The discovery and significance of the Indosinian diorites in western Gangdise, Xizang

The determinations of LA-ICP-MS zircon U-Pb dating, isotopic compositions and major elements give a magmatic crystallization age of 207.3±3.6 Ma for the pyroxene amphibole monzodiorite from the Daggyai Lake area, Coqen, western Gangdise, Xizang. The origin of matter may be related with the lower crustal basic lava and partial melting of the upper mantle. The late Indosinian intrusive rocks discovered for the first time in western Gangdise were formed in the orogenic tectonic setting, and attested to the continuous subduction of the Tethyan Ocean during the late Indosinian. The findings in this study will provide useful approaches to the tectonic evolution of the Gangdise region during the late Indosinian.