Session 1C: Inaugural Lectures by Fellows/Associates

Pulsed Tectonic Patterns In Early Earth Hot Orogens: Constraints From Diffusion Chronometry Along Nonlinear P–t Paths

In recent years, there is a resurgence of interest to know the nature of tectonics processes that operated in Early Earth. To address this issue, it becomes important to develop constraints on the timescales of metamorphic–tectonic events in early hot Earth. Presently, this is poorly understood. Speaker shall talk about the development of a high-resolution sequential diffusion chronometry tool that: (i) has a time resolution of ≤ 1 Myr, (ii) is independent of the age of the rocks, and (iii) can see through multiple, superposed thermal/tectonic events even at ultra-high temperature (UHT) (TMax>900oC) conditions. The tool is applied in rocks from 1.6 Ga orogenic domain of the Central Indian Tectonic Zone, where additional data are available to verify the results. The rock records three cycles of granulite facies metamorphism, the first two under UHT conditions. The results show that cooling from UHT conditions in the orogen took place in multiple pulses that occurred with a periodicity of ~10 Myr at rates that vary between 100’s and 10’s °C/Myr. Burial-/exhumationrates vary between 30 and 2 km/Myr respectively. Such details of tectonic processes with quantification of variable heating-, cooling-, burial-, and exhumation-rates of individual stages, have not been accessible until now.