Geologia da Formação Água Clara e rochas ígneas associadas no Estado de São Paulo
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Data
2021-12-21
Autores
Vieira, Otávio Augusto Ruiz Paccola [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A área de estudo se situa no extremo sul do estado de São Paulo e está inserida na porção central da Província Mantiqueira, na faixa centro-sul do Cinturão Ribeira e se relaciona a evolução neoproterozoica do Terreno Apiaí. Está localizada nos municípios de Ribeirão Branco, Guapiara e Capão Bonito e norte do distrito Araçaíba e faz parte do conjunto intrusivo meridional do Complexo Granítico Três Córregos. A configuração das unidades litológicas e das feições estruturais superimpostas de idade neoproterozoica seguem um padrão estrutural regional, cujo principal trend se associa à orientação regional NE-SW, delimitando a área por grandes zonas de cisalhamento que são denominadas, ao norte, de Itapirapuã, em contato tectônico com o Grupo Itaiacoca, e ao sul, de Quarenta Oitava, em contato tectônico com o Grupo Lajeado. Estas rochas ígneas estão inseridas em rochas da Formação Água Clara, a qual pertence ao Supergrupo Açungui, de idade mesoproterozoica e metamorfizadas e deformadas no Neoproterozoico. O embasamento, correspondente a Formação Água Clara, é dividido em duas unidades (xistosa e carbonática) e constituído por xisto, filito, quartzito, rochas calciossilicatadas, mármore, metabásicas e metaultrabásicas. O Complexo Granítico Três Córregos inclui vários corpos granitoides sin-colisionais de idade neoproterozoica (Barra do Chapéu, Saival e Capote), com contato intrusivo e tectônico com os metassedimentos e contato tectônico com rochas graníticas pós- a tardi- colisionais dos Granitos Correas, Capão Bonito e Sguario. Os granitoides sin-colisionais são hornblenda-biotita granodiorito e quartzo monzonito, biotita monzogranito e sienogranito com hornblenda. São leucocráticos, inequigranulares, porfiríticos, com fenocristais de microclínio branco a rosa (4 cm). Ambos têm granulação fina a grossa e coloração cinza ou rósea. É isotrópica a sub-orientada com discreta foliação milonítica e/ou cataclástica. Geoquimicamente, são classificados como cálcio-alcalino peraluminoso, sin colisional a arco vulcânico, da série de alto potássio a shoshonítica, magnesiano, com assinatura de granito do tipo I cordilheirano gerado pela fusão da crosta inferior e associado à evolução de arco magmático. Os granitos tardi a pós-colisionais são biotita sienogranito e álcali feldspato granito, holo a leucocráticos, equi- a inequigranulares, porfiríticos, com fenocristais de microclínio rosa (3 cm). A granulação da matriz é média a grossa, coloração rósea avermelhada e isotrópica. Encontram-se parcialmente encobertos, nos seus limites, por rochas sedimentares cambrianas da Bacia do Samambaia, no centro, e rochas sedimentares da bacia do Paraná na região norte. Intrusivas básicas mesozoicas associadas ao Magmatismo Serra Geral e correlacionadas ao Arco de Ponta Grossa são relativamente frequentes na área. O quadro estrutural-metamórfico é determinado dominantemente pelo arranjo tectônico do final do Neoproterozoico, em rochas epimetamórficas por uma evolução estrutural polifásica. As estruturas primárias ocorrem de forma escassa, com predominância do acamamento gradacional reliquiar S0 nas áreas menos deformadas, devido aos intensos processos de transposição e deformação milonítica. São reconhecidas três fases deformacionais. A fase D1 é registrada por uma foliação S1, que é uma clivagem ardosiana e xistosidade de atitude preferencial N47E/38SW, subparalela ao bandamento tectônico S0. A fase D2 compreende dobras isoclinais com foliação plano axial S2 marcada por um bandamento tectônico de atitude preferencial N20E/56NW. O ápice do metamorfismo regional progressivo, em D2 e fácies anfibolito médio, com valores de temperatura e pressão calculados em rochas metabásicas e metaultrabásicas, de 611°C a 621°C de temperatura e 6,5 kbar e 7,3 kbar (±0,6) de pressão. A granitogênese sin- colisional associa-se a esta fase, com a colocação das rochas do Complexo Granítico Três Córregos, com orientação dos minerais máficos (biotita e hornblenda) e geração de porfiroblastos de granada e actinolita/tremolita no xisto e rochas calciossilicatadas nas aureolas de metamorfismo de contato. A fase D3 é caracterizada por dobras abertas e suaves e foliação plano axial S3 de atitude preferencial N84E/82SE. Granitoides tardi a pós- colisionais (Capão Bonito, Sguario e Correas) ocorrem durante a fase D3, associados a zonas de cisalhamento. Essas rochas granitoides revelam uma estrutura fracamente milonítica e/ou cataclástica nas bordas do corpo.
The study area is located in the extreme south of São Paulo state and is inserted in the central portion of the Mantiqueira Province, in the central-southern strip of the Ribeira Belt and correlated with Apiaí Terrain neoproterozoic evolution. It is located in the Ribeirão Branco, Guapiara and Capão Bonito municipalities and north of the Araçaíba district and is part of Três Córregos Granitic Complex meridian intrusive set. The lithological units configuration and Neoproterozoic superimposed structural features follow a regional structural pattern, the main trend of which is associated with the NE-SW regional orientation, delimiting the area by large shear zones that are called, in the north, Itapirapuã, in tectonic contact with Itaiacoca Group, and to the south, Quarenta Oitava, in tectonic contact with Lajeado Group. These igneous rocks are inserted in Água Clara Formation rocks belonging to Açungui Supergroup, of Mesoproterozoic age, metamorphized and deformed in the Neoproterozoic. The embasement, corresponding to the Água Clara Formation, is divided into two units (Xistoso e Carbonático) and consists of schist, phyllite, quartzite, calk-silicate rocks, marble and metabasic to metaultrabasic. The Três Córregos Granitic Complex corresponds to the agglutination of several neoproterozoic syncollisional granite bodies called Barra do Chapéu, Saival and Capote granites, with intrusive to tectonic contact with the meta-sediments and tectonic contact with post-late collisional Correas, Capão Bonito and Sguario granitic rocks. Sin collisional granites are generally classified as hornblende-biotite granodiorite to quartz monzonite to biotite monzogranite to syenogranite with hornblende, leukocratic, inequigranular, porphyritic, with white to pink microcline crystals of dimensions less than 3 to 4 cm, granulation from fine to coarse matrix, gray or pink and isotropic to sub-oriented with slight milonitic and or cataclastic foliation. Geochemically, they are classified as peraluminous calk-alkaline, sin collisional to volcanic arc, high potassium to shoshonitic, magnesian series, presenting a I cordilleran type granite signature generated by the melting of the lower crust and associated with the Magmatic Arc evolution. Late to post collisional granites are generally described as biotite syenogranite to alkali feldspar granite, holo to leukocratic, equi to inequigranular, porphyritic, with pink microcline phenocrystals of dimensions less than 3 cm, medium to coarse matrix granulation, reddish pink coloration and isotropic. These are partially covered by their limits by Samambaia Basin Cambrian sedimentary rocks, in center, and Paraná basin sedimentary rocks in north. Basic mesozoic intrusives associated with Serra Geral Magmatism and correlated to the Ponta Grossa Arch are relatively frequent in the area. The structural-metamorphic picture is predominantly determined by the final neoproterozoic tectonic arrangement, evidenced in the epimetamorphic rocks by a polyphasic structural evolution. The maintenance of the primary structures, due to the intense processes of transposition of the posterior foliations and mylonitic deformation, occur in a scarce way, with predominance only of the S0 compositional banding in the less deformed areas. Three deformational phases are recorded. The D1 phase is registered by an S1 foliation, which is an ardosian cleavage to schistosity, of preferential direction N47E / 38SW, subparallel to S0 compositional banding. The D2 phase comprises isoclinical to closed folds and S2 axial plane foliation marked by a compositional bandage with preferential direction N20E / 56NW. Associated with phase D2 is the peak of progressive regional metamorphism, reaching medium amphibolite facies, with temperature and pressure values calculated in metabasic to metaultrabasic rocks, from 611°C to 621°C in temperature and 6.5 kbar to 7.3 kbar (± 0.6). Likewise, syncollisional granitogenesis is associated with this phase, with the emplacement of Três Córregos Granitic Complex rocks, seen mainly in the reorientation of mafic minerals (biotite and hornblende) and the generation of garnet and actinolite/tremolite porphyroblasts in the contact metamorphism aureoles developed laterally to the igneous bodies. The D3 phase constitutes smooth and open folds and S3 axial plane foliation with preferential direction N84E / 82SE. This deformation occurs associated with the late magmatic rise of the late to post-collision granitoids (Capão Bonito, Sguario and Correas), associated with shear zones. Granitoid rocks show a weakly milonitic and/or cataclastic character at their edges, when exposed to their contacts with the embedding rocks.
The study area is located in the extreme south of São Paulo state and is inserted in the central portion of the Mantiqueira Province, in the central-southern strip of the Ribeira Belt and correlated with Apiaí Terrain neoproterozoic evolution. It is located in the Ribeirão Branco, Guapiara and Capão Bonito municipalities and north of the Araçaíba district and is part of Três Córregos Granitic Complex meridian intrusive set. The lithological units configuration and Neoproterozoic superimposed structural features follow a regional structural pattern, the main trend of which is associated with the NE-SW regional orientation, delimiting the area by large shear zones that are called, in the north, Itapirapuã, in tectonic contact with Itaiacoca Group, and to the south, Quarenta Oitava, in tectonic contact with Lajeado Group. These igneous rocks are inserted in Água Clara Formation rocks belonging to Açungui Supergroup, of Mesoproterozoic age, metamorphized and deformed in the Neoproterozoic. The embasement, corresponding to the Água Clara Formation, is divided into two units (Xistoso e Carbonático) and consists of schist, phyllite, quartzite, calk-silicate rocks, marble and metabasic to metaultrabasic. The Três Córregos Granitic Complex corresponds to the agglutination of several neoproterozoic syncollisional granite bodies called Barra do Chapéu, Saival and Capote granites, with intrusive to tectonic contact with the meta-sediments and tectonic contact with post-late collisional Correas, Capão Bonito and Sguario granitic rocks. Sin collisional granites are generally classified as hornblende-biotite granodiorite to quartz monzonite to biotite monzogranite to syenogranite with hornblende, leukocratic, inequigranular, porphyritic, with white to pink microcline crystals of dimensions less than 3 to 4 cm, granulation from fine to coarse matrix, gray or pink and isotropic to sub-oriented with slight milonitic and or cataclastic foliation. Geochemically, they are classified as peraluminous calk-alkaline, sin collisional to volcanic arc, high potassium to shoshonitic, magnesian series, presenting a I cordilleran type granite signature generated by the melting of the lower crust and associated with the Magmatic Arc evolution. Late to post collisional granites are generally described as biotite syenogranite to alkali feldspar granite, holo to leukocratic, equi to inequigranular, porphyritic, with pink microcline phenocrystals of dimensions less than 3 cm, medium to coarse matrix granulation, reddish pink coloration and isotropic. These are partially covered by their limits by Samambaia Basin Cambrian sedimentary rocks, in center, and Paraná basin sedimentary rocks in north. Basic mesozoic intrusives associated with Serra Geral Magmatism and correlated to the Ponta Grossa Arch are relatively frequent in the area. The structural-metamorphic picture is predominantly determined by the final neoproterozoic tectonic arrangement, evidenced in the epimetamorphic rocks by a polyphasic structural evolution. The maintenance of the primary structures, due to the intense processes of transposition of the posterior foliations and mylonitic deformation, occur in a scarce way, with predominance only of the S0 compositional banding in the less deformed areas. Three deformational phases are recorded. The D1 phase is registered by an S1 foliation, which is an ardosian cleavage to schistosity, of preferential direction N47E / 38SW, subparallel to S0 compositional banding. The D2 phase comprises isoclinical to closed folds and S2 axial plane foliation marked by a compositional bandage with preferential direction N20E / 56NW. Associated with phase D2 is the peak of progressive regional metamorphism, reaching medium amphibolite facies, with temperature and pressure values calculated in metabasic to metaultrabasic rocks, from 611°C to 621°C in temperature and 6.5 kbar to 7.3 kbar (± 0.6). Likewise, syncollisional granitogenesis is associated with this phase, with the emplacement of Três Córregos Granitic Complex rocks, seen mainly in the reorientation of mafic minerals (biotite and hornblende) and the generation of garnet and actinolite/tremolite porphyroblasts in the contact metamorphism aureoles developed laterally to the igneous bodies. The D3 phase constitutes smooth and open folds and S3 axial plane foliation with preferential direction N84E / 82SE. This deformation occurs associated with the late magmatic rise of the late to post-collision granitoids (Capão Bonito, Sguario and Correas), associated with shear zones. Granitoid rocks show a weakly milonitic and/or cataclastic character at their edges, when exposed to their contacts with the embedding rocks.
Descrição
Palavras-chave
Granitogênese, Metamorfismo regional, Mapeamento geológico, Granitogenesis, Regional metamorphism, Geological mapping