O complexo mafico-ultramafico de Tijucas do Sul, correlação com o complexo de Pien, PR e considerações metalogeneticas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1993

RESUMO

The study aimed primarily to assess the auriferous deposits potential of gneissic terrains of medium to high metamorphic grade, with lenticular mafic-ultramafic bodies, which outline the suture zone between the Ribeira Belt and the Luís Alves Craton, at the southern border between paraná and Santa catarina. Geological mapping at 1:25.000 scale has been carried out over 90 km2, in Vossoroca region, and reconnaissance at 1:60.000 scale over 1.000 km2, extending to Tijucas do Sul and Pien, for correlation of the mapped lithological units. The evolution of geological knowledge is tipically slow, with intermitent data gathering, by which the target area is put at present into the domain of biotite-amphibole gneisses and deformed granitoids of Rio Iguaçu nappe, in contact by means of a thrust zone with the granulitic terrains of Luís Alves craton. The thrust belt is outlined by meta-peridotite, meta-pyroxenite, serpentinite, talc-schist, hornblende meta-gabbro, amphibolite and amphibolitic gneiss bodies, extending from pien to Tijucas do Sul-Vossoroca. These bodies are interpreted as obducted Brazilian phiolitic slices. In the geological context of the studied area, there are the Agudos and Morro Redondo intrusive granites, as well as the Guaratubinha and Campo Alegre eo palaeozoic vOlcano-sedimentary sequences. The mapped lithological units have been separated into mafic-ultramafic and granodioritic-tonalitic sequences. The ultramafic lenses are made up of serpentinized meta-peridotites, meta-pyroxenites and talc-schists, with MgO content between 21,1% and 30,6%. The mafic rocks range in composition from hornblende meta-gabbro, hornblende gneiss, hornblendite and amphibolite, which assemble with the gneissic rocks of the granodioritictonalitic sequence to make up a suite characterized by MgO content up to 12,4%. The pien complex rocks have been separated into three suites, staked out by MgO content between 33,0% and 40,0% in meta-peridotite and serpentinitei MgO content between 16,5% and 28,0% in meta-pyroxenite, meta-norite and talc-schisti and MgO content up to 11,3% in amphibolite, hornblende meta-gabbro and granulite. The described suites at Tijucas do Sul-Vossoroca are respectively correlated to the last two pien suites. Every studied rocks display evidence of a high grade metamorphic event, in the upper amphibolite to granulite facies, with a later retrometamorphic event overprinted by pyroxene uralitization, transformation of amphibole into fibrous varieties, and formation of epidote, biotite, chlorite, sericite, talc and serpentine. The retrometamorphic events are commonly related to fluid percolation in shear zones with mylonitic rocks, putting them into the greenschist zone of chlorite-sericite boundary. The described endogenetic processes and the supergenetic alteration promote mineralogical and chemical changes in rocks, alI stressed by rare-earth geochemical patterns, which make it difficult to unravel the area geological story.In previsional metalogenetic terms, the Luís Alves craton granulitic domain displays a good potential, although unknown so far because of the absence of prospecting and research programs. A few deposits of iron formation and pegmatitic bodies are reported. The Pien-Tijucas do Sul-Vossoroca suture zone displays a good potential for Ni-cu, Cu-Zn and platinoid sulphide deposits, in mafic-ultramafic assemblies, as well as Ag-Pb-Zn in aluminous gneisses and mafic granulite. Along with the rio Iguaçu nappe terrains, the suture zone displays high potential for gold deposits in quartz-sulphide veins within shear zones that cross mafic-ultramafic sequences, as ilustrated by the closed mines at Ferraria, Roça Velha and Morro da Esperança, west to curitiba, and the shows at Vossoroca, Serra da Prata, Morretes and Antonina

ASSUNTO(S)

ouro - minas e mineração - parana rochas - analise rochas ultrabasicas - parana

ACESSO AO ARTIGO

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