Petrographic and mineralogical characterization of the Serraria syenite nearby the contact with the gabbro, Jabaquara beach, São Sebastião Island (SP)

• Grant number: 15/14865-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2015
• End date: August 31, 2016
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Gaston Eduardo Enrich Rojas
• Grantee: Saulo Vieira da Silva Filho
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

This project to be performed in the Institute of Geosciences from the University of São Paulo aims to characterize the petrography and the mineral chemistry of the Serraria Stock syenite nearby the contact with the gabbro on the East Coast of Jabaquara beach, northern São Sebastião island. This work focuses on the description of magma interaction features such as enclaves, breccias and disconnected dykes. The geology of the São Sebastião island is constituted by an alkaline igneous association between a syenite and a gabbro, which belongs to the Alkaline province of Serra do Mar region, with about 85 Ma. The alkaline magmatism is composed by three syenitic stocks (Serraria, Mirante and São Sebastião), as well as smaller mafic intrusions with alkaline affinity composition. This research will embrace the petrographic description and chemical characterization of the most important mafic minerals, emphasizing the identification of mineral disequilibrium textures such as microenclaves and chemical zoning. The analytic procedures will combine optic microscopy, scanning electron microscope and electron probe micro-analyzer.