The emplacement epoch, petrogenesis and geological significance of Gabuzha granodiorite at the southern edge of Qiangtang, Tibet

Abstract: The Gabuzha granodiorite in Gerze area intruded into the Jurassic Sewa Formation at the southern edge of the southern Qiangtang terrane, and can be used to constrain the evolution of Bangong Co-Nujiang River suture zone. LA-ICP MS zircon U-Pb dating yielded a weighted mean age of (143.8±0.5) Ma, suggesting that the Gabuzha granodiorite formed during late Jurassic to early Cretaceous. The Gabuzha granodiorite is metaluminous I-type granite and belongs to high-K calc-alkaline series. Its REE model is characterized by enrichment of light REE, and Eu shows weak negative anomaly. Large ion lithophile elements are obviously enriched in Rb, Ba, K, Th and U. High field strength elements Nb, Ta, P and Ti show strong depletion. The results show that the magma source of Gabuzha granodiorite might have been derived from mixture of continental crust materials, subducting sediments and mantle-derived wedge, and experienced a certain degree of separation and crystallization as well. The Gabuzha granodiorite formed in an island arc environment related to northward subduction of the Bangong Co-Nujiang River Meso-Tethys Ocean beneath the Qiangtang terrane.