dates that are younger than the true age of deposition due to analytical uncertainties, e.g., Pb loss is one of the main issues in many data sets (Gehrels, 2014). However, the present study shows a good correlation between the measured ages and the stratigraphic positions, i.e., the youngest U–Pb zircon













Table 7

Summary of age data of the granitoids along the Mogok Metamorphic Belt (MMB).

Areas or provinces Sample Method Ma Geochemistry/tectonic environment References

Mogok Augite–biotite granite,

Leucogranite, Foliated

syenite

Granitic orthogneisses,

Metamorphic

recrystallized zircon

rims

Biotite granite

Garnet–tourmaline–

leucogranites

LA ICP-MS U–Pb

zircon

129 ± 8.2

32 ± 1

25

170.11 ± 1.09

Calc-alkaline; continental collision

granite (CCG)

Larue Kyaw Thu (2007)

(Unpublished)

Kyanigan Hills SHRIMP U–Pb zircon I-type Barley et al. (2003)

U–Th–Pb

LA-ICP-MS

(43.37 ± 0.80)

(ca. 59

47–29)

45.5 ± 0.6

171.71 ± 2.05

(47.25 ± 1.28)

33.11 ± 0.93

30.9 ± 0.7)

46.3

114 ± 3

45.9 ± 0.7

44.6 ± 0.5

45.9

59.5 ± 0.9

44.8 ± 2.7

149 ± 21

High-grade metamorphism

Two metamorphic events Searle et al. (2007)

zircon

SHRIMP U–Pb zircon

Syn-metamorphic crustal melting

I-type

High-grade metamorphism

Mandalay Hill Hornblende syenite

Metamorphic

recrystallized zircon

rims

Leucogranite dyke

Augen gneiss,

Pegmatitic granites,

Microdiorite,

Leucogranite dyke

Granite dyke

Granite

Tonalite and

granodiorite

Hornblende–biotite

granodiorite

Granite porphyry

Dacite porphyry

Diorite

Barley et al. (2003)

Kyaukse

Belin

U–Pb zircon

U–Pb zircon

–

–Searle et al. (2007)


MEC Granite, North

of Belin

Yebokson

U–Th–Pb zircon

U–Pb zircon

Rb/Sr whole rock

isochron

SHRIMP

U–Pb zircon

–

–

I-type, tonalite–granodiorite, related to

subduction of oceanic crust

–

Searle et al. (2007)


Cobbing et al. (1992)

121.1 ± 0.9 Barley et al. (2003)

Payangazu 122 ± 0.2

50 ± 0.6

20.7 ± 0.3

20.7 ± 0.5

128 ± 1

71.8 ± 0.5

48.0 ± 0.9

22 ± 7

Continental crust components

(Sr & Nd isotopes)


Yinmabin-west U–Pb zircon

Nattaung, Sedo Granite U–Pb zircon – Mitchell et al. (2012)

Yesin Dam Magacrystic biotite

syenogranites

Leucocratic biotite

syenogranite

Quartz diorite

Granite

Rb/Sr whole rock

isochron age

SHRIMP

U–Pb zircon

U–Pb zircon

Strongly peraluminous, ilmenite-series,

potassic syenogranites

–

Cobbing et al. (1992)

22.64 ± 0.4 Barley et al. (2003)

Low 87Sr/86Sr, juvenile mantle origin,

Gangdese affinity

Mokpalin, Sit-Kisin,

Kyaikhtiyo

90.8 ± 0.8

63.3 ± 0.6


The range of dating data which are in the rage of Cretaceous-Eocene are in bold.

ages decrease progressively up-section throughout the lowermember of the Pondaung Formation (Table 8), which suggest a record of active volcanism during sediment accumulation (e.g., Gehrels, 2014).

The detrital U–Pb zircon ages suggest that there were two distinct episodes of magmatism in Myanmar, during the middle Cretaceous and the middle Eocene, which also correspond to the two major tectono-magmatic events as recently proposed by Mitchell et al. (2012); (1) arc magmatism in Shan Scarps during Middle- to late Cretaceous, and (2) arc magmatism in Wuntho-Popa arc (i.e., mainly in Wuntho-Salingyi segment of the arc) due to the eastward subduction of the Tethys seafloor (Figs. 11 and 12).Detrital U–Pb zircon geochronology alone cannot distinguish the zircons with similar ages derived from different source regions. More detrital zircon Hf isotope studies need to be carried out to establish such distinctions (e.g., Belousova et al., 2006; Clements et al., 2012) in Myanmar. Although such detailed geochronology, geochemistry and isotope studies on the volcanic and granitic

rocks of the Wuntho-Salingyi area, and detrital zircons from clasticCenozoic strata in the Central Myanmar Basin are required for future research, our finding is further supported by Hf isotopic data of detrital zircons of Wang et al. (2014) for the Upper Cretaceous– Eocene stratigraphic units in the western part of Chindwin Basin which is correlative to the Gangdese arc in Tibet (Fig. 10B).

5.4. Regional mean palaeocurrent data

The results of petrography, geochemistry and geochronology,combined with the regional mean palaeocurrent direction (i.e.,253 530 , from ENE to WSW) recorded from the Pondaung and Yaw formations (Kyaw Linn Oo, 2008) indicate that a calc-alkaline, continental magmatic arc was situated to the northeast of the southern Chindwin Basin in the present geographic reference frame. Licht et al. (2013) also described the mean palaeocurrent direction of the two stratigraphic units, exposed in the northeast of Minbu Sub-Basin, as unimodal direction toward243 and 257 .












Table 8

Geochronological data of the volcaniclastic and sedimentary units of the Central Myanmar Basin, the youngest detrital U–Pb zircon ages of the present study decrease progressively upsection, a record of active volcanism during

sediment accumulation in the early Paleocene–middle Eocene.

Location Sample Method Ma Remarks Geochemistry/tectonic

environment

References

Positive eHf(T), juvenile mantleorigin

Positive eHf(T), juvenile mantle

origin

Hukaung Basin Amber (Burmite)-bearing volcaniclastic

fine silty sandstone

Late Cretaceous–Eocene sandstones

SIMS U–

Pb zircon

U–Pb

zircon Hf

isotope

Fission

Track

zircon

LA ICP-MS

U–Pb

zircon

LA ICP-MS

U–Pb

zircon

98.79 ± 0.62 Dacite–Andesitic

clasts

Volcanic clasts in

sandstones

Shi et al. (2012)

NW Chindwin

Basin

110–80, 70–

40

Wang et al. (2014)

NE of Minbu

Basin,

(Primate

localities)

Upper member of the Pondaung Fm. 37.2 ± 1.3 Andesitic arc Tsubamoto et al. (2002, 2009)

Tuff beds in variegated clay unit 38.8 ± 1.4

40.22 ± 0.86

40.31 ± 0.65

43.3 ± 4.4

99.5 ± 1.1

Khin Zaw et al. (2014a)

Southern

Chindwin

Basin

Lower member of the Pondaung Fm.

Detrital zircons in volcaniclastic

sandstones

1 – (PD-21/6) Andesite–rhyodacite–dacite, calc-

alkaline, continental, volcano-

plutonic arc

Present study

Youngest zircon ages and Major detrital peaks for each

sandstone sample, collected in stratigraphic order from the

lower to upper horizons from sample no. 5 to 1

The youngest U–Pb zircon ages decrease progressively

upsection

46.9 ± 2.4

88.6 ± 1.6

46.9 ± 2.4

100.0 ± 1.2

51.6 ± 2.0

101.7 ± 1.1

65.1 ± 1.6

80.4 ± 1.8

2 – (PD-24/2)

3 – (PD-1/5)

4 – (PD-28/3)

5 – (PD-28/9)

47.75 ± 0.87 Mean U–Pb age

of all five

samples

The major localities are in bold.

Kyaw

Linn O

o et al. / Journal of Asian E

arth Sciences xxx (2015) xxx–xxx

19

Please

cite

this

article

in

press

as:

Kyaw

Linn

Oo, ,

et al.

Provenance

of

the

Eocene

sandstones

in

the

southern

Chindw

in

Basin, M

yanmar:

Implications

for

the

unroofing

history

of

the

Cretaceous–E

ocene

magm

atic

arc.

Journal

of

Asian

Earth

Sciences

(2015),












Fig. 12. Schematic diagram (Left) illustrating the geochronology and erosional unroofing history of the Cretaceous–Eocene, magmatic arc formed along the SW-facing

Myanmar continental margin. The schematic map (Right) showing sediment supply from the unroofed Myanmar magmatic arc during the deposition of the Pondaung and

Yaw formations in the middle–late Eocene (after Licht et al., 2013). ITSZ, Indus-Tsangpo Suture Zone; CMB, Central Myanmar Basin, TSS, Tethyan Sedimentary Series; IBR,

Indo-Burman Ranges.

yielded 98.79 Ma, indicating late Cretaceous volcanic activitiesoccurred in the vicinity of the Hukaung Basin, in the northernmost part of Myanmar (Shi et al., 2012). U–Pb and eHf isotope analyses of

Robinson et al. (2014) demonstrated that the Middle- to Upper Eocene sedimentary rocks of the Central Myanmar Basin contain zircons originating from the Gangdese batholiths of Tibet. Zirconsof similar ages and isotopic signatures are common in the eastern Trans-Himalayan batholiths from southern Tibet through northeastern India to the Western Myanmar Arc in Myanmar.

Our current findings support the hypothesis that the Upper Cretaceous to Eocene deposits (i.e., including Pondaung and Yaw formations) of the Central Myanmar Basin may have been derived from the progressive exhumation and erosional unroofing of the local Myanmar Andean-type continental margin, rather than from the distal Tibetan region.

6. Conclusions

Our integrated detrital provenance study, focused on theMiddle to Upper Eocene fluvio-deltaic sandstones in the southern Chindwin Basin of Myanmar, has recorded an erosional unroofing history of a late Cretaceous to middle Eocene, calc-alkaline, Andean-type, continental magmatic arc, related to the prolonged, pre-collisional subduction of Neo-Tethyan oceanic crust beneath the south Asian margin within Myanmar (Fig. 12). The andesitic volcanic materials and the first-cycled magmatic detrital zircons, observed in the late Middle Eocene Pondaung sandstones, were probably derived from the Wuntho-Salingyi segment of the Western Myanmar Arc (WMA), and some contribution from the I-type plutons of the MMB with similar ages and geochemical signatures to the Gangdese batholiths in Tibet and Lohit batholiths in northeastern India (Lin et al., 2013).

Based on the youngest U–Pb detrital zircon ages of the Pondaung Formation in the Central Myanmar Basin, we suggest that the latest magmatic activities of the inferred magmatic arc must have occurred during the late middle Eocene (ca. 40.22–37.2 Ma). It is also constrained by the distinct petrofacies changes occurred at a major sequence boundary between the late Bartonian and the early Priabonian stages (Bar 2/Pr 1 at 37.2 ± 0.1 Ma).This arc originated along the western margin of Shan-Thai or Sibumasu Terrane (i.e., along the MMB) during the late Cretaceous and the middle Eocene (Our U–Pb detrital zircon ages:101.7–43.3 Ma). It is also evident from minor contribution of Proterozoic to Palaeozoic detrital zircons of Sibumasu origin. Most parts of the arc were eroded, unroofed and probably translated northwards from the Andaman sea region to the present position (i.e., Wuntho-Salingyi segment of the Western Myanmar Arc) by dextral movement of the Sagaing Fault during the Miocene.In-situ Hf and U–Pb isotope analyses of detrital zircons from the Irrawaddy riverbank sediments (Bodet and Schärer, 2000) and from an Upper Miocene sandstone of the Central Myanmar Basin (Liang et al., 2008) have recorded the late Cretaceous andPalaeogene zircons with high eHf(T) isotope values, a characteristic

of mantle-derived magmas similar to those of the Gangdese batholiths in southeastern Tibet and the Lohit batholiths in northeastern India. U–Pb dating of magmatic zircons recovered from the burmite-bearing (Burmese amber) volcaniclastic sandstones

Acknowledgements

This work is a part of the first author’s PhD dissertation submit-ted to the Department of Geology, University of Yangon, Myanmar in 2008. The first author owes his gratitude to his parents and wife for their financial and moral supports and all his supervisors and colleagues, including Prof. Aung Naing Soe (Mandalay University of Foreign Language) for his advice in selecting the field area for the PhD research, Aung Cho Win (University of Yangon) for assist- ing throughout the one-month field trip, U Soe Thura Tun (Myanmar Earthquake Committee and Myanmar Geosciences Society), U Zaw Naing Oo and U Kyaw Zin Win (Resources and Environment Myanmar Company Limited) for their assistance in preparing the geological maps and re-drafting the diagrams. Special thanks are also extended to the ARC Centre of Excellence in Ore Deposits (CODES), University of Tasmania for sponsoring the geochemical and LA ICP-MS U–Pb geochronological analyses. The authors are also deeply indebted to the reviewers, A.J. Barber and I. Sevastjanova for their constructive comments and Ian Metcalfe for his editorial input and handling the paper.

Appendix A. Supplementary material

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.jseaes.2015.04.029.























Dickinson, W.R., Suczek, C.A., 1979. Plate tectonics and sandstone composition.AAPG Bull. 63 (12), 2164–2182.

Engelhardt, D.W., 1993. Palynological analysis of 1993 field samples from CentralBurma. Earth Science and Research Institute, University of South Carolina, U.S.A,30 p.

Garzanti, E., Ando, S., 2007. Heavy mineral concentration in modern sands:implications for provenance interpretation. Dev. Sedimentol. 58, 517–545. Gehrels,

G.E., 2014. Detrital zircon U–Pb geochronology applied to tectonics. Annu.Rev. Earth Planet. Sci. 42, 127–149.

GIAC, 1999. Final Report on the Tectonics of Myanmar, Geodynamics of India–Asia Collision Scientific Party, A Joint Project of Scientific Co-operation between Total Myanmar Exploration and Production (TMEP), and Ecole Normale Superieure (ENS).Guzman-Speziale, M., Ni, J.F., 1996. Seismicity and active tectonics of the western Sunda arc. In: Hall, R., Blundell, D.J. (Eds.), Tectonic Evolution of Southeast Asia, vol. 106. Geological Society of London. Special Publication, pp. 63–84.Hall, R., 2002. Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer base reconstructions, model and animations. J. Asian Earth Sci. 20, 353–431.

Hall, R., 2009. Hydrocarbon basins in SE Asia: understanding why they are there.Petrol. Geosci. 15, 131–146.

Hall, R., 2012. Late Jurassic–Cenozoic reconstructions of the Indonesian region and

References

Aitchison, J.C., Ali, J.R., Davis, A.M., 2007. When and where did India and Asia collide? J. Geophys. Res., 112 http://dx.doi.org/10.1029/2006JB004706.Allen, R., Najman, Y., Carter, A., Barfod, D., Bickle, M., Chapman, H., Garzanti, E., Vezzoli, C., Ando, S., Parrish, R., 2008. Provenance of the Tertiary sedimentary rocks of the Indo-Burman Ranges, Burma (Myanmar): Burman Arc or Himalayan derived? J. Geol. Soc. 165, 1045–1057.Aung Khin, Kyaw Win, 1969. Geology and hydrocarbon prospect of Burma Tertiary geosyncline. Union Burma Sci. Technol. J 2, 53–81.Aung Naing Soe, Myitta, Soe Thura Tun, Aye Ko Aung, Tin Thein, Marandat, B., Ducrocq, S., Jaeger, J.-J., 2002. Sedimentary facies of the late Middle Eocene Pondaung Formation (central Myanmar) and the palaeoenvironments of its anthropoid Primates. Gen. Palaeontol. 1, 53–160.Aye Ko Aung, 1999. Revision on the stratigraphy and age of the primates-bearing Pondaung Formation. In: Pondaung Fossils Expedition Team (Ed.), Proceedings of the Pondaung Fossils Expedition Team. Office of Strategic Studies, Ministry of Defense, Yangon, Myanmar, pp. 131–151.Barley, M.E., Pickard, A.L., Khin Zaw, 1996. Zircon SHRIMP Ages for a Selection of Granites from Myanmar. Unpublished Report, Key Centre for Strategic Mineral Deposits, Department of Geology and Geophysics, The University of Western Australia, Nedlands, WA, Australia.Barley, M.E., Khin Zaw, Pickard, A.L., Pak, P., Doyle, M.G., 2003. Jurassic to Miocene magmatism and metamorphism in the Mogok Metamorphic Belt: implications for the India–Eurasia collision in Myanmar. Tectonics 22, 1019–1030.

Belousova, E.A., Griffin, W.L., O’Reilly, S.Y., 2006. Zircon crystal morphology, trace element signatures and Hf isotope composition as a tool for petrogenetic

modelling: examples from Eastern Australian granitoids. J. Petrol. 47, 329–353. Benammi, M., Aung Naing Soe, Than Tun, Bo, Bo, Chaimanee, Y., Ducrocq, S., Tin

Thein, San Wai, Jaeger, J.J., 2002. First magnetostratigraphic study of the

the Indian Ocean. Tectonophysics. http://dx.doi.org/10.1016/j.tecto.2012.04.021.

Hardenbol, J., Thierry, J., Farley, M.B., Jacquin, T., De Graciansky, P.C., Vail, P.R., 1998.Mesozoic and Cenozoic Sequence Chronostratigraphic framework of EuropeanBasins, vol. 60. SEPM Special Publication, pp. 3–13.

Harnois, L., 1988. The CIW index: a new chemical index of weathering. Sediment.Geol. 55, 319–322.

Hoskin, P.W.O., Schaltegger, U., 2003. The composition of zircon and igneous and metamorphic petrogenesis. In: Hanchar, J., Hoskin, P.W.O. (Eds.), Zircon. Mineralogical Society of America and Geochemical Society, pp. 27–62.Ingersoll, R.V., 1978. Petrofacies and petrologic evolution of the Late Cretaceous fore-arc basin, northern and central California. J. Geol. 86, 335–352.Ingersoll, R.V., Cavazza, W., 1991. Reconstruction of Oligo-Miocene Volcaniclastic Dispersal Patterns in North-Central New Mexico using Sandstone Petrofacies, vol. 45. SEPM Special Publication, pp. 227–236.Ingersoll, R.V., Bullard, T.F., Ford, R.L., Grimm, J.P., Pickle, J.D., Sares, S.W., 1984. The effect of grain size on detrital modes: a test of the Gazzi-Dickinson point- counting method. J. Petrol. 54, 103–106.Jaeger, J.J., Chaimanee, Y., Tafforeau, P., Ducrocq, S., Aung Naing Soe, Marivaux, L., Sudre, J., Soe Thura Tun, Htoon, W., Marandat, B., 2004. Systematics and palaeobiology of the anthropoid primate Pondaungia from the late middle Eocene of Myanmar. C.R. Palevol. 3, 243–255.Jochum, K.P., Nohl, U., 2008. Reference materials in geochemistry and environmental research and the GeoReM database. Chem. Geol. 253, 50–53.Khan, P.K., 2005. Variation in dip-angle of the India plate subducting beneath theBurma plate and its tectonic implications. Geosci. J. 9 (3), 227–237.Khin Zaw, 1990. Geological, petrological and geochemical characteristics of granitoid rocks in Burma: with special reference to the associated W-Sn mineralization and their tectonic setting. J. SE Asian Earth Sci. 4 (1), 293–335.Khin Zaw, Meffre, S., Lai, C.K., Santosh, M., Burrett, F.C., Graham, I.T., Manaka, T., Salam, A., Kamvong, T., Cromie, P., 2014a. Tectonics and metallogeny of mainland SE Asia – an overview and contribution. Special issue on tectonics and metallogeny of mainland SE Asia. Gondwana Res. 26 (1), 5–30.Khin Zaw, Meffre, S., Takai, M., Suzuki, H., Burrett, C., Thaung Htike, Zin Maung Maung Thein, Tsubamotoe, T., Egib, N., Maung Maung, 2014b. Dating the oldest anthropoid primates in SE Asia: evidence from LA ICP-MS U-Pb zircon age in the late Middle Eocene Pondaung Formation, Myanmar. Gondwana Res. 26 (1),122–131.Khin Zaw, Sutherland, F.L., Meffre, S., Yui, T.-F., Kyaw Thu, 2015. Vanadium-rich ruby and sapphire within Mogok Gemfield, Myanmar: implications for gem color and genesis. Miner. Deposita 50, 25–39. http://dx.doi.org/10.1007/ s00126-014-0545-0.Kosler, J., 2001. Laser-ablation ICPMS study of metamorphic minerals and processes.In: Sylvester, P.J. (Ed.), Laser-Ablation-ICPMS in the Earth Sciences: Principles and Applications, vol. 29. Mineralogical Association of Canada, pp. 85–202.

Kosler, J., Sláma, J., Belousova, E., Corfu, F., Gehrels, G.E., 2013. U–Pb detrital zirconanalysis results of inter-laboratory comparison. Geostand. Geoanal. Res. 37,243–259.Kyaw Linn Oo, 2008. Sedimentology of Eocene-Miocene Clastic Strata in the Southern Chindwin Basin, Myanmar. Unpublished Ph.D. Dissertation, Department of Geology, University of Yangon, Myanmar.Kyaw Linn Oo, Myitta, 2007. Stratigraphical and sedimentological significance of the highly ferruginous horizon between the Pondaung Formation and the Yaw Formation in the southern Chindwin Basin. J. Myanmar Acad. Arts Sci. 5, 5.Kyaw Linn Oo, Khin Zaw, Myitta, Day Wa Aung, 2009. Tectonic setting of Pondaung sandstones, Southern Chindwin Basin, Myanmar: evidence from XRF-major and trace element geochemical analysis and LA ICP-MS U-Pb zircon geochronology. In: 11th Regional Congress on Geology, Mineral and Energy Resources of Southeast Asia (GEOSEA), 8–10 June, Kuala Lumpur, Malaysia. Abstract volume56–57.Kyaw Win, Kirwin, D., 1998. Exploration, geology and mineralization of the Monywa copper deposits, central Myanmar. In: Porphyry and Hydrothermal Copper and Gold Deposits: A Global Perspective. Proceedings of the Australian Mineral Foundation Conference, Perth, pp. 61–74.

Pondaung Formation: implications for the age of the anthropoids of Myanmar. J. Geol. 110, 748–756.

Bender, F., 1983. Geology of Burma. Borntraeger, Berlin, 293.

Middle Eocene

Bertrand, G., Rangin, R., 2003. Tectonics of the western margin of the Shan plateau (central Myanmar): implication for the India–Indochina oblique convergence since the Oligocene. J. Asian Earth Sci. 21, 1139–1157.

Bijwaard, H., Spakman, W., 2000. Nonlinear global P-wave tomography by iteratedlinearized inversion. Geophys. J. Int. 141, 71–82.Black, L.P., Kamo, S.L., Allen, C.M., Aleinikoff, J.N., Davis, D.W., Korsch, R.J., Foudoulis, C., 2004. TEMORA 1: a new zircon standard for Phanerozoic U–Pb geochronology. Chem. Geol. 200, 155–170.

Bodet, F., Schärer, U., 2000. Evolution of the SE-Asian continent from U–Pb and Hfisotopes in single grains of zircon and baddeleyite from large rivers. Geochim. Cosmochim. Acta 64, 2067–2091.Cant, D.J., Walker, R.G., 1978. Fluvial processes and facies sequences in the sandy braided South Saskatchewan River, Canada. Sedimentology 25 (5), 625–

648.Chhibber, H.L., 1934. The Geology of Burma. Macmillan, London.

Clements, B., Sevastjanova, I., Hall, R., Belousova, E.A., Griffin, W.L., Pearson, N.,2012. Detrital zircon U–Pb age and Hf-isotope perspective on sediment provenance and tectonic models in SE Asia. In: Rasbury, E.T., Hemming, S.R., Riggs, N.R. (Eds.), Mineralogical and Geochemical Approaches to Provenance, vol. 487. Geological Society of America Special Paper, pp. 37–61. http:// dx.doi.org/10.1130/2012.2487(03).

Cobbing, E.J., Pitfield, P.E.J., Darbyshire, D.P.E., Mallick, D.J.J., 1992. The Granites of the South-East Asian Tin Belt. Overseas Memoir 10. British Geological Survey, London, pp. 369.Cotter, G.P. de, 1914. Some newly discovered coal seams near the Yaw River, Pakokku district, Upper Burma. Rec. Geol. Surv. India 44 (3), 163–185.Cox, R., Lowe, D.R., Cullers, R.D., 1995. The influence of sediment recycling and basement composition on evolution of mud rock chemistry in the south western United States. Geochim. Cosmochim. Acta 59, 2919–2940.Cumming, G., Khin Zaw, Sandy Chitko, Zaw Naing Oo, Zwingmann, H., 2009. Recent Pliocene volcanism recorded at Mount Popa, Central Myanmar. In: 11th Regional Congress on Geology, Mineral and Energy Resources of Southeast Asia (GEOSEA), 8–10 June, Kuala Lumpur, Malaysia. Abstract volume 46.Curray, J.R., Moore, D.G., Lawver, L.A., Emmel, F.J., Raitt, R.W., Henry, M., Kieckhefer, R., 1979. Tectonics of the Andaman Sea and Burma. In: Watkins, J., Montadert, L., Dickerson, P.W. (Eds.), Geological and Geophysical Investigations of Continental Margins, Memoirs 29. American Association of Petroleum Geologists, pp. 189–198.

Curray, J.R., 2005. Tectonics and history of the Andaman Sea region. J. Asian EarthSci. 25, 187–232.Darbyshire, D.P.F., Swainbank, I.G., 1988. Geochronology of a Selection of Granites from Burma. NERC Isotope Geology Centre Report No. 88/6.

Dasgupta, S., Mukhopadhyay, M., Bhattacharya, A., Jana, T.K., 2003. The geometry of the Burmese-Andaman subducting lithosphere. J. Seismol. 7 (2), 155–174.

Dickinson, W.R., 1970. Interpreting detrital modes of greywacke and arkose. J.Sediment. Petrol. 40, 695–707.

Dickinson, W.R., 1985. Interpreting provenance relations from detrital modes of sandstones. In: Zuma, G.G. (Ed.), Provenance of Arenites. Reidel, Dordrecht, pp.333–362.Dickinson, W.R., Gehrels, G.E., 2009. Use of U–Pb ages of detrital zircons to infer maximum depositional ages of strata: a test against a Colorado Plateau Mesozoic database. Earth Planet. Sci. Lett. 288, 115–125.



http://refhub.elsevier.com/S1367-9120(15)00238-2/h0145















































































































































































































































































































































http://dx.doi.org/10.1029/2006JB004706

http://dx.doi.org/10.1029/2006JB004706

http://dx.doi.org/10.1029/2006JB004706
































































































































































































































































































































































































































































































































http://dx.doi.org/10.1016/j.tecto.2012.04.021































































































































































































































































































































































































































































































































































































































































































































































































































































http://dx.doi.org/10.1007/s00126-014-0545-0

http://dx.doi.org/10.1007/s00126-014-0545-0

http://dx.doi.org/10.1007/s00126-014-0545-0

http://dx.doi.org/10.1007/s00126-014-0545-0





























































































































































































































































































































































































































































































































































http://dx.doi.org/10.1130/2012.2487(03)

http://dx.doi.org/10.1130/2012.2487(03)

http://dx.doi.org/10.1130/2012.2487(03)



































































































































































































































































































































































































































































































































































Larue Kyaw Thu, 2007. The Igneous Rocks of the Mogok Stone Tract: Their Distributions, Petrography, Petrochemistry, Sequence, Geochronology and Economic Geology. Unpublished PhD Dissertation, Department of Geology, University of Yangon, Myanmar.Larue, D.K., Sampayo, M.M., 1990. Lithic–volcanic sandstones derived from oceanic crust in the Franciscan Complex of California: sedimental memories of source rock geochemistry. Sedimentology 37, 879–889.

Le Dain, A.Y., Tapponnier, P., Molnar, P., 1984. Active faulting and tectonics of Burmaand surrounding regions. J. Geophys. Res. 89, 453–472.Liang, Y.H., Chung, S.L., Liu, D.Y., Xu, Y.G., Wu, F.Y., Yang, J.H., Wang, Y., Lo, C.H.,2008. Detrital zircon evidence from Burma for reorganization of the easternHimalayan river system. Am. J. Sci. 308, 618–638.Licht, A., France-Lanord, C., Reisberg, L., Fontain, C., Aung Naing Soe, Jaeger, J.J., 2013.A palaeo Tibet-Myanmar connection? Reconstructing the late Eocene drainage system of central Myanmar using a multi-proxy approach. J. Geol. Soc. Lond.170, 929–939.Licht, A., Boura, A., De Franceschi, D., Ducrocq, S., Aung Naing Soe, Jaeger, J.J., 2014a.Fossil woods from the late middle Eocene Pondaung Formation, Myanmar. Rev. Palaeobot. Palynol. 202, 29–46.

Licht, A., Cojan, I., Caner, L., Aung Naing Soe, Jaeger, J.J., France-Lanord, C., 2014b.Role of permeability barriers in alluvial hydromorphic palaeosols: the EocenePondaung Formation, Myanmar. Sedimentology 61, 362–382.Licht, A., Reisberg, L., France-Lanord, C., Aung Naing Soe, Jaeger, J.J., 2015a. Cenozoic evolution of the central Myanmar drainage system: insights from sediment provenance in the Minbu Sub-Basin, central Myanmar. Basin Res. http:// dx.doi.org/10.1111/bre.12108.Licht, A., Boura, A., De Francheschi, D., Utescher, T., Chit Sein, Jaeger, J.J., 2015b. Late middle Eocene fossil wood of Myanmar: implications for the landscape and the climate of the Eocene Bengal Bay. Rev. Palaeobot. Palynol. 216, 44–54.

Lin, T.H., Chung, S.L., Kumar, A., Wu, F.Y., Chiu, H.Y., Lin, I.J., 2013. Linking aprolonged Neo-Tethyan magmatic arc in South Asia: Zircon U–Pb and Hf isotopic constraints from the Lohit Batholith, NE India. Terra Nova. http:// dx.doi.org/10.1111/ter.12056.Maurin, T., Rangin, C., 2009. Structure and kinematics of the Indo-Burmese Wedge:recent and fast growth of the outer wedge. Tectonics 28, 2. http://dx.doi.org/10.1029/2008TC002276.Maury, R.C., Pubellier, M., Rangin, C., Wulput, L., Cotton, J., Socquet, A., Bellon, H., Guillaud, J.P., Hla Myo Htun, 2004. Quaternary calc-alkaline and alkaline volcanism in a hyper-oblique convergence setting, central Myanmar and western Yunnan. Geol. Soc. Fr. 175 (5), 461–472.McBride, E.F., 1963. A classification of common sandstones. J. Sediment. Petrol. 33,664–669.Meffre, S., Scott, R.J., Glen, R.A., Squire, R.J., 2007. Re-evaluation of contact relationships between Ordovician volcanic belts and the quartz-rich turbidites of the Lachlan Orogen. Aust. J. Earth Sci. 54, 363–383.Metcalfe, I., 2002. Permian tectonic framework and palaeogeography of SE Asia. J.Asian Earth Sci. 20, 551–566.Metcalfe, I., 2011. Tectonic framework and Phanerozoic evolution of Sundaland.Gondwana Res. 19, 3–21.Metcalfe, I., 2013. Gondwana dispersion and Asian accretion: tectonic and palaeogeographic evolution of eastern Tethys. J. Asian Earth Sci. 66, 1–33.Metivier, F., Gaudemer, Y., Tapponnier, P., Klein, M., 1999. Mass accumulation rates in Asia during the Cenozoic. Geophys. J. Int. 137, 280–318.

Mitchell, H.G., 1977. Tectonic settings for emplacement of Southeast Asia tingranites. Bull. Geol. Soc. Malay. 9, 123–140.Mitchell, A.H.G., 1993. Cretaceous–Cenozoic tectonic events in the westernMyanmar (Burma)-Assam region. J. Geol. Soc. Lond. 150, 1089–1102.Mitchell, A.H.G., Myint Thein Htay, Kyaw Min Htun, Myint Naing Win, Thura Oo, Tin Hlaing, 2007. Rock relationships in the Mogok metamorphic belt, Tatkon to Mandalay, Central Myanmar. J. Asian Earth Sci. 29, 891–910.

Mitchell, A.H.G., Chung, S.L., Thura Oo, Lin, T.H., Hung, C.H., 2012. Zircon U–Pb agesin Myanmar: magmatic–metamorphic events and the closure of a neo-Tethys ocean? J. Asian Earth Sci. 56, 1–23.Morley, C.K., 2004. Nested strike-slip duplexes, and other evidence for late Cretaceous-Palaeogene transpressional tectonics before and during India– Eurasia collision, in Thailand, Myanmar and Malaysia. J. Geol. Soc. Lond. 161,799–812.Morley, C.K., 2009. Evolution from an oblique subduction back-arc mobile belt to a highly oblique collisional margin: the Cenozoic tectonic development of Thailand and eastern Myanmar. Geol. Soc. Lond. Spec. Publ. 318, 373–403.Nesbitt, H.W., Young, G.M., 1982. Early Proterozoic climates and plate motion inferred from major element chemistry of lutites. Nature 299, 715–717.

Ni, J.F., Guzman-Speziale, M., Bevis, M., Holt, W.E., Wallace, T.C., Seager, W.R., 1989.Accretionary tectonics of Burma and the three-dimensional geometry of theBurma subduction zone. Geology 17, 68–71.Nielsen, C., Chamot-Rooke, N., Rangin, C., the ANDAMAN Cruise Team, 2004. From partial to full strain partitioning along the Indo-Burmese hyper-oblique subduction. Mar. Geol. 209, 303–327.Paton, C., Woodhead, J.D., Hellstrom, J.C., Hergt, J.M., Greig, A., Maas, R., 2010.Improved laser ablation U-Pb zircon geochronology through robust downhole fractionation correction. Geochem. Geophys. Geosyst. 11, 1–36.Pearce, J.A., Norry, M.J., 1979. Petrogenetic implications of Ti, Sr, Y and Nb variations in volcanic rocks. Contrib. Miner. Petrol. 69, 33–47.Pearce, J.A., Harris, N.B.W., Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J. Petrol. 25 (4),956–983.

Pivnik, D.A., Nahm, J., Tucker, R.S., Smith, G.O., Nyein, K., Nyunt, M., Maung, P.H.,1998. Polyphase deformation in a fore-arc/back-arc basin, Salin subbasin, Myanmar (Burma). AAPG Bull. 82, 1387–1856.

Pubellier, M., Ego, F., Chamot-Rooke, N., Rangin, C., 2003. The building of pericratonic mountain ranges: structural and kinematic constrains applied to GIS-based reconstructions of SE Asia. Bull. Soc. Geol. Fr. 174, 561–584.

Radha Krishna, M., Sanu, T.D., 2000. Seismotectonics and rates of active crustal deformation in the Burmese arc and adjacent regions. J. Geodyn. 30, 401–421.

Ramdarshan, A., Merceron, G., Tafforeau, P., Marivaux, L., 2010. Dietary reconstruction of the Amphipithecidae (Primates, Anthropoidea) from the

Palaeogene of South Asia and palaeoecological implications. J. Hum. Evol. 59,96–108.Rangin, C., Win Maw, San Lwin, Win Naing, Mouret, C., Bertrand, G., GIAC Scientific Party, 1999. Cenozoic pull-apart basins in central Myanmar: the trace of the path of India along the western margin of Sundaland. Terra Abstracts 4 (1), 59.

Rao, P., Kumar, R., 1999. Evidences for cessation of Indian plate subduction in theBurmese arc region. Geophys. Res. Lett. 26 (20), 3149–3152.Reimann, K.U., Aye Thaung, 1981. Results of palynological investigation of the Tertiary sequence in the Chindwin basin, Northwest Burma. In: International Palynological Conference IV, vol. 3, 380–395.Richards, S., Lister, G., Kennett, B., 2007. A slab in depth: three-dimensional geometry and evolution of the Indo-Australian plate. Geochem. Geophys. Geosyst. 8, 12. http://dx.doi.org/10.1029/2007GC001657.Robinson, P., 2003. XRF analysis of flux-fused discs. In: 5th International Conference on the Analysis of Geological and Environmental Materials. Abstracts 90.Robinson, R.A.J., Brezina, C.A., Parrish, R., Horstwood, M., Nay Win Oo, Bird, M.I., Myint Thein, Walters, A., Oliver, G.J.H., Khin Zaw, 2014. Large rivers and orogens: the evolution of the Yarlung Tsangpo-Irrawaddy system and the eastern Himalayan syntaxis. Gondwana Res. 26, 112–121.

Sahu, V.K., Gahalut, V.K., Rajput, S., Chadha, R.K., Laishram, S., Kumar, K.S., 2006.Crustal deformation in the Indo-Burmese arc region: implications from the

Myanmar and Southeast Asia GPS measurements. Curr. Sci. 90, 1688–1693. Satyabala, S.P., 1998. Subduction in the Indo-Burma region: is it still active?

Geophys. Res. Lett. 25 (16), 3189–3192.Satyabala, S.P., 2003. Oblique plate

convergence in the Indo-Burma (Myanmar)subduction region. Pure Appl. Geophys. 160 (9), 1611–1650.

Searle, M.P., Noble, S.R., Cottle, J.M., Waters, D.J., Mitchell, A.H.G., Hiang, T., Horstwood, M.S.A., 2007. Tectonic evolution of the Mogok Metamorphic Belt, Burma (Myanmar) constrained by U–Th–Pb dating of metamorphic and magmatic rocks. Tectonics 26 (Article number TC3014).Searle, M.P., Whitehouse, M.J., Robb, L.J., Ghani, A.A., Hutchison, C.S., Sone, M., Ng, S.W.P., Roselee, M.H., Chung, S.L., Oliver, G.J.H., 2012. Tectonic evolution of the Sibumasu-Indochina terrane collision zone in Thailand and Malaysia: constraints from new U–Pb zircon chronology of SE Asian tin granitoids. J. Geol. Soc. 169, 489–500.

Sevastjanova, I., Clements, B., Hall, R., Belousova, E.A., Griffin, W.L., Pearson, N.,2011. Granitic magmatism, basement ages, and provenance indicators in the Malay Peninsula: insights from detrital zircon U–Pb and Hf-isotope data. Gondwana Res. 19 (1024), 1039.Shi, G.-H., Jiang, N., Liu, Y., Wang, X., Zhang, Z.Y., Xu, Y.J., 2009. Zircon Hf isotope signature of the depleted mantle in the Myanmar jadeitite: implications for Mesozoic intra-oceanic subduction between the Eastern Indian Plate and the Burmese Platelet. Lithos 112, 342–350.Shi, G., Grimaldi, D.A., Harlow, G.E., Wang, J., Yang, M., Lei, W., Li, Q., Li, X., 2012. Age constraint on Burmese amber based on U–Pb dating of zircons. Cretac. Res. 37,

155–163.Socquet, A., Vigny, C., Chamot-Rooke, N., Simons, W., Rangin, C., Ambrosius, B., 2006.

India and Sunda plates motion and deformation along their boundary inMyanmar determined by GPS. J. Geophys. Res. 111. http://dx.doi.org/10.1029/2005JB003877.

Stamp, D.L., 1922. The geology of part of the Pondaung Range, Burma. Trans. Min.Geol. Inst. India 17, 20.Steckler, M.S., Akhter, S.H., Seeber, L., 2008. Collision of the Ganges-Brahmaputra Delta with the Burma arc: implications for earthquake hazard. Earth Planet. Sci. Lett. 273, 367–378.

Stephenson, D., Marshall, T.R., 1984. The petrology and mineralogy of Mt. Popavolcano and the nature of the late Cenozoic Burma volcanic arc. J. Geol. Soc. Lond. 141, 747–762.

Suttner, L.J., Dutta, P.K., 1986. Alluvial sandstone composition and palaeo-climate, 1.Framework mineralogy. J. Sediment. Petrol. 56, 329–345.Than Tin Aung, Okamura, Y., Satake, K., Win Swe, Tint Lwin Swe, Hla Saw, Soe Thura Tun, 2006. Palaeoseismological field survey along the western coast of Myanmar. Geological Survey of Japan, Annual report on Active Fault and Palaeoearthquake Research, vol. 6, pp. 171–188.Than Tin Aung, Satake, K., Okamura, Y., Schischikura, M., Win Swe, Hla Saw, Tint Lwin Swe, Soe Thura Tun, Aung Thura, 2008. Geologic evidence for three great earthquakes in the past 3400 years off Myanmar. J. Earthq. Tsunami 24, 259–

265.Tsubamoto, T., Takai, M., Shigehara, N., Egi, N., Soe Thura Tun, Aye Ko Aung, Maung Maung, , Danhara, T., Suzuki, H., 2002. Fission-track zircon age of the Eocene Pondaung Formation, Myanmar. J. Hum. Evol. 42, 361–369.Tsubamoto, Tin Thein, Zin Maung Maung, Suzuki, H., Maung, Maung, Iwano, H., Danhara, T., Takai, M., 2009. Fission-track ages of the upper member of the Pondaung Formation, Paukkaung area, central Myanmar. In: 116th Annual Meeting of the Geological Society of Japan Okayama, Japan. Abstract volume203.






















































































































































































































































































































































































http://dx.doi.org/10.1111/bre.12108

















































































http://dx.doi.org/10.1111/ter.12056




http://dx.doi.org/10.1029/2008TC002276

http://dx.doi.org/10.1029/2008TC002276

http://dx.doi.org/10.1029/2008TC002276



























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































http://dx.doi.org/10.1029/2007GC001657

http://dx.doi.org/10.1029/2007GC001657

http://dx.doi.org/10.1029/2007GC001657














































































































































































































































































































































































































































































































































































































































































































http://dx.doi.org/10.1029/2005JB003877

http://dx.doi.org/10.1029/2005JB003877

http://dx.doi.org/10.1029/2005JB003877

http://dx.doi.org/10.1029/2005JB003877


















































































































































































































































































































































































United Nations, 1978a. Geology and Exploration Geochemistry of the Pinlebu- Banmauk Area, Sagaing Division, Northern Burma. United Nations Development Programme, Technical Report, UN/BUR/72/002, 2.United Nations, 1978b. Geology and Exploration Geochemistry of the Salingyi- Shinmataung Area, Central Burma. United Nations Development Programme, Technical Report, UN/BUR/72/002, 5.

United Nations, 1978c. Atlas of Stratigraphy, vol. V. United Nations, ESCAP, NewYork.

van der Voo, R., Spakman, W., Bijwaard, H., 1999. Tethyan subducted slabs underIndia. Earth Planet. Sci. Lett. 171, 7–20.

Van Hattum, M.W.A., Hall, R., Pickard, A.L., 2013. Provenance and geochronology ofCenozoic sandstones of northern Borneo. J. Asian Earth Sci. 76, 266–282. Vigny, C., Socquet, A., Rangin, C., Chamot-Rooke, N., Pubellier, M., Bouin, M.N.,

Bertrand, G., Becker, M., 2003. Present-day crustal deformation around Sagaing fault, Myanmar. Journal of Geophysical Research. doi: 10.1029/2002JB001999.

Wang, J., Wu, F., Tan, X., Liu, C., 2014. Magmatic evolution of the Western Myanmar Arc documented by U–Pb and Hf isotopes in detrital zircon. Tectonophysics

612–613, 97–105.

Wang Yu, Sieh, K., Soe Thura Tun, Lai, K.Y., Than Myint, 2014. Active tectonics and earthquake potential of the Myanmar region. J. Geophys. Res.: Solid Earth 119,

3767–3822. http://dx.doi.org/10.1002/2013JB010762.Watson, J.S., 1996. Fast, simple method of powder pellet preparation for X-Ray fluorescence analysis. X-Ray Spectrom. 25, 173–174.Wiedenbeck, M., Alle, P., Corfu, F., Griffin, W.L., Meier, M., Oberli, F., Vonquadt, A., Roddick, J.C., Speigel, W., 1995. 3 Natural zircon standards for U–Th–Pb, Lu–Hf, trace-element and REE analyses. Geostand. Newslett. 19, 1–23.Win Swe, 1972. Strike-slip faulting in central belt of Burma. In: Haile N.S. (Ed.), Regional Conference on the Geology of Southeast Asia. Geological Society of Malaysia, Annex to Newsletter 34.Win Swe, 2012. Outline geology and economic mineral occurrences of the Union ofMyanmar. J. Myanmar Geosci. Soc., Special Publication 1.Win Swe, Soe Thura Tun, 2008. Marine terraces along the Myanmar coast and their active tectonic significance. J. Earthq. Tsunami 24, 267–277.Winchester, J.A., Floyd, P.A., 1977. Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chem. Geol.20, 325–343.
























































































































































http://dx.doi.org/10.1002/2013JB010762

http://dx.doi.org/10.1002/2013JB010762

http://dx.doi.org/10.1002/2013JB010762





















































































































































































































Kyaw linn oo et al ajes 2015 copy

Documents

Transcript of Kyaw linn oo et al ajes 2015 copy