The "China Geological Survey Results Express" recently announced the main results of the geological survey of the Tulargen-Huitongshan area in the Northern Mountains of Gansu and Mongolia.
The survey was completed by the Xi'an Geological Survey Center of the China Geological Survey. Through 1:50,000 anatomical mapping and regional comprehensive research in key areas, the project team identified the composition and properties of the Mingshui block in the Beishan orogenic belt, the material composition, structural structure and properties of the Hongshishan ophiolite mélange, and further deepened the tectonic evolution process of the Beishan key period, providing important basis for the division of tectonic units, tectonic evolution and mineralization geological background research of the Beishan orogenic belt.
The project team conducted a typical dissection of the Mingshui block, basically identified the material composition of the Precambrian strata of the Mingshui block, determined the characteristics of the four-stage tectonic deformation, and identified a large number of strongly deformed Paleozoic magmatic rocks in the original Neoarchean-Paleoproterozoic Beishan Group. It is believed that the block is a block involved in the orogenic belt, most of which disappeared during the orogenic process, and only a few cover layers are relatively well preserved. The area still has the possibility of the existence of a crystalline basement; the identification marks of the blocks involved in the orogenic belt were determined, and the mapping method of medium- and high-grade metamorphic rocks in the blocks involved in the orogenic belt was preliminarily summarized.
In the Beishan Mingshui block, the project team newly identified the A-type granite magmatic activity record of the Rodinia supercontinent breakup period about 780 million years ago, and on this basis systematically sorted out the thermal events of the Beishan blocks during the Mesoproterozoic-Neoproterozoic Rodinia supercontinent assembly and dispersal process; from the aspects of thermal event age, material composition and Hf isotope characteristics, etc., it provides evidence for the affinity study of the Beishan block, and believes that the Mingshui, Hanshan and other blocks involved in the Beishan orogenic belt may have a unified basement with the Dunhuang block in the Mesoproterozoic and before, and have affinity with the Tarim Craton after the Mesoproterozoic.
Newly identified Early Ordovician volcanic rocks on the Mingshui Block in Beishan indicate that they were formed in an extensional environment; Newly identified Devonian Dundunshan Group high-magnesium andesites in the southern Beishan accurately determined the formation age of the volcanic rocks in the Queershan Group in the northern Beishan, and discussed the Devonian rock genesis, tectonic environment and geodynamic background; Newly identified Early Cretaceous rhyolite in Luotuokou in the northern Beishan, the study found that it may represent the latest volcanic magmatic activity in the Beishan area
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