Petrography and geochemistry of the Cretaceous volcanic rocks in Tingri, southern Xizang

The geology, petrography, geochemistry and tectonic settings are described for the Cretaceous (volcanic) rocks in Tingri, southern Xizang. The volcanic rocks consist of altered dacite and andesite, which are assigned to the subalkaline, silica- and aluminum-oversaturated tholeiite series. The REE amounts range (between) (383.17)×(10^-6) and (266.52)×(10^-6). The REE distribution curves display highly right-leaning LREE-enriched patterns, whereas the trace element distribution patterns exhibit zigzag "polydome" patterns, similar to those for island-arc volcanic rocks. The trace element compositions are plotted into the volcanic arc field in the Rb-(Yb+Ta) diagram, and the lithochemical compositions fall into the island-arc orogenic basalt and andesite fields in the ATK diagram. The preceding results of research show that the Cretaceous volcanic rocks in the study area are interpreted to be formed in a continental marginal orogenic island-arc tectonic setting.