Temperature estimates in the subsurface plays an important role in earth science that control mineral deposition, petroleum zone and geodynamics. Temperature estimates in the sub-surface can be possible only through modelling surface heat flow, thermal conductivity and radiogenic heat production data along with geological and geophysical knowledge.
For the past five and half decades Thermal Geophysics group which was earlier known as Heat flow group has been involved in acquiring heat flow data in different geological provinces of the vast Indian shield along with measurement of thermal conductivity, radiogenic heat production of thousands of pertaining rock formations, both in-situ and in the laboratory. The above datasets have used to model crustal and sub-crustal continental lithosphere.
Heat flow studies carried out reveal that (i) heat flow is generally low (<60 mWm-2) but varies within a wide range 25 to 62 mWm-2 in the Precambrian provinces (e.g., Bundelkhand Craton, Dharwar Craton, Baster craton, Southern Granulite Province) and Cretaceous Deccan Volcanic Province, (ii) higher (51 to 96 mWm-2) in Proterozoic Aravalli Province, Singhbhum Thrust Zone, Proterozoic Cudappah Basin, Tertiary Cambay basin, (iii) highest (46 to 107 mWm-2) in Gondwana basins, e.g., Damodar, Godavari, Mahanadi, Satpura. Study also yield that temperature estimates in Moho vary in a wide range (250 to 550 oC) in various geological provinces.
Our systematic radio elemental study on granulite from a vast granulite terrain in the southern India yielded that the granulites are not always depleted in radioelements as used to consider earlier in most of the modelling, but could be high in radioelements and radiogenic heat production as much as granites. The difference in precursors/photoliths or the difference in P-T conditions of metamorphism or later metamorphism of the granulites are responsible for the observed variations within granulites.
Our systematic radio elemental study on a granitic pluton known as Bundelkhand craton indicated that the craton can be divided into three distinct radio elemental zones that can be correlated with its evolution in time and space. The above results have major implications for the geodynamics of the Indian shield.
Thermal conductivity and thermal diffusivity at higher temperature also carried out in the laboratory on granites and granulites which are importance parameters in thermal modelling of the sub-surface.
Thermal conductivity estimates on a large number of representative samples covering various types of granites and granulites also carried out from mineralogical data and mineral thermal conductivities using various mixing models and lead to very important outcome that harmonic mean model is one of the best models for estimating thermal conductivity for granitic and granulitic rocks.
Thermal modelling of the oceanic data reveals the existence of hydrothermal evidence in an oldest oceanic crust (135 m.y. old) which is very important finding in the field of Oceanic geothermics.
Rock Mechanics Laboratory undertakes geophysical research that involves characterization of rocks and related materials in terms of their petrophysical (e.g., density, ultrasonic velocity, magnetic susceptibility, electrical resistivity, and porosity) and mechanical properties (uniaxial strength, tensile strength, shear strength, cohesion and angle of internal friction), covering the Indian Shield and Himalaya. The laboratory data are useful to seismo-tectonics studies, mining and engineering research, mineral and hydrocarbon exploration, and geophysical modelling of crust and lithosphere. The principles of rock mechanics are also applied to planetary geoscience research particularly in the fields of meteorite impact cratering processes, seismo-tectonics and rock fragmentation that affect planetary bodies.
|Dr. Labani Ray||Principal Scientist|
|Dr. Lakshmi K. J. P||Principal Scientist|
|Mr. Ravi G||Technical Officer|
|Mr. Ravinder S||Technical Officer|
Page Last Updated On : 19-04-2021