Geochronology, petrogenesis and tectonic significance of the Jitang granitic pluton in eastern Tibet, SW China

Abstract

The Jitang granitic pluton, which is situated in the southern margin of the North Qiangtang block in eastern Tibet, may provide critical information about the source and derivation of the North Qiangtang block during Gondwana breakup and dispersion. In this paper we report relevant data such as zircon U–Pb age, whole-rock major and trace element abundances, and Sr–Nd isotopes for the Jitang pluton. The major rock types of the pluton are granodiorite and biotite granite. Whole-rock major element data reveal that the Jitang pluton is a peraluminous S-type granitic pluton. The U–Pb age of zircons from the pluton is 219.1±1.7Ma, which is ~10Ma younger than the age of high-pressure metamorphism in the Longmu Co–Shuanghu collisional suture between the North and South Qiangtang blocks. The Jitang granitoids show pronounced negative Ba–Eu–Sr anomalies, high initial 87Sr/86Sr ratios from 0.7266 to 0.7389 and low εNd(t) values for from −11.1 to −13.2, which are remarkably similar to the gneisses and meta-sedimentary rocks from the Indian craton as well as the North Qiangtang block. The results from this study indicate that the Jitang granitoids formed by melts derived from a crustal source with Sr–Nd isotopic compositions similar to those of the Indian cratonic crust. We concur with the previous interpretation based on detrital zircon records that the North Qiangtang block was derived from the Indian Gondwana.