The significance of granite fabrics in the neoproterozoic amalgamation of Western ...
| Grant number: | 06/06957-1 |
| Support type: | Regular Research Grants |
| Duration: | December 01, 2007 - November 30, 2010 |
| Field of knowledge: | Physical Sciences and Mathematics - Geosciences |
| Principal Investigator: | Miguel Angelo Stipp Basei |
| Grantee: | Miguel Angelo Stipp Basei |
| Home Institution: | Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil |
Abstract
The analysis of microstructures in combination with the reconstruction of the spatial distribution of linear and planar fabrics within plutonic rocks can make them delicate kinematic indicators in the unravelling of polyphase orogenic processes. Within the Dom Feliciano Belt of south-eastern Brazil and Uruguay large volumes of granitoid melts have formed extensive batholiths throughout the Neoproterozoic, that document the diachronic accretion of different basement domains during the Río Doce orogeny throughout the Ediacaran. In the Santa Catarina State collision started at ~610 Ma with the juxtaposition of the Brusque metamorphic complex against the Florianópolis batholith. This was followed by the thrusting of the Brusque Metamorphic Complex on top of the Itajaí foreland basin at ~535 Ma. Under the focus of the presented project is the understanding of the emplacement kinematics of three closely related granitoid suites within the Brusque metamorphic complex, i.e. the São João Batista, the Valsungana and the Nova Trento granitoid suites. All suites have been considered to be syn- to post-kinematically emplaced with respect to the collision between the Florianópolis batholith and the Brusque metamorphic complex. The determination of the anisotropy of magnetic susceptibility has proven to be a powerful tool in the analyses of the weakly developed linear and planar fabrics in igneous rocks. These in combination with a icrostructural study of the magmatic vs. sub-solidus origin of fabrics will elucidate the regional stress field during the latest stages of the formation of Western Gondwana. Geochronological and petrographic data will be discussed in terms of rotational exhumation of the granitoids and their host. Results will verify the original orientation of magmatic fabrics at the time of magmaemplacement. Additional information on the temperature development in the contact aureole of the granitic bodies in combination with supplementary age constrains provide a basis for the application of a thermal simulation code. Geochemical data including isotope results will be discussed in terms of the geological setting in which the granitic melt segregated. (AU)