Comparison of geochemical characteristics and forming environment of volcanic rocks in Northern Xinjiang and the Songliao Basin, China

The tectonic settings of Northern Xinjiang, Songliao Basin, and its peripheral areas all belong to the Paleoasian orogenic region. Their main structures are all composed of multiple continental segments and peripheral fold belts. Similar tectonic setting and complicated basement structure give rise to the similarities and differences in the forming environment and geochemical characteristics of volcanic rocks in the two regions. The similarities include lack of typical calc-alkalic volcanic rocks, inconsistent covariant relationship between oxide content and SiO2 with that of calc-alkalic volcanic rock in the consuming zone, the distribution pattern of trace elements featuring the enrichment of highly incompatible elements, Nb negative anomaly, La positive anomaly, Ba partially positive anomaly, as well as different enrichment degrees of light rare earth. The differences between the Northern Xinjiang and Songliao Basin are characterized by the developed alkalic basalt, rich highly incompatible elements and light rare earth. Volcanic rocks in Northern Xinjiang shows an increase in both total rare earth and light rare earth enrichment from south to north, whereas the total rare earth and light rare earth enrichment in Songliao Basin are also higher than the adjacent Daxing'anling. Generally, both the Carboniferous-Lower Permian volcanic rock in Northern Xinjiang and Mesozoic volcanic rock in Songliao Basin and its peripheral areas developed in the post-collision intracontinental extensional tectonic environment, indicating that the post-collision extensional basin in Junggar-Xingmeng Paleoasian Ocean orogenic region has promising oil-gas exploration potential for volcanic reservoirs.