Geochronological constraints on the evolution of Meghalaya massif, northeastern India: An ion microprobe study

摘要

Pb-207-Pb-206 isotope systematic of zircons from quartzofeldspathic gneisses and metasediments belonging to the basement gneiss and Shillong group of the Meghalaya massif has been investigated using an ion microprobe. The zircon age of the gneissic samples revealed the existence of multiple protolith components ranging in antiquity between similar to 1.5 and 2.6 Ga. The age distribution of the detrital metasedimentary zircons is similar to the range of the gneissic protoliths. Zircons from a charnockite sample yielded ages of 1.0-1.3 Ga, presumably recording. the global Grenvillian orogeny. Our data suggest that crust formation in the Meghalaya massif started during the Archaean and experienced a protracted and episodic evolution that has some similarity with the Eastern Ghats Province.