Isotopic characterization of thick sedimentary basins based on K-Ar, 40Ar-39Ar and Rb-Sr interpretations in clay minerals: implications on the burial history and estimation of the paleo-geothermal gradients

• Grant number: 10/17754-0
• Support Opportunities: Research Grants - Visiting Researcher Grant - International
• Start date: February 01, 2011
• End date: January 31, 2012
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Wilson Teixeira
• Grantee: Wilson Teixeira
• Visiting researcher: Gilda Collo
• Visiting researcher institution: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Thermal evolution models based on burial data from sedimentary successions are of great interest in the study of basins with Oil and Gas exploration potential. This project aims to characterize the clay minerals evolution from two deep clastic sequences, based mainly on combined isotopic analysis (Rb-Sr, K-Ar and 40Ar/39Ar), to better interpret their post-depositional history. On one hand, the sensitivity of clay minerals to temperature variations during the sedimentary evolution allows using this type of data in order to understand the thermal regime of a given sedimentary basin and, consequently, the mechanical properties of its rocks and other related aspects (e.g., tectonics); on the other, the isotopic characterization of the illite phases allow determining ages for the identified mineral growth episodes. The present research project will investigate Mio-Pliocene rocks in the Central Andes of Argentina: the Vinchina and Bermejo basins (which have been the research focus of Dr. Gilda Collo). Both basins constitute an ideal framework to test the integrated use of different isotopic markers in the reconstruction of clastic successions evolution, due to their large thickness (about 12 km), exceptional level of exposure, well-known stratigraphy and known thermal conditions. The characterization of clay minerals is based on X-ray diffraction and electron microscopy from samples already collected by Dr. Collo. The different bulk rock and clay fractions will be analyzed by the Rb-Sr, K-Ar and 40Ar/39Ar isotopic methods and ICP. The comparison of burial models with the trajectories inferred previously from thermal indicators will allow evaluating the research strategy and extrapolate the interpretations to other clastic basins with hydrocarbon potential in South America. This project also aims to consolidate an applied research line in the Centro de Pesquisas Geocronológicas of USP, resuming pioneering initiatives of its collaborators (U. Cordani, K. Kawashita, A. Thomaz-Filho, L G. Sant´Anna) and, at the same time, strengthen international scientific cooperation (G. Collo). (AU)