云南德钦县鲁春铜多金属矿床地质地球化学特征与成因研究

【作者】 胡永斌；

【导师】 邓明国； 曾普胜；

【作者基本信息】 昆明理工大学 ， 矿产普查与勘探， 2011， 硕士

【摘要】 本文从基础地质资料着手,通过作者和本课题科研团队扎实的野外和室内工作,同时收集了大量的地质地球化学资料,综合分析了鲁春铜多金属矿床地质、地球化学特征,初步探讨了矿床研究中非常重要的几个问题：成矿物质来源、成矿环境和矿床的成因模式。金沙江古特提斯造山带是中国重要的金属成矿带,鲁春铜多金属矿区即位于金沙江造山带的构造收紧部位。金沙江造山带为古特提斯金沙江洋盆向西俯冲消减和弧陆碰撞所形成,是由二叠纪的洋内弧和陆缘火山弧于早、中三叠世碰撞拼接而成的复合造山带。其东与中咱-香格里拉微陆块相接,其西邻接昌都-兰坪-思茅微陆块。其演化历史经历了泥盆纪-石炭纪的裂离、晚石炭世-早二叠世金沙江洋盆扩张形成、二叠纪金沙江洋壳向西的俯冲消减、早三叠世的弧后拉张和中、晚三叠世的弧-陆碰撞造山作用五个阶段。鲁春-红坡弧后裂谷盆地处于江达-德钦-维西陆缘火山弧中段,形成于金沙江洋俯冲消减后的弧后拉张环境,呈一近南北向展布的狭长状沉积盆地。由于区域上大规模的逆冲推覆-伸展滑脱构造发育,导致矿区地层发生倒转。矿区出露地层从老到新(从上到下)依次为下三叠统攀天阁组(T1p)、崔依比组(T1c)和中三叠统上兰组(T2s),地层总体走向南北,倾向东。绿泥石岩、硅质岩和条带状灰岩的常量元素、微量元素、稀土元素地球化学特征表明其形成与双峰式火山活动密切相关,绿泥石岩的原岩为流纹质的火山凝灰岩,纹层状硅质岩和条带状灰岩是与海底喷流热液(热水)沉积作用有关的热水沉积岩。锆石U-Pb同位素年代学研究表明,矿区出露的火山岩为一套发育于早三叠世的玄武岩-流纹岩双峰式火山岩组合。玄武岩主要为拉斑系列和钙碱性系列,流纹岩主要为钙碱性系列,是矿区的主要赋矿岩系。地质地球化学特征表明,矿区双峰式火山岩为金沙江洋盆经俯冲消减后弧后扩张环境下的产物。成矿元素和稀土元素特征表明,矿床的成矿物质来源于下伏双峰式火山岩,尤其是长英质岩系的热液萃取。研究结果表明,鲁春铜多金属矿床是在弧后拉张背景下形成于双峰式-长英质岩系中的Zn-Pb-Cu多金属型火山成因块状硫化物(VMS)矿床。更多还原

【Abstract】 The geological and geochemical characteristics of the Luchun copper-polymetallic deposit are discussed in the paper based on the basic geological data and a large amount of collected geological and geochemical data through the well-knit field and indoor work of the and the team researching the subject.Several problems of great importance to deposit research,including the source for metallogenic substance, metallogenic environment and the original pattern of deposit are primarily explored.Jinshajiang Paleo-Tethyan Orogenic belt is an important metallogenic belt of china. Luchun copper-polymetallic deposit is just located in the taking-up position of this belt. Jinshajiang Orogenic belt is formed by Palea-Tethys Jinshajiang ocean crust and arc rushing westward to subduction and collision. This composite orogenic belt collided and jointed by intra-oceanic arc and continental margin colcanic arc in early or middle Trissic period. To the East the belt is abutted with Zhongza-shangri-la micro-landmass and to the west it is adjacent to Changdu-Lanping-Simao micro-landmass. The belt was evolved by the breaking up during Devonian and Carboniferous, expanding and formation of oceanic basin during Late Carboniferous and Early Permian, westward subduction of Jinshajiang ocean crust, during Permian, extending at back-arc in times of Early Triassic and arc land colliding in the Late Triassic. Luchun-Hongpo back-arc rift basin is located in the middle section of Jiangda-Deqin-Weixi volcanic arc, and formed in the back-arc extension environment after the subduction of Jinshajiang ocean and is a strip-like sedimentary basin with a nearly N-S directed alignment.Revers of strata occurred through the area since the growth of large-scale over-thrust and nappe-extensional detachment structure. The strata in chronological order are Early Triassic Pantiange Formation (Tip), Cuiyibi Formation(T1c), Middle Triassic Shanlan Formation (T2S) and Hongpo Formation (T3h) from top to bottom. The strike direction of the strata are overall N-S and east-dipping. The geochemical characteristics of major elements, trace elements, and rare earth elements of Chlorite rocks, cherts and landed limestones show that their formations are closely related to the bimodal volcanic activities. Chlorite derived from rhyolitic volcanic tuff, laminated cherts and banded limestones are hydrothermal sedimentary rocks related to deposition of submarine exhalative hydrothermal (hot water).The research result of the zircon U-Pb geochronology shows that the volcanic rocks is a combination of bimodal volcanic rock developing in the Early Triassic. Typically the basalts are composed of tholeiite and calc-alkaline series, the rhyolites are mainly composed of calc-alkaline series, which are the main ore-hosting rocks. Geological and geochemical characteristics of the mineral area that indicate the bimodal volcanic rocks are the product of back-arc expanding environment formed by Jinshajiang ocean crust colliding with Changdu-Lanping block.The evidence from ore-forming elements and REE indicates that the ore-forming material of the deposit derived from the underlying bimodal volcanic rocks, especially the felsic rocks by the means of the hydrothermal leaching.The result shows that Luchun copper-polymetallic deposit is a the Zn-Pb-Cu polymatallic type of volcanogenic massive sulfide (VMS) depositformed in bimodal-felsic rocks under the environment of initial arc.更多还原