Liu, D., Zhao, Z.D., Zhu, D.C., Niu, Yaoling
, Liu, S.A., Wang, Q. Liu, Y.S. & Hu, Z.C. (2013). Zircon records of Miocene ultrapotassic rocks from southern Lhasa subterrane, Tiben Plateau. 岩石学报 = Acta Petrologica Sinica 29
Author(s) from Durham
Zircons entrained in mantle-derived magmas offer a prime opportunity to reveal cryptic magmatic episodes in the deep crust. We have investigated zircons from mantle-derived ultrapotassic veins in the Xuena area, southern Lhasa subterrane. Zircons in the Xuena ultrapotassic rocks reveal four major magmatic pulses around <100Ma, 300~400Ma, 450~500Ma, and 700~850Ma. The high U/Yb ratios and low Y contents of these zircons demonstrate their continental origin. Cenozoic-Mesozoic and Late Paleozoic magmatism have been widely identified from the southern Lhasa subterrane, suggesting the contribution from overlying juvenile crust. But similar Proterozoic-Early Paleozoic age distributions (450~500Ma and 700~850Ma) between these zircon xenocrysts and those dating records in the Himalayan orogenic belt corroborate the input from underthrusted Indian continental crust. Furthermore, the increasing (Dy/Yb)N ratio since ~60Ma and rapid decreasing zircon εHf(t) values, from +10~+5 to -10~-25, are interpreted to reflect significant and progressive crustal thickening in response to India-Asia convergence and the contribution from subducted Indian continental crust to postcollisional magmatism in the southern Lhasa sub-terrane.