The Early Cretaceous Duguer metagabbro from Qiangnan-Baoshan block, Tibet Plateau: Implications for the subduction and closure of Bangong Co-Nujiang Ocean

The subduction and closure of the Bangong Co-Nujiang Ocean are recognized as significant events in geotectonic evolution of Tibet Plateau. This study focused on the first identified Early Cretaceous metagabbro in Duguer area from central QiangnanBaoshan block. The authors report the results of petrological, zircon U-Pb age and whole-rock geochemical analyses. Zircon U-Pb age of 110.4±1.4Ma indicates emplacement during the late Early Cretaceous. Geochemical data for Duguer metagabbro indicate that it has an alkaline basalt affinity and is characterized by enrichment of light rare earth elements with no Eu anomaly, enrichment of Rb, Pb, Nd and Ti, and depletion of Ba, K, Sr and Y, similar to features of OIB. This metagabbro was derived from low partial melting of spinel-garnet lherzolites, with minor residual garnet. The ascending magma underwent minor lower crust contamination and orthopyroxene-donimated fractional crystallization. Combining the data obtained by the authors with previous research, the authors have reached the conclusion that the Duguer metagabbro was developed in an intraplate tectonic setting and was formed by ridge subduction after the closure of Bangong Co-Nujiang Ocean.