【摘要】 新疆东准噶尔乌伦古河两岸发育大量的二叠纪火山岩地层,其中卡拉岗组区域上以中酸性火山岩为主,局部以双峰式火山岩为主。本文以恰库尔图地区卡拉岗组双峰式火山岩——流纹岩和玄武岩为研究对象,进行了岩石学、年代学、地球化学等研究。锆石LA-ICP-MS U-Pb结果表明,流纹岩和玄武岩的年龄分别为279. 5±1. 4 Ma和280. 4±1. 3 Ma,说明卡拉岗组双峰式火山岩的形成时代为早二叠世。恰库尔图地区卡拉岗组流纹岩具有较高的Si O₂、K₂O、Na₂O,低Al₂O₃、Ca O和MgO,稀土配分图呈右倾Eu亏损的燕式分布,在微量元素标准化图上显示出Ba、Nb、Ta、Sr、P和Ti的亏损;玄武岩样品具有铕的轻微负异常,相对富集大离子亲石元素,亏损高场强元素Nb、Ta,并表现出Ti的亏损;流纹岩龄锆石的εHf（t）平均值为+15. 3,模式年龄TDM 1（305 Ma）和TDM 2（cc）（320 Ma）与其形成年龄（279. 5 Ma）相近,这表明其源区物质主要为新生地壳,是壳源岩石重熔作用的产物。本区双峰式火山岩的两个端元并非同源,流纹岩是幔源岩浆与壳源熔体混合作用的结果。恰库尔图地区在早二叠纪前准噶尔洋已完全闭合,处于后碰撞拉张体质,双峰式火山岩为后碰撞伸展构造环境的产物,准噶尔盆地古老的前寒武纪结晶基底存在的可能性说明该区具有良好的油气勘探潜力。更多还原

【Abstract】 Objectives: There were large scale volcanic rocks strata of Permian in East Junggar Basin,Xinjiang. the Kalagang Group is mainly intermediate acid volcanic rocks,local bimodal volcanic rocks. This artical based on Kalagang Group bimodal volcanic rocks——rhyolite and basalt,to discusses the Late Paleozoic tectonic setting inthe Qatukatu area,Eastern Junggar Basin. Combining with the previous research results,attempts to determine and explore the Early Permian tectonic settings provide the basis for defining the closure time of the Junggar Ocean and revealing the tectonic evolution of East Junggar Basin.Methods: This artical based on Kalagang Group bimodal volcanic rocks——rhyolite and basalt,to research the petrology,geochronology,geochemistry.Results: Zircon LA-ICP-MS U-Pb results showed that the rhyolite and basalt ages were 279.5 and 280.4 Ma,indicating the formation age of the volcanic rocks of Kalagang Group producted in the early permian. The rhyolites have high SiO2,K2 O,Na2 O,Al2 O3,CaO and low MgO. The REE distribution map shows a "Yan style"distribution and Eu is a negative anomaly. The elment of Ba,Nb,Ta,Sr,P and Ti are loss shown on the trace elemental normalization map. The basalt samples have a slight negative anomaly of Eu,enrich large ion lithophile elements,depletion of high field strength elements Nb,Ta,and loss of Ti; the average value of εHf( t) of rhyolite zircons is +15.3,TDM 1( 305 Ma) and TDM 2( cc)( 320 Ma) ages are similar to their formation age( 279.5 Ma).Conclusions: The bimodal volcanics in this area are not homologous,rhyolite is the result of the mixing of the mantle magma and the melt crustal source. The Qiakuertu region was completely closed before the Early Permian,and was in post-collision tensioning and bimodal volcanic rocks were the product of post-collision extensional tectonic setting.The possibility of the existence of the old Precambrian crystalline basement in the Junggar basin indicates that the area has good potential for oil and gas exploration.更多还原