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Combined use of structural and geochemical-isotopic tools in the study of the Cabreuva and Indaiatuba plutons, Itu Batholith, SP: implications to the dynamics of shallow granitic magma chambers

Grant number: 14/03725-9
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): October 01, 2014
Effective date (End): February 28, 2018
Field of knowledge:Physical Sciences and Mathematics - Geosciences
Cooperation agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
Principal Investigator:Valdecir de Assis Janasi
Grantee:Giovanna de Souza Pereira
Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The Cabreúva and Indaiatuba granitic plutons, both part of the ~580Ma Itu Batholith, represent the final result of amalgamation and interaction between several magmatic pulses of granitic composition placed at the shallow levels of the continental crust. In this sense, to understand the history of formation of these intrusions means to contribute for the knowledge of the dynamics of the processes that occur in magmatic chambers formed in the shallower parts of the upper crust, which are frequently linked to volcanic processes. The basis for this study will be the formulation of a structural model for both plutons using previous faciologic maps for reference, and trying to establish the geometry and temporal relations between different varieties of granitic rocks, as defined from contact relationships and features like foliation and magmatic banding. Particular attention will be given to the study of associated mafic rock bodies and microgranular enclaves that together bring essential information to the understanding of the processes of magma recharge and interaction. The mineralogical and geochemical diversity of granites and enclaves will be characterized by petrographic analyses, geochemistry of major and trace elements and isotopic geochemistry (Sr, Nd, Pb and Hf), allowing inferences on the conditions of crystallization, source areas and genetic relationships between the different granitic varieties. Geochemical studies at the mineral scale, identifying possible zoning of trace element and Sr-Pb isotopes in feldspars will be used as important tools to typify and quantify processes of magma evolution in both closed (fractional crystallization) and open systems (contamination, magma mixing). (AU)