Three-phase uplift of the Qinghai-Tibet plateau during the Cenozoic period: Igneous petrology constraints

Abstract

In northern Qinghai-Tibet plateau there are developed Cenozoic volcanic rocks. They constitute a trachybasalt-shoshonite-latite-trachydacite assemblage. According to the forming ages, three Cenozoic volcanic rock lithozones can be distinguished in the northern part of the plateau. Cenozoic volcanic rocks and muscovite/two-mica granites forming the three belts in pairs represent the northern and southern margins of the plateau in different periods. In fact, the tectonic setting of the northern part of the Qinghai-Tibet plateau is significantly different from that of the southern part—Himalayas. The southern part has experienced subduction and continent-continent collision. There are developed the Cenozoic S-type granites (muscovite/ two-mica granites) there. But the northern part is characterized by Cenozoic basaltic magmatism which obviously comes from the upper mantle. Slight doming of the upper mantle is recognized underneath the northern part of the plateau, which is the result of resistance of the Tarim plate to the north direction-sense movement of the Tibetan plate. And at the same time, the uplift machanism shows that the formation of the Qinghai-Tibet plateau involved three orogenic stages (35−23 Ma, 23−10 Ma and <2 Ma) of uplift in the vertical direction and extension in the horizontal direction with the Gangdise-Qiangtang orogenic belt as its core.