武当地块基性侵入岩群的地质特征与构造意义  

The geological features and tectonic significances of the basic swarms in Wudang terrain of Qinling orogen.

作　　者：胡健民[1] 赵国春[2] 孟庆任[3] 罗洪 王宗合 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]中国地质大学(北京),北京100083 [3]中国科学院地质与地球物理研究所,北京100029 [4]鄂西北地质调查研究所,襄樊441003

出　　处：《岩石学报》2003年第4期601-611,共11页Acta Petrologica Sinica

基　　金：国家自然科学基金(批准号:40072076;49972066;40272097)

摘　　要：南秦岭构造带武当地块中发育密集侵位的基性侵入岩群,由于武当地区构造变形复杂,这些基性侵入岩体的侵位特征一直没有明确的研究结果。而查明它们的侵位特征,对认识其侵位机制、判断岩浆侵位的大地构造背景以及开展进一步的岩石地球化学和岩浆动力学的研究都具有重要意义。本文通过在武当地块不同构造部位所做的一些详细的1∶5万地质填图以及相应的构造学研究表明,这些侵入岩体是顺层侵位到武当山岩群和耀岭河组中的,少数直接侵位到震旦系陡山沱组和邓影组中,侵入体密集发育的部位受武当地块古生代顺层伸展拆离构造的主拆离面控制。作者同时获得了402 Ma的单颗粒锆石U-Pb年龄,表明这些基性侵入岩群形成于中古生代。因此无论这些基性侵入岩群的地质特征,还是其同位素年代学测试结果,都表明与前人所说的元古代超大陆的裂解很可能没有直接的成因联系。考虑到这个时期南秦岭构造带中发生的紫阳-岚皋碱性岩浆活动、镇安-旬阳浅层塌陷盆地、武当地块伸展滑脱构造及随枣地区基性侵入岩群的侵位等地质构造事件,作者认为武当地块基性侵入岩群很可能是古生代时期南秦岭岩石圈拉伸所导致的深部基性岩浆上侵的结果。There are a large number of basic swarms in Wudang terrain of the south Qinling structural zone. The geological features of them are very important for researching on the intrusive mechanics and geotectonic setting and also for the studying on the geochemistry and magmatic dynamics of the swarms. But because of the complicated deformation, the intrusive features of the swarms have been not clear. Some of 1:50000 geological maps finished by the authors at the different areas of Wudang terrain show that most of the intrusive bodies were intruded along the main detachment plane and a series of sub-order planes of the Paleozoic extensional tectonics of Wudang terrain, into the middle Proterozoic Wudangshan group and the upper Proterozoic Yaolinghe formation and a few bodies were intruded into the Sinian Doushantuo formation and Dengying formation. The intrusion was controlled by the main detachment plane of the Palaeozoic extensional tectonics in Wudang terrain. The zircon, from the diabase-gabbros, U-Pb age of 402 Ma shows that the basic swarms were intruded in the middle Palaeozoic. Both of the geological and the geochronological features show that the basic swarms are not related with the rifting of the Rodinian continent suggested by the previous workers. Considering the alkali magmatism in Ziyang-Langao area, the rifting basins in Zhenan-Xunyang area, the extensional tectonics in Wudang area and the basic swarms in Suizhou-Zaoyang area at the same time, the authors believe that the basic swarms in Wudang terrain could be resulted from the Paleozoic extension of the lithosphere in the south Qinling tectonic zone.

关 键 词：基性侵入岩群 武当地块 南秦岭构造带 

分 类 号：P588.124[天文地球—岩石学]