LA-ICP-MS zircon U-Pb ages and petrogenesis of Rindu intrusion near Namling, middle Gangdise magmatic belt

This paper reports LA-ICP-MS zircon U-Pb ages and whole rock major and trace element analyses of two-mica granite in the middle part of the Gangdise terrane, Tibet. Magma zircons from the two-mica granite yielded a weighted 206Pb/238U mean age of 226.3±0.98Ma. The two-mica granite is of strongly peraluminous high-K calc-alkaline series, with SiO2 values from 72.83% to 74.99%, K2O/Na2O values from 1.58 to 2.37, total alkali content from 7.37% to 8.72%, A/CNK ratios from 1.21 to 1.39(>1.1), and ω(C-norm) higher than 1%. The ∑REE values vary from 61.71×10-6 to 175.16×10-6, LREE from 53.93×10-6 to 165.49×10-6, HREE from 7.588×10-6 to 13.880×10-6, REE patterns are inclined toward the HREE side with intensive enrichment of LREE, and (La/Yb)N values are from 10.49 to 42.17. Eu anomalies are strong, with Eu/Eu? values varying from 0.264 to 0.57. In the primitive mantel-normalized spidergrams of trace elements, the depletion of Ba, Nb, Sr, Ti and enrichment of Rb, K, U are obvious. It is suggested that the magma for the two-mica granite was dominantly derived from partial melting of argillaceous rocks in the crust, induced by dehydration of mica minerals.