Geochemical and textural properties of accessory minerals as petrological and geochronological indicators in granitic rocks and associated greisens

• Grant number: 19/17343-4
• Support type: Regular Research Grants
• Duration: March 01, 2020 - February 28, 2023
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal researcher: Silvio Roberto Farias Vlach
• Grantee: Silvio Roberto Farias Vlach
• Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Assoc. researchers: Frederico Castro Jobim Vilalva

Abstract

The geochemical and textural/microstructural properties registered in accessory minerals in granitic rocks allow unveiling and model the evolutionary path of magmatic and post-magmatic processes, to determine intensive crystallization parameters as well as the absolute chronology of the magmatic/post-magmatic events and became a scientific theme with increasing impact in the international literature. This proposal aims qualify and quantify the geochemical (elemental and isotope) and textural/microstructural records in primary and hydrothermal accessory primary minerals and apply them to identify and model magmatic and post-magmatic evolutionary processes from selected case studies in the Graciosa and Itu "A-type" granitic provinces, the most important Neoproterozoic young occurrences in S-SE Brazil, under a cutting edge perspective. Modern in situ analytical techniques with high spatial resolution (SEM, FE-EPMA, LA-ICPMS, LA-MC-ICPMS and SHRIMP) will be used to quantify major, minor and trace elements (LIL and particularly HFS) and U, Pb, Sr, Nd and Hf isotopes in primary (allanite, chevkinite, apatite, titanite, zircon and elpidite), inherited (zircon) and hydrothermal (e.g., zircon, various zirconosilicates, fluorite, columbite-tantalite, monazite, xenotime) under fine textural/microstructural controls given by extensive optical, electronic and X-ray analyses and imagery. These new data will allow determining geochemical signatures of these accessories and their relative stabilities as well as mineral/mineral and mineral/whole-rock geochemical balances, main crystallization environment parameters (T, P, volatile activities) and obtain unavailable U/Pb magmatic crystallization and inherited ages (zircon) and hydrothermal U/Pb and Th-U-PbT crystallization ages (zircon, monazite, xenotime). The results will, along with our previous data, constitute a consistent data set needed to compare the geochemical signatures among typical occurrences in the Graciosa and Itu provinces and to quantitatively model the main petrogenetic processes, with strong implications for the genesis and evolution of the "A-type" magmatism and its associated hydrothermalism, as well as for the geodynamic setting leading to the origin of these provinces in S-SE Brazil. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

SIACHOQUE, ASTRID; GARCIA, RODOLFO; VLACH, SILVIO R. F. Occurrence and Composition of Columbite-(Fe) In the Reduced A-Type Desemborque Pluton, Graciosa Province (S-SE Brazil). MINERALS, v. 10, n. 5 MAY 2020. Web of Science Citations: 0.