云南东川铜矿构造演化与辉长岩地球化学特征

【作者】 衣成利；

【导师】 胡煜昭；

【作者基本信息】 昆明理工大学 ， 构造地质学， 2010， 硕士

【摘要】 东川铜矿是赋存于中元古界昆阳群地层中的大型超大型铜矿床。本论文在全国危机矿山接替资源找矿勘查专项《云南省昆明市东川区东川铜矿接替资源勘查》(项目编码：200553026)的资助下完成的。东川铜矿床构造控矿、控岩作用明显,同时,岩浆及热液活动频繁。本文在前人研究成果的基础上,重点分析了矿区的断裂结构面力学性质及对矿体的影响,同时结合滇中地区及昆阳裂谷的构造演化史,恢复了矿区的构造变形史；并应用岩浆岩地球化学原理及方法,建立了基性辉长岩类的岩石类型判别和大地构造环境判别模式。通过实地观察及室内的综合分析,获得如下认识：(1)矿区内断裂极为发育,构造类型多样,特征明显。综合区域构造发展及断裂结构面力学性质的分析,把矿区构造至少分为三期六组；通过构造层和构造期的划分,结合建造分析和构造分析,重建了矿区的构造体系发展史；石英、方解石脉的ESR测年数据结果表明矿区后期改造依然强烈,晚期浅层脆性断层的活动年龄主要集中在22.4-32.8Ma。(2)研究区内与成矿有关的侵入岩主要为高钛、富碱的碱性辉长岩类,在全碱-Si02关系图上,所有样品全部落在碱性玄武岩范围内；辉长岩类在MORB标准化微量元素蛛网图上表现为左部“大隆起”式,显示大离子亲石元素K、Rb、Th明显富集,Sr、Ta、Nb、Ta、Sm、Y等元素亏损的特征,Nb/Ta<1, (0.42～0.83),其特征类似于大陆裂谷玄武岩,显示了板内玄武岩特征；轻、重稀土元素分馏明显,含量比值(LREE/HREE)在3.40和4.31之间变化；同时,样品具有明显的δEu正异常,这可能是由于深源岩浆上涌后处于地表高氧化状态下岩浆发生分异演化引起的。构造环境判别图解投入板内玄武岩区域,综合区域地质特征及前人的研究结果,本区辉长岩类可能形成于大陆裂谷的拉张阶段或初始裂谷阶段。(3)建立了矿区的构造及岩浆找矿标志,并根据地质情况,结合构造地球化学和物探的找矿标志,圈定了3个找矿靶区,同时预测靶区深部延深较好,并有隐伏矿体存在的可能性。本文研究成果为铜铁矿体及隐伏矿预测提供了可供参考的新思路、新方法,为指导区域找矿和下一步的工作提供了一定的理论依据。更多还原

【Abstract】 Dongchuan Copper deposit in Yunnan is a Large and Super-large copper deposit which occurs in the stratum of Mesoproterozoic Kunyang Group. The thesis sponsored by the national special prospecting of the resources crisis mines which named"Mineral resources survey of the Dongchuan Copper deposit in Yunnan"(Nunber:200553026).The rock-control and ore-control fuction of tectonic is obvious, meanwhile the magmatic and hydrothermal activity occurs frequently. Based on previous research, the thesis analysis emphasisly the mechanical property of tectonic structural plane and the impact on the ore body. Combined with the evolution history of Central Yunnan province and Kunyang rift valley,the history of tectonic deformation in Mining is restored. And applying the principles and methods of magmaticrock geochemistry, the thesis establishs the discrimination mode of the basic gabbro type and the tectonic environment. Through field investigation and indoor synthesized analysis, obtain the conclusions as below:(1) The orefield fractures highly developed, the construction types are various and the characteristics appear significantly. Combined with the tectonic development and the mechanical property of tectonic structural plane,the thesis divide the mine construction into at least three periods and six groups. Through the the division of the structural stage and the tectonic epochs, and meanwhile combined with the construction analysis and structural analysis, the paper reconstruct the mining history of structural system. The ESR dating data of quartz and calcite show that the post-transformation in mining still accurs intensely, the activities late age of the shallow brittle faults concentrated in the 22.4～32.8Ma.(2) The basic intrusive rock related to mineralization in Dongchuan copper deposit is the alkaline gabbro which shows the characteristics of higher Ti and richer alkali. All samples fall into the scope of alkali basalt. Total alkali vs silica diagram.The gabbro is characterized by "humped" in MORB normalized trace element sider diagram for gabbro, and is highly enriched K、Rb、Th, and Sr、Ta、Nb、Ta、Sm、Y are relatively deficit, Nb/Ta<1,(0.42～0.83),similar to the intea-contineral rift basalts and show the character of WPB.The REE pattern of gabbro is right dipped and the fractionation of LREE-HREE is obvious. The sample is characterized by obviously Eu positive anomaly, which maybe caused by the deep magma upwells and then occurs differentiation and evolution in the high oxidation state. Tectonic discrimination diagrams drop-in intraplate basalt region. Combined with regional geological features and prior research results, the gabbro in this district probably formed in the stretch stage or initial rift phase of the continental rift.(3)The thesis establish the orefield prospecting signs of the tectonic and magma, and according to geological conditions, combined with geochemical and geophysical prospecting signs, delineate 3 prospecting targets,and meanwhile forecast that the deep target extends deep well and conceales the existence possibility of the ore body. The researching results provide a new idea and method which can be useful in the structural control character, searching copper and iron ore deposit in magmatite region and the concealed orebody forecasting, which provides the theoretical basis for the mineing prospecting and the feature work.更多还原