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塔里木盆地西北部卷入了西南天山新生代板内造山活动,以发育一系列北东向展布的断层和断层相关褶皱为特征,但该区新生代构造变形的原因尚存在争议。文中以皮羌盆地为例报道了新生代火成岩的地质特征和测年结果,认为构造变形是对幔源岩浆活动的浅部响应,与印度-亚洲大陆碰撞没有必然的联系。皮羌盆地出露有大量的新生代基性岩墙和4个古火山颈,岩墙群整体走向NNW和NNE,产状近于直立,侵入于新生界湖相沉积地层中。火山颈相玄武岩锆石SHRIMPU-Pb定年结果为46Ma,全岩K-Ar等时线封闭年龄为(45.5±6.13)Ma,表明岩浆活动发生在始新世中期。岩浆活动时间比逆冲推覆构造启动时间(约24Ma)早约22Ma。按热传导模式估算,在此期间来自深部热源的热传递距离约为25km。假定深部热源为底侵或内侵幔源岩浆,新生代岩浆活动可能是塔里木盆地西北部大规模构造变形的触发机制。
The northwestern Tarim Basin is involved in the intracontinental orogeny of the southwestern Tianshan Mountains and is characterized by a series of faults and faults associated with the NE-trending distribution. However, the reasons for the structural deformation of the Cenozoic in this area are still in dispute. This paper reports the geological characteristics and dating results of Cenozoic igneous rocks in the Piqiang Basin. It is concluded that tectonic deformation is a shallow response to mantle magmatic activity and is not necessarily related to the Indian-Asian collision. There are a large number of Cenozoic mafic dikes and 4 ancient volcanic necks exposed in Piqiang Basin. The dyke swarms move towards NNW and NNE as a whole, and their occurrences are nearly erect, intruding into the sediments of the Neozoic lacustrine sediments. The zircon SHRIMPU-Pb dating of volcanic-eocene basalts is 46 Ma, and the closure age of the K-Ar isochron in the whole rock is (45.5 ± 6.13) Ma, indicating that the magmatic activity occurred in the mid-Eocene. The magmatic activity time is about 22Ma earlier than the start-up time of the thrust nappe (about 24Ma). Estimated by heat conduction mode, the heat transfer distance from the deep heat source during this period is about 25 km. Assuming that the deep heat source is underlying or intrusive mantle magmatism, the Cenozoic magmatic activity may be the trigger mechanism for large-scale structural deformation in the northwestern Tarim Basin.