Tectonic settings of the Late Carboniferous-Early Permian volcanic rocks,central Junggar Basin
Shao Yu1, Zhang Shuncun2, Shi Ji'an2, Zhi Dongming1, Sun Guoqiang2
1. Research Institute of Exploration and Development,Xijiang Oilfield Company, PetroChina,Kalamary,Xinjiang 834000;
2. Key Laboratory of Petroleum Resources Research,Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000
Studies on the tectonic settings of the Late Paleozoic Junggar region are traditionally focused on the folded mountain belts around Junggar Basin,due to lack of samples gained in the central region where it is covered with continuous sediments from Mesozoic to Cenozoic.This paper concentrates on petro-geochemistry and lithology of the holebore specimens,which occur in Upper Carboniferous-Lower Permian in central Junggar Basin.Then,it is proposed that: 1)The brown stuff specimens which suggest an eruption above continent are found in various holebore from many layers; 2)Upper Carboniferous-Lower Permian volcanic rocks obtained from central Junggar Basin are mainly alkali basalts and andesites,as well as a little dacites; the major parts of the samples are characterized with high alkali,which are probably erupted from thickened crust with suggesting continental tectonic settings; and 3)in Late Paleozoic the central Junggar Basin was probably continental tectonic settings as suggested by the observation of cores,microscopic sections and combined the analysis of the major and trace elemental data.Further conclusion arrives at that there may be more ancient continental basement below the Carboniferous volcanic rocks.