The long-lived partial melting of the Greater Himalayas in southern Tibet, constraints from the Miocene Gyirong anatectic pegmatite and its prospecting potential for rare element minerals

Abstract

The Cenozoic Himalayan leucogranite–pegmatite belt has been a hotspot for rare metal exploration in recent years. To determine the genesis of the pegmatite in the Himalayan region and its relationship with the partial melting of the Greater Himalayan crystalline complex (GHC), the Gyirong pegmatite in southern Tibet were chosen for geochronological and geochemical studies. The dating analyses indicate that the U‒Th‒Pb ages of zircon, monazite, and xenotime exhibit large variations (38.6-16.1 Ma), and the weighted average value of the four youngest points is 16.5 ± 0.3 Ma, which indicates that the final crystallization of the melt occurred in the Miocene. The age of the muscovite Ar–Ar inverse isochron is 15.2 ± 0.4 Ma, that is slightly later than the intrusion age, showing that a cooling process associated with rapid denudation occurred at 16-15 Ma. The εHf(t) values of the Cenozoic anatectic zircons are concentrated between -12 and -9 with an average of -11.4.