Mineral geochemistry of mantellic xenoliths from the Mesozoic subcontinental Brazilian platform constraints on mantle heterogeneities as sources of basalt and alkaline provinces

• Grant number: 21/05399-5
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: August 01, 2021
• End date: June 30, 2025
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Excelso Ruberti
• Grantee: Rafael Duarte Modesto
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 19/22084-8 - The Paraná Magmatic Province: petrogenesis, chronology and environmental impact of Cretaceous tholeiitic, alkaline and silicic magmatism in the Brazilian Platform, AP.TEM

Abstract

The main goal of the project presented here is the petrological study of a suite of xenoliths found in kimberlites and related rocks in different regions of the Brazilian platform by gathering petrographic information on the lithotypes present and to establish mineralogical and textural (faciological) variations of xenoliths in intrusions of kimberlitic fields of Minas Gerais, Goiás, Paraná and Rio Grande do Sul. The project also aims to determine major elements and trace elements of the main mineralogical components, such as garnet, ilmenite, spinel, perovskite, olivine, pyroxene and phlogopite, by using high spatial resolution techniques, in order to obtain parameters (eg P, T, fO2 etc.) that would permit a better understanding of the nature of the mineral species present and the variations of the mantelic sources. In addition, in situ isotopic analyzes of Sr in perovskite would be performed in order to obtain initial 87Sr/86Sr isotopic ratios. A comparison of chemical/mineralogical frameworks between xenoliths found in distinct regions is also intended, in order to establish their basic characteristics on a theoretical-scientific basis. The combination of the study of major elements and trace elements and isotopic ratios will allow us to infer their respective source areas and the processes of magma generation in the subcontinental lithospheric mantle, as well as to identify their affinities with signatures of mantle reservoirs, trace geochemical signatures and isotopes from different reservoirs (DMM, EMI, EMII, HIMU). (AU)