Chloritoid from low-grade schists. Singhbhum,Eastern India

Chloritoid-sericite schists from the chlorite zone of the regionally metamorphosed Singhbhum anticlinorium in Eastern India are described with regard to the formation of chloritoid during prograde metamorphism — the main stage of its crystallisation was coeval with the movement. The movements accompanying metamorphism have had a marked effect on the lattice orientation of this mineral, so that its crystallographic axis is roughly parallel to the regional fold axis. In one case chloritoid appears to be in stable association with hematite, i.e. it persists beyond the magnetite-hematite equilibrium, which is probably a local effect due to a slight rise in oxygen partial pressure in the last stages of metamorphism. The occurrence of phengitic mica in these schists is suggestive of high total pressures and high water pressures.