GEOGRAPHY

There was a new formulation during the formation of the Altyn fault


Recently, the team of Dai Shuang, a professor at the School of Geological Sciences and Mineral Resources of Lanzhou University, together with the Gansu Geological Survey and the Institute of Exploration and Development of Sinopec Shengli Oilfield Company, published the title “The evolution of the Jurassic Dunhuang Basin and its enlightenment to the early history of the Altyn Fault” in the international geoscience journal Geotectonics.

A brief geological map of the Qinghai-Tibet Plateau and Dunhuang Basin, showing that the Altun fault divides important geomorphological units and resource-rich areas in northwest China. Photo courtesy of the research group

The Altyn Fault is a huge fault in the interior of Asia, about 1,600 kilometers long from east to west, constituting the northeastern boundary of the Qinghai-Tibet Plateau, controlling the topographic development and seismic activity of the northern plateau, and at the same time, it also separates the most important Altun Mountain-Tarim and Qilian Mountain-Qaidam in northwest China, and the energy-metal-rich ore belt of the Hexi corridor. Therefore, studying its formation and evolution history is of great significance for understanding the tectonic-environmental evolution process in eastern Asia, testing and improving the theory of plate tectonics and continental dynamics, and guiding energy and mineral exploration, disaster prevention and mitigation in western China. For its formation history, the existing research results believe that the Late Triassic began about 230 million years ago, especially the Early-Middle Jurassic activity was strong more than 200 million to 170 million years ago, and then a horizontal strike-slip error occurred for more than 400 kilometers, staggering the Altunshan-Qilian Mountains copper-lead-zinc polymetallic metallogenic belt and a series of coal-bearing and oil and gas basins in the Tarim, Qaidam and Hexi corridors along the north-east direction.

Based on the traditional basin research paradigm, namely stratigraphy-sedimentation, basin occurrence and filling mode investigation and research, combined with deep drilling, clastic zircon U-Pb chronology source analysis and regional thermochronology data, the research team determined the comparison and chronology of Jurassic strata in the Dunhuang Basin, and clarified that the Jurassic sediments in the basin mainly came from Beishan, Altun-Qilian Mountains and the Sanwei Mountain area in the basin. Combined with the results of seismic reflection data interpretation, it is found that the early Jurassic Basin fault is caused by the boundary positive fault activity on both sides. The expansion of the Middle Jurassic basin is the result of the shrinkage of the deep crust toughness and the increase in heat flux, and the end or weakening of late Jurassic boundary fault activity leads to the transformation of the basin into a depression basin. The distribution area of the current Altyn fault is composed of three small positive faults in the Jurassic , rather than a left-handed strike-slip fault, indicating that there is no strike-slip fault in the Jurassic region, that is, the current form of the Altyn fault cannot be as early as the predecessors said (late Triassic). This research result is of great significance for understanding the activity history of the Altyn fault and its resource and environmental effects. (Source: China Science News, Wen Caifei, Faisha)

Related paper information:https://doi.org/10.1029/2022TC007620



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