Mantle-crust interaction and the genesis and evolution of the A-type: post-collisional magmatism: geochemical and isotopic records from the Graciosa Province, S-SE Brazil

Abstract

The origin of the post-collisional "A-type" magmatic provinces show important links with processes initiated at the subcontinental mantle and includes several contributions from this mantle and the overlying continental crust. The genesis and evolution of magmas generated in these environments are figures of merit in modern petrology. This project focuses on the identification of various mantle and crustal sources and magmatic evolution processes involved in the origin of the "A-type" granites, syenites, and related rocks from the Graciosa Province, S-SE Brazil. Detailed studies, in part complementary to our ongoing research, will be conducted in selected occurrences of the province, using tools such as field work, petrography, elemental and isotopic whole-rock geochemistry (major, minor, and trace elements, Sr-Nd isotopes), conventional zircon U-Pb dating (TIMS), with enphasis on mineralogical microanalysis (major and minor elements by EPMA and trace elements by LA-ICP-MS in rock-forming and main accessory minerals, Pb isotopes in alkali-feldspar, Hf isotopes in zircon, and zircon U-Pb dating by LA-ICP-MS). It is well demonstrated in the current literature that the integration of the information to be available with these analytical techniques has great potential to identify, evaluate and/or quantity the relative importance of contrasted mante and crustal components to the parental magmas constitution and the subsequent processes of magmatic evolution. Such information will also allow a fine comparison between the province and several analogous occurrences elsewhere in the world. (AU)