Determination of high resolution thermal and tectonic history of Archean terranes: Development of a tool through a case study from the Western Dharwar Craton and the Coorg block in S. India

• Applicant: Professor Dr. Sumit Chakraborty, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 276958716

The time period around 3.0 Ga is a critical period in the history of the Earth because in many models it is thought to be the period when a transition occurred to present day plate tectonic styles. This is considered to be the result of a shift in the balance between heat generation and heat loss; heat generation was thought to have dominated over heat loss before 3.0 Ga. However, the transition itself is thought to have been rapid (within < 0.5 Ga), and it is not clear if it was global and synchronous. The resolution of isotopic clocks do not always suffice to resolve the various closely spaced (in time) events in these ancient rocks. Therefore, it is necessary to develop new tools to quantify and understand such thermal processes better. We have developed the approach of sequential kinetic modelling (modelling the diffusive modification of compositional zoning in minerals in stages) and applied it successfully to present day volcanic systems as well as in ultrahigh temperature metamorphic systems. In this project we wish to use this tool to study the thermal evolution (heating/cooling and burial/exhumation histories) of a set of rocks from the Western Dharwar Craton and the Coorg Block in South India to characterize their tectonic style. These rocks experienced several episodes of thermal metamorphism in the critical period between 3.3. and 2.5 Ga, and contain mineral assemblages in which sequential kinetic modelling can be applied. Our objective in this project is to (a) obtain high resolution thermal histories of two adjacent blocks with contrasting signatures from the same time period, and (b) use these examples to develop the tool for general use in Archean rocks, so that it may be used in other Archean terranes as well in later projects to quantify the global thermal evolution during this critical period of the history of the Earth.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1833: Building a Habitable Earth
• International Connection: India
• Cooperation Partners: Professor Santanu Kumar Bhowmik; Professor Dr. Somnath Dasgupta; Professor Dr. Adrian Immenhauser; Dr. Ravindra Kumar; Professor Dr. Andreas Pack