Tectonic and cooling history of the Bihar Mica Belt, India, as revealed by fission-track analysis

Abstract

The fission track ages of four cogenetic minerals garnet, muscovite, biotite and apatite collected from the pegmatites of the Bihar Mica Belt of India, emplaced during Satpura Orogeny (~ 950 m.y.), are found to be 830 m.y., 760 m.y., 595 m.y. and 590 m.y., respectively. The discordance in these ages has been interpreted in terms of the tectonic and cooling history of the mica belt. The average rate of uplift for this region has been calculated as ~ 0.08 mm/year and the cooling of the pegmatite bodies subsequent to their crystallization has been at the rate of 3.2°C/m.y. from 950 m.y. to 830 m.y., 0.9°C/m.y. from 830 m.y. to 760 m.y., 0.6°C/m.y. from 760 m.y. to 600 m.y. The region has been near the earth's surface temperature for the last ~ 600 m.y.