Dong AG. Geological characteristics of Neogene volcanic rocks in the Heishi North Lake area, northwestern Tibet, and their implications for the Neogene tectonic evolution.

Volcanic rocks of the shoshonite series in the Heishi North Lake area, northwestern Tibet have the characteristics of continuous evolution from basic andesite in the early period to intermediate volcanic rocks in the late period. Three phases of volcanism may be distinguished. The volcanism was dominated by central eruption. The three phases have K-Ar ages of 9.23 Ma, 3.19 Ma and 3 Ma respectively. The characteristics of the REE, trace elements and isotopic compositions of the volcanic rocks are essentially close to those of Cenozoic volcanic rocks in other areas of northern Tibet, which show that the volcanic rocks have the features of mixing and hybridization of deep magma and shallow magma. Volcanic activities were the response to the neotectonic activities and were controlled by strike-slip faults produced during the uplift of the Qinghai-Tibet Plateau.