Petrographic evolution of rocks associated with zinc mineralization in the Nappe of Passos - MG

• Grant number: 12/01427-5
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): April 01, 2012
• Effective date (End): March 31, 2013
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal researcher: Antenor Zanardo
• Grantee: Edson Ricardo Maia Ferraz
• Home Institution: Instituto de Geociências e Ciências Exatas (IGCE). Universidade Estadual Paulista (UNESP). Campus de Rio Claro. Rio Claro , SP, Brazil

Abstract

Into the Nappe of Passos, in the southern part of the Minas Gerais State, Southeastern Brazil, can be found gneisses with evidences of resulting as tectonic and metamorphic transformations of rocks generated in magmatic arc environment affected by hydrothermal alteration (argillic and advanced argillic alteration zones) concentrating zinc, copper and lead. Those gneisses were exploration target of a mining company, resulting in a series of drilling cores that will be used in this research in addition to the surface outcrop survey. The Nappe of Passos is positioned on the Southwestern border of the São Francisco Craton and is constituted by metamorphic rocks from the Bambuí, Canastra and Araxa groups including tectonic slices of Archean type TTG basement rocks (Barbacena Complex). The tectonic sequence has characteristics of passive margin in the basal units and inverted metamorphism with greenschist facies at the base and high amphibolite to granulite facies at the top. The research will focus on the gneisses that occur interbedded with schists, quartz schists, quartzites, amphibolites and rare lenticular intercalations of metaultramaphic and/or calc-silicate rocks that constitute the intermediate to upper portion of the Araxá Group. The main objective is to obtain petrographic data to drive lithochemical and isotopic studies in order to investigate the possibility of amalgamation of active margin sequences or island arcs with the tectonic sequence that constitutes the Nappe of Passos. To achieve the objectives will be done office activities (cartographic compilation, bibliographic studies, photo interpretation and making maps, reports and texts for publications), field survey (lithological and structural data and sample collection) and laboratory studies (petrographic and microstructural analyses sample selection for lithochemical and isotopic studies). (AU)