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|Type:||Artigo de periódico|
|Title:||Microstructural Evolution Of Granite Formation Water And Long Filonitos, Setuva Antiform, Parana [evolução Microestrutural Do Granito água Comprida E Formação De Filonitos, Antiforme Setuva, Paraná]|
|Author:||De Mesquita M.J.|
|Abstract:||The Água Comprida Granite (ACG), described in the Santana do Bom Jardim region, Paraná, is part of the Água Comprida Suite, which forms the core of the Setuva Antiform in the southern portion of the Ribeira Belt. The ACG is a syeno to monzogranite with three foliations: Sn is primary-secondary irregular, generally brought into parallelism with Sn+1, the most recurrent in the area. Sn+1 is a mylonitic, spaced foliation with porphiroclasts of feldspar and schistosity domains marked by micas. The Dn+1 deformation transforms protomylonite into phyllonite and quartz mylonite by pressure-solution and hydrolytic weakening mechanisms of quartz and softening reactions following the breakdown of feldspar. The Sn +2 is a crenulation cleavage, spaced, zonal with Sn+1 preserved microlithons. It is well developed in phyllonite, though it occurs in all rock types. Four deformational domains are defined: protomylonite, mylonite, phyllonite and quartz mylonite. The protomylonites have a composite granite/ recrystallized matrix of biotite, titanite and epidote, flame perthite feldspar, and discontinuous quartz ribbons. In mylonitic rocks grainsize reduction of matrix and porphyroclasts occur, and quartz forms continuous ribbons and veins. The paragenesis white mica, epidote and quartz grows from plagioclase with a possible contribution of potassium from perthitic transformation and albite formation. The main change to phyllonite is the breakdown of feldspars into white mica, biotite and opaque minerals. Microstructures in quartz provide evidence of dissolution and formation of quartz mylonite, a rock composed of nearly 100% quartz. The features described permit to characterize the shear zones as hydrated, controlled by the action of fluids with hydrothermal metamorphism under condition equivalent to greenschist facies, biotite zone.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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