西藏念青唐古拉古近纪矽卡岩型铁铜铅锌矿床成因机制与成矿模式

发布时间：2018-06-21 15:57

本文选题：西藏 + 念青唐古拉　；参考：《中国地质大学》2017年博士论文

【摘要】：论文围绕念青唐古拉铁铜铅锌矿成矿带东西两段的典型古近纪不同矿化类型的矽卡岩矿床(亚贵拉铅锌银钼、蒙亚啊铅锌银(钼)、加多捕勒铁铜、恰功铁(铅)矿床为典型矿床)进行对比研究,在野外地质调查的基础上,通过详细室内观察分析,系统总结了念青唐古拉成矿带内古近纪矽卡岩的矿床地质特征和成矿地质条件。区内各矿床中的岩浆演化序列主要集中于早白垩世(110-125 Ma),晚白垩世(80-90 Ma),古新世(50-65 Ma),中新世(13-20 Ma)四个时期,且以古新世(50-65 Ma)为主。区内矽卡岩Fe-Cu-Pb-Zn矿床蚀变-矿化时限主要集中于50-65Ma,因此约束了区内的Fe-Cu-Pb-Zn矽卡岩成矿事件主要形成于印亚大陆碰撞初期,是新特提斯洋板片陡深俯冲后折返引发上部地壳部分熔融的产物。岩石地球化学特征揭示区内的铅锌矽卡岩矿化岩浆源区主要为中上地壳,而铁铜矽卡岩矿化多源于下地壳,有较多的幔源物质的参与。岩浆演化方面,铅锌矿较铁铜矿而言,成矿岩体具更高的分异特征。详细的矿物学研究显示加多捕勒Fe-Cu矿床早期铜矿化具有近源高温特征,晚期具有低温叠加特征。石榴子石矽卡岩中的硫化物中含有自形粒状的石榴子石,斑铜矿-黄铜矿组合呈近1:1的固溶体分离结构特征;且斑铜矿中含有大量的Bi(0.41 wt.%),此外在受到热液蚀变作用后形成了独立的含Bi矿物,如硫铋铜矿,显示呈固溶体分离结构的黄铜矿-斑铜矿形成于高温阶段,属于进变质阶段产物。加多捕勒Fe-Cu矿床石榴子石的微量元素,尤其是Sn,显示从早阶段(364-15 ppm)到最晚阶段(34-0.14 ppm),暗示在石榴子石演化过程中Sn发生了分离。结合磁铁矿中Sn含量的变化(岩浆磁铁矿中为7.3-2.7 ppm,南部块状磁铁矿矿石中为71-13ppm,中部含黄铜矿的磁铁矿中为8.3-3.3 ppm),推测石榴子石中Sn的含量可以反映流体中Fe-Cu元素的分离。亚贵拉Pb-Zn-Ag与Mo矿化为同一成矿作用,与古新世同碰撞背景下由于中上地壳部分熔融形成的岩浆有关,成矿岩体为石英斑岩,成矿流体主要来自于岩浆热液,沸腾作用是Pb-Zn与Mo矿化沉淀的主要机制。蒙亚啊Pb-Zn-Ag矿床成矿年龄为53 Ma,目前地表未发现与成矿相关的岩体,推测可能在深部或者外围。热液受到矿区普遍发育的断裂控制,后受到大气降水的混合作用而沉淀成矿。加多捕勒Fe、Cu矿化均与黑云母二长花岗岩相关,为同一期热液作用的产物,显示Fe、Cu在南北矿段分带特征,降温是加多捕勒Fe矿化沉淀的主要因素,早阶段Cu矿化具有高温的特征(400℃),其后流体受到大气降水混合的影响而致使晚阶段铜矿化的叠加;恰功矽卡岩Fe与断裂控制的热液脉型Pb矿化为同一期岩浆作用的产物,早阶段成矿流体由于压力的下降,流体发生液-液不混溶作用,为磁铁矿的沉淀提供了有利条件;晚阶段沸腾作用是远端受断裂控制的Pb矿化沉淀的重要因素。加多捕勒与恰功矿床中不同世代的石榴子石的Eu异常反映了流体盐度的变化。
[Abstract]:In this paper, the paper revolves around the typical Paleogene different mineralization types of skarn deposits in the two segment of the mineralogical belt of the tangqilan iron copper lead zinc ore belt. The geological features and metallogenic conditions of the Paleogene skarn in the Yuqing Tanggula metallogenic belt are systematically summarized. The magma evolution sequence in the deposits in the area mainly concentrated on the early Cretaceous (110-125 Ma), the late Cretaceous (80-90 Ma), the Paleocene (50-65 Ma), the Miocene (13-20 Ma), and the Palaeocene (50-65 Ma). The alteration mineralization time limit of the skarn Fe-Cu-Pb-Zn deposit is mainly concentrated on the 50-65Ma, so the Fe-Cu-Pb-Zn skarn mineralization in the restricted area is mainly formed in the early stage of the collision in the Indo Asian continent. It is the product of the partial melting of the upper crust caused by the dive deep subduction of the new Tethys oceanic plate. The geochemical characteristics of the rock reveal the lead and zinc silicon in the region. The main source area of the karyan mineralized magma is the middle upper crust, while the iron copper skarn mineralization is mostly derived from the lower crust, with the participation of more mantle derived materials. In terms of the magma evolution, the ore body has higher differentiation characteristics than the iron and copper ore. The detailed mineralogical study shows that the early copper mineralization of the polyshalen Fe-Cu deposit has the characteristics of near source high temperature. The late stage has the characteristics of low temperature superposition. The sulfides in the garnet skarn contain self shaped granite, and the chalcopyrite assemblage of the chalcopyrite is nearly 1:1 solid solution separation structure, and there is a large amount of Bi (0.41 wt.%) in the porphyry copper mine. In addition, a separate Bi mineral, such as bismuth copper ore, is formed after the hydrothermal alteration. The chalcopyrite - porphyry that shows solid solution separation structure is formed at the high temperature stage and belongs to the progressive metamorphic stage. The trace elements of the garnet Fe-Cu deposit, especially the Sn, show that from the early stage (364-15 ppm) to the late stage (34-0.14 ppm), it is suggested that Sn was separated during the evolution of the garnet and Sn contained in magnetite. The variation of the quantity (7.3-2.7 ppm in magmagnetite, 71-13ppm in the massive magnetite ore in the South and 8.3-3.3 ppm in the magnetite with chalcopyrite in the middle is 8.3-3.3 ppm). It is conjectured that the content of Sn in the garnet can reflect the separation of the Fe-Cu elements in the fluid. The magma formed by partial melting of the middle and upper crust, the ore-forming body is quartz porphyry, and the ore-forming fluid is mainly derived from magmatic hydrothermal fluid. The boiling action is the main mechanism of Pb-Zn and Mo mineralization. The metallogenic age of the monya Pb-Zn-Ag deposit is 53 Ma, and at present there is no rock related to the surface of the earth. It is presumed that the hydrothermal solution may be in the deep or peripheral. Fe and Cu mineralization are related to the biotite two feldspar, which is the product of the same phase of hydrothermal fluid, which shows that Fe and Cu are divided into the South and North ore segments, and the cooling is the main factor of adding the Fe mineralized precipitation and the early stage Cu mineralization. The characteristics of the high temperature (400 degrees C), then the fluid is influenced by the mixing of atmospheric precipitation, resulting in the superposition of the late stage copper mineralization; the qigigun skarn Fe and the fracture controlled hydrothermal vein type Pb mineralized as the product of the same phase of magmatism. The early stage ore-forming fluid is due to the decrease of pressure and the fluid liquid immiscibility in the flow body, which is the precipitation extraction of magnetite. Favorable conditions are provided, and the late stage boiling is an important factor for the Pb mineralization controlled by the distal fracture. The Eu anomaly of the garnet in the different generations of the qetruntre and Chia Gong deposits reflects the change of the salinity of the fluid.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P618.4

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