Several granitic bodies have been identified in the easternmost part of the Araguaia Belt, locate... more Several granitic bodies have been identified in the easternmost part of the Araguaia Belt, located in the highest metamorphic grade domain (Estrondo Group). These granites are interpreted as late kinematic in relation to the main tectonic and regional metamorphism in the evolution of this belt, at the end of the Neoproterozoic. The Presidente Kennedy Granodiorite (PKG) and the Barrolândia Granite (BG), cropping out in the central portion of the Araguaia Belt, are plutons of this granitogenesis. PKG and BG are small-elongated stocks concordant with foliation of mica schist and feldspathic schist of the Estrondo Group, without metamorphic thermal contact effects. They are hololeucocratic rocks of granodioritic and monzogranitic composition, containing two micas (biotite and muscovite), and eventually garnet. In general, the granites are grayish-gray, slightly pink, equigranular, with hipidiomorfic or alotriomorfic granular textures. However, tectono-...
Along the domain of low metamorphic grade (Midwestern portion) of the Araguaia Belt, outcrop doze... more Along the domain of low metamorphic grade (Midwestern portion) of the Araguaia Belt, outcrop dozens mafic and/or ultramafic bodies of ophiolitic suites. An example is the Morro do Agostinho Ophiolite Suite, in the surroundings of the city of Araguacema (Tocantins) that configures a small isolated body that sustains the Morro do Agostinho and is tectonically emplaced in meta-sandstones, slates and phyllites of Couto Magalhães Formation (Tocantins Group). The Morro do Agostinho Ophiolite Suite consists of serpentinized peridotites, basalts and ferriferous cherts. The association of basalts is characterized by a significant layer of submarine pillow lavas overlying serpentinized peridotites. The basalts were classified into massive and hialobasalts types. Massive basalts are homogenous, with intersertal texture that is essentially composed of thin laths and acicular crystals of plagioclase and clinopyroxene and present rare crystals of olivine, chalcocite and chalcopyrite. Hyalobasalt ...
Resumo Estudos de planejamento turístico, espeleológicos, geológicos, geomorfológicos e arqueológ... more Resumo Estudos de planejamento turístico, espeleológicos, geológicos, geomorfológicos e arqueológicos, entre outros, foram realizados no Parque Estadual da Serra dos Martírios-Andorinhas localizado no sudeste do estado do Pará, fronteira com o Tocantins, sendo objeto da edição de um livro com resultados de pesquisas de caráter multidisciplinar dos últimos 10 anos. O Parque situado em um ambiente serrano destaca-se no relevo isolado na planície do rio Araguaia, na região de transição Floresta Amazônica-Cerrado. Reúne grande diversidade da fauna e flora com sistemas aquáticos diversificados, sítios arqueológicos com impressionantes gravuras rupestres; pedrais, ilhas e corredeiras no rio Araguaia que com toda a beleza cênica potencializam a região para o ecoturismo e que, somados às características arqueológicas e geológicas reúnem todas as condições para transformar-se em um Geoparque. Palavras-Chave: Parque Estadual da Serra dos Martírios-Andorinhas; Geoturismo, Cinturão Araguaia, Ne...
The Parapuí Suite is na important volcanic unit of the Jaibaras Graben, northwestern Ceará and re... more The Parapuí Suite is na important volcanic unit of the Jaibaras Graben, northwestern Ceará and represents an intense basalt volcanic activity during the Neoproterozoic/Eopaleozoic. Three main sequences are identified including basalts (labradorite/andesine basalts, trachybasalts and magnetite-ilmenite basalts), rhyolites and volcanoclastic rocks that occur intercalated with arkosian sandstones of the Jaibaras Group. The basalts and trachybasalts are the most abundant rock types in this Suite and occur as successions of large massive and amigdaloidal lava flows. They are holocrystalline or hypocrystalline, porphyritic or aphyric with flow structures. The main minerals are labradorite/andesine, titanoaugite and minor olivine, albite, sanidina, magnetite/ilmenite, pirite, titanite and apatite. The chemical signature is characterized by high contents of alkalis, TiO2 and P2O5, and enrichement in LREE with small negative Eu anomalies, high to moderate (La/Yb)N and (Ti/Y)N > 1. In disc...
The Northwestern region of Borborema Province features a wide variety of granitic bodies with div... more The Northwestern region of Borborema Province features a wide variety of granitic bodies with diverse nature and tectonic evolution, since the Paleoproterozoic to Early Paleozoic, presenting higher incidence related to Neoproterozoic emplaced at different stages of Brasiliano (Panafrican) orogeny. One of these examples is the Chaval Granite representing a batholith body intruded in orthogneisses of Granja Complex and supracrustal rocks of Martinópole Group, outcropped near the Ceará and Piauí Atlantic coasts, Northeastern Brazil. The batholith is partly covered by Cenozoic coastal deposits and sedimentary rocks of the Paleozoic Parnaíba Basin. The Chaval Granite has a striking textural feature, which is represented by porphyritic highlighting microcline megacrysts in syenogranites and monzogranites, and many others textural/structural features of magmatic origin. They allowed interpreting the plutonic evolution at relatively shallow crustal level emplacement acting processes of fractional crystallization, magma mixing with intense magmatic flow, and gravitational force due to density difference of magma that lead to fluctuation of megacrysts of microcline and plagioclase in the residual magma, and accommodation of small bodies of leucogranite and pegmatites in the final stages of plutonic magmatic evolution of such plutonism. On the other hand, across the Eastern half of the pluton, there is a rich collection of shear structures related to the tectonic construction of the Santa Rosa Transcurrent Shear Zone, which led to tectono-metamorphic transformations superimposed on magmatic features that reached peak metamorphic conditions in the low amphibolite facies. Cartographically, three homogeneous structural domains were individualized, and each of them presents a variety of petrographic-structural features of the Chaval of igneous or tectonic nature. The plutonic rocks were deformed and progressively modified Eastward, in which the rocks change to darker gray, and comminution and dynamic recrystallization processes [...]
Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Ar... more Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Araguaia Belt, central Brazil, yield Pb/Pb zircon evaporation ages for detrital zircons from quartzites concentrated around 1000–1200 Ma and 2800–2900 Ma; Sm–Nd TDM model ages of schists and phyllites scatter around 1600–1700 Ma. Facies analysis of low-grade metasedimentary rocks from drill cores suggests a sedimentary environment of basin floor and lowerto upper-slope turbidites. Nearby sources are indicated by the textural and mineralogical immaturity; together with structural geological data indicating tectonic transport of the supracrustal pile towards the NW, this suggests probable provenance from the southeastern portion of the Araguaia Belt and not from the Amazonian Craton as usually believed. The Goias Massif, Goias Magmatic Arc, Sao Francisco Craton and Paranapanema block are considered to be the best candidates. They may have formed a larger continental mass during West Gondwana...
Manuscript ID: 20160097. Received in: 08/12/2016. Approved in: 03/27/2017. ABSTRACT: The Porangat... more Manuscript ID: 20160097. Received in: 08/12/2016. Approved in: 03/27/2017. ABSTRACT: The Porangatu Granulite Complex is exposed in the central part of the Neoproterozoic Tocantins province in central Brazil, along the boundary between the Brasília Belt to the east and the Araguaia Belt to the west. This is part of the transcontinental Transbrasiliano-Kandi shear system. The complex includes garnet-rich enderbite and charnockite, high-grade gneisses as well as lenses of garnet-bearing mafic granulite or amphibolites, and in situ anatectic charnockite, elongated in the NNE-SSW direction along the Talismã Shear Zone (TSZ). These rocks represent suites of ortho-derived rocks of calc-alkaline affinity and small contributions of tholeiitic basalts and aluminous paragneisses. The structural framework records thrust components probably related to the early stages of an oblique collision during the evolution of Neoproterozoic Brasiliano orogens, and can be understood as involving a collision...
... CHAVES, César Lisboa, GORAYEB, Paulo Sergio de Sousa and MOURA, Candido Augusto Veloso. ... T... more ... CHAVES, César Lisboa, GORAYEB, Paulo Sergio de Sousa and MOURA, Candido Augusto Veloso. ... This work presents the geologic characterization of the Ipueiras Intrusive Suite, which comprises four granitic plutons, named do Carmo, Areias, Ipueiras and Itália, located in ...
The region of Tucurui, northeastern Para, is located in the transition between the Amazon Craton ... more The region of Tucurui, northeastern Para, is located in the transition between the Amazon Craton and the Araguaia Belt. In this region, there is an extensive graben filled by a volcano-sedimentary succession, 35 km wide that extends over 100 km in the NNW-SSE direction and which is represented by the Tucurui Group. This group consists of a succession of basaltic flows and diabase sills interbedded with sub-arkose and siltstones. Together with the metasedimentary rocks of the Tocantins Group, these rocks represent the latest records of the Araguaia Orogen in the extreme North of Brazil. The volcanic deposits consist of basalt flows and volcanic breccias associated with diabase sills. The flows are predominantly composed of massive and locally amygdaloidal basalts and basaltic breccias. The basalts are aphanitic, fine-grained or glassy, holo-to hypocrystalline, and are made up of labradorite, augite, Fe–Ti minerals oxides, sulfides, and apatite. The massive basalts have intergranular ...
Geological Society, London, Special Publications, 2008
Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Ar... more Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Araguaia Belt, central Brazil, yield 207Pb/206Pb zircon evaporation ages for detrital zircons from quartzites concentrated around 1000–1200 Ma and 2800–2900 Ma; Sm–Nd TDM model ages of schists and phyllites scatter around 1600–1700 Ma. Facies analysis of low-grade metasedimentary rocks from drill cores suggests a sedimentary environment of basin floor and lower- to upper-slope turbidites. Nearby sources are indicated by the textural and mineralogical immaturity; together with structural geological data indicating tectonic transport of the supracrustal pile towards the NW, this suggests probable provenance from the southeastern portion of the Araguaia Belt and not from the Amazonian Craton as usually believed. The Goiás Massif, Goiás Magmatic Arc, São Francisco Craton and Paranapanema block are considered to be the best candidates. They may have formed a larger continental mass during West ...
Records of large crustal masses in the northwest of Borborema Province (BP) spread over more than... more Records of large crustal masses in the northwest of Borborema Province (BP) spread over more than 300 km are found as numerous granitic bodies amid a high-grade metamorphic gneissic-migmatitic terrain. The Tamboril-Santa Quitéria Complex (TSQC) is a Neoproterozoic example of these records; it is located in the north of the Ceará Central Domain (CECD) and its origin is related to a continental magmatic arc at different evolutionary stages of the arc. The Uruburetama Granite (UG), object of this study, fits into this context and constitutes one of the most representative batholiths occupying an area of 1,500 km 2. Dozens of other similar plutons have been recorded in cartographic works that show similarities which suggests the grouping of these bodies in the Uruburetama Granitic Suite (UGS), previously included in the TSQC. The UG consists of a variety of plutonic rocks associated with mafic-dioritic dikes and its metamorphic products. Six petrographic facies were identified among the plutonic rocks: biotite-hornblende monzogranites and syenogranitic varieties, biotite-hornblende granodiorites, in addition to quartz syenite, leucomonzogranites, and diorites rocks. These rocks are affected by deformation, with greater intensity at the edges of the batholith, where thrust shear zones with transcurrent components were installed, generating tectonic fabrics (mylonitic foliations, stretch lineation, almond feldspar porphyroclasts, and ribbon quartz). Despite the superimposed deformational effects, magmatic relict textures are partially preserved, mainly toward the central portion of the pluton. The UG and the associated plutons are hosted by migmatized orthogneisses, paragneisses with garnet, sillimanite or kyanite, marbles, calcium-silicate gneisses, micaschists, sillimanite quartzites, and amphibolite lenses. The contact relations are diffuse with gradation for migmatites, and in rare cases, intrusive contacts with gneiss mega-xenolites are registered. The geochronological data obtained by Pb-evaporation zircon in two samples of the UG show average ages of 655 ± 2 and 656 ± 1 Ma. U-Pb zircon data for the same samples showed slightly younger age values of 559 ± 10 and 634 ± 10 Ma, respectively. The ages obtained are considered as representative of the magmatic phases of UG crystallization in the context of the evolution of the Santa Quitéria Magmatic Arc (SQMA), with the main magmatic phase of the UG in the Cryogenian. However, the age of 559 Ma would represent a younger magmatic event in the evolution of the arch. Overall, these ages correspond to the "Pre-Collisional I" or "Early-Sin-Orogenic" phase of a large collisional belt in the west of BP, and the younger ages must represent events related to the continuity of the orogen convergence of the Latest-Pre-collisional I (634 Ma) and Post-Collisional I (559 Ma) phases. Sm-Nd whole-rock isotopes data showed ε Nd (t) values predominantly negative (-25.6 and-0.9), and Nd-T DM model ages of 2.90 and 1.2 Ga. The results of the Lu-Hf isotopes analysis for the Bt-Hbl monzogranite sample showed negative ε Hf values (-26.75 to-35.48) and Hf-T DM C model ages of 3.12 to 3.65 Ga while the results for Bt-Hbl granodiorite showed ε Hf values of-2.07 to +1.08 and Hf-T DM C model ages of 1.46 to 1.66 Ga. These data point to the existence of two distinct and older crustal sources in the generation of these granitoids, one in the Mesoarchean, and the other in the Mesoproterozoic. The Archean ages correspond to the basement in the south of the CECD (Tróia Massif and Granjeiro Complex); on the other hand, the Mesoproterozoic ages are up for discussion, since terrains with this type of age do not occur adjacent to the BP. On the other hand, it can be interpreted as a mixture of sources, one of them probably juvenile, neoproterozoic, with contamination of the Archean crust. Thus, the UG is considered one of the most important records of the beginning of the evolution of the Santa Quitéria Magmatic Arc associated with a wide collisional belt in the "West Gondwana Orogen" in the west of Borborema Province.
The northwestern region of Borborema Province is represented by the Ceara Central and Northwest C... more The northwestern region of Borborema Province is represented by the Ceara Central and Northwest Ceara crustal blocks connected by an extensive transcurrent shear zone that represents the northern portion of the Transbrasiliano Lineament in a complex geological context, which brings together geological units of nature, origin, and ages of the Archean to the Paleozoic. In this scenario, there is a large amount of granitic bodies, with different natures, age and tectonic environment, but predominantly representing a more intense granitogenesis in the Paleozoic Neoproterozoic and early Paleozoic, with plutons emplaced in different stages of the Brazilian Orogeny. In this context, the Chaval Granite corresponds to an isolated body in the extreme northwest of Borborema Province, located near the Atlantic coast, in the northern states of Ceará and Piauí. It is an intrusive batholith housed in Siderian orthogneisses (Granja Complex) and in Neoproterozoic supracrustal rocks (Martinopole Group), but is partly covered by sedimentary rocks from the Parnaíba Paleozoic Basin (Serra Grande Group), and coastal Cenozoic deposits. Field data and petrographic studies highlight the porphyritic texture with microcline megacrystals involved in coarce matrix as a remarkable feature. The predominant petrographic types are granodiorites, with variations for monzogranites and tonalites. The predominant primary mineral constituents are pertitic microcline, oligoclase, and quartz; biotite and rarely hornblende as qualified minerals and additionally titanite, apatite, zircon, alanite, and opaque minerals. Another peculiar characteristic is the deformational features related to the installation of the Santa Rosa Transcurrent Shear Zone along its eastern flank. The effects of the transcurrent shear deformation led to the modification of the original magmatic fabrics in much of the eastern half of the batolith, generating various types of mylonites. Thus, the typically igneous textures preserved in the western half of the pluton were gradually replaced by tectonic fabrics, which initially evolved into proto-mylonites in the central portion of the body, grading to mylonites eastward, highlighting strongly stretching, comminution associated with dynamic recrystallization, highlighting the formation of microcline and plagioclase porphyroclasts in a mylonitic matrix, which are involved by mylonitic foliation. Geochemical studies reveal compositional similarities, compatible with petrographic classifications, in which they mostly present granodioritic composition, followed by monzogranites and tonalites, classified as I-type granites, peraluminous with compatible with the calcium-alkaline series. The geochemical signatures of the Chaval Granite indicate the character of the tectonic magmatic arc environment. U-Pb zircon analysis by Mass Spectrometry (LA-ICP-MS) indicates crystallization age of 633 Ma, placing it in the Neoproterozoic, late Cryogenic-Early Ediacaran period, being one of the oldest granitoids in northwestern Borborema Province, correlated to the granites of the Santa Quitéria Magmatic Arc in the Ceara Central Domain. Hf-T DM model ages (2.65 to 2.13 Ga) and εHf(t = 633 Ma) values from-9.6 to-18.1 suggest incorporation of neoarchean and paleoproterozoic crustal sources in their formation with a long crustal residence time. Similar Sm-Nd data in whole-rock indicate Nd-T DM model ages of 1.27, 1.72 and 2.04 Ga and negative εNd(t = 633 Ma) values of-2.64 to-9.13, indicating paleoproterozoic and mesoproterozoic sources, with considerable crustal residence time implying a more evolved nature.
Several granitic bodies have been identified in the easternmost part of the Araguaia Belt, locate... more Several granitic bodies have been identified in the easternmost part of the Araguaia Belt, located in the highest metamorphic grade domain (Estrondo Group). These granites are interpreted as late kinematic in relation to the main tectonic and regional metamorphism in the evolution of this belt, at the end of the Neoproterozoic. The Presidente Kennedy Granodiorite (PKG) and the Barrolândia Granite (BG), cropping out in the central portion of the Araguaia Belt, are plutons of this granitogenesis. PKG and BG are small-elongated stocks concordant with foliation of mica schist and feldspathic schist of the Estrondo Group, without metamorphic thermal contact effects. They are hololeucocratic rocks of granodioritic and monzogranitic composition, containing two micas (biotite and muscovite), and eventually garnet. In general, the granites are grayish-gray, slightly pink, equigranular, with hipidiomorfic or alotriomorfic granular textures. However, tectono-...
Along the domain of low metamorphic grade (Midwestern portion) of the Araguaia Belt, outcrop doze... more Along the domain of low metamorphic grade (Midwestern portion) of the Araguaia Belt, outcrop dozens mafic and/or ultramafic bodies of ophiolitic suites. An example is the Morro do Agostinho Ophiolite Suite, in the surroundings of the city of Araguacema (Tocantins) that configures a small isolated body that sustains the Morro do Agostinho and is tectonically emplaced in meta-sandstones, slates and phyllites of Couto Magalhães Formation (Tocantins Group). The Morro do Agostinho Ophiolite Suite consists of serpentinized peridotites, basalts and ferriferous cherts. The association of basalts is characterized by a significant layer of submarine pillow lavas overlying serpentinized peridotites. The basalts were classified into massive and hialobasalts types. Massive basalts are homogenous, with intersertal texture that is essentially composed of thin laths and acicular crystals of plagioclase and clinopyroxene and present rare crystals of olivine, chalcocite and chalcopyrite. Hyalobasalt ...
Resumo Estudos de planejamento turístico, espeleológicos, geológicos, geomorfológicos e arqueológ... more Resumo Estudos de planejamento turístico, espeleológicos, geológicos, geomorfológicos e arqueológicos, entre outros, foram realizados no Parque Estadual da Serra dos Martírios-Andorinhas localizado no sudeste do estado do Pará, fronteira com o Tocantins, sendo objeto da edição de um livro com resultados de pesquisas de caráter multidisciplinar dos últimos 10 anos. O Parque situado em um ambiente serrano destaca-se no relevo isolado na planície do rio Araguaia, na região de transição Floresta Amazônica-Cerrado. Reúne grande diversidade da fauna e flora com sistemas aquáticos diversificados, sítios arqueológicos com impressionantes gravuras rupestres; pedrais, ilhas e corredeiras no rio Araguaia que com toda a beleza cênica potencializam a região para o ecoturismo e que, somados às características arqueológicas e geológicas reúnem todas as condições para transformar-se em um Geoparque. Palavras-Chave: Parque Estadual da Serra dos Martírios-Andorinhas; Geoturismo, Cinturão Araguaia, Ne...
The Parapuí Suite is na important volcanic unit of the Jaibaras Graben, northwestern Ceará and re... more The Parapuí Suite is na important volcanic unit of the Jaibaras Graben, northwestern Ceará and represents an intense basalt volcanic activity during the Neoproterozoic/Eopaleozoic. Three main sequences are identified including basalts (labradorite/andesine basalts, trachybasalts and magnetite-ilmenite basalts), rhyolites and volcanoclastic rocks that occur intercalated with arkosian sandstones of the Jaibaras Group. The basalts and trachybasalts are the most abundant rock types in this Suite and occur as successions of large massive and amigdaloidal lava flows. They are holocrystalline or hypocrystalline, porphyritic or aphyric with flow structures. The main minerals are labradorite/andesine, titanoaugite and minor olivine, albite, sanidina, magnetite/ilmenite, pirite, titanite and apatite. The chemical signature is characterized by high contents of alkalis, TiO2 and P2O5, and enrichement in LREE with small negative Eu anomalies, high to moderate (La/Yb)N and (Ti/Y)N > 1. In disc...
The Northwestern region of Borborema Province features a wide variety of granitic bodies with div... more The Northwestern region of Borborema Province features a wide variety of granitic bodies with diverse nature and tectonic evolution, since the Paleoproterozoic to Early Paleozoic, presenting higher incidence related to Neoproterozoic emplaced at different stages of Brasiliano (Panafrican) orogeny. One of these examples is the Chaval Granite representing a batholith body intruded in orthogneisses of Granja Complex and supracrustal rocks of Martinópole Group, outcropped near the Ceará and Piauí Atlantic coasts, Northeastern Brazil. The batholith is partly covered by Cenozoic coastal deposits and sedimentary rocks of the Paleozoic Parnaíba Basin. The Chaval Granite has a striking textural feature, which is represented by porphyritic highlighting microcline megacrysts in syenogranites and monzogranites, and many others textural/structural features of magmatic origin. They allowed interpreting the plutonic evolution at relatively shallow crustal level emplacement acting processes of fractional crystallization, magma mixing with intense magmatic flow, and gravitational force due to density difference of magma that lead to fluctuation of megacrysts of microcline and plagioclase in the residual magma, and accommodation of small bodies of leucogranite and pegmatites in the final stages of plutonic magmatic evolution of such plutonism. On the other hand, across the Eastern half of the pluton, there is a rich collection of shear structures related to the tectonic construction of the Santa Rosa Transcurrent Shear Zone, which led to tectono-metamorphic transformations superimposed on magmatic features that reached peak metamorphic conditions in the low amphibolite facies. Cartographically, three homogeneous structural domains were individualized, and each of them presents a variety of petrographic-structural features of the Chaval of igneous or tectonic nature. The plutonic rocks were deformed and progressively modified Eastward, in which the rocks change to darker gray, and comminution and dynamic recrystallization processes [...]
Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Ar... more Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Araguaia Belt, central Brazil, yield Pb/Pb zircon evaporation ages for detrital zircons from quartzites concentrated around 1000–1200 Ma and 2800–2900 Ma; Sm–Nd TDM model ages of schists and phyllites scatter around 1600–1700 Ma. Facies analysis of low-grade metasedimentary rocks from drill cores suggests a sedimentary environment of basin floor and lowerto upper-slope turbidites. Nearby sources are indicated by the textural and mineralogical immaturity; together with structural geological data indicating tectonic transport of the supracrustal pile towards the NW, this suggests probable provenance from the southeastern portion of the Araguaia Belt and not from the Amazonian Craton as usually believed. The Goias Massif, Goias Magmatic Arc, Sao Francisco Craton and Paranapanema block are considered to be the best candidates. They may have formed a larger continental mass during West Gondwana...
Manuscript ID: 20160097. Received in: 08/12/2016. Approved in: 03/27/2017. ABSTRACT: The Porangat... more Manuscript ID: 20160097. Received in: 08/12/2016. Approved in: 03/27/2017. ABSTRACT: The Porangatu Granulite Complex is exposed in the central part of the Neoproterozoic Tocantins province in central Brazil, along the boundary between the Brasília Belt to the east and the Araguaia Belt to the west. This is part of the transcontinental Transbrasiliano-Kandi shear system. The complex includes garnet-rich enderbite and charnockite, high-grade gneisses as well as lenses of garnet-bearing mafic granulite or amphibolites, and in situ anatectic charnockite, elongated in the NNE-SSW direction along the Talismã Shear Zone (TSZ). These rocks represent suites of ortho-derived rocks of calc-alkaline affinity and small contributions of tholeiitic basalts and aluminous paragneisses. The structural framework records thrust components probably related to the early stages of an oblique collision during the evolution of Neoproterozoic Brasiliano orogens, and can be understood as involving a collision...
... CHAVES, César Lisboa, GORAYEB, Paulo Sergio de Sousa and MOURA, Candido Augusto Veloso. ... T... more ... CHAVES, César Lisboa, GORAYEB, Paulo Sergio de Sousa and MOURA, Candido Augusto Veloso. ... This work presents the geologic characterization of the Ipueiras Intrusive Suite, which comprises four granitic plutons, named do Carmo, Areias, Ipueiras and Itália, located in ...
The region of Tucurui, northeastern Para, is located in the transition between the Amazon Craton ... more The region of Tucurui, northeastern Para, is located in the transition between the Amazon Craton and the Araguaia Belt. In this region, there is an extensive graben filled by a volcano-sedimentary succession, 35 km wide that extends over 100 km in the NNW-SSE direction and which is represented by the Tucurui Group. This group consists of a succession of basaltic flows and diabase sills interbedded with sub-arkose and siltstones. Together with the metasedimentary rocks of the Tocantins Group, these rocks represent the latest records of the Araguaia Orogen in the extreme North of Brazil. The volcanic deposits consist of basalt flows and volcanic breccias associated with diabase sills. The flows are predominantly composed of massive and locally amygdaloidal basalts and basaltic breccias. The basalts are aphanitic, fine-grained or glassy, holo-to hypocrystalline, and are made up of labradorite, augite, Fe–Ti minerals oxides, sulfides, and apatite. The massive basalts have intergranular ...
Geological Society, London, Special Publications, 2008
Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Ar... more Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Araguaia Belt, central Brazil, yield 207Pb/206Pb zircon evaporation ages for detrital zircons from quartzites concentrated around 1000–1200 Ma and 2800–2900 Ma; Sm–Nd TDM model ages of schists and phyllites scatter around 1600–1700 Ma. Facies analysis of low-grade metasedimentary rocks from drill cores suggests a sedimentary environment of basin floor and lower- to upper-slope turbidites. Nearby sources are indicated by the textural and mineralogical immaturity; together with structural geological data indicating tectonic transport of the supracrustal pile towards the NW, this suggests probable provenance from the southeastern portion of the Araguaia Belt and not from the Amazonian Craton as usually believed. The Goiás Massif, Goiás Magmatic Arc, São Francisco Craton and Paranapanema block are considered to be the best candidates. They may have formed a larger continental mass during West ...
Records of large crustal masses in the northwest of Borborema Province (BP) spread over more than... more Records of large crustal masses in the northwest of Borborema Province (BP) spread over more than 300 km are found as numerous granitic bodies amid a high-grade metamorphic gneissic-migmatitic terrain. The Tamboril-Santa Quitéria Complex (TSQC) is a Neoproterozoic example of these records; it is located in the north of the Ceará Central Domain (CECD) and its origin is related to a continental magmatic arc at different evolutionary stages of the arc. The Uruburetama Granite (UG), object of this study, fits into this context and constitutes one of the most representative batholiths occupying an area of 1,500 km 2. Dozens of other similar plutons have been recorded in cartographic works that show similarities which suggests the grouping of these bodies in the Uruburetama Granitic Suite (UGS), previously included in the TSQC. The UG consists of a variety of plutonic rocks associated with mafic-dioritic dikes and its metamorphic products. Six petrographic facies were identified among the plutonic rocks: biotite-hornblende monzogranites and syenogranitic varieties, biotite-hornblende granodiorites, in addition to quartz syenite, leucomonzogranites, and diorites rocks. These rocks are affected by deformation, with greater intensity at the edges of the batholith, where thrust shear zones with transcurrent components were installed, generating tectonic fabrics (mylonitic foliations, stretch lineation, almond feldspar porphyroclasts, and ribbon quartz). Despite the superimposed deformational effects, magmatic relict textures are partially preserved, mainly toward the central portion of the pluton. The UG and the associated plutons are hosted by migmatized orthogneisses, paragneisses with garnet, sillimanite or kyanite, marbles, calcium-silicate gneisses, micaschists, sillimanite quartzites, and amphibolite lenses. The contact relations are diffuse with gradation for migmatites, and in rare cases, intrusive contacts with gneiss mega-xenolites are registered. The geochronological data obtained by Pb-evaporation zircon in two samples of the UG show average ages of 655 ± 2 and 656 ± 1 Ma. U-Pb zircon data for the same samples showed slightly younger age values of 559 ± 10 and 634 ± 10 Ma, respectively. The ages obtained are considered as representative of the magmatic phases of UG crystallization in the context of the evolution of the Santa Quitéria Magmatic Arc (SQMA), with the main magmatic phase of the UG in the Cryogenian. However, the age of 559 Ma would represent a younger magmatic event in the evolution of the arch. Overall, these ages correspond to the "Pre-Collisional I" or "Early-Sin-Orogenic" phase of a large collisional belt in the west of BP, and the younger ages must represent events related to the continuity of the orogen convergence of the Latest-Pre-collisional I (634 Ma) and Post-Collisional I (559 Ma) phases. Sm-Nd whole-rock isotopes data showed ε Nd (t) values predominantly negative (-25.6 and-0.9), and Nd-T DM model ages of 2.90 and 1.2 Ga. The results of the Lu-Hf isotopes analysis for the Bt-Hbl monzogranite sample showed negative ε Hf values (-26.75 to-35.48) and Hf-T DM C model ages of 3.12 to 3.65 Ga while the results for Bt-Hbl granodiorite showed ε Hf values of-2.07 to +1.08 and Hf-T DM C model ages of 1.46 to 1.66 Ga. These data point to the existence of two distinct and older crustal sources in the generation of these granitoids, one in the Mesoarchean, and the other in the Mesoproterozoic. The Archean ages correspond to the basement in the south of the CECD (Tróia Massif and Granjeiro Complex); on the other hand, the Mesoproterozoic ages are up for discussion, since terrains with this type of age do not occur adjacent to the BP. On the other hand, it can be interpreted as a mixture of sources, one of them probably juvenile, neoproterozoic, with contamination of the Archean crust. Thus, the UG is considered one of the most important records of the beginning of the evolution of the Santa Quitéria Magmatic Arc associated with a wide collisional belt in the "West Gondwana Orogen" in the west of Borborema Province.
The northwestern region of Borborema Province is represented by the Ceara Central and Northwest C... more The northwestern region of Borborema Province is represented by the Ceara Central and Northwest Ceara crustal blocks connected by an extensive transcurrent shear zone that represents the northern portion of the Transbrasiliano Lineament in a complex geological context, which brings together geological units of nature, origin, and ages of the Archean to the Paleozoic. In this scenario, there is a large amount of granitic bodies, with different natures, age and tectonic environment, but predominantly representing a more intense granitogenesis in the Paleozoic Neoproterozoic and early Paleozoic, with plutons emplaced in different stages of the Brazilian Orogeny. In this context, the Chaval Granite corresponds to an isolated body in the extreme northwest of Borborema Province, located near the Atlantic coast, in the northern states of Ceará and Piauí. It is an intrusive batholith housed in Siderian orthogneisses (Granja Complex) and in Neoproterozoic supracrustal rocks (Martinopole Group), but is partly covered by sedimentary rocks from the Parnaíba Paleozoic Basin (Serra Grande Group), and coastal Cenozoic deposits. Field data and petrographic studies highlight the porphyritic texture with microcline megacrystals involved in coarce matrix as a remarkable feature. The predominant petrographic types are granodiorites, with variations for monzogranites and tonalites. The predominant primary mineral constituents are pertitic microcline, oligoclase, and quartz; biotite and rarely hornblende as qualified minerals and additionally titanite, apatite, zircon, alanite, and opaque minerals. Another peculiar characteristic is the deformational features related to the installation of the Santa Rosa Transcurrent Shear Zone along its eastern flank. The effects of the transcurrent shear deformation led to the modification of the original magmatic fabrics in much of the eastern half of the batolith, generating various types of mylonites. Thus, the typically igneous textures preserved in the western half of the pluton were gradually replaced by tectonic fabrics, which initially evolved into proto-mylonites in the central portion of the body, grading to mylonites eastward, highlighting strongly stretching, comminution associated with dynamic recrystallization, highlighting the formation of microcline and plagioclase porphyroclasts in a mylonitic matrix, which are involved by mylonitic foliation. Geochemical studies reveal compositional similarities, compatible with petrographic classifications, in which they mostly present granodioritic composition, followed by monzogranites and tonalites, classified as I-type granites, peraluminous with compatible with the calcium-alkaline series. The geochemical signatures of the Chaval Granite indicate the character of the tectonic magmatic arc environment. U-Pb zircon analysis by Mass Spectrometry (LA-ICP-MS) indicates crystallization age of 633 Ma, placing it in the Neoproterozoic, late Cryogenic-Early Ediacaran period, being one of the oldest granitoids in northwestern Borborema Province, correlated to the granites of the Santa Quitéria Magmatic Arc in the Ceara Central Domain. Hf-T DM model ages (2.65 to 2.13 Ga) and εHf(t = 633 Ma) values from-9.6 to-18.1 suggest incorporation of neoarchean and paleoproterozoic crustal sources in their formation with a long crustal residence time. Similar Sm-Nd data in whole-rock indicate Nd-T DM model ages of 1.27, 1.72 and 2.04 Ga and negative εNd(t = 633 Ma) values of-2.64 to-9.13, indicating paleoproterozoic and mesoproterozoic sources, with considerable crustal residence time implying a more evolved nature.
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Papers by Sergio Gorayeb