内蒙古赤峰地区二叠纪火山岩的发现及其地质意义

Recognition of the Early Permian Volcanic Rocks and Its Geological Significance in Chifeng Region of Inner Mongolia

为探讨赤峰西部铭山隆起带上的大面积火山岩的地质意义,对该区开展1︰5万区域矿产地质调查时,通过野外地质调查、岩石学、LA-ICP-MS锆石U-Pb同位素测年及区域地层对比,发现该区火山岩不同于晚侏罗世—早白垩世火山岩,且发育明显的绿色蚀变现象;下部角闪安山岩的测年结果为273.6±2.2Ma,为二叠系额里图组。该区火山岩属钙碱性-高钾钙碱性系列,岩浆经历了矿物的分离结晶过程,是同源岩浆连续演化的产物,具有由底至顶由中基性向中酸性岩浆演化、稀土元素总量逐渐增高的特点。研究认为,该期火山岩的形成与晚古生代古亚洲洋向华北地块的俯冲作用有关,应是太古界至元古代的结晶基底和晚泥盆世岩浆产物的重熔岩浆喷发形成,其形成的构造环境为安山弧。

In order to investigate the geological significance of the large area of volcanics in the Uplift belt of Mingshan in western Chifeng,When carrying out the 1!5million regional mineral geological survey in the area,Through the research work of field geology investigation, petrology, LA-ICP-MS zircon U-Pb isotopic dating and regional stratigraphic correlation and so on,Found that the volcano rocks in the area is different from the Late Jurassic-Early Cretaceous volcanic rocks,And the obvious green alteration phenomenon was developed.The dating results of the Hornblende andesite in the lower parts is 273.6±2.2Ma,it should belong to the Permian Elitu formation.The Volcanics in the area belong to Calc-alkaline-high-K calc-alkaline series volcanic rocks,And volcanic magma experienced the separation and crystallization of minerals,it was the product of the continuous evolution of cognate magma,having the Characteristics that from bottom to top Intermediate-Mafic to Acidic magmatic evolution and the REE content increased gradually.Studies suggest that the Formation of volcanic rocks in the area is related to the ancient Asian Ocean to the North China block subduction in the Late Paleozoic period,It should be formed in the Archean to Proterozoic crystalline basement and late devonian magma Remelting eruption,the tectonic environment formation of the volcanics in this area was andreessen arc.