Noble gas isotopic systematics of Feâ€“Tiâ€“V oxide ore-related … · 2017-05-09 ·...

Available online at www.sciencedirect.com

www.elsevier.com/locate/gca

Geochimica et Cosmochimica Acta 75 (2011) 6727–6741

Noble gas isotopic systematics of Fe–Ti–V oxide ore-relatedmafic–ultramafic layered intrusions in the Panxi area, China:

The role of recycled oceanic crust in their petrogenesis

Tong Hou a, Zhaochong Zhang a,⇑, Xianren Ye b, John Encarnacion c,Marc K. Reichow d

a State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing 100083, Chinab Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, China

c Department of Earth and Atmospheric Sciences, Saint Louis University, 3642 Lindell Avenue, St. Louis, MO 63108, USAd Department of Geology, University of Leicester, Leicester LE1 7RH, UK

Received 15 April 2011; accepted in revised form 1 September 2011; available online 8 September 2011

Abstract

Olivine and clinopyroxene grains have been separated from four large Fe–Ti–V oxide ore-bearing intrusions (Panzhihua,Hongge, Baima and Taihe) in the Panxi area, Emeishan large igneous province, Southwest China, for He and Ar isotopestudies. The samples examined revealed extremely low 3He/4He ratios (0.078–4.34 Ra with the mean value 0.78 Ra) for gasesextracted by stepwise heating. This feature, combined with low 40Ar/36Ar ratios can be interpreted as due to addition ofsubduction-related fluids and melts that had been stored in the lithospheric mantle for long periods. Considering the regionalgeologic history, such addition can be attributed to the paleo subduction that occurred along the western margin of theYangtze Block during the Neoproterozoic. The subducted oceanic crust beneath the Panxi area underwent eclogite-faciesmetamorphism and subsequent exhumation. The infiltration of subduction-related melts and fluids into the lithospheric man-tle led to enriched isotopic signatures from that of the slightly depleted asthenopheric mantle which has been suggested by theSr, Nd and Pb isotopic data of the Emeishan basalts and picrites. In addition, considerable amounts of eclogitic melts pro-duced by partial melting of eclogite-facies oceanic crust extensively contaminated the lithospheric mantle. During the latePermian, partial melting of an upwelling mantle plume that contained an eclogite or pyroxenite component generated theparental Fe-rich magma that supplied the ore-bearing intrusions. The combination of these factors may have been the crucialreason that many world-class Fe–Ti–V oxides deposits are clustered in the Panxi area.� 2011 Elsevier Ltd. All rights reserved.

1. INTRODUCTION

It is believed that the Emeishan large igneous province(ELIP) is genetically related to a major �260 Ma plumeevent (e.g., Thompson et al., 2001; Xu et al., 2004; Aliet al., 2010), which has a genetic connection with severalworld-class Fe–Ti–V oxide deposits, as well as several

0016-7037/$ - see front matter � 2011 Elsevier Ltd. All rights reserved.

doi:10.1016/j.gca.2011.09.003

⇑ Corresponding author. Tel.: +86 010 82322195; fax: +86 01082322176.

E-mail address: [email protected] (Z. Zhang).

Cu–Ni–(PGE) sulfide deposits (e.g., Zhang et al., 2009and references therein). These particular features distin-guish the Emeishan LIP from other LIPs that formed nearthe end of the Permian in widely separated locations such asthe Siberian Traps (Sharma, 1997; Dobretsov, 2005) andPanjal Traps of northwestern India (e.g., Bhat et al.,1981). An important question we address in this paper is:what factors led to the formation of so many largeFe–Ti–V oxide deposits in the ELIP? What role did the geo-logic setting, nature of mantle source(s), partial meltingprocesses, and magma chamber processes play in the originof this magmatic and ore province?

http://dx.doi.org/10.1016/j.gca.2011.09.003

mailto:[email protected]

http://dx.doi.org/016/j.gca.2011.09.003

6728 T. Hou et al. / Geochimica et Cosmochimica Acta 75 (2011) 6727–6741

Most previous petrologic and geochemical studies fo-cused on magma chamber processes (e.g., Zhong et al.,2002, 2004, 2011; Zhou et al., 2005; Wang et al., 2008; Panget al., 2010) and the depth of melting (e.g., Zhou et al.,2008). The metallogenesis of the Fe–Ti–V oxide depositsis generally thought to be closely related to the nature oftheir sources (e.g., Zhang et al., 2009). However, the aspectof the source composition has so far received little atten-tion. For the ore-bearing mafic–ultramafic intrusions inthe ELIP, Zhou et al. (2008) proposed that both Cu–Ni–(PGE) and Fe–Ti–V oxide ore-bearing intrusions are de-rived from a heterogeneous mantle plume, but the formerwas generated by higher degrees of melting of shallower fer-tile mantle, whereas the latter was sourced from a deeperrefractory garnet bearing peridotite-zone mantle. Theseconclusions were challenged by Zhang et al. (2009), basedon isotopic analyses of three mafic–ultramafic intrusions,which host both types of mineralization. These authorsdemonstrated that the Sr, Nd and Pb isotopic compositionsof most samples from the three intrusions overlap withthose of the Emeishan basalts and OIB, suggesting thatthey have been derived from a slightly enriched astheno-spheric melt presumably generated by the same mantleplume that formed the Emeishan flood basalts. Zhanget al. (2009) also suggested that the ascending plume-de-rived magma was contaminated by a Fe- and Ti-rich litho-spheric mantle and that this was a crucial factor in thegeneration of the Fe–Ti–V oxide ore-bearing intrusions.However, some important issues, such as the evidence forthe presence of such a Fe- and Ti-rich lithospheric mantleand the details of the ore generation process remain poorlyunderstood (e.g., Hergt et al., 1991; Hawkesworth et al.,2000).

On the basis of trace element and Pb–Sr–Nd isotopicinvestigations, Song et al. (2004) and Xiao et al. (2004) pro-posed that the primitive magmas of the ELIP were pro-duced by partial melting of a rising mantle plume thatreacted with the lithospheric mantle, which had been previ-ously modified and enriched by pelagic sediments duringNeoproterozoic subduction. Nevertheless, in the case ofthe Fe–Ti–V oxide ore-bearing intrusions, the involvementof lithospheric mantle and the subducted oceanic crust intheir source has not been evaluated. Moreover, the roleand extent of each component, especially the old recycledcomponent, in the source cannot be unambiguously as-sessed from a combination of trace elements, Sr, Nd andPb isotopes alone, because different geochemical sourcesmay produce similar geochemical signatures (e.g., Martyet al., 1996). For example, it is difficult to distinguish the ef-fects of crustal assimilation from assimilation or melting ofenriched subcontinental lithospheric mantle (SCLM) whichhad been modified by recycled materials, using incompati-ble element and Pb–Sr–Nd isotopic data. In addition, theseore-bearing intrusions have experienced post-magmaticlow-temperature alteration, which may have changed theirPb and Sr isotopic signatures (Beswick, 1982).

The relative proportions of radiogenic and primordialnoble gas isotopes are dependent on the extent and timingof episodes of gas loss from the mantle (Kellogg and Was-serburg, 1990). Much of the utility of noble gases is based

on the wide variations in their isotopic compositions. Thisis related to their overall depletion, which has made theseelements sensitive to isotopic modification from additionof radiogenic isotopes derived from more abundant parentisotopes (Porcelli et al., 2002). The wide applicability ofnoble gas systematics is due to the range of such processesstated above. They provide a powerful tool to better under-stand the evolution of the Earth’s interior, its chemicalstructure, and its volatile fluxes (e.g., Ozima and Podosek,2002). However, recent research has largely concentratedon gases in submarine basalts (e.g., Moreira and Kurz,2001; Raquin et al., 2008), mantle-derived volcanic rocks(e.g., Nuccio et al., 2008; Yamamoto et al., 2009; Starkeyet al., 2009), or xenoliths of presumed upper-mantle origin(e.g., Yamamoto et al., 2004; Gautheron et al., 2005; Czup-pon et al., 2009; Sumino et al., 2010; Hopp and Ionov,2011). Over the past decades, limited results on the non-radiogenic gases in ordinary plutonic igneous rocks fromcontinental crust have been reported (Rayleigh, 1939;Damon and Kulp, 1958; Butler et al., 1963; Kuroda andSherrill, 1978; Smith, 1984). It is noteworthy that the gasextracted from these plutonic rocks by heating techniquerepresent bulk sample analyses of multi grain aliquotes pos-sibly holding different numbers, densities, and sizes of inclu-sions, thus the noble gas abundances cannot be easilyrelated to any magmatic processes. For example, usingthe one-step heating, gases extracted from a bulk sampleinevitably contain some adsorbed gases and those fromthe post-contemporary inclusions. These gases are regardedto have no obviously relations to the magmatic processes.Therefore, little importance is usually placed on noble gasdata derived from bulk analysis in recent years (e.g., Nuccioet al., 2008).

To assess the influences of recycled oceanic crust compo-nents on Fe- and Ti-rich lithospheric mantle, we present thefirst He and Ar contents and isotopic compositions by step-wise heating of olivine and clinopyroxene grains separatedfrom gabbro and olivine-gabbro samples collected fromthe four renowned world-class Fe–Ti–V oxide deposits(Panzhihua, Hongge, Baima and Taihe) in the Panxi area.Our results provide important constraints on the petrogen-esis of ore-bearing intrusions and related Fe–Ti–V oxidemineralization.

2. GEOLOGICAL BACKGROUND

2.1. Regional geology

Southwestern China comprises the western margin ofthe Yangtze Block to the east and the easternmost part ofthe Tibetan Plateau to the west. The Yangtze Block consistsof Mesoproterozoic granitic gneisses and metasedimentaryrocks, which have been intruded by the Kangdian(�800 Ma) granites (Zhou et al., 2002b). The Neoprotero-zoic granites are overlain by a series of marine and terres-trial rocks from the late Neoproterozoic (�600 Ma) to theLate Permian (Yan et al., 2003).The Permian lithologies in-clude carbonate-rich rocks and the Emeishan continentalflood basalts. The Triassic comprise both continental andmarine sedimentary rocks, whereas Jurassic to Cretaceous

Noble gas systematics of Panxi layered intrusions 6729

are entirely terrestrial. Neoproterozoic arc plutonic–meta-morphic assemblages occur along the western and northernmargin of the Yangtze Block, which are believed to havebeen related to subduction of Rodinian oceanic lithospheretoward the Yangtze Block during a period from 860 to760 Ma (Zhou et al., 2002a). A late Paleozoic to earlyMesozoic (ca. 280–230 Ma) rifting event has also been rec-ognized (Cong, 1988). The region was further deformedduring the Paleogene India–Asia collision (Yin and Harri-son, 2000).

2.2. Emeishen large igneous province (ELIP) and associated

Fe–Ti oxide deposits

The ELIP is dominated by flood basalts (the Emeishanflood basalts) ranging in thickness from a few hundred me-ters to a maximum of �5 km and covering an area of atleast 2.5 � 105 km2. The flood basalts were likely emplacedat or close to sea level (Thompson et al., 2001; UkstinsPeate and Bryan, 2009). In contrast to the Siberian floodbasalts, which formed at relatively high northern latitude,emplacement of the Emeishan flood basalts occurred nearthe Equator (Enkin et al., 1992). Overall, the province ap-pears to be slightly older than the geochronologicallywell-constrained �251 Ma Siberian Traps (e.g., Reichowet al., 2009) with reported 40Ar/39Ar ages of 254 ± 5 Ma(Boven et al., 2002), 255 Ma, and 251–253 Ma (Lo et al.,2002) for lava flows and two late-stage intrusions. However,more recent SHRIMP U � Pb dating for mafic intrusions,dykes and volcanic rocks have indicated emplacement be-tween 257 and 263 Ma (Guo et al., 2004; Zhong and Zhu,2006; He et al., 2007), which suggests a link between theELIP and the end-Guadalupian mass extinction (MiddlePermian).

The Panxi region lies in the central-western part of theELIP where the flood basalts are variably deformed, up-lifted and eroded due to strong tectonic activity in theCenozoic. Magmatic Fe–Ti–V oxide deposits are docu-mented in several layered intrusions in this region whoseexposure is controlled by major N–S trending faults. Theore deposits and host layered intrusions share the samenames including Panzhihua, Hongge, Baima, Taihe andXinjie. Most of the intrusions have been dated by theU � Pb zircon method providing ages of �260 Ma(Fig. 2). Giant Fe–Ti–V oxide deposits occur in several rel-atively large layered intrusions which are spatially associ-ated with contemporaneous flood basalts and copiousgranitoids (Zhang et al., 1999; Ma et al., 2001), includingthe Panzhihua, Hongge, Baima and Taihe intrusions(Fig. 1; Zhong et al., 2002, 2003, 2004, 2005; Zhou et al.,2005, 2008). The total oxide ore reserves of four large Fe–Ti–V oxide deposits are estimated to be 7544 million tonneswith an average ore grade of 36 wt.% Fetotal, 0.28 wt.%V2O5 and 12.6 wt.% TiO2 (Zhong et al., 2002, 2003; Maet al., 2003; Zhou et al., 2005).

2.3. Geology of the ore-bearing intrusions

Detailed descriptions of the geology of these ore-bearingintrusions have been presented by several workers, i.e. Pan-

zhihua (e.g., Zhang et al., 2009; Pang et al., 2010), Hongge(e.g., Zhong et al., 2002), Baima (e.g., Zhou et al., 2008;Pang et al., 2010) and Taihe (e.g., Pang et al., 2010) anda brief summary presented here. These four largest depositsi.e., Panzhihua, Hongge, Baima and Taihe, share similarcharacteristics, e.g. the major Fe–Ti–V layers (the orebodies) occur as iron beds associated with the layered gab-bros and are generally concentrated in the lower parts ofthe intrusion (Fig. 3; e.g., Zhou et al., 2005). Additionally,throughout the intrusion, the frequency of Fe–Ti–V oxidelayers decreases upwards. Mineral compositions also showregular variations with for example Fo (Fo82–Fo63) and An(An68–An40) contents of olivine and plagioclase, respec-tively, decreasing upwards in Panzhihua. The compositionsof clinopyroxenes are with i.e., En41–46Fs10–17Wo37–48 lessvariable. Moreover, these intrusions are undeformed,unmetamorphosed, and generally less affected by alteration.Local alteration consists of clinopyroxene and plagioclasebeing replaced by tremolite and albite, respectively.

3. SAMPLES AND EXPERIMENTAL PROCEDURE

Samples were initially checked for weathering and tracesof alteration were removed before the rocks were reducedto chips. The freshest chips were selected for analysis usinga binocular microscope. Rock samples were crushed to agrain size below 2 mm using a jaw crusher, and the clinopy-roxene and olivine grains separated by standard gravimetricand magnetic methods. Crystals for noble gas analysis werehand selected under a binocular microscope. These selectedminerals were crushed into small grains with a diameter ofabout 0.5 mm and hand-picked again for the experiment.

Noble gases were released from fresh olivine and clino-pyroxenes by stepwise heating. Olivines and clinopyroxenesare retentive for noble gases; in-situ additions of radiogenic4He and 40Ar are quite small because of very low contentsof U, Th, and K in such minerals (e.g., Krause et al.,2007). Although U and Th in mineral inclusions or neigh-boring minerals can be a source of a-particles, the limitedrange of a-particles (tens of microns) means that the re-moval of the rims of mineral grains, e.g. by acid etchingor physical abrasion, can reduce this nucleogenic compo-nent (Baxter, 2010). Stepwise heating is thought to be apowerful and widely used technique in noble gas analysis,for it has been quite successful in discriminating noble gasestrapped in fluid or melt inclusions. The effect of cosmogenicnuclides due to surface exposure has a negligible effect onour samples because most samples were collected fromlocations that were only recently exposed by mining.

Before stepwise heating, mineral grains were washedultrasonically for 30 min with distilled water, and then eth-anol and acetone, and dried at 80 �C overnight. More than500 mg of such prepared sample was wrapped in thin Al-foil. The sample bags were loaded into the sample turnplateconnected with a stainless steel ultra-high vacuum extrac-tion line. Up to ten samples could be mounted on the lineat the same time. The sample chamber and the gas prepar-ing system were baked out about 150 �C for more than 24 hand the samples were also preheated during the baking per-iod to remove atmospheric noble gases adsorbed in the

Fig. 1. Geological map of the Panxi area and associated mineralized layered intrusions (modified from Zhong et al., 2011). Insert illustratesdistribution of major terannes in China and study area (after Chung and Jahn, 1995). Abbreviations are as follows: IC = Indochina;NCB = North China block; QD = Qaidam; YZB = Yangtze block; SG = Songpan-Ganze accretionary complex.

Fig. 2. Crystallization age of the ore-bearing intrusions in thisstudy. The ages for Panzhihua and Baima are analyzed by sensitivehigh-resolution ion microprobe (Zhou et al., 2005), the age forHongge are analyzed by isotope dilution thermal ionization massspectrometry (Zhong and Zhu, 2006), the age for Taihe areanalyzed by laser ablation inductively coupled plasma massspectrometry (Zhong et al., 2009).


sample grains. The tantalum and molybdenum cruciblesused for melting samples were heated up 1700 �C for morethan 24 h in order to reduce the heat blank. A samplewould fall into the molybdenum crucible when the sampleturnplate was turned, and the gases contained in the samplewere extracted. The gas released at each individual temper-ature was purified through a 800 �C titanium furnace and aZrAl getter held at room temperature. He, Ne, Ar, Kr andXe were absorbed and separated by activated carbon at aconstant temperature in a mixture of liquid nitrogen andice–water. The contents and isotopic compositions of noblegases were measured by a MM5400 mass spectrometer in-

stalled in the Laboratory of Gas Geochemistry (Lanzhou),Institute of Geology and Geophysics, Chinese Academy ofSciences. The gases were pumped away between samples toeliminate interference to the following sample. The accu-racy of our data was checked by repeatedly measuring anair standard collected from the top of Gaolan Mountainat Lanzhou City, China. A total of 18 runs of air 3He/4Heratios were reproducible to within 3He/4He ratios of1.134 ± 0.013 and 40Ar/36Ar ratios of 297.9 ± 1.2. Hot-blanks were run using the same procedure as the samplesand the hot-blank levels of He and Ar at 1600 �C (cm3STP)are 4He = 2.46 � 10�10 and 40Ar = 1.39 � 10�8, respec-tively. All results were calibrated to hot-blank. All noblegases isotopic compositions in hot-blank were approxi-mately air value. In order to confirm the experimental re-sults, we have repeatedly verified our data. A relativeerror of less than 2.5% in our analytical techniques can beregarded to be very satisfactory.

4. RESULTS

4.1. Helium

Noble gas isotopic results are summarized in Table 1.The measured 3He/4He ratios are plotted versus tempera-tures in Fig. 4. Except for the high 3He/4He ratio obtainedin the 600 �C fraction of clinopyroxene in HG02 (�4.5 RA;RA is the atmospheric ratio of 1.40 � 10�6) during step-

Fig. 3. Stratigraphy of the Panzhihua, Hongge, Baima and Taihe intrusions, simplified from Li et al. (1981) and Pang et al. (2010). Note thevertical exaggeration to illustrate the details of the ore-bearing part of the intrusions. Abbreviations are as follows: FW = “footwall” or roofof intrusion, HW = “hanging wall” or floor of intrusion, UZ = “upper zone”, MZ = “middle zone”, LZ = “lower zone”, and MGZ =“marginal zone”.


heating gas extraction, the 3He/4He ratios cover a narrowrange from �2.5 RA down to <1 RA, and do not varyamong different localities. This may indicate that these min-erals have trapped the same fluid and that post-emplace-ment processes have not significantly affected the 3He/4Heratio. The observed values are much lower than those ofMORB- and plume-type mantle (Kurz, 1991; Hiltonet al., 1993), xenoliths from Eastern Australia (Matsumotoet al., 1998, 2000; Czuppon et al., 2009, 2010), Europeansub-continental lithospheric mantle (SCLM; Dunai andBaur, 1995; Gautheron et al., 2005), Japanese island arc(Nagao and Takahashi, 1993; Ikeda et al., 2001), and backarc basalts (Honda et al., 1993; Bach and Niedermann,1998; Ikeda et al., 1998; Sano et al., 1998). However, theyoverlap with values of some mantle xenoliths which arethought to be influenced by ancient recycled materials, suchas eastern China (Tang et al., 2007) and far eastern Russia(Yamamoto et al., 2004) (Fig. 6.).

4.2. Argon

The measured 40Ar/36Ar ratios show large variationsranging from 297.1, which is close to the atmospheric valueof 295.5 (Nier, 1950), to 16636.6. Low temperature extrac-tions yield low values whereas the high temperature frac-tions were generally characterized by higher isotopicratios, especially the values obtained at 1100 �C, which

are always the highest in our samples. The lack of correla-tion in 40Ar/36Ar vs. 40Ar (Fig. 5b) suggests that the isoto-pic ratios have not been dramatically affected by K decay inthe samples after emplacement.

5. DISCUSSION

5.1. Genesis of extremely low 3He/4He ratios in mafic–

ultramafic intrusions

This study shows that mafic minerals, i.e. olivines andclinopyroxenes, in mafic–ultramafic Fe–Ti–V oxide ore-bearing intrusions in Panxi area display extremely low3He/4He ratios (the lowest is �0.1 RA) for gases extractedby stepwise heating. Such low 3He/4He ratios are rarelyseen in rocks or minerals separated from LIPs. Previouswork (e.g., Marty et al., 1996) has revealed that only somelow-Ti basalt samples in Oligocene continental flood basaltsfrom Ethiopia show similar extremely low 3He/4He ratios(�0.035 RA), which have been explained by accumulationof radiogenic 4He in their mantle source with concomitantcrustal contamination. Since helium has high diffusivitiesin the mantle (e.g., Hart, 1984; Lux, 1987; Trull and Kurz,1993), an extensive mantle heterogeneity would be required,in order to maintain the He isotope anomaly for significantperiods of time. For instance, in order to maintain a sourcebody with 6.8 RA in a mantle with 30 RA for a billion years,

Table 1

Noble gas abundance and isotopic compositions of olivine and clinopyroxene from ore-bearing intrusions in Pan-Xi area, analyzed by stepwise heating method.

Sample Mineral Weight (g) Temperature 4He(10�7) r 40Ar (10�7) r 3He/4He(R/RA) r 40Ar/36Ar r

PZH01 Ol 0.649 600 �C 0.181 0.018 0.163 0.015 0.497 0.014 594.8 88.70.649 1100 �C 69.5 4.7 48.6 4.9 1.01 0.11 1585.5 33.50.649 1600 �C 38.3 2.6 3.65 0.26 1.8113 0.0033 2873.2 106.6

Total 108 7.3 52.4 5.2 1.293 0.092 1627.5 36.9

PZH02 Cpx 0.650 600 �C 0.422 0.062 0.692 0.051 0.452 0.019 1160.2 85.50.650 1100 �C 20.7 1.4 6.13 0.41 0.8911 0.0062 472.4 9.00.650 1600 �C 17.2 1.2 0.263 0.023 0.6456 0.0077 2962.8 27.9

Total 38.3 2.7 7.08 0.48 0.7761 0.0074 632.0 15.2

PZH03 Ol 0.514 600 �C 0.575 0.044 0.615 0.046 1.497 0.013 1511.3 8.80.514 1100 �C 69.9 4.7 45.3 3.1 2.3229 0.0084 2235.5 21.70.514 1600 �C 36.4 2.4 4.23 0.29 1.6908 0.0019 1936.5 35.4

Total 106.9 7.1 50.1 3.4 2.1032 0.0059 2201.4 22.9

HG01 Cpx 0.650 600 �C 0.0484 0.0072 0.0204 0.0027 0.5057 0.0066 297.1 2.10.650 1100 �C 106.4 7.1 3.85 0.26 0.1672 0.0015 654.5 6.50.650 1600 �C 10.41 0.70 1.148 0.080 0.1667 0.0045 1387.5 1.5

Total 116.9 7.8 5.02 0.34 0.1673 0.0018 740.6 5.8

HG02 Cpx 0.651 600 �C 0.0303 0.0055 0.0733 0.0052 4.34 0.17 1166.7 4.30.651 1100 �C 50.6 3.4 1.64 0.11 0.2071 0.0029 616.2 1.20.651 1600 �C 33.9 2.3 1.297 0.090 0.2121 0.0021 2045.1 28.0

Total 84.5 5.7 3.01 0.21 0.2106 0.0026 1220.9 9.3

HG03 Cpx 0.651 600 �C 0.132 0.013 0.274 0.021 0.0624 0.0021 617.1 11.80.651 1100 �C 57.9 3.9 3.64 0.25 0.1037 0.0015 793.7 20.40.651 1600 �C 59.5 4.0 0.0630 0.0058 0.08344 0.00083 677.5 1.2

Total 117.5 7.9 3.98 0.28 0.0934 0.0011 779.7 19.4

HG04 Cpx 0.650 600 �C 2.50 0.17 5.53 0.39 0.2148 0.0026 2307 5.10.650 1100 �C 57.3 3.9 1.69 0.12 0.21692 0.00085 889.8 17.60.650 1600 �C 44.7 3.0 0.386 0.028 0.2184 0.0015 769.3 17.8

Total 104.5 7.1 7.61 0.54 0.2175 0.0012 1914.1 12.3

HG05 Cpx 0.511 600 �C 0.319 0.026 0.463 0.036 0.537 0.013 2352.2 64.90.511 1100 �C 15.1 1.0 12.94 0.90 0.411 0.010 1547.0 29.40.511 1600 �C 18.6 1.2 1.63 0.12 0.5296 0.0029 4042.4 110.0

Total 34.0 2.2 15.0 1.1 0.4770 0.0067 1842.4 37.1

HG03 Ol 0.649 600 �C 0.143 0.013 0.227 0.017 0.3456 0.0091 307.9 1.40.649 1100 �C 6.81 0.46 0.454 0.035 0.1776 0.0030 5469.4 25.70.649 1600 �C 4.83 0.33 0.279 0.020 0.08059 0.00013 1250.7 42.9

Total 11.78 0.80 0.960 0.072 0.1399 0.0015 3164.7 42.0

BM01 Ol 0.650 600 �C 0.0253 0.0039 0.230 0.019 0.8900 0.0760 722.2 20.30.650 1100 �C 2.44 0.17 0.955 0.067 1.8303 0.0022 440.6 0.80.650 1600 �C 2.39 0.16 0.375 0.027 1.5130 0.0130 1596.9 37.4

Total 4.86 0.33 1.56 0.11 1.6692 0.0088 760.1 8.3

BM02 Ol 0.508 600 �C 0.0201 0.0029 0.0618 0.0080 1.870 0.042 414.4 13.30.508 1100 �C 1.92 0.13 1.055 0.077 1.893 0.017 575 0.80.508 1600 �C 1.75 0.12 0.299 0.026 1.059 0.012 2073.4 2.5

Total 3.69 0.25 1.42 0.11 1.497 0.015 884.4 2.4

BM01 Cpx 0.511 600 �C 0.206 0.020 0.529 0.039 0.8047 0.0089 1089.7 7.30.511 1100 �C 14.36 0.96 2.02 0.14 0.1124 0.0011 16636.3 114.80.511 1600 �C 32.6 2.2 2.23 0.15 0.23125 0.00095 5002.4 93

Total 47.2 3.2 4.78 0.33 0.1976 0.0012 9486.7 117.0

BM02 Cpx 0.512 600 �C 0.124 0.012 0.288 0.026 n.d. n.d. 1596.8 11.70.512 1100 �C 21.0 1.4 2.30 0.16 0.07785 0.00056 3401.1 100.70.512 1600 �C 41.7 2.8 5.66 0.39 0.12340 0.00097 1815.3 54.1

Total 62.8 4.2 8.25 0.58 0.10814 0.00083 2249.9 65.2

TH01 Cpx 0.515 600 �C 0.0486 0.0073 0.0281 0.0038 0.433 0.027 1149.6 55.50.515 1100 �C 46.8 3.1 16.5 1.1 0.7260 0.0019 15717.1 1312.40.515 1600 �C 74.3 5.0 2.14 0.15 1.0276 0.0077 6843.6 193.0

Total 121.1 8.1 18.7 1.3 0.9109 0.0051 14678 1131.8

All tabulated data were corrected for blanks. Unit of concentrations are cm3STP g�1. Errors are 1 s.d. Ol and Cpx are short for olivine andclinopyroxene, respectively. n.d. is not detectable. RA: atmospheric 3He/4He = 1.40 � 10�6.


Fig. 4. 3He/4He ratios versus stepwise heating temperatures. Toavoid overlapping of symbols the data are partly offset fromtemperatures. The uncertainties are given as 1r.

Fig. 6. 3He/4He versus 4He ratios of olivine and pyroxeneseparates from Fe–Ti–V oxide-bearing intrusions in the Panxiarea. For comparison, arrays of published data are shown forxenolith data from Japan island arc (Nagao and Takahashi, 1993;Ikeda et al., 2001), European subcontinental lithospheric mantle(SCLM; Dunai and Baur, 1995; Gautheron et al., 2005), EasternAustralia (Matsumoto et al., 1998, 2000; Czuppon et al., 2009,2010), Eastern China (Tang et al., 2007), and Far Eastern Russia(Yamamoto et al., 2004). The compiled backarc basin basalts3He/4He data are from Honda et al. (1993), Bach and Niedermann(1998), Ikeda et al. (1998) and Sano et al. (1998). MORB data arefrom Kurz (1991) and Hilton et al. (1993).


the thickness of the source body is required to be on the or-der of 1 km (Hanyu and Kaneoka, 1998). To explain the ex-tremely low 3He/4He ratios observed in our separatedolivine and clinopyroxene minerals, we raise several possi-bilities and discuss each of them below.

5.1.1. Atmospheric contamination

The concentration of He in the atmosphere is �5 ppmand He is generally thought to be not recycled back intothe mantle (e.g., Ozima and Podosek, 2002). The 3He/4Heratios much lower than the atmospheric value cannot bereadily explained by a simple binary mixing with atmo-spheric component. Thus, contamination of atmosphericHe directly in the magma reservoir of these intrusionswas unlikely.

5.1.2. Crustal contamination

The magmas forming these intrusions ascended throughand were emplaced into continental crust. It is thereforeimportant to assess the extent to which crustal contamina-tion may have influenced these intrusions before we candetermine the noble gas isotopic signature of their mantle

Fig. 5. 3He/4He ratios versus 4He. (a) and 40Ar/36Ar ratios versus 40Ar (intrusions in Panxi area. Effects on isotope ratios and 4He abundance byarrows. The uncertainties are 1r. Symbols as in Fig. 2.

source. Assuming the most favorable condition for contam-ination of zero helium content in magma, any 4He contribu-tion from crustal fluids would diffuse through the magmaby tens of centimeters over a time scale of years (basedon He diffusivity in basalt melts; Lux, 1987; Heber et al.,2007; Tolstikhin et al., 2010). The diffusion of crustal Heinto the melt would be less efficient if the concentrationof magmatic He is higher than zero and if we recognize thatdegassing processes cause a He flux from magma to countryrocks. Based on Sr, Nd, Pb, and O isotope data, Zhanget al. (2009) argued that the magma that supplied the Pan-zhihua intrusion were derived from the mantle with little orno crustal contamination making a crustal contribution tothe He in these samples less likely. Thus, we infer that the

b) of olivine and pyroxene separates from Fe–Ti–V oxide -bearingaddition of cosmogenic and radiogenic components are shown by


addition of crustal He could hardly cause the observed ex-tremely low 3He/4He ratios in the samples.

5.1.3. Preferential depletion of helium

If significant He loss occurred after emplacement ofthese intrusions, mass-dependent fractionation would sig-nificantly lower the 3He/4He ratio in the minerals. To ex-plain the observed low 3He/4He values by this processfrom an assumed initial value of a plume-type mantle suchas the Hawaiian mantle source, an anomalously high initialHe concentration is required; much higher than that of“popping rocks” (1 � 10�4 cm3STP/g; Marty and Ozima,1986; Burnard et al., 1997) which are the most gas-richbasaltic glass.

There is also a potential for loss of helium from clinopy-roxene after emplacement of the magma. This hypothesis ispredominantly based on the common idea that pyroxenecrystallization postdates olivine crystallization and contin-ues to exchange helium with the magma, due to the lowereffective closure temperature for He in pyroxene (Shawet al., 2006). Indeed, olivine has a crystal structure that re-duces any secondary exchange after crystallization, thus pre-serving the original magmatic signature (Craig and Lupton,1976; Ozima and Podosek, 1983; Martelli et al., 2004). How-ever, in the case of the intrusions in the Panxi area, both oli-vines and clinopyroxenes are early phases in thecrystallization of the ore-bearing magma (e.g., Zhou et al.,2005). Moreover, both our olivine and clinopyroxene datahave similar values (Table 1) and no systematic differencein noble gas concentrations and isotopic compositions insamples from different localities have been observed. Hence,it appears that both olivine and clinopyroxene trapped sim-ilar fluids and melts during the crystallization processes andit is difficult to explain the low 3He/4He ratios by significanthelium loss from the fluid and melt inclusions unless similaramounts of He loss and fractionation happened for both theolivines and clinopyroxenes, which is unlikely.

5.1.4. Accumulation of radiogenic 4He after emplacement

Radiogenic and/or nucleogenic 4He is mostly generatedwithin the crystal lattice after emplacement of the intrusion.Such components are thought to be exclusively extracted atrelatively higher temperature during the stepwise heatingexperiment. Considering the ages of these intrusions(�260 Ma), it is plausible that the accumulation of nucleo-genic 4He can account for the low 3He/4He ratios. How-ever, production of 4He by U and Th decay within thecrystal lattice is very low, due to the very low content ofthese radioactive nuclides inside the minerals (Zindler andHart, 1986). If the gases extracted at high temperature wereaffected by nuclides generated in-situ within the crystal lat-tice, the 3He/4He ratios should show a negative correlationwith 4He concentrations. Given that such a correlation isnot been observed (Fig. 5a), the low 3He/4He ratios in thesamples are unlikely the result of addition of radiogenicnuclides generated in situ after emplacement.

5.1.5. Addition of radiogenic 4He in the mantle

Based on the above discussion, we conclude that the low3He/4He ratio in the samples from the Panxi area must re-

flect an inherent feature of the mantle source for these ore-bearing intrusions. A reason other than those discussedabove must be assumed to explain the extremely low3He/4He ratios. Considering that variable contributions oflithospheric materials were involved in generating theparental magmas of these intrusions based on Sr–Nd–Pbisotopic analyses (Zhang et al., 2009), we prefer to attributethe low 3He/4He ratios to the addition of radiogenic 4Hepredominantly to the lithospheric mantle. The addition ofradiogenic 4He could be due to the addition of mantle fluidsenriched in 4He, or due to in-situ growth of radiogenic 4Heafter influx of a fluid with a high U/He ratio into the man-tle, or a combination of both. Such additions have usuallybeen interpreted as the addition of a component recycled inthe mantle via subduction process (e.g., Yamamoto et al.,2004). Regarding the former possibility, some source is re-quired to produce the mantle fluids with low 3He/4He ra-tios. For example, it is possible that an old subductedslab was stored in the upper mantle for a sufficiently longtime to have accumulated enough radiogenic 4He. In thelatter case, for example, infiltration of U-bearing fluids intothe Panxi lithospheric mantle could cause heterogeneousand low 3He/4He ratios.

Neoproterozoic arc plutonic–metamorphic assemblagesoccur along the western and northern margin of the Yan-gtze Block, which are believed to have been related to sub-duction of Rodinian oceanic lithosphere toward theYangtze Block during the period from 760 to 860 Ma(Zhou et al., 2002a). Hence, the lithospheric mantle beneathPanxi area, which is located at the western margin of theYangtze Block, was probably affected by fluids and/ormelts derived from the ancient subducted slab. Infiltrationof U-bearing fluids into the Panxi lithospheric mantle couldcause heterogeneous and low 3He/4He ratios, because U issoluble in slab-derived fluids to considerable depth (e.g.,Brenan et al., 1995; Kogiso et al., 1997) and tends to be rel-atively enriched in potential silicate melts due to its incom-patibility during partial melting processes. This wouldallow U-bearing fluids and/or melts to infiltrate the mantlewedge from the subducted slab. Moreover, the infiltrationof subduction-related melts and fluids into the lithosphericmantle led to enriched isotopic signatures from that of theslightly depleted asthenopheric mantle which has been sug-gested by the Sr, Nd and Pb isotopic data of the Emeishanbasalts and picrites (Xiao et al., 2004; Zhang et al., 2006).

5.2. Assessment of addition of subduction-related components

on 40Ar/36Ar ratios

In contrast to He, heavy noble gases like Ar, have isoto-pic compositions of mantle end-members such as MORBsand OIBs that are difficult to distinguish, mainly becauseof high abundance of relatively nonradiogenic Ar in theatmosphere (40Ar/36Ar = 295.5) coupled with highly radio-genic Ar in mantle samples (40Ar/36Ar P12,000 for OIBs(Poreda and Farley, 1992), and P28,000 in MORBs(Staudacher et al., 1989; Fisher, 1994). Although 40Ar/36Arratios in our samples reach up to �16,000, it is not possibleto assert conclusively that the relatively high 40Ar/36Ar ra-tio compared to the atmospheric value are due to plume-de-

Fig. 7. 3He/4He versus 40Ar/36Ar diagram for samples analyzed inthe present study. The isotopic compositions of the mantle plume(P), MORB (M), atmosphere (A), old oceanic crust field (C) andSamoan hotspot lavas (Somoa) (Data sources: Kaneoka andTakaoka (1985), Staudacher and Allegre (1988) and Farley et al.(1992)). The field enclosed by the lines connecting P–A–Crepresents the isotopic ratios produced by three-component mixing(Kaneoka and Takaoka, 1985; Nagao and Takahashi, 1993). Theuncertainties are 1r. Symbols as in Fig. 4.


rived components with even higher Ar ratios that had beensimply mixed with atmospheric components which isthought to be added during subduction. In addition, oldoceanic crust and continental crust also have high40Ar/36Ar ratios as a result of growth of radiogenic nuclidesduring K decay. Hence, the origin of high 40Ar/36Ar ratiosin our data is not clearly identified. Nevertheless, it seemspossible that the low 40Ar/36Ar ratios analyzed in our sam-ples are due to the addition of low 40Ar/36Ar ratio compo-nents such as air and/or deep-sea sediments which werecontaminated by atmospheric components (Igarashi et al.,1987). As mentioned above, the Panxi upper mantle mayhave been metasomatized by subduction-related melt orfluid. Such an effect should be more strongly reflected inthe 40Ar/36Ar ratio, if the fluid was surface-derived. How-ever, there are four possibilities that can cause the additionof the atmospheric gases into the samples: (1) Atmosphericadsorption on the surface of the samples; (2) Incorporationof surface water with dissolved Ar in samples as hydrate orhydrous minerals formed by alteration after emplacementof magma; (3) Infiltration of ground water with dissolvedAr circulating within the crust into the samples; (4) Perco-lation of subducted atmospheric noble gases dissolved insea water through the mantle as the solution dehydratedfrom the subducted slab.

Ballentine and Barfod (2000) have argued that mostatmospheric addition is only due to a very superficial con-tamination that might occur in the laboratory especiallyfor heavier noble gases. However, for noble gas analysis,samples and analytical lines are always preheated in orderto reduce adhered atmospheric gases. The amounts of36Ar in procedural blanks were in some cases a few ordersof magnitude lower than those extracted from the samplesin heating experiments. Furthermore, atmospheric contam-inants borne by hydrous minerals generated by low temper-ature alteration or weathering are likely to be removed inrelatively low temperature fractions (600 �C) and by carefulhandpicking of mineral separates. Our samples were col-lected in freshly exposed sections uncovered by shot-firingin the open pit, and the influence of ground water is verylimited. These lines of evidence suggest that possibilities(1), (2), (3) are unlikely. Accordingly, the low 40Ar/36Ar ra-tios we measured are likely to reflect the isotopic composi-tions of the mantle source, and require that the mantlesource was contaminated by materials with lower 40Ar/36Arratios, such as fluids derived from subduction-related com-ponents containing atmospheric argon (Sarda et al., 1999,2000; Matsumoto et al., 2001).

5.3. Role of recycled components in the lithospheric mantle

What has been discussed above suggests an importantrecycling of atmospheric argon back into the mantle andchallenges the so-called “noble gases subduction barrier”

which says that noble gases of the subducted oceanic crust(and sediments) are largely returned back to the atmo-sphere through arc volcanism (Staudacher and Allegre,1988). The isotopic compositions for plume-type mantlesuch as the mantle source of the Hawaiian hotspot (P),MORB-type (M) mantle, atmosphere (A), and old oceanic

crust/continental crust region (C) are shown on a 3He/4Hevs. 40Ar/36Ar diagram (Kaneoka and Takaoka, 1985)(Fig. 7). Noble gas compositions in most samples fromthese intrusions in Panxi area plot within the field enclosedby the lines connecting P, A, and C. Some samples showlower 3He/4He ratio than the atmospheric value togetherwith moderately higher 40Ar/36Ar ratios. Accordingly, thesamples plotting within the P–A–C field can be plausiblyexplained by three-component mixing of noble gases amongplume-derived magma, an atmospheric component derivedfrom subducted deep-sea water and a C-type sourcestrongly enriched in radiogenic 4He and 40Ar from a crustalmaterial like oceanic sediments (Kaneoka and Takaoka,1985). However, the extremely low 3He/4He ratios requireclarifying the contribution from a putative plume. Basedon radiogenic Sr-, Nd-, and Pb data (e.g., Zhang et al.,2009), and as mentioned above, the ore-bearing intrusionsin the Panxi area are interpreted to be derived from theinteraction between the Permian plume and lithosphericmantle. Therefore, we incline to attribute the noble gas iso-topic signature to be inherited from both the plume and thelithospheric mantle. Although partial melting of a plumesource contributed largely to the generation of magmas inELIP, it is noteworthy that noble gas concentrations inplume-derived rocks, e.g. OIBs, are comparatively low(Ozima and Podosek, 2002) This in particular as they areat least 2-orders of magnitude lower compared to the meta-somatic xenoliths from the enriched lithospheric mantle(e.g., Yamamoto et al., 2004). Thus, since the lithosphericmantle was metasomatized by subduction-related melt orfluid derived from the ancient subducted slab, a relativelyhigh abundance of noble gas in the lithospheric mantle

Fig. 8. Simplified plot of 3He/4He versus 87Sr/86Sr for samplesfrom Fe–Ti–V oxide-bearing intrusions in the Panxi area and otherterrestrial fields. Data sources: the 87Sr/86Sr isotopic compositionsof Panxi samples are from Zhong et al. (2002), Zhou et al. (2005,2008), Shellnutt and Zhou (2007), Zhang et al. (2009), Shellnuttet al. (2009), and Zhong et al. (2002). Compositional fields ofSamoa, Iceland and Loihi Seamount are taken from Kurz et al.(1982), Farley et al. (1992) and Starkey et al. (2009). Effects toisotope ratios by addition of radiogenic components are indicatedby arrows.


would be expected. Infiltration of subduction-related meltsand/or fluids into the Panxi lithospheric mantle could causeheterogeneous and extremely low 3He/4He ratios and addi-tion of low 40Ar/36Ar ratio components such as air and/ordeep-sea sediments which were contaminated by atmo-spheric components in the lithospheric mantle as mentionedin Section 5.1.5. Therefore, even a small addition of mate-rial from the lithospheric mantle could significantly influ-ence the noble gas signature of the magma. In the case ofthe ELIP this could have lead to an extreme decrease in3He/4He and 40Ar/36Ar ratios in the magma generated bythe Permian plume-lithosphere interaction.

Comprehensive noble gas studies from these intrusionsin the Panxi area have attempted to relate He isotopic vari-ations to different contributions of radiogenic He from sub-ducted materials (e.g., Craig et al., 1975). However, thereare still two alternative mechanisms for producing the low3He/4He ratio in the mantle. The first is an incorporationof fluids and/or melts derived from the ocean floor sedi-ments (e.g., Matsuda and Nagao, 1986), and the second isderived from the oceanic basaltic crust (e.g., Staudacherand Allegre, 1988).

Correlations of 3He/4He with 87Sr/86Sr in oceanic rockshave been used to infer the large-scale structure of the man-tle and interactions between sources (Kurz et al., 1982;Poreda et al., 1986). The high 3He/4He (�3 � 10�5/27R/RA) and relatively low 87Sr/86Sr (0.703–0.7035) of hot spotssuch as Hawaii are explained by undegassed lower mantle(Kaneoka and Takaoka, 1985; Valbracht et al., 1997).Combined with published Sr isotopic data of these intru-sions (Zhong et al., 2002; Zhou et al., 2005, 2008; Shellnuttand Zhou, 2007; Zhang et al., 2009; Shellnutt et al., 2009),the 3He/4He vs. 87Sr/86Sr diagram for the intrusions isshown in Fig. 8. The near-vertical fields for these intrusionsfrom the Panxi area in He–Sr isotope space point to anEMI-type mantle end-member. The low 3He/4He ratios ofthe samples indicate that the mantle source should have ele-vated time-integrated (U + Th)/3He. This can be inter-preted to reflect a recycled component of degassedoceanic sediment and crust with low He/(Th + U) and ele-vated 87Sr/86Sr (Kurz et al., 1982; Graham et al., 1990; Far-ley et al., 1992). If these recycled materials have been storedin the mantle for long periods, the Sr, Nd, and Pb isotopiccompositions would have EMI signatures (e.g., Cohen andO’Nions, 1982; Weaver et al., 1986).

As stated earlier, during the Neoproterozoic period, asubduction zone was present on the western margin of Yan-gtze Block, including the Panxi area. Widely distributedadakitic plutons, such as Datian and Dajianshan felsic plu-tons in the Panxi area, were the products of melting of asubducted oceanic slab, in the presence of garnet as a resi-due in the source, i.e. in the form of eclogite (e.g., Zhouet al., 2002a, 2008; Zhao et al., 2008). Such melts arethought to have contaminated the lithospheric mantle be-neath the Panxi area, perhaps remaining in the lithosphericmantle as a grain-boundary component or as melt inclu-sions. These melts may also have contained an atmosphericcomponent inherited from the deep-sea water or sedimentsin the subducted slab. The fluids derived from the subduct-ed slab are likely to have high U/3He ratios (Farley, 1995)

due to the mobility of U in water and therefore likely topartition into aqueous fluids when the slab dehydrates (Bre-nan et al., 1995; Kogiso et al., 1997). The high U/3He ratioin the fluids will consequently lead to a rapid decrease in the3He/4He ratio over time. These inferences are supported bylow d18O values (3.9–4.9&) of clinopyroxenes separatedfrom Panzhihua intrusion (Zhang et al., 2009) that are low-er than that of lithospheric and asthenosphric mantle(�6&; e.g., Kyser et al., 1986; Mattey et al., 1994). Thisis consistent with the addition of subduction-related fluidsand melts.

5.4. Implications for petrogenesis of the ore-bearing

intrusions

As discussed earlier, during the Neoproterozoic, sub-ducted oceanic crust beneath the Panxi area underwenteclogite-facies metamorphism and subsequent exhumation.The infiltration of subduction-related melts and fluids intolithospheric mantle led to an addition of subducted atmo-spheric argon and pronounced decrease in the 3He/4He ra-tio over geological time. Considerable amounts of meltswere produced by partial melting of eclogite-facies oceaniccrust as reflected by the Neoproterozoic adakitic plutons inthe Panxi area (e.g., Zhao et al., 2008). Such melts wouldhave moved upwards through the lithospheric mantle andreacted with olivine in the surrounding peridotite to formorthopyoxene and garnet (Gibson, 2002). Re-melting ofresidual eclogite could also produce andesitic partial meltsthat react with the surrounding peridotite and enrich it ingarnet and clinopyroxene (Yaxley, 2000), i.e. equivalentof eclogite. Melting of this relatively anhydrous, ‘re-fertil-


ized’ peridotite produces Fe-rich melts that are enriched inincompatible trace elements (Yaxley and Green, 1998).Such a ‘re-fertilized’ peridotite source has a lower solidustemperature than normal peridotite (Yaxley, 2000). Duringthe late Permian, when the Emeishan plume ascended fromthe lower mantle (Zhang et al., 2008) it encountered the en-riched lithospheric mantle containing the eclogitic material.Thus, the primary magmas were likely produced by partialmelting of both, the plume and the eclogitic material. Themagmas fed the ore-bearing intrusions, carrying an en-riched noble gas signature such as low 3He/4He ratios, de-rived from a hybridized mantle source which containednormal garnet-zone lherzolitic components (e.g., Zhouet al., 2008; Zhang et al., 2009) and a mixture of ‘re-fertil-ized’ peridotite and recycled material.

It was assumed by several researchers that the parentalmagma of these Fe–Ti–V oxide ore-bearing intrusions areferrobasalt (Zhou et al., 2005) or ferropicrite (Zhanget al., 2009) based on bulk major element data. Moreover,it has been inferred that the Fe-rich parental magma hadbeen derived from an Fe-rich mantle source. However,whether such a Fe-rich mantle exists and how it wasformed is still not clear (e.g., Pang et al., 2008). Tuffet al. (2005) demonstrated that ferropicritic magmas canbe generated by melting of garnet pyroxenite under highpressure (�5 GPa) and temperature (�1550 �C). This isconsistent with previous experiments suggesting that theiron content of primary magmas increases with bothincreasing mean degree of partial melting and increasingmean temperature at a given pressure (Langmuir and Han-son, 1980). In the Panxi area, the Fe-rich magma couldhave been generated by this process, i.e. partial meltingof a mixture of an upwelling mantle plume and the sub-continental lithospheric mantle that comprises the equiva-lent of eclogite and other recycled materials due to the an-cient subduction-related enrichment. This type of meltinginvolving an eclogite or pyroxenite component is also capa-ble of explaining the significant volumes of melts seen inthe ELIP and other LIPs (e.g., Cordery et al., 1997; Camp-bell, 1998; Takahashi et al., 1998; Yaxley, 2000; Leitch andDavies, 2001). However, it is also possible that the parentalferropicritic and ferrobasaltic magma was produced bypartial melting of upwelling mantle plume that entrainedgarnet pyroxenite ‘streaks’ derived from subducted maficoceanic crust (Gibson et al., 2000). Considering that sub-duction occurred in the Neoproterozoic whereas the plumeactivity occurred during the Permian, it is unlikely that theupwelling plume entrained the ‘streaks’ or ‘blobs’ of eclog-ite/pyroxenite matrix. Therefore, the equivalent of eclogiteand other recycled material should have been stored in thelithospheric mantle due to the ancient subduction-relatedenrichment.

The discussion and evidence provided here that the Heand Ar noble gas isotopic composition of the studied intru-sions is best explained by involving subducted crustal com-ponents, which is consistent with the ideas above that theparental magma of these ore-bearing intrusions is ferropi-critic and derived from possible eclogitic materials offormer oceanic crust. The junction of these subduction-generated mantle sources and the Emeishan plume can well

explain why many world-class Fe–Ti–V oxide deposits areclustered in the Panxi area.

6. CONCLUSIONS

Extremely low 3He/4He ratios are a widespread featureof the Fe–Ti–V oxide ore-bearing intrusions in Panxi area.This feature, combined with the variable 40Ar/36Ar ratios, isbest explained by addition of subduction-related fluids andmelts that have been stored in the lithospheric mantle forlong periods. A paleo-subduction zone that formed in thewestern margin of Yangtze Block including the Panxi areaduring the Neoproterozoic period probably accounts forsuch a mantle enrichment process. Eclogite-derived meltsfrom the deep-subducted oceanic slab extensively affectedthe lithospheric mantle. Partial melting of an upwellingmantle plume that involved an eclogite or pyroxenite com-ponent in the lithospheric mantle could have resulted in theparental Fe-rich magma that supplied the ore-bearingintrusions. The junction of these sources and processesmay have been the crucial factor in generating manyworld-class Fe–Ti–V oxide deposits clustered in the Panxiarea.

ACKNOWLEDGEMENTS

Constructive reviews and suggestions by Dr. Joyashish Tha-kurta, Dr. Franco Pirajno and an anonymous reviewer helped toimprove the manuscript. The authors greatly acknowledge Dr.Tang, H-Y for helpful discussion and the management of the min-ing company of Panzhihua Iron & Steel Group for logistical sup-port during fieldwork in the Panxi area. Sichuan Department ofLand & Resources is thanked for their help. Financial supportfor this work was supported by Special Fund for Scientific Re-search in the Public Interest (200911007-25), National Nature Sci-ence Foundation of China (Grant No. 40925006), 973 Project(Grant No. 2012CB416800 and 2009CB421002), The FundamentalResearch Funds for the Central Universities, 111 Project (B07011)and PCSIRT.

REFERENCES

Ali J. R., Fitton J. G. and Herzberg C. (2010) Emeishan largeigneous province (SW China) and the mantle plume up-dominghypothesis. J. Geol. Soc. London 167, 953–959.

Bach W. and Niedermann S. (1998) Atmospheric noble gases involcanic glasses from the southern Lau Basin: origin from thesubducting slab?. Earth Planet Sci. Lett. 160 297–309.

Ballentine C. J. and Barfod D. N. (2000) The origin of air-likenoble gases in MORB and OIB. Earth Planet. Sci. Lett. 180,

39–48.

Baxter E. F. (2010) Diffusion of noble gases in minerals. Rev.

Mineral Geochem. 72, 509–557.

Beswick A. E. (1982) Some geochemical aspects of alteration andgenetic relations in komatiitic suites. In Komatiities (eds. N. T.Arndt and E. G. Nisbet). George Allen and Unwin, London,

pp. 283–308.

Bhat I., Zainuddin S. M. and Rais A. (1981) The Panjal Trapchemistry; witness to the birth of Tethys. Geol. Mag. 118, 367–

375.

Boven A., Pasteels P., Punzalan L. E., Liu J., Luo X., Zhang W.,Guo Z. and Hertogen J. (2002) 40Ar/39Ar geochronological


constraints on the age and evolution of the Permo-TriassicEmeishan volcanic province, southwest China. J. Asian Earth

Sci. 20, 157–175.

Brenan J. M., Shaw H. F., Ryerson F. J. and Phinney D. L. (1995)Mineral-aqueous fluid partitioning of trace elements at 900 Cand 2.0 GPa: constraints on the trace element chemistry ofmantle and deep crust fluids. Geochim. Cosmochim. Acta 59,

3331–3350.

Burnard P. G., Graham D. W. and Turner G. (1997) Vesicle-specific noble gas analyses of “popping rock”: implications forprimordial noble gases gases in earth. Science 276, 568–571.

Butler W. A., Jeffery P. M., Reynolds J. H. and Wasserburg G. J.(1963) Isotopic variations in terrestrial xenon. J. Geophys. Res.

68, 3283–3291.

Campbell I. H. (1998) The mantle’s chemical structure: insightsfrom the melting products of mantle plumes. In Earth’s Mantle:

Composition, Structure and Evolution (ed. I. Jackson). Cam-

bridge University Press, Cambridge, pp. 259–310.

Cohen R. S. and O’Nions R. K. (1982) Identification of recycledcontinental material in the mantle from Sr, Nd and Pb isotopeinvestigations. Earth Planet. Sci. Lett. 61, 73–84.

Cong B. L. (1988) Formation and evolution of the Pan-Xi paleorift

(in Chinese). Science Press, Beijing, pp. 424, (in Chinese).Cordery M. J., Davies G. F. and Campbell I. H. (1997) Genesis of

flood basalts from eclogite-bearing mantle plumes. J. Geophys.

Res. 102, 20179–20197.

Craig H. and Lupton J. E. (1976) Primordial neon, helium andhydrogen in oceanic basalts. Earth Planet. Sci. Lett. 31, 369–

385.

Craig H., Clarke W. B. and Beg M. A. (1975) Excess 3He in deepwater on the East Pacific Rise. Earth Planet Sci. Lett. 26, 125–

132.

Chung S. L. and Jahn B. M. (1995) Plume-lithosphere interactionin generation of the Emeishan flood basalts at the Permian-Triassic boundary. Geology 23, 889–892.

Czuppon G., Matsumoto T., Handler M. R. and Matsuda J. (2009)Noble gases in spinel peridotite xenoliths from Mt Quincan,North Queensland, Australia: undisturbed MORB-type noblegases in the subcontinental lithospheric mantle. Chem. Geol.

266, 19–28.

Czuppon G., Matsumoto T., Matsuda J., Everard J. and Suther-land L. (2010) Noble gases in anhydrous mantle xenoliths fromTasmania in comparison with other localities from easternAustralia: implications for the tectonic evolution. Earth Planet.

Sci. Lett. 299, 317–327.

Damon P. E. and Kulp J. L. (1958) Excess helium and argon inberyl and other minerals. Amer. Mineral. 43, 433–459.

Dobretsov N. L. (2005) 250 Ma large igneous province of Asia:Siberian and Emeishan traps (plateau basalts) and associatedgranitoids. Russ. Geol. Geophys 46, 879–890.

Dunai T. J. and Baur H. (1995) Helium, neon and argonsystematics of the European subcontinental mantle: implica-tions for its geochemical evolution. Geochim. Cosmochim. Acta

59, 2767–2783.

Enkin R. J., Courtillot V., Leloup Ph., Yang Z., Xing L., Zhang J.and Zhuang Z. (1992) The paleomagnetic record of UppermostPermian, Lower Triassic rocks from the South China Block.Geophys. Res. Lett. 19, 2147–2150.

Farley K. A. (1995) Rapid cycling of subducted sediments into theSamoan mantle plume. Geology 23, 531–534.

Farley K. A., Natland J. H. and Craig H. (1992) Binary mixing ofenriched and undegassed (primitive?) mantle components (He,Sr, Nd, Pb) in Samoan lavas. Earth Planet. Sci. Lett. 111, 183–

199.

Fisher D. E. (1994) Mantle and atmospheric-like argon in vesiclesof MORB glasses. Earth Planet Sci. Lett. 123, 199–204.

Gautheron C., Moreira M. and Allegre C. (2005) He, Ne and Arcomposition of the European lithospheric mantle. Chem. Geol.

217, 97–112.

Gibson S. A. (2002) Major element heterogeneity in Archean toRecent mantle plume starting-heads. Earth Planet. Sci. Lett.

195, 59–74.

Gibson S. A., Thompson R. N. and Dickin A. P. (2000)Ferropicrites: geochemical evidence for Fe-rich streaks inupwelling mantle plumes. Earth Planet. Sci. Lett. 174, 355–374.

Graham D., Lupton J., Albarede F. and Condomines M. (1990)Extreme temporal homogeneity of helium isotopes at Piton dela Fournaise Reunion Island. Nature 347, 545–548.

Guo F., Fan W. M., Wang Y. J. and Li C. W. (2004) When did theEmeishan plume activity start? Geochronological evidence fromultramafic–mafic dikes in Southwestern China. Int. Geol. Rev.

46, 226–234.

Hanyu T. and Kaneoka I. (1998) Open system behavior of heliumin case of the HIMU source area. Geophys. Res. Lett. 25, 687–

690.

Hart S. R. (1984) He diffusion in olivine. Earth Planet. Sci. Lett. 70,

297–302.

Hawkesworth C. J., Gallagher K., Kirstein L., Mantovani M.,Peate D. W. and Turner S. P. (2000) Tectonic controls onmagmatism associated with continental break-up: an examplefrom the Parana-Etendeka Province. Earth Planet. Sci. Lett.

179, 335–349.

He B., Xu Y. G., Huang X. L., Luo Z. Y., Shi Y. R., Yang Q. J.and Yu S. Y. (2007) Age and duration of the Emeishan floodvolcanism, SW China: geochemistry and SHRIMP zirconU � Pb dating of silicic ignimbrites, post-volcanic. Earth

Planet. Sci. Lett. 255, 306–323.

Heber V. S., Brooker R. A., Kelley S. P. and Wood B. J. (2007)Crystal-melt partitioning of noble gases (helium, neon, argon,krypton, and xenon) for olivine and clinopyroxene. Geochim.

Cosmochim. Acta 71, 1041–1061.

Hergt J., Peate D. and Hawkesworth C. J. (1991) The petrogenesisof Mesozoic Gondwana low-Ti flood basalts. Earth Planet. Sci.

Lett. 105, 134–148.

Hilton D. R., Hammerschmidt K., Loock G. and Friedrichsen H.(1993) Helium and argon isotope systematics of the central LauBasin and Valu Fa Ridge: evidence of crust-mantle interactionsin a back-arc basin. Geochim. Cosmochim. Acta 57, 2819–2841.

Honda M., McDougall I., Patterson D. B., Doulgeris A. andClague D. A. (1993) Noble gases in submarine pillow basaltglasses from Loihi and Kilauea, Hawaii: a solar component inthe Earth. Geochim. Cosmochim. Acta 57, 859–874.

Hopp J. and Ionov D. A. (2011) Tracing partial melting andsubduction-related metasomatism in the Kamchatkan mantlewedge using noble gas compositions. Earth Planet Sci. Lett.

302, 121–131.

Igarashi G., Kodera M., Ozima M., Sano Y., Wakita H. andBoulegue J. (1987) Noble gas elemental and isotopic abun-dances in deep-sea trenches in the western Pacific. Earth Planet.

Sci. Lett. 86, 77–84.

Ikeda Y., Nagao K. and Kagami H. (2001) Effects of recycledmaterials involved in a mantle source beneath the southwestJapan arc region: evidence from noble gas, Sr, and Nd isotopicsystematics. Chem. Geol. 175, 509–522.

Ikeda Y., Nagao K., Stern R. J., Yuasa M. and Newman S. (1998)Noble gases in pillow basalt glasses from the northern MarianaTrough back-arc basin. Isl. Arc 7, 471–478.

Kaneoka I. and Takaoka N. (1985) Noble-gas state in the earth’sinterior – some constraints on the present state. Chem. Geol. 52,

75–95.

Kellogg L. H. and Wasserburg G. J. (1990) The role of plumes inmantle helium fluxes. Earth Planet Sci. Lett. 99, 276–289.


Kogiso T., Tatsumi Y. and Nakano S. (1997) Trace elementtransport during dehydration processes in the subductedoceanic crust: 1. Experiments and implications for the originof ocean island basalts. Earth Planet. Sci. Lett. 148, 193–205.

Krause J., Brugmann G. E. and Pushkarev E. V. (2007) Accessoryand rock forming minerals monitoring the evolution of zonedmafic–ultramafic complexes in the Central Ural Mountains.Lithos 95, 19–42.

Kuroda P. K. and Sherrill R. D. (1978) Abundances and isotopiccompositions of rare gases in granites and thucolites. InTerrestrial Rare Gases (ed. E. C. Alexander Jr. M. Ozima).Center for Academic Publications, Japan, pp. 63–64.

Kurz M. D. (1991) Noble gas isotopes in oceanic basalts:controversial constraints on mantle models. In Short Course

Handbook on Applications of Radiogenic Isotope Systems to

Problems in Geology (eds. L. Heaman and J. N. Ludden).Mineral. Assoc. Canada.

Kurz M. D., Jenkins W. J. and Hart S. R. (1982) Helium isotopicsystematics of oceanic islands and mantle heterogeneity. Nature

297, 43–46.

Kyser T. K., Carmeron W. E. and Nisbet E. G. (1986) Boninitepetrogenesis and alteration history; constraints from stableisotope compositions of boninites from Caoe Vogel, NewCaledonia and Cyprus. Contrib. Mineral Petr. 93, 222–226.

Langmuir C. H. and Hanson G. N. (1980) An evaluation of majorelement heterogeneity in the mantle sources of basalts. Phil.

Trans. R. Soc. B, Series A 297, 383–407.

Leitch A. M. and Davies G. F. (2001) Mantle plumes and floodbasalts: enhanced melting from plume ascent and an eclogitecomponent. J. Geophys. Res. 106, 2047–2059.

Li D. H., Chen Z. X. and Han Z. W. (1981) Rhythm and petrologyof Taihe layered intrusion in Xichang. J. Chengdu Univ.

Technol. (Sci. Technol. Ed.) 3, 9–21 (in Chinese).

Lo C. H., Chung S. L., Lee T. and Wu G. (2002) Age of theEmeishan flood magmatism and relations to Permian-Triassicboundary events. Earth Planet. Sci. Lett. 198, 449–458.

Lux G. (1987) The behaviour of noble gases in silicate liquids:solution, diffusion, bubbles and surface effects, with applica-tions to natural samples. Geochim. Cosmochim. Acta 51, 1549–

1560.

Ma Y., Ji X. T., Li J. C., Huang M. and Kan Z. Z. (2003) Mineral

Resources of the Panzhihua Region. Sichuan Science andTechnology Press, Chengdu, pp. 275, (in Chinese).

Ma Y., Liu J. F., Wang H. F., Mao Y. S., Ji X. T., Wang D. K. andYan Z. Z. (2001) Geology of the Panzhihua Region. SichuanScience and Technology Press, Chengdu, pp. 367, (in Chinese).

Martelli M., Nuccio P. M., Stuart F. M., Burgess R., Ellam R. M.and Italiano F. (2004) Helium-strontium isotope constraints onmantle evolution beneath the Roman Comagmatic Province,Italy. Earth Planet. Sci. Lett. 224, 295–308.

Marty B. and Ozima M. (1986) Noble gas distribution in oceanicbasalt glasses. Geochim. Cosmochim. Acta 50, 1093–1098.

Marty B., Pik R. and Gezahegn Y. (1996) Helium isotopicvariations in Ethiopian Plume Lavas: nature of magmaticsources and limit on lower mantle contribution. Earth Planet.

Sci. Lett. 144, 223–237.

Matsuda J. and Nagao K. (1986) Noble gas abundances in deep-sea sediment core from eastern equatrorial Pacific. Geochem. J.

20, 71–80.

Matsumoto T., Chen Y. and Matsuda J. (2001) Concomitantoccurrence of primordial and recycled noble gases in the Earth’smantle. Earth Planet. Sci. Lett. 185, 35–47.

Matsumoto T., Honda M., McDougall I. and O’Reilly S. Y. (1998)Noble gases in anhydrous lherzolites from the newer volcanics,southeastern Australia: a MORB-like reservoir in the subcon-tinental mantle. Geochim. Cosmochim. Acta 62, 2335–2345.

Matsumoto T., Honda M., McDougall I., O’Reilly S. Y., NormanM. and Yaxley G. (2000) Noble gases in pyroxenites andmetasomatised peridotites from the Newer Volcanics, south-eastern Australia: implications for mantle metasomatism.Chem. Geol. 168, 49–73.

Mattey D., Lowry D. and Macpherson C. (1994) Oxygen isotopecomposition of mantle peridotite. Earth Planet. Sci. Lett. 128,

231–241.

Moreira M. and Kurz M. (2001) Subducted oceanic lithosphereand the origin of the ‘high l’ basalt helium isotopic signature.Earth Planet Sci. Lett. 189, 49–57.

Nagao K. and Takahashi E. (1993) Noble gases in the mantlewedge and lower crust: an inference from the isotopic analysesof xenoliths from Oki-Dogo and Ichinomegata Japan. Geo-

chem. J. 27, 229–240.

Nier A. O. (1950) A redetermination of the relative abundances ofthe isotopes of carbon, nitrogen, oxygen, argon and potassium.Phys. Rev. 77, 789–793.

Nuccio P. M., Paonita A., Rizzo A. and Rosciglione A. (2008)Elemental and isotope covariation of noble gases in mineralphases from Etnean volcanics erupted during 2001–2005, andgenetic relation with peripheral gas discharges. Earth Planet

Sci. Lett. 272, 683–690.

Ozima M. and Podosek F. A. (2002) Noble Gas Geochemistry, 2nded. Cambridge University Press, Cambridge.

Ozima M. and Podosek F. A. (1983) Noble Gas Geochemistry.Cambridge University Press, Cambridge.

Pang K. N., Zhou M. F., Lindsley D., Zhao D. G. and Malpas J.(2008) Origin of Fe–Ti oxide ores in mafic intrusion: evidencefrom the Panzhihua intrusion, SW China. J. Petrol. 49, 295–

313.

Pang K. N., Zhou M. F., Qi L., Shellnutt G., Wang C. Y. andZhao D. (2010) Flood basalt-related Fe–Ti oxide deposits in theEmeishan large igneous province, SW China. Lithos 119, 123–

136.

Porcelli D., Ballentine C. J. and Wieler R. (2002) An overview ofnoble gas geochemistry and cosmochemistry. In Noble Gases in

Geochemistry and Cosmochemistry, Vol. 47 (eds. D. Porcelli, C.J. Ballentine and R. Wieler). Mineral Soc. Am, pp. 1–18.

Poreda R. J. and Farley K. A. (1992) Rare gases in Samoanxenoliths. Earth Planet. Sci. Lett. 113, 129–144.

Poreda R., Schilling J. G. and Craig H. (1986) Helium andhydrogen isotopes in ocean-ridge basalts north and south ofIceland. Earth Planet. Sci. Lett. 78, 1–17.

Raquin A., Moreira M. and Guillon F. (2008) He, Ne and Arsystematics in single vesicles: mantle isotopic ratios and originof the air component in basaltic glasses. Earth Planet Sci. Lett.

274, 142–150.

Rayleigh L. (1939) Nitrogen, argon and neon in the earth’s crustwith applications to cosmology. Proc. R. Soc. London. A170,

451–464.

Reichow M. K., Pringle M. S., Al’Mukhamedov A. I., Allen M. B.,Andreichev V. L., Buslov M. M., Davies C. E., Fedoseev G. S.,Fitton J. G., Inger S., Medvedev A. Ya., Mitchell C., PuchkovV. N., Safonova I. Yu., Scott R. A. and Saunders A. D. (2009)The timing and extent of the eruption of the Siberian Trapslarge igneous province: implications for the end-Permianenvironmental crisis. Earth Planet. Sci. Lett. 277, 9–20.

Sano Y., Nishio Y., Gamo T., Jambon A. and Marty B. (1998)Noble gas and carbon isotopes in Mariana Trough basaltglasses. Appl. Geochem. 13, 441–449.

Sarda P., Moreira M. and Staudacher T. (1999) Argon-leadisotopic correlation in Mid-atlantic ridge basalts. Science 283,

666–668.

Sarda P., Moreira M., Staudacher T., Schilling J. G. and Allegre C.J. (2000) Rare gas systematics on the southernmost Mid-


Atlantic Ridge: constraints on the lower mantle and the Dupalsource. J. Geophys. Res. 105, 5973–5996.

Sharma M. A. (1997) Siberian Traps. In Large Igneous Provinces:

Continental, Oceanic, and Planetary Flood Volcanism (eds. J. J.Mahoney and M. F. Coffin). Geophysical Monographs,American Geophysical Union 100. pp. 273–295.

Shaw A. M., Hilton D. R., Fisher T. P., Walker J. A. and DeLeeuw G. A. M. (2006) Helium isotope variations in mineralseparates from Costa Rica and Nicaragua: assessing crustalcontribution, timescale variations and diffusion-related mecha-nism. Chem. Geol. 230, 124–139.

Shellnutt J. G. and Zhou M. F. (2007) Permian peralkaline,peraluminous and metaluminous A-type granites in the Panxidistrict, SW China: their relationship to the Emeishan mantleplume. Chem. Geol. 243, 286–313.

Shellnutt J. G., Zhou M. F. and Zellmer G. (2009) Formation ofperalkaline A-type granitoids: insights from the Permian Fe–Ti-oxide bearing Baima Igneous Complex(China). Chem. Geol.

259, 204–217.

Smith S. P. (1984) Atmospheric and juvenile noble gases in theSkaergaard layered igneous intrusion. Geochim. Cosmoshim.

Acta 48, 1033–1041.

Song X. Y., Zhou M. F., Cao Z. M. and Robinson P. T. (2004)Late Permian rifting of the South China Craton caused by theEmeishan mantle plume? J. Geol. Soc. 161, 773–781.

Starkey N. A., Stuart F. M., Ellam R. M., Fitton J. G., Basu S. andLarsen L. M. (2009) Helium isotopes in early Iceland plumepicrites: constraints on the composition of high 3He/4Hemantle. Earth Planet Sci. Lett. 277, 91–100.

Staudacher T. and Allegre C. J. (1988) Recycling of oceanic crustand sediments: the noble gas subduction barrier. Earth Planet

Sci. Lett. 89, 173–183.

Staudacher T., Sarda P., Richardson S. H., Allegre C. J., Sagna I.and Dimitriev L. V. (1989) Noble gases in basalt glasses from aMid-Atlantic Ridge topographic high at 140N: geodynamicconsequences. Earth Planet. Sci. Lett. 96, 119–133.

Sumino H., Burgess R., Mizukami T., Wallis S. R., Holland G. andBallentine C. J. (2010) Seawater-derived noble gases andhalogen preserved in exhumed mantle wedge peridotites. Earth

Planet Sci. Lett. 294, 163–172.

Takahashi E., Nakajima K. and Wright T. L. (1998) Origin of theColumbia River basalts: melting model of a heterogeneousplume head. Earth Planet. Sci. Lett. 162, 63–80.

Tang H. Y., Zheng J. P. and Yu C. M. (2007) Mantle fluids andnoble gas isotopic compositions of peridotitic olivines inCenozoic basalts from eastern North China. Acta Petrol. Sin.

23, 1531–1542 (in Chinese with English abstarct).

Thompson G. M., Ali J. R., Song X. and Jolley D. W. (2001)Emeishan Basalts, SW China: reappraisal of the formation’stype area stratigraphy and a discussion of its significance as alarge igneous province. J. Geol. Soc. London 158, 593–

599.

Tolstikhin I., Kamensky I., Tarakanov S., Kramers J., Pekala M.,Skiba V., Gannibal M. and Novikov D. (2010) Noble gasisotope sites and mobility in mafic rocks and olivine. Geochim.


Trull T. W. and Kurz M. D. (1993) Experimental measurements of3He and 4He mobility in olivine and clinopyroxene at magmatictemperatures. Geochim. Cosmochim. Acta 57, 1313–1324.

Tuff J., Takahashi E. and Gibson S. A. (2005) Experimentalconstraints on the role of garnet pyroxenites in the genesis ofhigh-Fe mantle plume derived melts. J. Petrol. 46, 2023–

2058.

Ukstins Peate I. and Bryan S. E. (2009) Re-evaluating plume-induced uplift in the Emeishan large igneous province. Nat.

Geosci. 1, 625–629.

Valbracht P. J., Staudacher T., Malahoff A. and Allegre C. J.(1997) Noble gas systematics of deep rift zone glasses fromLoihi Seamount, Hawaii. Earth Planet. Sci. Lett. 150, 399–411.

Wang C. Y., Zhou M. F. and Zhao D. G. (2008) Fe–Ti-Cr oxidesfrom the Permian Xinjie mafic–ultramafic layered intrusion inthe Emeishan large igneous province, SW China: crystallizationfrom Fe- and Ti-rich basalt magmas. Lithos 102, 198–217.

Weaver B. L., Wood D. A., Tarney J. and Joron J. L. (1986) Roleof subducted sediments in the genesis of ocean island basalt:geochemical evidence from South Atlantic ocean islands.Geology 14, 275–278.

Xiao L., Xu Y. G., Mei H. J., Zheng Y. F., He B. and Pirajno F.(2004) Distinct mantle sources of low-Ti and high-Ti basaltsfrom the western Emeishan large igneous province, SW China:implications for plume-lithosphere interaction. Earth Planet.

Sci. Lett. 228, 525–546.

Xu Y. G., He B., Chung S. L., Menzies M. A. and Frey F. A.(2004) The geologic, geochemical and geophysical consequencesof plume involvement in the Emeishan flood basalt province.Geology 30, 917–920.

Yamamoto J., Kaneoka I., Nakai S., Kagi H., Prikhod’ko V. S.and Arai S. (2004) Evidence for subduction-related componentsin the subcontinental mantle from low 3He/4He and 40Ar/36Arratio in mantle xenoliths from Far Eastern Russia. Chem. Geol.

207, 237–259.

Yamamoto J., Nishimura K., Sugimoto T., Takemura K., Takah-ata N. and Sano Y. (2009) Diffusive fractionation of noble gasesin mantle with magma channels: Origin of low He/Ar inmantle-derived rocks. Earth Planet Sci. Lett. 280, 167–174.

Yan D. P., Zhou M. F., Song H. L., Wang X. W. and Malpas J.(2003) Origin and tectonic significance of a Mesozoic multi-layer over-thrust system within the Yangtze Block (SouthChina). Tectonophysics 361, 239–254.

Yaxley G. M. (2000) Experimental study of the phase and meltingrelations of homogeneous basalt t peridotite mixtures andimplications for the petrogenesis of flood basalts. Contrib.

Mineral Pet. 139, 326–338.

Yaxley G. M. and Green D. H. (1998) Reactions between eclogiteand peridotite: mantle refertilisation by subduction of oceaniccrust. Schweiz. Mineral. Petrogr. Mitt. 78, 243–255.

Yin A. and Harrison T. M. (2000) Geologic evolution of theHimalayan–Tibetan orogen. Annu. Rev. Earth Planet Sci. 28,

211–280.

Zhang Z. C., Mahoney J. J., Mao J. W. and Wang F. S. (2006)Geochemistry of picritic and associated basalt flows of thewestern Emeishan flood basalt province. China. J. Petrol. 47,

1997–2019.

Zhang Z. C., Zhi X., Chen L., Saunders A. D. and Reichow M. K.(2008) Re–Os isotopic compositions of picrites from theEmeishan flood basalt province, China. Earth Planet. Sci. Lett.

276, 30–39.

Zhang Z. C., Mao J. W., Saunders A. D., Ai Y., Li Y. and Zhao L.(2009) Petrogenetic modeling of three mafic–ultramafic layeredintrusions in the Emeishan large igneous province, SW China,based on isotopic and bulk chemical constraints. Lithos 113,

369–392.

Zhang Z. Q., Lu J. R. and Tang S. H. (1999) Sm–Nd ages of thePanxi layered basic–ultrabasic intrusions in Sichuan. Acta Geol.

Sin. 73, 263–271 (in Chinese with English abstract).

Zhao J. H., Zhou M. F., Yan D. P., Yang Y. H. and Sun M. (2008)Zircon Lu–Hf isotopic constraints on Neoproterozoic subduc-tion-related crustal growth along the western margin of theYangtze Block, South China. Precambrian Res. 163, 189–209.

Zhong H. and Zhu W. G. (2006) Geochronology of layered maficintrusions from the Pan-Xi area in the Emeishan large igneousprovince, SW China. Miner. Deposita 41, 599–606.


Zhong H., Zhou X. H., Zhou M. F., Sun M. and Liu B. G. (2002)Platinum-group element geochemistry of the Hongge Fe–V–Tideposit in the Pan-Xi area, southwestern China. Miner.

Deposita 37, 226–239.

Zhong H., Yao Y., Hu S. F., Zhou X. H., Liu B. G., Sun M., ZhouM. F. and Viljoen M. J. (2003) Trace-element and Sr–Ndisotopic geochemistry of the PGE-bearing Hongge layeredintrusion, southwestern China. Int. Geol. Rev. 45, 371–382.

Zhong H., Yao Y., Prevec S. A., Wilson A. H., Viljoen M. J.,Viljoen R. P., Liu B. G. and Luo Y. N. (2004) Trace-elementand Sr–Nd isotopic geochemistry of the PGE-bearing Xinjielayered intrusion in SW China. Chem. Geol. 203, 237–252.

Zhong H., Hu R. Z., Wilson A. H. and Zhu W. G. (2005) Reviewof the link between the Hongge layered intrusion and Emeishanflood basalts, southwest China. Int. Geol. Rev. 47, 971–985.

Zhong H., Zhu W. G., Hu R. Z., Xie L. W., He D. F., Liu F. andChu Z. Y. (2009) Zircon U � Pb age and Sr–Nd–Hf isotopegeochemistry of the Panzhihua A-type syenitic intrusion in theEmeishan large igneous province, southwest China and impli-cations for growth of juvenile crust. Lithos 110, 109–128.

Zhong H., Qi L., Hu R. Z., Zhou M. F., Gou T. Z., Zhu W. G., LiuB. G. and Chu Z. Y. (2011) Rhenium–osmium isotope andplatinum-group elements in the Xinjie layered intrusion, SWChina: implications for source mantle composition, mantleevolution, PGE fractionation and mineralization. Geochim.


Zhou M. F., Malpas J., Song X. Y., Robinson P. T., Sun M.,Kennedy A. K., Lesher C. M. and Keays R. R. (2002a) Atemporal link between the Emeishan large igneous province(SW China) and the end-Guadalupian mass extinction. Earth

Planet. Sci. Lett. 196, 113–122.

Zhou M. F., Yan D. P., Kennedy A. K., Li Y. and Ding J. (2002b)SHRIMP U � Pb zircon geochronological and geochemicalevidence for neoproterozoic arc-magmatism along the westernmargin of the Yangtze block, South China. Earth Planet. Sci.

Lett. 196, 51–67.

Zhou M. F., Robinson P. T., Lesher C. M., Keays R. R., Zhang C.J. and Malpas J. (2005) Geochemistry, petrogenesis andmetallogenesis of the Panzhihua gabbroic layered intrusionand associated Fe–Ti–V oxide deposits, Sichuan province, SWChina. J. Petrol. 46, 2253–2280.

Zhou M. F., Arndt N. T., Malpas J., Wang C. Y. and Kennedy A.K. (2008) Two magma series and associated ore deposit types inthe Permian Emeishan large igneous province, SW China.Lithos 103, 352–368.

Zindler A. and Hart S. R. (1986) Helium: problematic primordialsignals. Earth Planet Sci. Lett. 79, 1–8.

Associate editor: Edward M. Ripley

Noble gas isotopic systematics of Feâ€“Tiâ€“V oxide ore-related … · 2017-05-09 ·...

Documents

Transcript of Noble gas isotopic systematics of Feâ€“Tiâ€“V oxide ore-related … · 2017-05-09 ·...