云南高赤坪岩体的岩石成因及成矿潜力:锆石U-Pb年代学、地球化学及Sr-Nd-Hf同位素制约  

Petrogenesis and Metallogenic Potential of the Gaochiping Pluton in Yunnan:Constraints from Zircon U-Pb Chronology,Geochemistry,and Sr-Nd-Hf Isotopes

作　　者：李凯旋 冷成彪 蓝江波[2] 郭国林 朱志军[1] 陈喜连[1] LI Kaixuan;LENG Chengbiao;LAN Jiangbo;GUO Guolin;ZHU Zhijun;CHEN Xilian(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;State Key Laboratory of Mineral Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,Guizhou,China)

机构地区：[1]东华理工大学,核资源与环境国家重点实验室,江西南昌330013 [2]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵州贵阳550081

出　　处：《大地构造与成矿学》2024年第6期1366-1384,I0009,I0010,共21页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(42102098、42022021);第二次青藏高原科考项目(2021QZKK0301);矿床地球化学国家重点实验室开放基金项目(201808)联合资助。

摘　　要：高赤坪岩体位于云南中甸斑岩成矿带的北端,主要由边缘相辉石闪长岩及中心相闪长玢岩组成,岩体存在铜金矿化。该岩体的成岩时代、地球化学特征及成矿潜力均未见报道。本文对该岩体进行了全岩主量和微量元素、锆石U-Pb年代学、微量元素以及Hf同位素和全岩Sr-Nd同位素等分析,旨在揭示其岩石成因并评价其成矿潜力。研究结果表明,从辉石闪长岩到闪长玢岩,Na_(2)O、CaO含量略有降低,K_(2)O、Fe_(2)O_(3)^(T)含量明显升高,呈现出由拉斑玄武质闪长岩类向钙碱性或高钾钙碱性二长岩类方向的演化。两类岩石的稀土和微量元素配分模式基本一致,均富集轻稀土元素、大离子亲石元素(Ba、Th、U、Sr等),亏损重稀土元素、高场强元素(Ta、Nb、Y、Ti等),且轻重稀土元素分异强烈、无明显Eu异常。从边缘相到中心相,岩体中Rb、Ba含量明显升高,Sr略有降低,这与中心相闪长玢岩中斜长石含量减少,出现黑云母、钾长石、磁铁矿特征相符。辉石闪长岩的锆石U-Pb年龄为232.3±1.3 Ma,结合区域地质研究资料,高赤坪岩体形成于印支期甘孜理塘洋壳俯冲的陆缘弧构造背景。辉石闪长岩锆石ε_(Hf)(t)值为-0.94~+1.68,两阶段模式年龄(t_(DM2))为1132~1294 Ma;辉石闪长岩和闪长玢岩的全岩(^(87)Sr/^(86)Sr)i、ε_(Nd)(t)值分别为0.706138~0.706179、0.705863~0.706519和-3.61~-1.76、-3.79~0.66,结合二者都具有低硅埃达克岩的化学特征及高的Mg^(#)值,指示岩浆源于板片脱水或熔体蚀变的地幔楔的部分熔融,且可能有下地壳组分以MASH的形式加入。高赤坪辉石闪长岩的氧逸度略低于区内典型成矿岩体普朗斑岩,蚀变规模也较小,暗示其成矿潜力不及普朗斑岩;但更加演化的富水和高氧逸度的闪长玢岩则与区内典型成矿岩体的地球化学性质一致,表明其具有一定的成矿潜力,在未来的找矿勘查中应予以重视。The Gaochiping pluton in Northwest Yunnan is located in the north part of the Zhongdian porphyry metallogenic belt.The pluton is mainly composed of pyroxene diorite in the margin and diorite porphyrite in the center.The pluton is associated with copper-gold mineralization.However,its geochemical characteristics,age,petrogenesis,and metallogenic potential have not yet been reported.In this paper,we report the whole-rock major and trace element compositions,zircon U-Pb age and trace element and Hf isotopic compositions,and whole-rock Sr-Nd isotope compositions of the rocks and evaluate their metallogenic potential.From the pyroxene diorite to the diorite porphyrite,Na2O and CaO are slightly decreased,while K_(2)O and Fe_(2)O_(3)^(T) are significantly increased,manifesting an evolution trend of tholeiitic diorite to calc-alkaline or high-K calc-alkaline monzonite.The rocks have similar rare earth and trace element signatures,enriched in light rare earth and large-ion lithophile elements(Ba,Th,U,Sr),depleted in heavy rare earth and high field strength elements(Ta,Nb,Y,Ti),and strong differentiation of light and heavy rare earths,without obvious Eu anomalies,but Rb and Ba are significantly increased,and Sr is slightly decreased in the diorite porphyrite.These characteristics are consistent with the decrease of plagioclase and the common occurrence of biotite,K-feldspar,and magnetite in the diorite porphyrite,indicating increased water content and oxygen fugacity during the evolution from pyroxene diorite to diorite porphyrite.The zircon Pb-U age of 232.3±1.3 Ma indicates the Indosinian continental margin arc setting of the Ganzi-Litang oceanic crust.The zircon ε_(Hf)(t)values range is from -0.94 to +1.68,and the two-stage model ages(t_(DM2))range is from 1132 to 1294 Ma.The whole-rock(^(87)Sr/^(86)Sr)i and ε_(Nd)(t)values of the pyroxene diorite and diorite porphyrite are 0.706138 to 0.706179,0.705863 to 0.706519 and-3.61 to-1.76,-3.79 to 0.66,respectively.The continental margin arc setting,isotopic compositions,to

关 键 词：高赤坪 岩石成因 锆石 成矿潜力 滇西北 

分 类 号：P581[天文地球—岩石学] P59[天文地球—地质学]