云南省永胜分水岭—大理笔架山铜多金属矿床成矿岩体特征及构造背景研究

发布时间：2018-04-28 09:55

  本文选题：滇西 + 岩浆类型　； 参考：《中国地质大学(北京)》2017年博士论文

【摘要】：研究区位于三江地区富碱侵入岩带上,铜矿体主要产于斑岩体及其外围接触带,矿化与斑岩体密切相关。本文以笔架山、小龙潭、分水岭三个典型斑岩型Cu多金属矿床为研究对象,在详细的野外地质调查的基础上,运用锆石LA-MC-ICP-MS U-Pb同位素年代学方法探讨了研究区典型斑岩型Cu多金属矿床的成岩、成矿时代;运用岩石学、地球化学分析,探讨了研究区成矿斑岩体的岩浆成因类型;运用Lu-Hf同位素方法,探讨了研究区成矿斑岩体的岩浆来源;以电子探针分析结果为基础,运用角闪石—斜长石地质温压计推算了研究区成矿斑岩体的岩浆侵位深度,并探讨了成矿岩体的剥蚀程度;最终,综合野外观测及实验数据分析,讨论了矿床的成因、成矿地质体特征、成矿构造与成矿结构面、成矿作用特征标志,构建了成矿地质模型,以期为滇西地区斑岩型铜矿找矿工作提供一定理论指导。对研究区三个典型矿区主要侵入岩开展了全岩地球化学、锆石LA-ICP-MS U-Pb年代学和Hf同位素研究,获得含矿二长斑岩的206Pb/238U加权平均年龄分别为:笔架山35.6±0.2Ma,小龙潭36.0±0.2Ma,分水岭36.0±0.2Ma,表明研究区斑岩体为始新世岩浆活动的产物。岩体Si O2含量变化较大,高钾、富碱,属钙碱性—碱性(少量过碱性)、准铝质—过铝质岩石;富集大离子亲石元素(K、Rb、Ba、La、Nd)、亏损高场强元素(Ta、Nb、Sr、P、Ti),富集轻稀土元素、亏损重稀土元素;虽被划入富碱侵入岩及A型花岗岩斑岩矿床,但具C型埃达克岩地球化学特征。斑岩体锆石εHf(t)值变化较大,显示研究区始新世斑岩体来源于下地壳物质的部分熔融,并有幔源物质的加入。应用电子探针分析和角闪石—斜长石温压计获得滇西典型铜多金属矿区出露于地表的斑岩体结晶温压分别为:笔架山833.99℃,284.18 MPa;小龙潭804.72℃,163.88MPa;分水岭748.67℃,116.70MPa;进而得出研究区斑岩体侵位深度变化较大,笔架山岩体平均为10.53km,小龙潭6.07km,分水岭4.33km,显示从南西到北东侵位越来越浅的趋势。成矿模式总结为“斑岩侵位,次级构造,热流循环,接触交代,表生富集,再生成矿”。结合区域演化特征,认为研究区斑岩体形成于造山期后的拉张环境,陆陆碰撞挤压后应力松驰,岩浆沿断裂及次级断裂上侵,进而形成铜多金属矿床。
[Abstract]:The study area is located in the alkali-rich intrusive rock belt in Sanjiang area, and the copper ore body mainly occurs in the porphyry and its peripheral contact zone, and the mineralization is closely related to the porphyry. In this paper, three typical porphyry Cu polymetallic deposits, Bijiashan, Xiaolongtan and watershed, are taken as research objects, and on the basis of detailed field geological survey, The diagenesis and metallogenic age of typical porphyry Cu polymetallic deposits in the study area are discussed by means of zircon LA-MC-ICP-MS U-Pb isotopic chronology, and the magmatic genetic types of ore-forming porphyry bodies in the study area are discussed by means of petrology and geochemical analysis. The magma source of the ore-forming porphyry in the study area is discussed by using Lu-Hf isotope method, and the magmatic emplacement depth of the ore-forming porphyry body in the study area is calculated by using the hornblende plagioclase thermometer based on the results of electron probe analysis. The denudation degree of ore-forming rock mass is discussed, and finally, the genesis of ore deposit, the characteristics of ore-forming geological body, metallogenic structure and ore-forming structure plane, and the characteristics of metallogenic process are discussed by synthesizing field observation and experimental data analysis. A metallogenic geological model is constructed to provide theoretical guidance for porphyry copper deposit prospecting in western Yunnan. The whole rock geochemistry, zircon LA-ICP-MS U-Pb chronology and HF isotopic studies have been carried out on the main intrusive rocks in three typical ore areas in the study area. The 206Pb/238U weighted mean ages of the porphyry are respectively: Bijiashan 35.6 卤0.2Ma, Xiaolongtan 36.0 卤0.2Ma, watershed 36.0 卤0.2Ma. this indicates that the porphyry in the study area is the product of Eocene magmatic activity. The content of Sio _ 2 in the rock mass varies greatly and is high in potassium and alkali, belonging to calc-alkaline-alkaline (a small amount of peralkaline, quasi-aluminum-peraluminous rock), rich in large ion lipophilic elements (K ~ (+) Rb ~ (+) B _ (+) La _ (+) NdN _ (+), and depleted in the high field strength element (Tao Nb _ (B) _ (Sr _ (+) _ (P _ (+) _ (Ti), enriched in light rare earth elements and depleted in heavy Although it has been classified into alkali-rich intrusive rocks and A-type granite porphyry deposits, it has the geochemical characteristics of C type adakite. The zircon 蔚 HF t) values of the porphyry body vary greatly, indicating that the Eocene porphyry body in the study area originated from the partial melting of the lower crustal material with the addition of mantle-derived material. Using electron probe analysis and hornblende plagioclase thermometer, the crystallization temperature and pressure of porphyry rock exposed to the surface of typical copper polymetallic mining areas in western Yunnan were obtained as follows: Bijiashan 833.99 鈩，

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