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Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil

By HARTMANN LÉO A. and CHEMALE-JÚNIOR FARID

Abstract

Valuable information is retrieved from the integrated investigation of the field relationships, microstructure and mineral compositions of harzburgites from the Neoproterozoic Cerro Mantiqueiras Ophiolite. This important tectonic marker of the geological evolution of southernmost Brazilian Shield was thoroughly serpentinized during progressive metamorphism, because the oldest mineral assemblage is: olivine + orthopyroxene + tremolite + chlorite + chromite. This M1 was stabilized in mid amphibolite facies - 550-600ºC as calculated from mineral equilibria. No microstructural (e.g. ductile deformation of olivine or chromite) or compositional (e.g. mantle spinel) remnant of mantle history was identified. A metamorphic event M2 occurred in the low amphibolite facies along 100 m-wide shear zones, followed by intense serpentinization (M3) and narrow 1-3 m-wide shear zones (M4) containing asbestos

Topics: mineral chemistry, Cerro Mantiqueiras Ophiolite, metamorphism, Neoproterozoic, Biology (General), QH301-705.5, Science, Q, DOAJ:Biology, DOAJ:Biology and Life Sciences
Publisher: Academia Brasileira de Ciências
Year: 2003
OAI identifier: oai:doaj.org/article:0b72e9c1fa844f508f9233c99399adfc
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