藏南扎西康矿集区地下结构与成矿模式探讨

发布时间：2018-11-17 20:38

【摘要】：在印度大陆和亚欧大陆对接碰撞的过程中,壳幔物质发生大规模的相互作用,形成一系列的变质核杂岩穹窿,同时引发大规模的成矿作用,扎西康多金属矿集区形成于这样的背景。对其控矿因素、找矿模式研究已有一定资料和认识积累,多方面地质信息显示扎西康矿床的形成与区内错那洞核杂岩体关系密切,而两者距离较远、地表位置相对独立,有必要对其深部联系进行挖掘。但受自然环境条件制约该区地球物理工作程度较低,许多地质认识缺乏地球物理资料的支撑。本研究通过大地电磁(MT)反演结果结合大比例尺(1:5万)重磁三维资料,详细揭示错那洞岩体形态特征(岩体顶面起伏形态、埋深、延伸以及侧伏状况)以及矿区构造格架,综合研究该地区地下深部结构特征,为扎西康多金属矿集区的成矿模式研究提供了地球物理证据。大地电磁资料(MT)反演视电阻率剖面和重力三维反演资料、磁法视物性反演结果均显示,扎西康下方约4km深处存在隐伏的穹窿构造,该穹窿整体表现为高视电阻率、低密度以及弱的负磁性的地球物理场响应。大地电磁资料(MT)显示,矿区下方推断的隐伏穹窿构造与错那洞核杂岩体之间没有连通,表现的是低阻板岩、砂岩、页岩等沉积地层的电阻率响应;而重磁反演资料显示,南部错那洞核杂岩体向北倾斜,深入地下10km以上,浅部密度分布不均匀,指示其经过了多期侵入和蚀变不均,对应其复杂多元的岩性、结构特征,扎西康下方的隐伏穹窿构造上侵界面呈“S”型凹凸起伏,暗示着矿区可能存在侵入岩支,两个低密度异常体之间表现为低密度特征,综合MT反演结果及研究区构造演化、岩石物性资料认为,该条带状低密度异常为地下破碎构造带,并不是两个穹窿构造之间的物质连通的体现。本研究的地球物理成果揭示了矿区和南部错那洞核杂岩地区的地下结构,重点针对地下穹窿的结构特征,填补了研究区地球物理资料的空白,从提供了一定深部结构信息,包括研究区地下隐伏穹窿构造的规模、形态及与矿床、其他穹窿构造间的相互作用关系,支持扎西康地区成矿作用深刻受穹窿影响的观点,也为矿区开展三维建模、深部找矿工作提供了基础资料。
[Abstract]:During the docking collision between the Indian continent and the Eurasian continent, a series of metamorphic core complex dome was formed by large-scale interaction of crust-mantle materials, which also led to large-scale mineralization. The Zaxi-Kang polymetallic ore concentration area was formed in this background. For the ore-controlling factors, the ore-prospecting model has been studied and accumulated. Many aspects of geological information show that the formation of the Zaxikang deposit is closely related to the Thona Cave nuclear complex in the area, and the distance between the two is relatively long, and the surface position is relatively independent. It is necessary to excavate its deep connection. However, the degree of geophysical work in this area is low due to natural environment conditions, and many geological understandings lack the support of geophysical data. Based on magnetotelluric (MT) inversion results and gravity and magnetic 3D data of large scale (1: 50, 000), this study reveals in detail the morphological characteristics of the rock mass in the staggered cavity (the undulating shape of the rock body top surface, the depth of the rock mass, and the depth of the rock mass). The extension and lateral potential) and the tectonic framework of the mining area provide geophysical evidence for the study of the metallogenic model of the Zaxi-Kang polymetallic ore concentration area by synthetically studying the characteristics of the deep underground structure of the area. (MT) inversion of apparent resistivity profile and gravity 3D inversion data from magnetotelluric data show that there is a concealed dome structure in the depth of about 4km under Zaxikang, and the whole dome shows high apparent resistivity. Low density and weak negative magnetic geophysical field response. The magnetotelluric data (MT) show that there is no connection between the concealed dome structure inferred under the mining area and the dislocation cavern core complex, and the resistivity response of sedimentary strata such as low resistivity slate, sandstone, shale, etc. The gravity and magnetic inversion data show that the southern Sinahole nuclear complex inclines to the north, goes deeper into the underground 10km, and its shallow density distribution is uneven, indicating that it has undergone multiple periods of invasion and uneven alteration, corresponding to its complex and multivariate lithology and structural characteristics. The intrusive interface of the concealed fornix beneath Zaxikang is "S" type concave and convex, indicating that there may be intrusive rock branches in the mining area, and the characteristics of low density between the two low-density anomaly bodies are presented. The result of MT inversion and the tectonic evolution of the study area are synthesized. According to the petrophysical data, the zonal low density anomaly is an underground fractured structural zone, which is not the manifestation of the material connection between the two dome structures. The geophysical results of this study reveal the underground structure of the mining area and the southern area of the Dana Cave nuclear complex, focusing on the structural characteristics of the underground dome, filling up the gap of geophysical data in the study area, and providing certain information on the deep structure of the area. Including the scale, shape and interaction with ore deposits and other fornix structures in the study area, which supports the view that mineralization in Zaxikang area is deeply influenced by fornix, and develops 3D modeling for mining area. The deep prospecting provides basic data.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P612

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