Field and petrographic data of 1.90 to 1.88 Ga I- and A ...
Transcript of Field and petrographic data of 1.90 to 1.88 Ga I- and A ...
Revista Brasileira de Geociências 42(4): 690-712, dezembro de 2012
690 Arquivo digital disponível on-line no site www.sbgeo.org.br
ABSTRACT The SW Presidente Figueiredo district, which is located in the northeastern Amazonas State of the central Amazonian Craton, Brazil, consists of 1890 to 1898 Ma I-type granitoids (Terra Preta Granite, Água Branca Suite), A-type hornblende-bearing syenogranites (Canoas Syenogranite, Mapuera Suite), felsic to intermediate volcanic rocks (Iricoumé Group), and 1883 to 1889 Ma rapakivi granites (São Gabriel Granite, Mapuera Suite) and related rocks (quartz-gabbro-anorthosite and diorite), in addition to Castanhal quartz-monzonite, mylonites, and hornfels. The quartz-diorite facies of Terra Preta Granite were formed by mingling processes between a synplutonic quartz-gabbro dike and a hornblende granodiorite. Partially assimilated globules of Canoas hornblende-bearing syenogranite and their clear contacts with Terra Preta hornblende granodiorite suggest that Canoas Syenogranite is slightly younger than Terra Preta Granite. Canoas Syenogranite xenoliths inside São Gabriel Granite show that the granite is younger than the Canoas Syenogranite. New geologic and petrographic evidence improve the petrological understanding of these rocks and suggest that, in addition to fractional crystallization, assimilation and magma mingling played a role, at least at the local scale, in the evolution and compositional variation of the plutons. Such evidence is found in Terra Preta Granite mingled quartz-diorite, felsic material associated with the Canoas Syenogranite and in the intermediate microgranular enclaves, which exhibit primary biotite in hornblende-bearing rocks, plagioclase dissolution, corrosion of feldspars rims, alkali feldspar mantles, second apatite generation, and high xenocrystal contents in intermediate enclaves formed from the fragmentation of mafic intrusions. Petrographic analyses show that a deformational event recorded in the western part of the study area (with progressive deformation from E to W) is dated between the 1.90 Ga postcollisional magmatism and the intrusions of the São Gabriel Granite and related mafic/intermediate rocks (intra-plate). However, it is extremely necessary to obtain absolute ages for this metamorphic event.
Keywords: field data; petrography; I- and A- type granitoids; lithostratigraphy; NE Amazonas State.
RESUMO Dados de campo e petrográficos de granitoides dos tipos I e A de 1,90 a 1,88 Ga da região central do Cráton amazônico, NE do Estado do Amazonas, Brasil. O SW do município de Presidente Figueiredo, localizado no Estado do Amazonas, Nordeste do Cráton Amazônico Central, Brasil, hospeda granitoides do tipo I de idade entre 1890 a 1898 Ma (Terra Preta Granito, Suíte Água Branca), hornblenda-sienogranitos do tipo A (Sienogranito Canoas da Suíte Mapuera), rochas vulcânicas ácidas à intermediárias (Grupo Iricoumé) e granitos rapakivi de idades entre 1883 a 1889 Ma (Granito São Gabriel da Suíte Mapuera), e rochas afins (quartzo-gabro-anortosito e diorito), além de quartzo-monzonito Castanhal, milonitos e hornfels. A fácies quartzo-diorito do granito Terra Preta foi formada por processos de mistura entre um dique quartzo-gabro sinplutônico e um granodiorito hornblenda. Glóbulos parcialmente assimilados de sienogranitos hornblenda Canoas e seus contatos com o granodiorito hornblenda Terra Preta sugerem que o sienogranito Canoas é um pouco mais jovem do que o Granito Terra Preta. Xenólitos do sienogranito Canoas no interior do Granito São Gabriel mostram que o granito é mais jovem do que o sienogranito Canoas. Novas evidências geológicas e petrográficas avançam na compreensão petrológica destas rochas e sugerem que, além de cristalização fracionada, assimilação e mistura de magma, desempenharam um papel importante, pelo menos em escala local, na evolução e variação composicionais dos plutons. Tal evidência é encontrada no Granito Terra Preta misturado com materiais quartzo-diorito, félsico associado ao sienogranito Canoas e nos enclaves microgranulares intermediários, que apresentam biotita e hornblenda primárias, além de dissolução plagioclásio, corrosão de feldspatos, mantos feldspatos alcalinos, segunda geração de apatita, e elevados teores xenocristais em enclaves intermediários formados a partir da fragmentação de intrusões máficas. Análises petrográficas mostram que um evento deformacional registrado na parte Ocidental da área de estudo (com deformação progressiva de E para W) é estimado entre o magmatismo pós-colisional de 1,90 Ga e as invasões do Granito São Gabriel e rochas afins máficas/intermediárias (intraplaca). No entanto, torna-se extremamente necessário obter idades absolutas para este evento metamórfico.
Palavras-chave: dados de campo; petrografia; granitoides dos tipos I e A; litoestratigrafia; NE do Estado do Amazonas.
1Geosciences Institute, Federal University of Roraima, Boa Vista (RR), Brazil. E-mail: [email protected] of Isotope Geology, Geosciences Institute, Federal University of Pará, Belém (PA), Brazil. E-mail: [email protected] Institute, University of Brasília, Brasília (DF), Brazil. E-mail: [email protected]*Corresponding author
Field and petrographic data of 1.90 to 1.88 Ga I- and A-type granitoids from the central region of the Amazonian Craton,
NE Amazonas State, Brazil
Cristóvão da Silva Valério1*, Moacir José Buenano Macambira2, Valmir da Silva Souza3
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INTRODUCTION The igneous associations in the northeastern Amazonas State, southern Uatumã-Anauá domain, are generically included in regional units based on limited knowledge of their field re-lationships and petrography. Recently, new outcrops of granitoids and related rocks, in addition to gran-itoids that recorded subsolidus deformation, were found. These rocks and their contact relationships re-vealed important information that allowed updating the lithostratigraphy of the southern Uatumã-Anauá domain. Moreover, detailed field and petrographic studies showed the first insights on the dynamic pro-cesses involved in the generation of the granitoid fa-cies, and a new tectonic interpretation based on mi-cro-deformational analysis was proposed.
In spite of modern methodologies advance, classic methods still supply enough information for understanding of the geology of remote areas. These methods are fundamental in areas in which the geo-logical history is poorly understood, such as in the central Amazonian craton.
The objectives of this study were: present-ing an integrated geological map, proposing a new lithostratigraphy for rocks of the southern region of the Uatumã-Anauá domain, discussing petrological and deformational features, and summarizing new data on the field of relationships and petrography of the 1.90 to 1.88 Ga I- and A-type granitoids and relat-ed rocks from the south portion of the Uatumã-Anauá domain in the central Amazonian craton, Brazil.
GEOLOGICAL SETTING Tassinari & Macambira (1999 and 2004) and Tassinari et al. (2000) subdivided the Amazonian Craton into Central Amazon (> 2.3 Ga), Maroni-Itacaiunas (2.2 – 1.95 Ga), Ventuari-Tapajós (1.95 – 1.8 Ga), Rio Negro-Juruena (1.8 – 1.55 Ga), Rondoniana-San Ignácio (1.5 – 1.3 Ga), and Sunsás (1.25 – 1.0 Ga) geotectonic provinces (Fig. 1A). Based on this mod-el, this study was carried out in the central portion of the Ventuari-Tapajós Province, central Amazonian Craton, in the Uatumã-Anauá domain (CPRM 2006, Almeida 2006, Almeida et al. 2008).
The Uatumã-Anauá domain has rocks from the entire Orosirian period, mainly composed of igneous units, in addition to Paleoproterozoic and Phanerozoic sedimentary cover that filled the Amazonas basin, as seen in Fig. 1B (CPRM 2000 & 2006, Faria et al. 2003, Ferron 2006, Valério 2006, Almeida 2006). Early regional mapping carried out
in this region identified several felsic and mafic igne-ous rocks (Santos et al. 1974, Araújo Neto & Moreira 1976, Veiga Jr. et al. 1979, Costi et al. 1984). Later studies have focused on the petrography, geochemis-try, and geochronology of felsic to intermediate gran-itoids and volcanic rocks (Valério et al. 2005, 2006 A & B 2009, & 2010, Souza et al. 2006, Marques et al. 2007, Souza et al. 2007, Freitas et al. 2007, Souza & Nogueira 2009, Costi et al. 2009).
The country rock of the Uatumã-Anauá do-main consists of tonalite-trondhjemite-granodio-rite (TTG)-like calc-alkaline meta-granitoids of the Anauá Complex (2.03 Ga) in association with meta-volcanic sedimentary rocks of the Uai-Uai Group (1.97 Ga?), both representing volcanic arc and back-arc basin settings (Faria et al. 2002 & 2003). According to Almeida (2006) and Almeida & Macambira (2007), the Anauá basement was intruded by S- (Serra Dourada, 1.96 Ga) and I-types (Matins Pereira, 1.97 Ga), and calc-alkaline granitoids in a collisional setting.
The youngest igneous rocks of the Uatumã-Anauá domain are 1.89 to 1.90 Ga I-type, high-K calc-alkaline granitoids of the Água Branca Suite, felsic to intermediate volcanic rocks of the Iricoumé Group, A-type granites of the Mapuera Suite (1.87 to 1.89 Ga, Abonari and São Gabriel granites), and re-lated rocks (quartz-gabbro, diorite and minor anor-thosite), in addition to quartz-monzonites, mylonites and hornfels (Valério et al. 2009 & 2010 and Costi et al. 2009). According to Santos et al. (2001 and 2006), the Mapuera granites are also associated with 1.87 Ga charnockites. After the first generation of the Mapuera A-type granites and a gap of ca. 60 Ma, a second generation of tin-bearing, A-type, anorogen-ic granites (1.81 Ga) of the Madeira Suite intruded in the Pitinga region (Costi et al. 2000). These latter have a similar age to the Moderna Granite in north-ernmost Brazil (Santos et al. 1997). In addition to the youngest units, metagranites, metamafics and gneiss in the southern portion of the Guyana Shield have been grouped into Jauaperi complex (CPRM 2006).
IGNEOUS ASSOCIATIONS The study area con-sists of I-type, high-K calc-alkaline granitoids of the Terra Preta Granite (Água Branca Suite), volca-nic and pyroclastic rocks (Iricoumé Group), A-type hornblende-bearing syenogranites of the Canoas Syenogranite (Mapuera Suite), rapakivi granites of the São Gabriel Granite (Mapuera Suite), and
1.90 to 1.88 Ga I- and A-type granitoids from NE Amazonas State
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Solimões BasinAmazon Basin
Atlantic Ocean
500 kmFigura 1b
Neoproterozoic mobile beltSunsás (1.25-1.0 Ga)Rondonian-San Ignácio (1.5-1.3 Ga)Rio Negro-Juruen (1.80-1.55 Ga)
Ventuari-Tapajós (1.95-1.80 Ga)Maroni-Itacaiunas (2.2-1.95 Ga)Central Amazonian (.2.5 Ga)
Undated mafic
Cenozoic deposit
Alter do Chão Formation
Trombetas Group
BR-174 roadLineamentsPitinga Sn Province
Fig. 2
Prosperança Formation
Seringa Formation (1.18 Ga) continental flood basalts
Quarentena Ilhas Formation (1.79 Ga) Continental flood basalts
Urupi Formation (1.79-1.90 Ga)sedimentary and volcaniclastic rocks
Madeira Suite (1.79-1.82 Ga)A-type granites
Iricoumé volcanics (1.86-1.88 Ga)rhyolitic-andestic lava and mass flows deposits
Jauaperi Complex1.89-1.90 Ga? metagranitoidsÁgua Branca Suite (1.89-1.90 Ga)I-type high-K calk-alkaline granitoids
Phanerozoic
Neoproterozoic
Mesoproterozoic
Paleoproterozoic
A
B
Figure 1 – (A) Tectonic provinces of the Amazonian Craton (Tassinari and Macambira 1999, modified by Macambira et al. 2009); (B) simplified geological map of the central Amazonian Craton, NE Amazonas State (modified from CPRM 2006, Ferron et al. 2006, and Valério et al. 2006b and 2009).
Castanhal quartz-monzonite. The area also includes mafic dikes associated with granitoids, younger mafic
stocks and dikes likely belonging to the Seringa and/or Quarenta Ilhas formations. Some of the granitoids
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display features of dynamo-static crystallization and static re-crystallization (thermal metamorphism), probably linked to shear zones and mafic intrusions, which have not yet been well characterized (Fig. 2).
Terra Preta Granite The size and shape of the Terra Preta Granite remain undefined due to rework-ing of its western and southern borders caused by a poorly defined deformational event, and the cover of the Amazon basin. Its compositional variation con-sists on quartz-diorite (mingled), hornblende monzo-diorite, hornblende tonalite, hornblende granodiorite, biotite-hornblende granodiorite, hornblende mon-zogranite, biotite-hornblende monzogranite, biotite monzogranite, and biotite syenogranite.
Terra Preta Granite hosts aplite, mafic and in-termediate dikes, and enclaves. The contacts of the aplite dikes with the wall rock are sharp and have no chilled borders. The granite has two types of en-claves: volcanic xenoliths and mafic and intermedi-ate microgranular enclaves. The xenoliths of glome-roporphyritic andesite have sub-rounded shapes and their contacts with the wall rock are abrupt, irregular and lack chilled borders. The mafic enclaves are cir-cular to ellipsoidal, with 5 to 40 cm in diameter or length and display a mesocratic color-index, irregular transitional contacts and a high content of wall rock crystals (feldspars and quartz xenocrysts). Another important feature is a NE-striking gabbro dike that intruded into the contact between the Terra Preta
Granite and Canoas Syenogranite (Fig. 3A). Radar imagery shows that the southern part of the dike was inflected to strike NW-SE. The contact of the dike with the Terra Preta hornblende granodiorite is char-acterized by the formation of a transitional zone con-taining features of magma mingling (Fig. 3B), as well as dike fragmentation and formation of sub-angular to rounded microgranular enclaves and a mingled rock (quartz-diorite), as observed in Fig. 3C. Such aspects indicate a synplutonic dike that was partially fragmented and that physically and chemically inter-acted with the granodioritic magma before complete-ly chilling.
Iricoumé Group The rocks of the Iricoumé Group include pyroclastic flows (eutaxitic ignim-brite, ignimbrite, and co-ignimbrite), lava flow (an-desite/traquiandesite and rhyolite/rhyodacite) de-posits, and intrusions of autoclastic breccias. The lithostratigraphic sequence shows alternations of lava flow deposits above fiamme-rich ignimbrites, followed by ignimbrites and co-ignimbrites.
The basis of the mass flow deposits is formed by ignimbrites with highly flattened pumices (fi-ammes), and crystal and lithic fragments character-ized by eutaxitic textures. Its origin, at least in the ignimbrites, was the welding compaction of pumice clasts (Bull & McPhie 2007). The ignimbrites/co-ignimbrites display fragmentary textures and a fine matrix, layers with gradational fining upward cycles
Nhamundá FormationProsperança FormationGabbo-diorite±anorthositeMuscovite-actinolite hornfels,Actionlite hornfels
Mafic dike
Hornblend±biotiteHornblende monzogranite
Hornblend quartz-monzonite
Hornblend-bearing syenogranite, horn-bearing alkai feldspar granite
Piroclastic flow depositLava flow deposit
Biotite syenograniteBiotite monzograniteBiotite-hornblende monzograniteMingled quartz-dioriteHornbçende granodioriteHornblende tonaliteHornblende quartz-monzodiorite
BR-174 roadacess dirty roadPermanent drainageFault (zones)
São Gabriel Granite1883-1889 Ma, low-quartz rapakivi granite mapuera Suite (A-type)
Castanhal quartz-monzoniteMapuera Suite
Canoas Syenogranite (A-type)Mapuera Suite
Terra Preta Granite1890-1898 Ma high-K calc-alkalineÁgua Branca (I-type
Iricoumé volcanics (~1.88 Ga)
Lithostraigraphy
Mafic dike
Mafic dike
Figure 2 – Geological map of the southwestern Presidente Figueiredo district, NE Amazonas State, central Amazonian Craton. The boundaries of the granitoid and volcanic facies and main fault zones have been estimated from the integration of field data, SAR/SIPAM remote sensing products, and airborne geophysical data.
1.90 to 1.88 Ga I- and A-type granitoids from NE Amazonas State
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containing ≤ 20 cm ejected fragments (bombs), and gas escape-related vesicular cavities between the lay-er boundaries.
The andesites/traquiandesites display several amygdaloidal cavities related to gas release. The pres-ence of autoclastic breccias suggests an emplacement similar to cauldron collapse. The breccias have a rhyo-lite-rhyodacite matrix and are composed of highly var-ied rock fragments of andesite, rhyolite, and pumice.
Canoas Syenogranite The Canoas Syenogranite consists of a group of ellipsoidal NW-SE stocks with 5 to 15 km length, mainly composed of red-dish syenogranite and minor alkali feldspar-gran-ite (Fig. 2). It has two types of contacts with the Terra Preta Granite. The intrusions measuring less than 5 km in diameter generated outward and in-ward aureoles. The outward aureole is characterized by a thick alteration zone (> 1 m) marked by a color change likely caused by low temperature of aqueous fluids. The narrow inward aureole (< 20 cm) is char-acterized by increasing grain size and quartz con-tent, and it is likely recrystallized. The fine-grained stock borders reflect rapid heat loss to the wall rock that characterizes chilled borders. The contact be-tween a large stock (> 15 km length) and the wall rock (Terra Preta hornblende granodiorite) is in-terdigited, and chilled borders were not observed. The presence of rounded globules of syenogranite assimilated by granodioritic magma and the con-tact type suggest physical interaction between both magmas before complete crystallization. Therefore, it is plausible that the Canoas Syenogranite is slight-ly younger than the Terra Preta Granite. The maf-ic enclaves of the Canoas Syenogranite are circu-lar, with part of their ellipsoidal shape preserved, and the contacts with the wall rock are irregular and show strong assimilation.
Quartz-gabbro dikes oriented WNW-ESE/70ºSW are the main features that indicate mag-ma mingling processes. The features include fractur-ing and fragmentation of the dike borders (8 to 15 cm angular and < 5 cm rounded fragments), with the formation of mingled material among the maf-ic fragments. The irregular and interdigited contact with the wall rock is marked by a narrow transition-al zone (~ 5 cm) containing < 1 cm rounded mafic enclaves (Fig. 3D). The contact presents evidence of thermal contrast and interaction between the dike and the wall rock, whereas the small rounded enclaves
reveal extensive interaction between both felsic and mafic systems.
São Gabriel Granite Rapakivi-type hornblende monzogranite, hornblende syenogranite, and bio-tite-hornblende syenogranite are the major petro-graphic variations observed in São Gabriel Granite. Microgranite porphyry and microdiorite occur infre-quently as dikes near the boundaries of the batholith.
The São Gabriel Granite is an irregular, NW-SE striking, sub-ellipsoidal-shaped pluton (Fig. 2). Its main field features include volcanic, granitic and mafic enclaves, in addition to mafic and intermediate dikes. The volcanic xenoliths are sub-rounded and present dacitic compositions. The borders of the en-claves are irregular, sharp, and composed of imbri-cated quartz and feldspars crystals. The eastern and southeastern borders of the granite are characterized by sub-angular xenoliths of recrystallized alkali feld-spar-rich syenogranites (muscovite-actinolite horn-fels), likely from the Canoas Syenogranite, whose contacts with the wall rock vary from straight and abrupt to irregular ones (Fig. 3E).
The presence of these xenoliths demonstrates that the Canoas stocks are slightly older than the São Gabriel Granite. The textural dissimilarity between the preserved Canoas plutons (granoblastic) and the sub-angular xenoliths (granolepidoblastic) suggests that these fragments, which are partially assimilat-ed by São Gabriel magma, preserved the effects of a dynamo-thermal deformation event, which was fol-lowed by a mafic intrusion-related thermal event. Alternatively, the foliation of xenoliths could have been caused by the increasing turbulent flux close to the borders of the São Gabriel magma chamber.
The contact between the biotite-hornblende syenogranite and the microgranite porphyry is clear (Fig. 3F). In general, the São Gabriel mafic enclaves are sub-rounded and include high contents of xeno-crystals from the host rock. Along the granite pluton boundaries, they are stretched according to the igne-ous foliation. Mafic dikes that fill fractures in the São Gabriel Granite do not have features that support a genetic correlation. However, the intermediate dikes were frequently linked to all petrographic types.
Mafic and intermediate intrusions The dikes and stocks of the gabbros, diorites and anorthosites are associated with each other according to geograph-ic criteria and petrographic similarities (segregation
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and fractionation) as it was elsewhere observed (Campbell 1996). In the field, the intrusions did not display clear relationships with the wall rocks, and
the outcrops are restricted to blocks and flagstones located along tracks and small creeks. The rocks are often very weathered.
Figure 3 – Field features of the Terra Preta, Canoas and São Gabriel granitoids and related rocks. (A) Quartz-gabbro dike emplacement into the contact zone between Terra Preta hornblende granodiorite and Canoas syenogranite; (B) zone of transitional contact between a quartz-gabbro dike and Terra Preta hornblende granodiorite, showing fragmentation and mingling of the dike, and subangular to rounded mafic enclaves without visible xenocrystals (dropped crystals); (C) Terra Preta mingled quartz-diorite with variable feldspar xenocrystals; (D) contact between a mafic dike and wallrock (muscovite-actinolite hornfels). Arrows show the formation of mingled material among the incompletely crystallized mafic fragments and a narrow (~ 5 cm) transitional zone. (E) Sub-angular xenoliths of recrystallized syenogranite (muscovite-actinolite hornfels) of Canoas Syenogranite inside São Gabriel Granite; (F) regular contact between biotite-hornblende syenogranite and microgranite porphyry dike.
A
C
E
B
D
F
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PETROGRAPHY Material and methods The petrographic analy-sis consisted on the microscopic characterization of 165 polished thin sections that represent the composi-tional variations and geographical distribution of the rocks from the study area. The classification of granit-oid varieties and enclaves, totalizing 62 samples, was based on the modal parameters obtained by count-ing 1,500 points for medium- and fine-grained rocks and 1,800 for coarse-grained types. The composition of plagioclase zones was obtained from the Michel-Lèvy conventional method and, when possible, from the 010 cleavage-Albite Law twining and Albite Law-Carlsbad twining methods (variations of the Michel-Lèvy method), as described by Hibbard (1995).
Terra Preta Granite According to their mineral-ogical compositions, the main facies observed in the Terra Preta Granite are hornblende monzodiorite, horn-blende tonalite, hornblende granodiorite, hornblende-biotite granodiorite, hornblende monzogranite, horn-blende-biotite monzogranite, and biotite syenogranite, besides the mingled quartz-diorite (Tab. 1, Fig. 4A). The main texture is seriate but it varies to porphyritic, fine-grained equigranular and, locally, to granophyric.
Two types of plagioclase, both euhedral, were identified. Plagioclase-1 measures 1.5 to 4.0 mm and varies from An22–21 in the core to An25–22 in the rims. Progressive oscillatory zoning is common, whereas sudden oscillatory zoning is rare. Apatite and zircon inclusions are common in the core and rims, where-as Fe-Ti oxides inclusions only happen in the rims. Plagioclase-2 (< 0.5 mm) is usually zoned, and its composition varies from An28 in the core to An22–25 in
the rim. In both types, the contacts with all other min-erals are straight (Tab. 2).
Three types of quartz were identified. Quartz-1 is sub-hedral – anhedral (≤ 1 mm) and has opaque ti-tanite and hornblende inclusions. Quartz-2 is associ-ated with alkali feldspar-2 to form magmatic grano-phyric textures in the granodiorites. Quartz-3 is a hydrothermal phase that was precipitated on the al-kali feldspar-1.
Three types of alkali feldspar were identified: alkali feldspar-1 is euhedral and measures from 2 to 8 mm in length. Film-, strings- and interlocking-type perthites are common. In the monzogranite, the insular perthite surrounds perthitic alkali feldspar, whereas the albite chessboard is developed in the syenogranites. A second-generation of perthite (flames-type) is linked
to subsequent deformation processes. In the contacts with alkali feldspar, it developed a swapped rim struc-ture related to albite intergranular migration caused by Na-K exchange (Smith & Brown 1988). Alkali feld-spar-2 represents those portions of the granophyric textures of the granodiorites. The anhedral alkali feld-spar-3 (0.5 – 2.0 mm) has planar contacts with quartz 1 and -2 and interpenetrative contacts with quartz 3. Interlocking and flame perthites are frequent, whereas the beads-type one occurs locally. Apatite and zircon inclusions are common in this mineral. In the porphyry portion of the granodiorite, alkali feldspar-3 exhibits strings, veins, microfilms and recrystallization-linked flame perthites.
The hornblende is euhedral and sub-hedral and displays planar contacts with the quartz and al-kali feldspar and interpenetrative contacts with the ti-tanite. Fe-Ti oxides, zircon and apatite inclusions are very common. In the alkali feldspar-poor petrograph-ic types, hornblende also occurs as a product of an early reaction between the liquidus and clinopyrox-enes, forming clinopyroxene pseudomorphs.
Sub-hedral biotite-1 has hornblende, Fe-Ti ox-ides and titanite inclusions, while biotite-2 occurs as anhedral interstitial crystals associated with titanite.
The Fe-Ti oxides occur both associated with varietal minerals and as inclusions. The titanite is euhedral and is commonly associated with varietals. The apatite needles are euhedral–sub-hedral and measure < 0.1 mm. In the granodiorites, apatite crys-tals grew up to 2 mm (type-2 apatite). The zircons are euhedral–sub-hedral and zoned, and they always happen in association with apatite.
The epidote is originated from more calcic portions of plagioclase and hornblende. The seric-ite-muscovite and argilic minerals commonly occur on alkali feldspar and less commonly on plagioclase. The intergranular albite and individual crystals are associated with exsolution of the sodic phase from alkali feldspar to form perthites. The actinolite ap-pears as individual crystals and rims of hornblende and clinopyroxene pseudomorphs.
MAFIC DIKES AND ENCLAVES The gab-bro dikes and related mafic enclaves (sub-angular) possess intergranular textures and high clinopyrox-ene pseudomorph contents. Despite being intensely decalcified, some measurements of plagioclase re-vealed calcic andesine compositions (An41–48). The sub-hedral calcic andesine contains inclusions of
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.942
.353
.546
.946
.240
.146
.339
.348
.940
.7Pl
agio
clas
e9.
014
.018
.118
.58.
04.
117
.36.
62.
07.
13.
0A
mph
ibol
e 2.
02.
01.
02.
12.
03.
10.
00.
51.
91.
20.
3B
iotit
e0.
00.
00.
00.
00.
00.
00.
00.
00.
00.
40.
3O
paqu
es1.
02.
02.
02.
11.
00.
10.
50.
01.
33.
50.
5Ti
tani
te
1.0
1.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
Apa
tite
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Zirc
on
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Mos
covi
te0.
00.
00.
00.
00.
00.
00.
01.
01.
01.
01.
5Fe
lsic
95.8
94.8
96.8
95.7
96.8
96.5
97.4
98.3
95.6
93.7
97.2
Mafi
c3.
04.
03.
04.
13.
03.
20.
50.
53.
25.
11.
1
Tabl
e 1
– M
odal
com
posi
tion
of st
udie
d gr
anito
ids.
The
amph
ibol
e an
d m
usco
vite
from
stat
ical
ly re
crys
talli
zed
rock
s are
met
amor
phic
min
eral
sA
ssoc
iatio
nTE
RR
A P
RET
A G
RA
NIT
EFa
cies
mQ
Dm
QD
mQ
D H
QM
DH
QM
DH
QM
DH
TH
GH
GH
GH
G(p
)H
GH
GB
HG
(f)
HM
BH
MB
HM
HB
M(f
)B
MB
MB
MB
M(f
)B
M(f
g)B
SB
SB
SB
SB
SS(
f)S(
fg)
Sam
ples
CC
-13
9HCC
-49
HCC
-14
3HCC
-13
2aCC
-13
2bCC
-65
CC-1
7CC
-14
C-38
04CC
-16
CC-4
7C-
6504
CC-5
0C-
6304
C-40
04C-
1504
CC-6
4C-
3504
C-09
04a
C-21
04b
C-21
04a
C-29
04C-
1804
C-08
04V
S-08
bV
S-08
aC-
0404
bC-
5004
C-04
04a
C-05
04
Qua
rtz
7.9
9.3
7,1
12,1
14,4
11.5
13.7
25.7
22.5
22.4
20.5
21.5
37.5
24.0
26.3
28.8
34.6
45.9
29.1
29.9
32.9
37.3
26.2
28.2
33.6
24.4
28.2
22,2
31.9
37,5
Alk
ali f
elds
par
0.1
0.8
0,5
15,0
17,3
21.6
1.0
22.3
16.4
7.4
22.9
15.7
13.7
17.7
23.9
31.7
39.9
21.9
35.3
35.9
35.0
25.9
44.4
45.4
48.9
47.7
43.3
60,5
48.9
21,0
Plag
iocl
ase
59.5
36.9
31,9
54,0
54,7
42.4
38.0
43.3
39.7
53.7
50.5
43.7
33.1
49.0
34.1
28.8
18.9
10.5
24.9
27.9
24.7
27.0
22.2
16.1
16.3
17.7
18.1
11,1
15.0
37,7
Pyro
xene
0.
40.
00,
30,
00,
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00.
00,
00.
00,
0A
mph
ibol
e 31
.652
.659
,617
,312
,122
.246
.98.
419
.415
.65.
415
.412
.54.
714
.03.
83.
12.
20.
00.
00.
00.
00.
00.
00.
00.
00.
00,
00.
00,
2B
iotit
e0.
00.
00,
00,
00,
10.
00.
00.
00.
60.
00.
20.
40.
82.
10.
02.
92.
111
.56.
24.
05.
19.
35.
08.
10.
07.
86.
03,
00.
01,
0O
paqu
es0.
10.
10,
30,
11,
11.
60.
10.
20.
50.
30.
31.
60.
91.
51.
21.
90.
17.
72.
11.
01.
00.
11.
00.
10.
10.
10.
11,
00.
12,
2Ti
tani
te
0.1
0.1
0,1
1,3
0,1
0.6
0.1
0.0
0.7
0.4
0.1
1.4
0.8
0.9
0.3
1.9
1.0
0.1
2.1
1.0
1.0
0.1
1.0
0.1
0.1
0.1
0.1
2,0
0.1
0,2
Apa
tite
0.1
0.1
0,1
0,1
0,1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.6
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0,1
0.1
0,1
Zirc
on
0.1
0.1
0,1
0,1
0,1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0,1
0.1
0,1
Alla
nite
0.0
0.0
0,0
0,0
0,0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0,0
0.0
0,0
Fels
ic67
.647
.039
,581
,186
,475
.452
.791
.278
.683
.593
.881
.084
.390
.684
.389
.393
.478
.389
.493
.892
.690
.292
.789
.798
.889
.889
.793
,895
.896
,2M
afic
32.1
52.7
59,9
17,3
12,2
23.8
47.3
8.6
20.5
15.9
5.9
17.4
14.2
8.3
15.2
8.6
5.4
21.4
8.3
5.0
6.2
9.4
6.0
8.2
0.1
7.9
6.1
3,0
0.1
1,2
Ass
ocia
tion
SÃO
GA
BR
IEL
GR
AN
ITE
Faci
esH
MH
M(s
r)H
MH
MH
M(f
)H
MH
MH
MH
BM
HS(
sr)
HS(
sr)
HS
HS(
f)H
SH
BS
HB
SH
BS
BS(
f)Sa
mpl
es
CC
-46
CC
-83
CC
-95
CC
-01
CC
-80
CC
-55
CC
-02
C-4
404
CC
-61
CC
-86
CC
-88
CC
-45
CC
-72
C-1
704
C-5
204
C-5
104
C-5
404
C-2
004
Qua
rtz
27.5
41.0
31.9
19.4
27.6
29.3
21.8
18.5
20.9
37.5
48.1
18.3
31.2
21.6
26.7
32.3
34.6
52.8
Alk
ali f
elds
par
23.6
16.9
26.5
33.5
30.0
26.7
22.4
27.1
25.7
38.1
33.1
58.9
47.8
60.2
39.0
47.0
48.8
35.9
Plag
iocl
ase
44.6
32.5
29.8
31.2
30.0
36.9
35.1
31.8
44.8
18.8
14.2
14.4
16.7
10.9
28.0
15.7
12.0
9.0
Am
phib
ole
1.9
5.9
6.0
12.1
9.7
5.8
19.2
17.9
2.5
4.0
3.3
5.1
2.3
3.8
2.8
2.1
1.7
0.5
Bio
tite
0.4
1.5
0.7
0.0
0.0
0.4
0.0
1.3
2.7
0.0
0.3
1.2
0.3
1.3
3.1
2.6
2.5
1.5
Opa
ques
1.5
0.3
2.4
3.6
2.2
0.3
1.2
3.2
1.2
0.6
0.5
1.5
1.4
1.9
0.1
0.1
0.1
0.1
Tita
nite
0.
30.
82.
50.
00.
20.
50.
00.
01.
80.
80.
30.
20.
00.
10.
10.
10.
10.
1A
patit
e 0.
11.
00.
10.
10.
10.
10.
10.
10.
10.
10.
10.
20.
10.
10.
10.
10.
10.
1Zi
rcon
0.
10.
10.
10.
10.
10.
10.
10.
10.
20.
10.
10.
20.
10.
10.
10.
10.
10.
1A
llani
te0.
00.
00.
00.
00.
00.
00.
00.
00.
10.
00.
00.
00.
00.
00.
00.
00.
00.
0Fe
lsic
95.7
90.4
88.2
84.1
87.7
92.8
79.4
77.4
91.4
94.4
95.4
91.6
95.8
92.7
93.7
94.9
95.4
97.6
Mafi
c3.
87.
79.
115
.711
.96.
520
.422
.46.
44.
64.
17.
84.
07.
06.
04.
84.
32.
1
QD
: qua
rtz-d
iorit
e; Q
MD
: qua
rtz-m
onzo
dior
ite; T
: ton
alite
; G: g
rano
dior
ite; M
: mon
zogr
anite
; S: s
yeno
gran
ite; A
FG: a
lkal
i-fel
dspa
r gr
anite
; H: h
ornb
lend
e; B
: bio
tite;
f: f
olia
ted;
fg:
fine
-gra
ined
; g:
gra
noph
iric;
p: p
orph
yriti
c; sr
: sta
tic re
-cry
stal
lizat
ion;
m: m
ingl
ed
1.90 to 1.88 Ga I- and A-type granitoids from NE Amazonas State
698 Revista Brasileira de Geociências, volume 42(4), 2012
Fe-Ti oxides and displays interpenetrative contacts with hornblende. Actinolite and chlorite are the prod-ucts for the substitution of clinopyroxene and horn-blende, respectively. They are usually fibrous and include Fe-Ti oxide inclusions when altered to bio-tite (Tab. 3). The dikes have rounded clasts filled by fine-grained tremolite-actinolite and subordinate pla-gioclase. Their rims are formed by fibrous crystals (≤ 1 mm) of tremolite-actinolite that display sutured contacts with the host rock (Fig. 5A). The absence of inclusions, granulation, and contact type suggest that the mineral clasts are a late crystallized vesicular
phase filled by secondary minerals (amygdales), sug-gesting near-surface chilling.
MINGLED QUARTZ-DIORITE AND RELATED EN-CLAVES The mingled quartz-diorite displays intergranular textures and a mineralogical assemblage formed by poikilitic crystals of quartz and alkali feld-spar (string and flames perthites), xenocrystals of quartz, plagioclase and alkali feldspar, plagioclase, hornblende, high titanite content Fe-Ti oxides, apatite, zircon, and actinolite. The poikilitic crystals include hornblende, plagioclase, and titanite inclusions. All xenocrystals from the wallrock exhibit re-absorption/re-equilibrium features (engulfing, corroded core and patchy zones) (Fig. 5B). The preserved mafic phase possesses two types of plagioclase, both of which are intensely altered. The 1-type (from 2 to 3 mm) has a euhedral habit and oscillatory zoning with preserved sodic rims. It contains Fe-Ti oxides, apatite and zircon inclusions in the core and hornblende in the rims, andsharp contacts with oth-er minerals except hornblende, which have interpenetra-tive contacts. Plagioclase-2 is sub-hedral (< 1 mm) and is frequently associated with hornblende. Hornblende-1 is euhedral–sub-hedral with Fe-Ti oxides and titanite in-clusions. This hornblende has interpenetrative contacts with plagioclase-1 and straight contacts with quartz and alkali feldspar. Hornblende-2, quartz and alkali feldspar are interstitials. Two types of apatite were also identified: a long/narrow (20:1) and a short/wide (5:1).
Iricoumé GroupPYROCLASTIC FLOW DEPOSITS Lithic frag-ments and bent fiamme lenses make up the eutaxitic or fiamme-rich ignimbrite. The lithic clasts are angu-lar and very fragmented. The fiammes show wrinkled rims and are locally smooth. The ash matrix has an accentuated orientation and high degree of welding by compaction. The ignimbrite exhibits a microlith-ic texture and strong mineral foliation or orientation from pyroclastic flow. The ignimbrite is composed of fragments of quartz, alkali feldspar, plagioclase, bi-otite and Fe-Ti oxides, pumice fragments, and fine-grained ash matrix. The co-ignimbrite consists of similar proportions of clasts of quartz, alkali feldspar, plagioclase and opaques, as well as ash matrix.
LAVA FLOW DEPOSITS The andesite has a glomeroporphyritic amygdaloidal texture and consists of phenocrystals of quartz, calcic oligoclase (An22–25), pyroxene and hornblende in a trachytic matrix, with
A Q60
20
5A 10 35 65 90 P
mingled rockmicrogranularenclave
qz-monzodiorite
monzo-granitemonzo-diorite
syen
ogra
nite
Tonalite
qz-diorite
QTerra Preta Granite
10 35 65 90 P
B Canoas Syenogranite
muscovite-actinolitehornfels
qz-richgranitoid
monzo-granite
syeno-granite
alkali
feld
spar
gran
ite
60
Q
20
5
A
20
5
rapakivi-typeSão Gabriel Granite QQ
10 35 65 90 P
monzo-granite
monzo-diorite
actinolite hornfels
syen
ogra
nite
C
A
60
Figure 4 – QAP modal composition of the studied plutons (Streckeisen 1976). Granitic series according to Lameyre and Bowden (1982). (A–C) calc-alkaline granodioritic subseries (A – Corsica, Sardinia; B – Chile, C – Peru). The dashed field corresponds to granites generated from crustal melting, according to Lameyre & Bowden (1982).
Cristóvão da Silva Valério et al.
Revista Brasileira de Geociências, volume 42(4), 2012 699
Plut
on, U
nit
Terr
a Pr
eta
Gra
nite
, Águ
a Br
anca
Sui
teC
anoa
s Sye
nogr
anite
, Map
uera
Sui
teSã
o G
abrie
l Gra
nite
, Map
uera
Sui
te
Petro
grap
hic
varia
tion
(Hor
nble
nde)
quar
tz-d
iorit
e, m
onzo
dior
ite,
tona
lite,
gra
nodi
orite
, and
(bio
tite)
mon
zogr
anite
an
d -s
yeno
gran
ite.
Hor
nble
nde-
bear
ing
syen
ogra
nite
and
alk
ali
feld
spar
gra
nite
.H
ornb
lend
e m
onzo
gran
ite, h
ornb
lend
e sy
enog
rani
te, b
iotit
e-ho
rnbl
ende
syen
ogra
nite
.
Text
ural
var
iatio
n Th
e se
riate
text
ure
varie
s to
porp
hyrit
ic, fi
ne-
grai
ned
equi
gran
ular
and
loca
lized
gra
noph
yric
te
xtur
es.
Med
ium
- to
fine-
grai
ned
seria
te te
xtur
e.M
ediu
m- t
o co
arse
-gra
ined
seria
te te
xtur
e.
Esse
ntia
l min
eral
s
Plag
iocl
ase-
1
Leng
th 1
.5–4
.0 m
m, c
alci
c ol
igoc
lase
(An 22
–21 i
n co
re),
(An 25
–22 i
n rim
s), p
rogr
essi
ve o
scill
ator
y zo
ning
, apa
tite
and
zirc
on in
clus
ions
are
co
mm
on in
cor
e an
d rim
s, Fe
-Ti o
xide
s in
clus
ions
onl
y in
rim
s, co
ntac
ts w
ith a
ll ot
hers
m
iner
als a
re re
ctili
near
.
Euhe
dral
, 0.5
–3.0
mm
, unz
onin
g, so
dic
olig
ocla
se (A
n 10-1
2), tw
inin
g A
lbite
and
Alb
ite-
Car
lsba
d La
ws.
Its c
onta
ct w
ith th
e al
kali
feld
spar
and
qua
rtz is
rect
iline
ar a
nd w
ith
horn
blen
de is
inte
rdig
ited.
Euhe
dral
(2–6
.5 m
m),
An 22
–An 28
in c
ore,
An 22
–17 in
rim
s, co
ntac
t is
rect
iline
ar w
ith th
e ho
rnbl
ende
-1 a
nd in
terp
enet
rativ
e w
ith th
e qu
artz
-1, c
onta
ins h
ornb
lend
e-Fe
-Ti o
xide
s, ap
atite
and
zirc
on
incl
usio
ns. T
win
ning
Alb
ite a
nd A
lbite
-Car
lsba
d La
ws a
nd m
ajor
no
rmal
zon
ings
, and
abr
upt a
nd se
ctor
ed o
scill
ator
y zo
ning
s.
Plag
iocl
ase-
2<
0.5
mm
, ind
efini
te z
onin
g, A
n 28 in
cor
e an
d A
n 22–2
5 in
rim
s, co
ntac
ts w
ith a
ll ot
hers
min
eral
s ar
e re
ctili
near
.ab
sent
pha
se
0.5–
1.5
mm
, anh
edra
l–su
bhed
ral,
abru
pt o
scill
ator
y zo
ning
. Occ
urs
fillin
g in
inte
rstic
es a
mon
g gr
ains
and
con
tain
s inc
lusi
ons o
f qua
rtz-1
an
d bi
otite
-2. A
n 27–2
5 in
core
and
An 21
–17 i
n rim
s, al
tera
tion
to e
pido
te
and
seric
ite in
cal
cic
zone
.
Alk
ali f
elds
par-1
Eued
ral,
leng
th 2
–8 m
m. F
ilm-,
strin
gs- a
nd
inte
rlock
ing-
type
per
thite
are
com
mon
. In
mon
zogr
anite
s, th
e in
sula
r per
thite
occ
urs
surr
ound
ing
perth
itic
alka
li fe
ldsp
ar, a
lbite
-ch
essb
oard
dev
elop
ed in
syen
ogra
nite
s. A
pe
rthite
seco
nd-g
ener
atio
n (fl
ames
-type
) is
linke
d to
subs
eque
nt d
efor
mat
ion
proc
esse
s. In
co
ntac
ts w
ith o
ther
s alk
ali f
elds
par d
evel
oped
sw
appe
d rim
s.
Subh
edra
l, st
rong
ly p
erth
itic
(stri
ngle
ts, s
tring
s, in
terlo
ckin
g an
d ch
essb
oard
alb
ite) w
ith
gene
ratio
n of
subh
edra
l cry
stal
s of a
lbite
. It
poss
esse
s sev
eral
pla
gioc
lase
incl
usio
ns a
nd it
s co
ntac
t with
the
plag
iocl
ase
and
quar
tz is
fain
tly
inte
rdig
ited.
Subh
edra
l, 2.
5–6.
0 m
m, c
omm
only
occ
urs a
ssoc
iate
d to
the
quar
tz-1
, lo
cal i
nter
lock
ing
and
bead
s per
thite
s, al
bite
inte
rgra
nula
r occ
ur,
corr
oded
rim
s for
m o
void
shap
e (r
apak
ivi t
extu
re).
Bot
h al
kali
feld
spar
pre
sent
Alb
ite-P
eric
line
Law
twin
ing,
slig
htly
tra
nsfo
rmed
to se
ricite
and
arg
ilic
min
eral
s, co
ntai
n pl
agio
clas
e-2,
ho
rnbl
ende
-1, z
ircon
and
apa
tite
as in
clus
ions
and
alb
ite m
icro
film
s an
d st
ring
perth
ite a
re v
ery
com
mon
.
Alk
ali f
elds
par-2
Ane
dral
, 0.5
–2.0
mm
, rec
tilin
ear c
onta
ct w
ith
the
quar
tz-1
and
-2 a
nd in
terp
enet
rativ
e w
ith th
e qu
artz
-3.
abse
nt p
hase
It is
subh
edra
l–an
hedr
al, m
easu
res 0
.5–2
.5 m
m.
Qua
rtz-1
Sube
dral
–ane
dral
(≤ 1
mm
), tit
anite
, opa
ques
an
d ho
rnbl
ende
incl
usio
ns.
Ane
dral
and
con
tain
s tita
nite
and
opa
ques
in
clus
ions
Anh
edra
l–su
bhed
ral,
1–1.
5 m
m.
Qua
rtz-2
Alk
ali f
elds
par-2
-ass
ocia
ted
to fo
rm a
mag
mat
ic
gran
ophy
ric te
xtur
e.ab
sent
pha
seIn
ters
titia
l, oc
curs
ass
ocia
ted
to th
e bi
otite
-2.
Qua
rtz-3
Rep
rese
nts a
hyd
roth
erm
al p
hase
pre
cipi
tate
d on
th
e al
kali
feld
spar
-1.
abse
nt p
hase
It sh
ows s
trong
ly u
ndul
ator
y ex
tinct
ion,
typi
cally
occ
urs i
nclu
ded
in
the
alka
li fe
ldsp
ar-1
.
Tabl
e 2
– Pe
trogr
aphi
c ch
arac
teri
stic
s of s
tudi
ed g
rani
tic p
luto
ns
Con
tinua
...
1.90 to 1.88 Ga I- and A-type granitoids from NE Amazonas State
700 Revista Brasileira de Geociências, volume 42(4), 2012
Tabl
e 2
– C
ontin
uatio
nVa
riet
al m
iner
als
Hor
nble
nde-
1
Euhe
dral
–sub
hedr
al, r
ectu
m c
onta
ct w
ith q
uartz
an
d al
kali
feld
spar
and
inte
rpen
etra
tive
with
th
e tit
anite
. Fe-
Ti o
xide
s, zi
rcon
and
apa
tite
incl
usio
ns a
re v
ery
freq
uent
. It a
lso
occu
rs a
s cl
inop
yrox
ene
pseu
dom
orph
s.
Stro
ngly
alte
red
to c
hlor
ite, o
ccur
s com
mon
ly
as in
ters
titia
ls c
ryst
als c
onta
inin
g in
clus
ions
of
Fe-T
i oxi
des.
Subh
edra
l to
euhe
dral
. It i
s ass
ocia
ted
to F
-Ti o
xide
s tita
nite
, al
tera
tion
to c
hlor
ite, e
pido
te a
nd b
iotit
e. T
he c
onta
ct w
ith th
e pl
agio
clas
e-1
is re
ctili
near
and
with
the
quar
tz-1
and
alk
ali f
elds
par-1
is
inte
rdig
ited.
Con
tain
s inc
lusi
ons o
f Fe-
Ti o
xide
s.
Hor
nble
nde-
2 ab
sent
pha
seab
sent
pha
seas
soci
ated
to q
uartz
-2, o
ccur
s filli
ng in
inte
rstit
ials
and
mai
nly
clea
vage
s of p
lagi
ocla
ses
Bio
tite-
1Su
bedr
al, c
onta
ins h
ornb
lend
e, F
e-Ti
oxi
des a
nd
titan
ite a
s inc
lusi
ons.
abse
nt p
hase
Subh
edra
l, co
ntai
ns se
vera
l cor
rode
d m
agne
tite
and
ilmen
ita
incl
usio
ns.
Bio
tite-
2O
ccur
s as a
nhed
ral i
nter
stiti
al c
ryst
als a
nd
titan
ite-a
ssoc
iate
d.ab
sent
pha
seO
ccur
s as p
rodu
ct o
f tra
nsfo
rmat
ion
of h
ornb
lend
es a
nd a
s filli
ng in
in
ters
tices
.
Acce
ssor
y m
iner
als
Fe-T
i oxi
des
Occ
ur a
ssoc
iate
d to
var
ieta
ls a
nd a
s inc
lusi
ons.
mis
char
acte
rized
They
com
bine
with
Fe-
Mg
hydr
ated
min
eral
s and
tita
nite
.
Tita
nite
Eued
ral,
occu
rs c
omm
only
ass
ocia
ted
to
varie
tals
.So
me
crys
tals
hav
e be
en a
ltere
d to
epi
dote
Occ
urs a
s euh
edra
l cry
stal
s of u
p to
2 m
m a
nd is
ass
ocia
ted
to th
e ho
rnbl
ende
and
Fe-
Ti o
xide
s. So
me
crys
tals
con
tain
flui
d in
clus
ions
in
bub
ble
shap
e.
Apa
tite-
1A
patit
e ne
edle
s are
euh
edra
l–su
bhed
ral a
nd
mea
sure
< 0
.1 m
m.
mis
char
acte
rized
Euhe
dral
, aci
cula
r and
hex
agon
al, a
nd e
xhib
its in
timat
e re
latio
ns
with
the
horn
blen
de-2
and
pla
gioc
lase
s.
Apa
tite-
2C
ryst
als g
rew
up
to 2
mm
.ab
sent
pha
seab
sent
pha
se
Zirc
onEu
hedr
al–s
ubhe
dral
, zon
ed, a
lway
s occ
urs
asso
ciat
ed to
apa
tite.
Euhe
dral
, mea
sure
s up
to 0
.2 m
m a
nd so
me
crys
tals
hav
e be
en h
ugel
y al
tere
d to
epi
dote
.Eu
hedr
al–s
ubhe
dral
and
shar
ply
zone
d.
Gar
net
abse
nt p
hase
Ve
ry fi
ne c
ryst
als i
n ev
olve
d te
rms
abse
nt p
hase
Seco
ndar
y m
iner
als
Epito
deO
rigin
ated
from
mor
e ca
lcic
por
tions
of
plag
iocl
ase
and
horn
blen
de.
From
cal
cic
porti
on o
f pla
gioc
lase
s. It
stan
ds o
ut b
y fo
rmin
g eu
hedr
al c
ryst
als.
Seric
ite-m
usco
vite
M
ajor
ly o
ccur
on
alka
li fe
ldsp
ar a
nd p
lagi
ocla
se.
From
alk
ali f
elds
par a
nd p
lagi
ocla
se.
Occ
urs a
ssoc
iate
d to
cal
cic
porti
ons o
f pla
gioc
lase
s.
Arg
ilic
min
eral
sO
ccur
on
alka
li fe
ldsp
ar a
nd p
lagi
ocla
se.
From
alk
ali f
elds
par.
The
argi
lizat
ion
occu
rred
with
smal
l int
ensi
ty in
alk
ali f
elds
pars
.
Inte
rgra
nula
r alb
iteA
re a
ssoc
iate
d to
sepa
ratio
n of
the
sodi
c ph
ase
from
alk
ali f
elds
par t
o fo
rm p
erth
ites.
From
per
thite
and
alb
ite c
hess
boar
d.
It is
pro
duct
from
the
perth
ite.
Act
inol
iteO
ccur
s as i
ndiv
idua
l cry
stal
s and
rim
s of
horn
blen
de a
nd c
linop
yrox
ene
pseu
dom
orph
s.Fr
om h
ornb
lend
e.ab
sent
pha
se
Chl
orite
Occ
urs f
aint
ly fr
om b
iotit
es.
From
hor
nble
nde.
Fr
om h
ornb
lend
e an
d bi
otite
.
Hem
atite
abse
nt p
hase
Occ
urs a
s im
preg
natio
n on
alk
ali f
elds
par,
as
fillin
g in
to m
icro
frac
ture
s.
Com
mon
in th
e al
kali
feld
spar
-ric
h gr
anite
s, as
impr
egna
tion
in so
dic
lam
ella
s of p
erth
ites,
inte
rstit
ial p
ortio
ns a
nd m
icro
frac
ture
s and
as
esph
erul
itic
crys
tals
.
Cristóvão da Silva Valério et al.
Revista Brasileira de Geociências, volume 42(4), 2012 701
Plut
onTe
rra
Pret
a G
rani
teC
anoa
s Sye
nogr
anite
São
Gab
riel G
rani
te
Fels
ic d
ike
Mic
rosy
enog
rani
te, r
hyol
ite w
ith in
equi
gran
ular
and
mic
ropo
rphy
ritic
te
xtur
es. A
lkal
i fel
dspa
r phe
nocr
ysta
ls a
re p
erth
itic
and
pres
ents
A
lbite
-Per
iclin
e La
w tw
inni
ng.
Xen
olith
s
Glo
mer
opor
phyr
itic
ande
site
with
a v
ery
fine-
grai
ned
mat
rix fo
rmed
by
clu
ster
s of a
mph
ibol
es, f
elds
pars
and
qua
rtz. T
wo
phen
ocry
stal
s ty
pes o
f pla
gioc
lase
:1-ty
pe h
as 2
–8 m
m, A
n 24 in
cor
e an
d A
n 21 in
rim
; 2-
type
has
< 0
.5 m
m, A
n 28 in
cor
e an
d A
n 26 in
rim
.
1. M
usco
vite
-act
inol
ite-h
orfe
ls (C
anoa
s Sy
enog
rani
te) w
ith in
terlo
bate
gra
nobl
astic
text
ure.
2.
Hor
nble
nde-
rhyo
daci
te.
Mafi
c di
ke
Inte
rgra
nula
r tex
ture
gab
bros
and
hig
h cl
inop
yrox
ene
pseu
dom
orph
s co
nten
t em
phas
ize
the
gabb
ro d
ike
and
encl
aves
ass
ocia
ted.
subh
edra
l ca
lcic
and
esin
e (A
n 41–4
8). It
als
o is
form
ed b
y ci
rcul
ar fi
ne-g
rain
ed
trem
olite
-act
inol
ite c
rust
s and
subo
rdin
ated
pla
gioc
lase
, who
se ri
ms
are
form
ed b
y fib
rous
cry
stal
s of t
rem
olite
-act
inol
ite.
Show
s int
ergr
anul
ar a
nd su
b-op
hitic
te
xtur
es, h
igh
amph
ibol
es c
onte
nts
and
plag
iocl
ase
xeno
crys
tals
. The
xe
nocr
ysta
ls h
ave
been
par
tially
di
ssol
ved
in th
eir c
ore
and
rims.
Mafi
c en
clav
eId
em to
mafi
c di
ke.
Inte
rmed
iate
enc
lave
Qua
rtz-d
iorit
e, in
terg
ranu
lar t
extu
re, a
min
eral
ogic
al a
ssem
bly
form
ed
by p
oiki
litic
cry
stal
s of q
uartz
and
alk
ali f
elds
par (
strin
g an
d fla
mes
pe
rthite
s), x
enoc
ryst
als o
f qua
rtz, p
lagi
ocla
se a
nd a
lkal
i fel
dspa
r, an
d,
high
tita
nite
con
tent
. Xen
ocry
stal
s exh
ibit
engu
lfing
, cor
rode
d co
re
and
patc
hy z
one,
and
als
o po
sses
ses a
mafi
c ph
ase
pres
erve
d an
d tw
o ap
atite
type
s, a
long
/nar
row
(20:
1) a
nd a
noth
er sh
ort/w
ide
(5:1
).
Qua
rtz-d
iorit
e ke
pt p
etro
grap
hic
feat
ures
sim
ilar t
o Te
rra
Pret
a m
afic
encl
aves
. Exc
eptio
ns in
clud
e th
e bi
otite
pre
senc
e, a
mph
ibol
e ps
eudo
mor
phs a
nd p
lagi
ocla
ses
light
ly m
ore
calc
ic (A
n 27-3
0).
Met
agra
nito
ids
Dyn
amo-
stat
ic d
efor
mat
ion
prog
ress
ivel
y in
crea
sing
from
E to
W in
to th
e W
sect
or o
f stu
died
are
a. It
s in
tens
ity e
mbr
aces
low,
low
–med
ium
and
med
ium
–hig
h te
mpe
ratu
re d
egre
es.
Iric
oum
é ig
nim
brite
Lith
ic fr
agm
ents
and
ben
t fiam
mes
con
stitu
te th
e fia
mm
e-ric
h ig
nim
brite
. It i
s for
med
by
cry
stal
s fra
gmen
ts o
f qua
rtz, a
lkal
i fel
dspa
r, pl
agio
clas
e, b
iotit
e an
d Fe
-Ti o
xide
s, an
d pu
mic
e fr
agm
ents
and
fine
-gra
ined
ash
mat
rix. T
he c
o-ig
nim
brite
con
sist
s of s
imila
r pr
opor
tions
of c
last
s of q
uartz
, alk
ali f
elds
par,
plag
iocl
ase
and
opaq
ues,
besi
des a
sh m
atrix
.
Iric
oum
é an
desi
te/tr
achy
ande
site
Glo
mer
opor
phyr
itic
amyg
dalo
idal
text
ure
and
cons
ists
of p
heno
crys
tals
of q
uartz
, cal
cic
olig
ocla
se (A
n 22–2
5), p
yrox
ene
and
amph
ibol
e in
a tr
achy
tic m
atrix
.
Iric
oum
é rh
yolit
e/rh
yoda
cite
The
horn
blen
de-rh
yolit
e/rh
yoda
cite
con
sists
of p
heno
crys
tals
of fe
ldsp
ars,
horn
blen
de a
nd
Fe-T
i oxi
des i
n m
atrix
of q
uartz
, fel
dspa
rs a
nd h
ornb
lend
e. S
mal
l clu
sters
of h
ornb
lend
e fo
rm
radi
al a
rrang
emen
t. Tw
o ph
enoc
rysta
ls ty
pes o
f pla
gioc
lase
. 1-ty
pe is
subh
edra
l–eu
hedr
al
(1–2
mm
), an
d ha
s cal
cic
olig
ocla
se (A
n 29) i
n co
mpo
sitio
n. T
he p
lagi
ocla
se-2
(< 0
.5 m
m) i
s eu
hedr
al, h
as A
n 26 in
com
posit
ion.
The
alk
ali f
elds
par (
1–2
mm
) phe
nocr
ysta
l is s
ubhe
dral
an
d co
ntai
ns in
clus
ions
of p
lagi
ocla
se-2
. The
bul
bous
-type
myr
mek
ite is
ver
y fre
quen
t.
Mic
rogr
anite
por
phyr
y di
keTh
e po
rphy
ritic
text
ure
cont
aini
ng fe
ldsp
ars c
ryst
als
of u
p to
2 c
m, m
ediu
m- t
o fin
e-gr
aine
d m
atrix
and
lo
caliz
ed g
rano
phyr
ic in
terg
row
ths.
Hor
nfel
s
Into
the
NE
sect
or, m
afic
rock
s and
gra
nito
ids,
abov
e al
l, C
anoa
s Sye
nogr
anite
, wer
e st
atic
ally
recr
ysta
llize
d. P
rese
nt in
terlo
bate
gra
nobl
astic
text
ure
and
less
recr
ysta
llize
d ro
cks p
osse
ss ig
neou
s loc
ally
pre
serv
ed te
xtur
e, w
here
is p
ossi
ble
desc
ribe
fibro
us v
eins
, cr
ysta
lpla
stic
def
orm
atio
n of
qua
rtz a
nd fr
agile
def
orm
atio
n of
feld
spar
s.
Tabl
e 3
– M
ain
petro
grap
hic
and
min
eral
ogic
al c
hara
cter
istic
s of r
ocks
ass
ocia
ted
to a
ppra
ised
gra
nitic
plu
tons
.
1.90 to 1.88 Ga I- and A-type granitoids from NE Amazonas State
702 Revista Brasileira de Geociências, volume 42(4), 2012
both being slightly following the magmatic flow. The quartz is usually anhedral and occurs as phenocrys-tals, as strings in amygdales rims and partially filling amygdales. The euhedral calcic oligoclase displays twinning according to the Albite-Carlsbad law. The pyroxene is scattered and is commonly associated with andesine and Fe-Ti oxides. The actinolite-tremo-lite, generated from the alteration of hornblende, is as fibrous crystals filling amygdales.
The hornblende rhyolite/rhyodacite consists of phenocrystals of feldspars, hornblende and Fe-Ti ox-ides in a matrix of quartz, feldspars and hornblende. Zircon and apatite are the most common accessory minerals. The hornblende phenocrystals are sub-hedral and commonly associated with the Fe-Ti oxides. They present inclusions of Fe-Ti oxides, and their contacts with the matrix are gradual. Clusters of small horn-blende crystals in radial arrangements are common.
Two types of plagioclase phenocrystals have been recorded. Plagioclase-1 is sub-hedral–euhedral (from 1 to 2 mm) and has a calcic oligoclase (An29) composition. Plagioclase-2 (< 0.5 mm) is euhedral, has An26 composition, and also occurs as inclusion in the alkali feldspar. Both types of plagioclase exhibit Albite and Albite-Carlsbad law twinning. Their calcic cores break up into muscovite, sericite, and clay minerals.
The alkali feldspar phenocrystals (from 1 to 2 mm) are sub-hedral with inclusions of plagio-clase-2. The bulbous-type myrmekite is very com-mon and mainly occurs in the rims of larger crystals. Feldspars show strong wavy extinction and deforma-tion lamellas. Such aspects are only observed in the phenocrystals and are absent in the matrix compo-nents. This suggests synvolcanic deformation associ-ated with the attrition of crystals at the eruption vent, which only affected the phenocrystals that had already been formed. Among some feldspar crystals, there are clusters of intermediate size quartz-feldspar between the matrix and the phenocrystals. Some of the crystals in the clusters have the same optical orientation as the phenocrystals (Fig. 5C), which indicate the variations of mineral nucleation and growth rates involved in the formation of these volcanic rocks.
Canoas Syenogranite The hornblende-bearing sy-enogranites and minor hornblende-bearing alkali feld-spar granites have a medium-grained seriate texture (Tab. 1, Fig. 4B). The alkali feldspar is sub-hedral and strongly perthitic (stringlets, strings, interlocking and chessboard albite) with generation of sub-hedral
albite crystals. It contains plagioclase inclusions, and its contacts with the plagioclase and quartz are faintly interdigited. The euhedral, normal-zoned plagioclase measures between 0.5 and 3.0 mm. It is a sodic oligo-clase (An10-12) and displays Albite and Albite-Carlsbad Laws twining. Its contacts with the alkali feldspar and quartz are rectilinear, and those with hornblende are interdigited. The hornblende, strongly altered to chlo-rite, commonly occurs as interstitial crystals contain-ing Fe-Ti oxide inclusions. The zircon is euhedral and measures up to 0.2 mm. Some sub-hedral titanite crys-tals have been greatly altered to epidote. According to geologist Desaix Silva (Brazilian Geological Service, personal communication), the garnet happens only in more evolved rocks as very fine crystals. The relat-ed mafic dikes are represented by quartz-gabbro and have intergranular and sub-ophitic textures, high am-phibole contents, and plagioclase xenocrystals. The xenocrystals have been partially dissolved in their cores and rims.
São Gabriel Granite Hornblende monzogran-ite, hornblende syenogranite and biotite-hornblende syenogranite are the major petrographic variations observed in São Gabriel Granite (Tab. 1, Fig. 4C). Microgranite porphyry and microdiorite occur infre-quently as dikes near the boundaries of the batholith. Medium-grained rapakivi-type textures predominate in all litho-types. Albite and Albite-Carlsbad Law twinning and major normal zoning, as well as mi-nor abrupt and sectored oscillatory zoning, are in two plagioclase types (Tab. 2).
Plagioclase-1 is euhedral (from 2 to 6.5 mm), has an An22–An28 composition in the core (seen in different hydrothermal transformation zones) and an An22–17 one in the rims. The contacts are rectilin-ear with the hornblende-1 and are interpenetrative with the quartz-1. This plagioclase contains amphi-bole, Fe-Ti oxides, apatite, and zircon inclusions. The amphibole and Fe-Ti oxides inclusions are fre-quently located in the core of the plagioclase crys-tals. Plagioclase-1 and -2 form clusters similar to the Synneusis. Plagioclase-2 (0.5 – 1.5 mm) is anhedral–sub-hedral, unzoned and zoned (oscillatory). It is in the interstices between grains and contains inclusions of quartz-1 and biotite-2. In composition, it is An27–25 in the core and An21–17 in the rims. The alteration of the zoned plagioclase-2 resulted in anhedral crystals of epidote and sericite, whereas in the unzoned pla-gioclase-2, only sericite was formed.
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Albite-Pericline law twining is common in two alkali feldspar types. Manebach twining is only ob-served in the alkali feldspar-2. The alkali feldspar-1 is sub-hedral (from 2.5 to 6 mm) and commonly oc-curs associated with quartz-1. The alkali feldspar-2 is sub-hedral–anhedral and measures 0.5 – 2.5 mm in length. Both alkali feldspars are slightly changed to sericite and clay minerals. Inclusions of plagio-clase-2, hornblende-1, zircon, apatite, and perthite are very common. Albite microfilms grew along con-tacts and shift to a string-type arrangement coin-ciding with 001 cleavage. Locally interlocking and beaded perthites developed in the alkali feldspar-1 of the biotite-hornblende syenogranite. Intergranular al-bite is in all facies, however it is very abundant in the syenogranites. Some mantled alkali feldspar crys-tals (1-type) have ovoid shapes due to corroded rims (Fig. 5D). The product of alkali feldspar-1 exsolution seems to have grown on plagioclase-2 with corroded rims (anti-rapakivi-like) and on plagioclase-mantled alkali feldspar-1 (double mantle rapakivi-like).
Quartz-1 is anhedral–sub-hedral and measures 1 – 1.5 mm length. Quartz-2 is interstitial and is as-sociated with biotite-2. Quartz-3 shows strong undu-latory extinction and is typically precipitated on the alkali feldspar-1.
Hornblende-1 is sub-hedral to euhedral and is associated with Fe-Ti oxides and titanite. Alteration to chlorite is very common, but epidote and biotite are also observed. The contacts with the plagioclase-1 are rectilinear, whereas those with the quartz-1 and alka-li feldspar-1 display re-entrances. The hornblende-1 has inclusions of Fe-Ti oxides. Hornblende-2 is as-sociated with quartz-2 and fills interstices and cleav-ages of the plagioclase.
Sub-hedral crystals of biotite-1 display sev-eral apically corroded magnetite and ilmenite inclu-sions. The biotite-2 is a product of breaking-up horn-blende-1 and -2, filling the interstices between grains.
The Fe-Ti oxides are coupled with hydrat-ed Fe-Mg minerals and titanite. The latter happens as euhedral crystals up to 2 mm long and is asso-ciated with hornblende-1 and Fe-Ti oxides. Some titanite crystals have fluid inclusions with bubble shapes. The apatite is euhedral, acicular and hex-agonal, and exhibits intimate relationships with hornblende-2 and plagioclases with simultaneous extinctions that suggest contemporaneous phases (Hibbard 1995). The zircon is euhedral to sub-he-dral and sharply zoned.
The sericite-muscovite is associated with cal-cic portions of plagioclase. Low intensity argilization also occurred in the alkali feldspar. The epidote stands out by forming euhedral crystals, reflecting the high decalcification rates of calcic plagioclase. The albite is formed from the perthite. Hematite is common in alkali feldspar-rich granites. It is in sodic lamellas of perthite, interstitial among other minerals, filling microfractures, and as espherulitic crystals. Most of the hematite must have originated from magnetite-il-menite alteration or substitution, precipitation on the feldspars by hydrothermal aqueous fluids.
The microgranite porphyry dikes contain feld-spar crystals up to 2 cm in length (Fig. 5E), medi-um- to fine-grained matrix and local granophyric intergrowths, which mark the intrusive stage. The re-lationship between the phenocrystals and the matrix is similar to lava flow rhyolite, suggesting correlation.
The mingled microgranular enclaves (quartz-diorite, Fig. 5F) of São Gabriel Granite present tex-tural and mineralogical features similar to those de-scribed for the mafic enclaves of Terra Preta Granite. Exceptions include the presence of biotite, amphi-bole pseudomorphs, and slightly more calcic plagio-clases (An27-30).
Crystallization sequences The crystallization sequence of Terra Preta Granite (Fig. 6A) involves the stabilization of precocious minerals (apatite and zircon), followed by nucleation of plagioclase-1 (core) and stabilization of the Fe-Ti oxides. The high integrity of the oxides suggests slight participation in the formation of titanite. The synneusis relation-ship indicates that the plagioclase-2 grew concomi-tantly with some plagioclase-1 crystals. The presence of clinopyroxene pseudomorphs indicates a crystal-lization sequence, which includes deuteric reactions between varietal minerals and liquid.
The crystallization sequence of Canoas Syenogranite starts with the crystallization of zircon and apatite, followed by the consecutive crystalliza-tion of Fe-Ti oxides, plagioclase, quartz, hornblende, alkali feldspar, and titanite (Fig. 6B).
In São Gabriel Granite, the crystallization of the Fe-Ti oxides, Fe-Mg minerals, plagioclase, alkali feldspars and quartz were in a similar way as in the analyzed facies. The crystallization order (Fig. 6C) consisted of the stabilization of oxides, titanite, horn-blende-1, biotite-1, plagioclase-1 core, apatite-zir-con, plagioclase-1 rims, plagioclase-2 core, quartz-1,
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and alkali feldspar-1. After the crystallization of the first phase, destabilization of the lower minerals tem-perature occurred, which resulted in the partial or to-tal corrosion of the rims and congruent dissolution of the calcic core of the plagioclase-1 by forming plagioclase-3. The alkali feldspar-1 had their rims
corroded to form ovoid crystals, whereas part of the quartz-1 was solubilized. Stabilization of the crystals of hornblende-2 and quartz-2, alkali feldspar-2 and plagioclase-2 rims happened soon after. Some of the alkali feldspar-2 and plagioclase-2 appears to have only epitaxially grown on the plagioclases, corroded
Figure 5 – Microtextural features of the studied plutons and related rocks. (A) Tremolite-actinolite and minor plagioclase in amygdaloidal structures in the Terra Preta Granite-related synplutonic quartz-gabbro. (B) Re-absorption features in xenocrystals of Terra Preta Granite hybrid quartz-diorite. (C) Intermediate-size crystal clusters between matrix and phenocrystals, displaying the same optical orientation as the phenocrystals. (D) Ovoid plagioclase mantled by perthitic alkali feldspars crystal (rapakivi texture). (E) Alkali feldspar crystal in microgranite porphyry dike. (F) Microgranular enclave of São Gabriel Granite. pl: plagioclase, af: alkali feldspar and qz: quartz.
A
C
E
B
D
F
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post-magmatic crystalizationmagmatic crystalizationFe-Ti oxides
titaniteplagioclasse-1 core pl-1 rim, plagioclase-2
quartz-1 quartz-2
alkali feldspar-1
hornblende
apatite, zircon
biotite-1 biotite-2
af-2 af-3
hematiteepidoteepidote, sericite, argilic minerals,muscovite, carbonate
actinolite, chlorite, biotite,epitode, titanite?
argilic minerals, albite intergranular,perthite, albite chessboard
quartz-3
A
post-magmatic crystalizationmagmatic crystalizationFe-Ti oxides
titaniteplagioclase
quartz-1
alkali feldspar
hornblende
apatite, zircon
hematiteepidoteepidote, sericite, argilic minerals,muscovite, carbonate
chlorite
argilic minerals, albite intergranular,perthite, albite chessboard, albite
quartz-3
B
post-magmatic crystalizationmagmatic crystalizationFe-Ti oxides
titanite
plag-1 core plagioclase-2 rimplag-1 rim, plag2 core
quartz-1 quartz-2
alkali feldspar-1 alkali feldspar-2
hornblende-1 hornblende-2, biotite-1 bt-2
apatite, zircon
hematiteepidote
epidote, sericite, argilic minerals,muscovite, carbonate
chlorite, biotite
perthites, albite intergranular,argilic minerals, myrmekite
quartz-3
C
Figure 6 – Magmatic crystallization sequence and the postmagmatic minerals of Terra Preta Granite (A), Canoas Syenogranite (B), and São Gabriel Granite (C). The crystallization sequence was suggested from mineral inclusions and contacted relationships between crystals.
alkali feldspar rims, and the mantled alkali feldspar. These features are named stricto sensu anti-rapaki-vi and rapakivi and double-mantle rapakivi textures, respectively (Rämö 1991, Hibbard 1995, Rämö & Haapala 1995, Haapala & Rämö 1999).
Dynamostatic rocks The field and microdefor-mational features revealed increasingly intense de-formation from E to W, recorded mainly in Terra Preta granitoids and minor Canoas syenogranites in the western sector of the study area. According to Paschier and Trouw’s (1998) criteria, the deformed rocks registered low, low-medium, and medium-high temperatures.
The less deformed rocks have medium-grained granular texture. The quartz is ellipsoidal and moder-ately flattened, with rims that present undulatory ex-tinction and sutured contacts. Mantles composed of small new-grains surround slightly deformed or un-deformed porphyrclasts of quartz and feldspars. The quartz with strong undulatory extinction developed
deformation bands, whereas trails of neoblasts of quartz were formed in the boundaries of subgrains (Fig. 7A). The fragile structure of the alkali feldspar crystals allowed the local development of fractures filled by quartz, and it formed curved and rarely sig-moidal, antitaxial and fibrous quartz veins (Fig. 7B). The foliation is spaced and disjunctive and composes about 20% of the cleavage domain and 70% of the microlithes. The cleavage domain is irregular and its spatial relationship and transitions to the microlithe domains are anastomosed and gradual.
In the low-medium deformed rocks, recov-ery rate involves strong undulatory extinction and deformation bands and subgrains. Subgrain rotation is common and grain boundary migration is local. Some feldspar porphyroclasts have mantles of quartz neoblasts and trails, and fluid inclusions. Alkali feld-spar porphyroclasts are surrounded by new grains of quartz and feldspar (mantle-core structure). Plagioclase inclusions, flame perthite and bulbous myrmekite rims are also common (Fig. 7C). The fo-liation is spaced, irregular disjunctive in about 30% of the cleavage domain, anastomosed, and gradual.
In the medium-high degree zone, the rocks are formed of a matrix of quartz and feldspars that are broadly recrystallized, in addition to quartz and feld-spar porphyroclasts, biotite, and Fe-Ti-oxide trails. The quartz porphyroclasts occur as trail-shaped poly-crystalline crystals due to accentuated stretching and formation/rotation of subgrains. Interdigited subgrain contacts are associated with grain boundary migration of denser grains onto less dense ones. The feldspar porphyroclasts exhibit prominent mantle-core struc-ture (Fig. 7D). The bulbous myrmekite is very com-mon on alkali feldspars. Locally, the perthitic alka-li feldspar displays antitaxial fibrous veins of quartz, suggesting that the pressure solution remained active during deformation. The alkali feldspar cores were preserved and myrmekites were formed on border-core boundaries. The foliation is spaced disjunctive, regular in about 80% of the cleavage domain and the contacts with microlithes are abrupt.
Static metamorphic rocks In the NE sector of the studied area, intermediate rocks and granit-oids of São Gabriel Granite, and especially Canoas Syenogranite, have been statically recrystallized by a thermal event likely linked to intrusions of mafic dikes/stocks. The metagranites contain diabase dikes and pods displaying fractures that were filled by the
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same material provided by one of the host rocks (Canoas Syenogranite).
DIABASE The recrystallized diabase (nemato-blastic texture) displays schistose textures due to the emplacement structures (dikes) and spaced, disjunc-tive and irregular foliation with a cleavage domain of about 80% (Fig. 7E). It locally happens as lenses (augen) composed of actinolite inclusions in escapo-lite porphyroblasts. The augen seems to have been composed of amphibole, escapolite (meionite?) and epidote (clinozoisite) probably generated from py-roxene + H2O → hornblende and plagioclase + H2O → escapolite + epidote reactions. Hydrothermal re-actions are observed in hornblende rims formed by actinolite. Escapolite occurs as < 0.1 mm crystals and 3 to 5 mm plagioclase pseudomorphs. The sub-he-dral–euhedral (up to 0.2 mm) epidote is usually asso-ciated with escapolite and actinolite.
GRANITOIDS The predominant texture of the re-crystallized granitoids is interlobate granoblastic, ranging from seriate to equigranular. Minor recrys-tallized rocks locally preserve igneous textures, in-cluding fibrous veins, crystal-plastic deformation of quartz, and fragile deformation of feldspars (Fig. 7F). With the exception of mafic dikes, all rocks contain muscovite associated with deformation, which is more abundant in the rocks that have no preserved igneous textures. The muscovite may have been gen-erated by the hydration reaction of alkali feldspar + H2O → muscovite + quartz. The granolepidoblastic texture of Canoas muscovite hornfels xenoliths con-trast with the equigranular interlobate granoblastic texture of São Gabriel Granite wall rock. This oc-curs by virtue of the decreasing thermal contrast be-tween the partially assimilated wall rock fragments (sub-angular) and the host magma, preserving pre-vious characteristics of a dynamo-thermal deforma-tion event. These features and the presence of a dyna-mo-thermal event suggest a different deformational event between 1.88 Ga and younger mafic intrusions. Alternatively, the textural orientation of the enclaves may have happened due to increasing turbulent flux near the borders of São Gabriel magma chamber.
DISCUSSIONLithostratigraphic units The main 1.90 to 1.89 Ga calc-alkaline rocks of the central portion of Amazonian Craton are associated with Água
Branca Suite (CPRM 2006, Ferron 2006, Almeida 2006, Valério et al. 2006b). The more thoroughly studied pluton (Caroebe Granite) consists of a gran-itoid association of Peru- or Sierra Nevada-type granodiorite of the calc-alkaline series (Almeida 2006, Almeida & Macambira 2007). The Terra Preta Granite is classified in this study as an I-type, high-K calk-alkaline pluton, whose size and shape re-main undefined due to reworking of its western and southern borders caused by a poorly defined defor-mational event and the cover of the Amazon basin (Valério et al. 2009 & 2010).
The Jauaperi Complex term was applied by CPRM (2006) to characterize gneiss and metagran-ites occurring in the southern region of the Guyana Shield. Our study showed that this region is domi-nated by Água Branca group and Mapuera granitoids and undivided mafic rocks, which recorded the ef-fects of a supposed regional metamorphism whose age, amplitude, and magnitude were not delimited.
Based on their geochemical signatures and plutonic association types, the volcanic rocks from the NE Amazonas (1.89 – 1.87 Ga) were classified into a high-K calc-alkaline group associated with Água Branca granitoids (Jatapu volcanics) and an alkaline potassic-type related to the Mapuera gran-ites (Almeida 2006, CPRM 2006, Valério et al. 2006A & B, Ferron et al. 2006 & 2010, Almeida & Macambira 2007, Marques et al. 2007). Ferron et al. (2006) proposed separating the volcanic rocks of Iricoumé Group into formations, and argued that Pitinga Province‘s volcanism is associated with the generation of alkaline-K, high-Sr, A-type gran-ites. Part of this volcano-plutonic event was de-veloped from preserved caldera structures (Ferron et al. 2006, Souza et al. 2007). Due to the high ero-sion rates that are characteristic of the area near the northern border of the Amazon basin, the supposed caldera structure of the study region was only faint-ly preserved.
However, the structural features are similar to classic models of eroded calderas (cauldrons) with-out sedimentary events (Lipman 1984 & 1997, Cole et al. 2005, Acocella 2007), such as the presence of effusive andesite, explosive eruptions caused by un-der-pressure (Acocella 2007), and presence of sev-eral ignimbrite deposits, intrusions of autoclastic breccias and microgranite porphyry, and lava flow deposits (hornblende rhyolite/rhyodacite) associated with the postcollapse phase.
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Figure 7 – Microtextural features of studied pluton-related metamorphic rocks. (A) Less deformed rocks of the study area. The quartz crystals present strong undulatory extinction and development of deformation bands, subgrains and trails of quartz neoblasts. (B) Antitaxial, fibrous quartz veins in fractured alkali feldspar crystals. (C) Rims of bulbous myrmekite and new grains on the plagioclase. (D) Prominent mantle-core structure in an alkali feldspar porphyroclast. (E) Detail of lenses composed of actinolite inclusions in an escapolite porphyroblast in diabase linked to statically recrystallized Canoas hornblende-bearing syenogranite (muscovite-actinolite hornfels). (F) Details of muscovite crystals in muscovite-actinolite hornfels. pl: plagioclase; af: alkali feldspar; qz: quartz; bt: biotite; ms: muscovite.
A
C
E F
B
D
The Mapuera Suite is made up of several large A-type granite plutons emplaced at 1.89 to 1.86 Ga (CPRM 2006, Almeida 2006). Several stocks
of reddish syenogranites and minor alkali feldspar-granite associations were generically grouped into the Mapuera Suite, mainly based on geochemistry
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and absolute ages, but without taking into consid-eration problems such as geochemical convergence and absence of field evidence. Valério et al. (2006a) showed that there are petrographic and geochemi-cal similarities between biotite-hornblende syeno-granite from the south/southeastern borders of São Gabriel Granite and other large granitic bodies of the Mapuera Suite, however this is not conclusive for Canoas Syenogranite. In addition, the major re-lationship of Canoas Syenogranite with Terra Preta granitoids has driven to classify some of these syeno-granitic bodies as the São Gabriel Granite. Another aspect that supports this stratigraphic arrangement is the textural dissimilarity between the hornfels xe-noliths (granolepidoblastic) and São Gabriel Granite wall rock (granoblastic).
Some of the mafic rocks from the southwest sector of the study area, described along the Pardo River (e.g., olivine-gabbro), have been includ-ed in the Seringa Formation, with 1.20 to 1.07 Ga (CPRM 2000). According to its original definition (Veiga Jr. et al. 1979), the Seringa Formation is characterized by mafic dikes and lava flow depos-its. Differentiated diorites and quartz-diorites, not associated with calcic-alkaline granitoids, are only mentioned in the Quarenta Ilhas Formation (1.79 Ga) (CPRM 2006) and are never cited as rocks re-lated to the studied granitoids.
Petrological considerations In the central-southern Guyana Shield (SE Roraima State, Brazil), Almeida et al. (2002) and Almeida & Macambira (2003) described important field and petrographic features that demonstrated the evolutionary pro-cesses of Água Branca magma, including the local assimilation of wall rocks. Ague & Brimhall (1987) observed similar aspects in calc-alkaline granit-oids from Sierra Nevada. They showed that granit-oid magmas were variably contaminated at region-al and local scales by crustal igneous, metamorphic and sedimentary rocks. Chappell (1996) conclud-ed that the assimilation processes and hybridization between mafic and felsic magmas do not result in great compositional variations and argued that the partial melting of the lower crust alone would ex-plain such variations. Other authors have proposed that homogeneous petrographic types of granitoids could be formed by hybridization of crustal liquids with mafic magma (Frost & Mahood 1987, Huppert & Sparks 1988, Rämö 1991, Haapala & Rämö 1992
& 1999, Rämö & Haapala 1995) or with dioritic and tonalitic magmas derived, by fractional crystal-lization, from mantle basaltic liquids (Castro et al. 1990 & 1991).
Based only on the F, Zr, Nb and rare earth ele-ments contents of the Mapuera magma, Ferron et al. (2010) advocated a mantle origin before being modi-fied by subduction in a post-collision tectonic setting. However, they have also considered a bimodal origin in and extensional environment, as previously argued by Almeida (2006).
The present evaluation, based on field and pe-trographic data, suggest that, in addition to fraction-al crystallization, processes of wall rock assimilation and magma mingling had played a role, at least at the local scale, in the evolution of granitoids from the NE Amazonas State.
Texture and deformation of Terra Preta and Canoas granitoids Barker (1970) showed that granophyric intergrowths could be formed in re-sponse to the simultaneous/rapid crystallization of alkali feldspar and quartz from liquid or vapor. The origin of intergrowths would involve volatile-rich liquids in the final processes of crystallization in epi-zonal environments (Hibbard 1979, & 1987, Hughes 1982). These magmatic conditions are compatible with underformed granitoids with restricted grano-phyric textures that are likely related to the presence of aplite dikes formed from sudden replacement of H2O-saturated phases, due to pressure loss that ac-celerated the nucleation rates (Hibbard 1995). In re-crystallized granitoids, however, the granophyric textures must be associated with dynamo-thermal deformation.
The bulbous and intergranular myrmekites that were developed along alkali feldspar boundaries showed different crystallographic orientations. For Phillips (1974, 1980), and Smith & Brown (1988), the myrmekite is formed by the exsolution of alka-li feldspar accompanied of pressure-induced disso-lution and reprecipitation in a subsolidus state with some participation of primary quartz and K-feldspar. Smith & Brown (1988) suggested that subsequent processes could partially or completely modify the myrmekite by recrystallizing it. This points out myr-mekites as petrogenetic indicators and suggests that myrmekites in the dynamically crystallized studied granitoids must have been originated from subsolidus deformational processes.
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The origin theories of the deformation pro-cess proposed for rocks of the area study are con-troversial, not only due to limited geochronological data, but also because of the incomplete knowledge of structural features at the field level. The reconsti-tution of events shows that Terra Preta Granite was emplaced during the postcollisional uplift, followed by deformation induced by the effects of oceanic plate subduction under the Vantuari-Tapajós paleo-continent at the beginning of Rio Negro Province building (Valério et al. 2009). This model can be valid if we consider the different crustal levels be-tween the undeformed São Gabriel Granite (and related rock) and Terra Preta Granite and Canoas Syenogranite (deformed). In contrast, CPRM (2000) and Valério et al. (2006b) presented a collisional model that is incompatible with the small differ-ence in age (~ 10 Ma) and petrographic dissimilari-ties between the syncollisional and anorogenic bod-ies. Therefore, based on petrographic analysis, it is simpler to think that this deformation and metamor-phism must be linked to an event slightly younger than the Terra Preta magmatism, which was likely associated with strike-slip faults in an extension-al setting, whose effects were not registered by the subvolcanic, shallower São Gabriel Granite and re-lated rocks.
CONCLUSION REMARKS Field and petro-graphic features supported by previous works raised in this study lead to the following conclusions:• Transitional contact zones between par-
tially fragmented mafic dikes and wall rocks (Terra Preta hornblende granodiorite), where mafic and intermediate enclaves with low and high xenocrystals contents, respective-ly, and mingled quartz-diorite, have been formed. These features indicate that at least one generation of mafic dikes was emplaced before the complete crystallization of Terra Preta Granite.
• The diffuse contact and recrystallized xeno-liths suggests that Canoas Syenogranite is slightly younger than Terra Preta Granite and older than São Gabriel Granite. We considered that the Canoas hornblende-bearing syeno-granites were generated from Mapuera mag-ma. However, the intimate field relationships with the Terra Preta granitoids and differenti-ated mineral paragenesis point to a divergent
evolution, and therefore its association with Mapuera magma is not conclusive.
• Interaction features and petrographic evi-dence suggest that, in addition to fraction-al crystallization, assimilation and magma mingling processes played a role at least in the local scale, in the evolution of the Terra Preta Granite, Canoas Syenogranite and São Gabriel Granite. Microfeatures of magma mingling have been found in all granitoid plutons at variable rates, such as plagioclase dissolution, feldspar rim corrosion, alkali feldspar and plagioclase mantles, a second generation of apatite and high xenocrystals contents in mafic enclaves.
• The crystallization sequences support frac-tional crystallization as a dominant differ-entiation process of Terra Preta Granite and Canoas Syenogranite, while in São Gabriel Granite, magma mingling seems to have been in harmony with all phases of fractional crystallization.
• Undeformed gabbros, diorites and minor anor-thosite likely are linked to the rapakivi-type São Gabriel Granite. Except near these un-deformed rocks, all granitoids in the western sector of the study area recorded apprecia-ble and progressive dynamostatic deforma-tion from E to W. Such event must have oc-curred between 1.90 Ga (Terra Preta Granite) and the intrusions of the São Gabriel Granite (1.89 Ga) and related rocks. We point to an alternative origin, which is associated with an event slightly younger than the postcollision-al uplift. However, it is extremely necessary to obtain absolute ages for this metamorphic event, which is the purpose of these authors’ next paper.
ACKNOWLEDGEMENTS This research was financed by the Institute of Geosciences, Federal University of Pará and the CT-Amazonia proj-ect (MCT-CNPq 575520/2008-6). We thank the Brazilian National Council of Technological and Scientific Development (CNPq) scholarship (140758/2007-0) granted for funding the first au-thor, and the Department of Geosciences, Federal University of Amazonas, for storing the sam-ples gathered in the field and for partial sample preparation.
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Acocella V. 2007. Understanding caldera structure and development: An overview of analogue models compared to natural calderas. Earth-Science Reviews, 85:125-160.
Ague J.J. & Brimhall G.H. 1987. Granites of batholiths of California: Products of local assimilation and regional-scale crustal contamination. Geology, 15:63-66.
Almeida M.E. 2006. Evolução geológica da porção centro-sul do escudo das Guianas com base no estudo geoquímico, geocronológico (evaporação de Pb e U-Pb ID-TIMS em zircão) e isotópico (Nd-Pb) dos granitóides Paleoproterozóicos do sudeste de Roraima. Tese de Doutorado, Programa de Pós-Graduação em Geologia e Geoquímica, Instituto de Geociências, Universidade Federal do Pará, Belém, 227 p. (in portuguese).
Almeida M.E., Macambira M.J.B., Faria MSG. 2002. A Granitogênese paleoproterozóica do sul de Roraima. In: SBG, Congresso Brasileiro de Geologia, 41, Anais, p. 434. (in portuguese).
Almeida M.E. & Macambira M.J.B. 2003. Aspectos geológicos e litoquímicos dos granitóides cálcio-alcalinos Paleoproterozóicos do sudeste de Roraima. In: SBGq, Congresso Brasileiro de Geoquímica, 9, Anais, p. 775-778. (in portuguese).
Almeida M.E. & Macambira M.J.B. 2007. Geology and petrography of the paleoproterozoic granitoid rocks from Uatumã-Anauá domain, central region of Guyana Shield, southeastern Roraima, Brazil. Revista Brasileira de Geologia, 37(1):2-21.
Almeida M.E., Macambira M.J.B., Oliveira E.C. 2007. Geochemistry and zircon geochronology of the I-type high-K calc-alkaline and S-type granitoid rocks from southeastern Roraima, Brazil: Orosirian collisional magmatism evidence (1.97–1.96 Ga) in central portion of Guyana Shield. Precambrian Research., 155(1-2):69-97.
Almeida M.E., Macambira M.J.B., Valente S.C. 2008. New geological and single-zircon Pb evaporation data from the Central Guyana Domain, southeastern Roraima, Brazil: Tectonic implications. Journal of South American Earth Sciences, 26:318-328.
Araújo Neto H. & Moreira H.L. 1976. Projeto Estanho de Abonari. Brasília, Ministério de Minas e Energia, Departamento Nacional de Produção Mineral, Companhia de Pesquisa e Recursos Minerais (MME/DNPM/CPRM), Relatório, 1:232. (in portuguese).
Barker D.S. 1970. Composition of granophyre, myrmekite, and graphic granite. Geological Society of America Bulletin, 81:3339-3350.
Bull K.F. & McPhie J. 2007. Fiamme textures in volcanic successions: Flaming issues of definition and interpretation. Journal of Volcanology and Geothermal Research, 164:205-216.
Campbell L.H. 1996. Fluid dynamic process in basaltic magma chamber. In: Cawthorn R.G. (ed). Layered intrusions (Developments in Petrology). Elsevier Science, London, 519 p.
Castro A., De la Rosa J.D., Stephen W.E. 1990. Magma mixing in the subvolcanic environment: petrology of the Genera interaction zone near Seville, Spain. Contributions to Mineralogy and Petrology, 105:9-26.
Castro A., Moreno-Ventas I., De la Rosa J.D. 1991. H-type (hybrid) granitoids: a proposed revision of the granite-type classification and nomenclature. Earth-Science Reviews, 31:237-253.
Chappel B.W. 1996. Magma mixing and the production of compositional variation within granite suites: evidence from the granites of southeastern Australia. Journal of Petrology, 37(3):449-470.
Cole J.W., Milner D.M., Spinks K.D. 2005. Calderas and caldera structures: a review. Earth-Science Reviews, 69:1-96.
Costi H.T., Santiago A.F., Pinheiro S.S. 1984. Projeto Uatumã-Jatapu, Relatório Final. Manaus: CPRM – SUREG-MA. 133 p. (in portuguese).
Costi, H.T., Dall´Agnol, R., Moura, C.A.V. 2000. Geology and Pb-Pb geochronology of Paleoproterozoic volcanic and granitic rocks of the Pitinga Province, northern Brazil. International Geology Reviews, 42:832-849.
Costi H.T., Valério C.S., Alves M.A.S., Souza V.S. 2009. Overview of the geology of southernmost Guyana Shield, Presidente Figueiredo district, NE Amazonas: Guide and field trip program. In: SBG-Núcleo Norte, Simpósio de Geologia na Amazônia, 11, Manaus (AM), CD-Rom.
CPRM – Serviço Geológico do Brasil. 2000. Programa Levantamentos Geológicos Básicos do Brasil. Caracaraí, Folhas NA.20-Z-B e NA.20-Z-D inteiras e parte das folhas NA.20-Z-A, NA.20-Z-C, NA.21-Y-C e NA.21-Y-A. Estado de Roraima. Escala 1:500.000. Brasília, CD-Rom. (in portuguese).
CPRM – Serviço Geológico do Brasil. 2006. Geologia e recursos minerais do estado do Amazonas. Escala 1:1.000.000, CPRM/CIAMA, Manaus, 180 p. (in portuguese).
Faria, M.S.G., Santos, J.O.S., Luzardo, R., Hartmann, L.A., 2002. The oldest Island Arc of Roraima state, Brazil – 2.03Ga: Zircon Shrimp U–Pb geochronology of Anauá Complex. In: SBG, Congresso Brasileiro de Geologia, vol. 41. João Pessoa, PB, Anais, p. 38.
Faria M.S.G., Almeida M.E., Santos J.O.S., Chemale Jr. F. 2003. Evolução geológica da região do alto Rio Anauá - Roraima. In: SBG-Núcleo Norte, Simpósio de Geologia no Amazonas, 8, Manaus (AM), CD-Rom. (in portuguese).
Ferron J.M.T.M. 2006. Geologia regional, geoquímica, geocronologia Pb-Pb de rochas graníticas e vulcânicas paleoproterozóicas as Província Pitinga, Cráton Amazônico. Tese de Doutorado, Programa de Pós-Graduação Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, 331 p. (in portuguese).
References
Cristóvão da Silva Valério et al.
Revista Brasileira de Geociências, volume 42(4), 2012 711
Ferron J.M.T.M., Bastos Neto A.C., Lima E.F., Costi H.T., Moura C.A.V., Prado M., Pierosan R., Galarza M.A. 2006. Geologia e geocronologia Pb-Pb de rochas graníticas e vulcânicas ácidas a intermediárias paleoproterozóicas da Província Pitinga, Cráton Amazônico. Revista Brasileira de Geociências, 36(3):499-512. (in portuguese).
Ferron J.M.T.M., Bastos Neto A.C., Lima E.F., Nardi L.V.S., Costi H.T., Pierosan R., Prado M. 2010. Petrology, Geochemistry, and Geochronology of Paleoproterozoic Volcanic and Granitic Rocks (1.89 to 1.88 Ga) of the Pitinga Province, Amazonian Craton, Brazil. Journal of South American Earth Sciences, 29:483-497.
Freitas M.E., Chagas A.N.B., Araújo F.M., Mejia N.I.M. 2007. Interpretação das texturas das rochas vulcânicas do Grupo Iricoumé na região de Presidente Figueiredo – AM. In: SBG-Núcleo Norte, Simpósio de Geologia no Amazonas, 10, Porto Velho (RO), CD-Rom. (in portuguese).
Frost T.P. & Mahood G.A. 1987. Field, chemical, and physical constraints on mafic-felsic magma interaction in the Lamarck granodiorite, Sierra Nevada, California. Geological Society of America Bulletin, 99:272-291.
Haapala I. & Rämö O.T. 1992. Tectonic setting and origin of The Proterozoic rapakivi granites of southeastern Fennoscandia. Transactions of the Royal Society of Edinburgh: Earth and Environmental Science, 83:165-171.
Haapala I. & Rämö O.T. 1999. Rapakivi granites and related rocks: an introduction. Precambrian Research, 95:1-7.
Hibbard M.J. 1979. Myrmekite as a marker between pre and post aqueous phase saturation in granitic systems. Geological Society of America Bulletin, 90:1047-1062.
Hibbard M.J. 1987. Deformation of incompletely crystallized magma systems: granite gneisses and their tectonic implication. Journal of Geology, 95:543-561.
Hibbard M.J. 1995. Petrography to petrogenesis. Prentice Hall Inc., New Jersey, USA, 587 p.
Hughes C.J. 1982. Igneous Petrology. Elservier Science, New York, Developments in Petrology, 7, 551 p.
Huppert H.E. & Sparks R.S.J. 1988. The generation of granitic magma by intrusion of basalt into continental crust. Journal of Petrology, 29:599-624.
Lameyre J. & Bowden P. 1982. Plutonic rocks type series: discrimination of various granitoid series and related rocks. Journal of Volcanology and Geothermal Research, 14:169-186.
Lipman P.W. 1984. The roots of ash flow calderas in Western North America: windows into the tops of granitic batholiths. Journal of Geophysical Research, 89:8801-8841.
Lipman P.W. 1997. Subsidence of ash-flow calderas: relation to caldera size and magma-chamber geometry. Bulletin of Volcanology., 59:198-218.
Macambira M.J.B., Vasquez M.L., Silva D.C.C., Galarza M.A., Barros C.E.M., Camelo J.F. 2009. Crustal growth of the central-eastern Paleoproterozoic domain, SE Amazonian craton: Juvenile accretion vs. reworking. Journal of South American Earth Science, 27:235-246.
Marques S.N.S., Nascimento R.S.C., Souza V.S., Dantas E.L. 2007. Características geoquímicas das rochas vulcânicas do Grupo Iricoumé, em perfis estratigráficos, na região de Presidente Figueiredo-AM. In: SBG-Núcleo Norte, Simpósio de Geologia no Amazonas, 10, Porto Velho-RO, CD-Rom. (in portuguese).
Paschier C.W. & Trouw R.A.J. 1998. Microtectonics. Springer, CD-Rom.
Phillips E.R. 1974. Myrmekite – one hundred years later. Lithos, 7:181-194.
Phillips E.R. 1980. On polygenetic myrmekite. Geological Magazine, 117:29-36.
Rämö O.T. 1991. Petrogenesis of the Proterozoic rapakivi granites and related basic rocks of southeastern Fennoscandia: Nd and Pb isotopic and general geochemical constraints. Geological Survey of Finland Bulletin, 355, 161 p.
Rämö O.T. & Haapala I. 1995. One hundred years of rapakivi granite. Mineralogy and Petrology, 52:129-185.
Santos J.O.S., Moreira A.S., Pessoa M.R., Oliveira J.R., Malouf R.F., Veiga Jr. J.P., Nascimento J.O. 1974. Projeto Norte da Amazônia, domínio baixo Rio Negro. DNPM/CPRM, Relatório Final Integrado, Manaus, Vol. 4:. (in portuguese).
Santos J.O.S., Silva L.C., Faria M.S.G., Macambira M.J.B. 1997. Pb-Pb single crystal, evaporation isotopic study on the post-tectonic, subalkalic, A-type Moderna granite (Mapuera Intrusive Suite), State of Roraima, northern Brazil. In: International Symposium on granites and related mineralizations. Salvador, Extended Abstracts, 1:273-275.
Santos J.O.S., Faria M.S.G., Hartmann L.A., McNaughton N.J., Fletcher I.R. 2001. Oldest charnockite magmatism in the Amazon craton: zircon U–Pb SHRIMP geochronology of the Jaburu Charnockite. Southern Roraima, Brazil. In: SBG/NO, Simpósio de Geologia da Amazônia, 7, Belém, Workshop II, 4 p.
Santos J.O.S., Hartmann L.A., Faria M.S.G., Riker S.R.L., Souza M.M., Almeida M.E., McNaughton N.J. 2006. A compartimentação do Cráton Amazonas em províncias: avanços ocorridos no período de 2000–2006. In: SBG-NO, Simpósio de Geologia da Amazônia, 9, Belém, CD-Rom.(in portuguese).
Smith J.V. & Brown W.L. 1988. Feldspar minerals: crystals structures, physical, chemistry and textural properties. Spring Verlag, Berlin, 2, 2ed. 828 p.
Souza A.G.H., Milliotti C.A., Luzardo R. 2006. Caracterização petrográfica das rochas aflorantes na pedreira do Getúlio, região de Presidente Figueiredo (AM). In: SBG, Congresso Brasileiro de Geologia, 43, CD-Rom. (in portuguese).
Souza V.S., Marques S.N.S., Nascimento R.S., Valério C.S. 2007. Texturas e estruturas em rochas piroclásticas e vulcânicas paleoproterozóicas do Grupo Iricoumé, sudeste do Município de Presidente Figueiredo (AM). In: SBG-NO, Simpósio de Geologia no Amazonas, 10, Porto Velho-RO, CD-Rom. (in portuguese).
1.90 to 1.88 Ga I- and A-type granitoids from NE Amazonas State
712 Revista Brasileira de Geociências, volume 42(4), 2012
Souza V.S. & Nogueira A.C.R. 2009. Seção geológica Manaus–Presidente Figueiredo (AM), borda norte da Bacia do Amazonas: Um guia para excursão de campo. Revista Brasileira de Geociências, 39(1):16-19. (in portuguese).
Streckeisen A. 1976. To each plutonic rock its proper name. Earth-Sciences Reviews, 12:1-33.
Tassinari C.C.G., Macambira M.J.B. 1999. Geochronological provinces of the Amazonian Craton. Episodes, 22(3):174-182.
Tassinari, C.C.G., Bettencourt, J.S., Geraldes, M.C., Macambira, M.J.B., Lafon, J.M., 2000. The Amazonian Craton. In: UG Cordani, EJ Milani, A Thomaz Filho, DA Campos (Edit.). Tectonic Evolution of South America. 31st International Geological Congress, Rio de Janeiro, Brazil, p.41–95.
Tassinari, C.C.G. & Macambira, M.J.B. 2004. A evolução tectônica do cráton Amazônico. In: V. Mantesso-Neto, A. Bartorelli, C. Dal Ré Carneiro, B.B. Brito-Neves. Geologia do Continente Sul-Americano: Evolução da obra de Fernando Flávio Marques de Almeida. Beca, São Paulo, p.471–485 (in portuguese).
Valério C.S., Souza V.S., Macambira M.J.B., Milliotti C.A, Carvalho A.S. 2005. Geoquímica e idade Pb-Pb de zircão do Grupo Iricoumé na região da borda norte da bacia do Amazonas, município de Presidente Figueiredo (AM). In: SBG, Simpósio de Vulcanismo e Ambientes Associados, 3, p. 47-52. (in portuguese).
Valério C.S. 2006. Magmatismo Paleoproterozóico do extremo sul do Escudo das Guianas, município de Presidente Figueiredo (AM): geologia, geoquímica e geocronologia Pb-Pb em zircão. Dissertação de Mestrado, Departamento de Geologia, Programa de
Pós-graduação em Geociências, Universidade Federal do Amazonas, Manaus, 112 p. (in portuguese).
Valério C.S., Souza V.S., Macambira M.J.B., Galarza M.A. 2006A. Aspectos geoquímicos e idade Pb-Pb da borda sudeste do batólito São Gabriel, Município de Presidente Figueiredo (AM), Escudo das Guianas: Implicações tectônicas. In: SBG/NO, Simpósio de Geologia no Amazonas, 9. CD-Rom (in portuguese).
Valério C.S., Souza V.S., Macambira M.J.B, Galarza M.A. 2006B. Geoquímica e geocronologia Pb-Pb da Suíte Intrusiva Água Branca, Município de Presidente Figueiredo (AM): evidências de colisão no Paleoproterozóico da Amazônia Ocidental. Revista Brasileira de Geociências, 36(2):359-370. (in portuguese).
Valério C.S., Souza V.S., Macambira M.J.B. 2009. The 1.90–1.88 Ga magmatism in the southernmost Guyana Shield, Amazonas, Brazil: geology, geochemistry, zircon geochronology, and tectonic implications. Journal of South American Earth Sciences, 28(3):304-320.
Valério C.S., Macambira M.J.B., Souza V.S. 2010. Litoestratigrafia e aspectos petrogenéticos de granitóides tipos I e A (1,90–1,88 Ga) do SW do município de Presidente Figueiredo, NE do Amazonas. In: SBG, Congresso Brasileiro de Geologia, 45, Belém, CD-Rom. (in portuguese).
Veiga Jr. J.P., Nunes A.C.B., Souza E.C., Santos J.O.S., Amaral J.E., Pessoa M.R., Souza S.A.S. 1979. Projeto Sulfetos do Uatumã. Manaus, DNPM/CPRM. Relatório Final, vol.6. (in portuguese).
Manuscrito ID 21782Recebido em: 27/06/2011
Aprovado em: 24/07/2012