西羌塘地体勒玛擦铜铁矿化区岩浆属性与成矿条件  

Magmatic attribute and ore-forming condition of Lemaca Cu-Fe mineralization area in western Qiangtang Terrane

作　　者：赵晓燕[1,2] 杨竹森 刘畅[3] 李应栩[4] 徐培言[4] 董艳蕊 崔师源 杨文杰 ZHAO XiaoYan;YANG ZhuSen;LIU Chang;LI YingXu;XU PeiYan;DONG YanRui;CUI ShiYuan;YANG WenJie(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;SinoProbe Laboratory,Beijing 100094,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Chengdu Center,China Geological Survey,Chengdu 610081,China)

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]自然资源部深地科学与探测技术实验室,北京100094 [3]中国地质大学地球科学与资源学院,北京100083 [4]中国地质调查局成都地质调查中心,成都610081

出　　处：《岩石学报》2025年第2期565-584,共20页Acta Petrologica Sinica

基　　金：第二次青藏高原综合科学考察研究(2021QZKK0302);国家自然科学基金项目(42072107);中国地质调查局深部地质调查项目(DD20230008、DD20230230)联合资助.

摘　　要：勒玛擦矿化区位于多龙矿集区的西北侧,地表出露大面积的岩浆岩,发育斑岩和矽卡岩型铜铁矿化,但岩浆岩的地球化学特征以及起源演化仍未可知,该区域的成矿潜力还需进一步探索。为此,文章对勒玛擦矿化区出露的岩浆岩进行了详细的锆石U-Pb年代学、全岩主微量、Sr-Nd同位素分析,并对岩浆岩中的角闪石开展了电子探针和原位微量元素分析,探讨岩浆岩的源区及演化过程,厘定其温压条件、岩浆氧逸度及含水性等要素,为进一步评价区域的成矿潜力提供支撑。研究显示,勒玛擦矿化区岩浆岩主要包括角闪石堆晶岩、闪长玢岩、石英闪长玢岩、花岗闪长岩和花岗斑岩,锆石U-Pb年龄集中在122~118Ma,为早白垩世岩浆活动的产物。角闪石堆晶岩具有明显的堆晶结构,SiO 2含量(44.97%~45.91%)接近玄武质原生岩浆的范围,稀土元素配分曲线呈右倾平缓样式;闪长玢岩、石英闪长玢岩和花岗闪长岩均属于高钾钙碱性系列,为弱准铝质-过铝质岩浆岩。四类岩石均显示弧岩浆岩属性,且具有一致的Sr-Nd同位素组成,其(^(87)Sr/^(86)Sr)_(i)和ε_(Nd)(t)值分别介于0.7058~0.7063和-3.7~-2.8之间,均处于MORB和下地壳的混合线上。由角闪石阳离子数计算的角闪石堆晶岩、闪长玢岩、石英闪长玢岩和花岗闪长岩的矿物结晶温度的平均值分别为:923℃、873℃、847℃和763℃,结晶压力对应的侵位深度分别为:12.6km、5.8km、5.7km和2.5km,氧逸度平均值分别为ΔNNO+0.35、ΔNNO+1.36、ΔNNO+0.88和ΔNNO+1.97,含水量平均值分别为7.14%、4.28%、4.95%、4.23%。四类岩石均起源于俯冲板片交代地幔楔部分熔融,其中角闪石堆晶岩为源区岩浆在一定深度发生角闪石堆积形成的岩块,而闪长玢岩、石英闪长玢岩和花岗闪长岩为角闪石堆晶后的残余熔体继续演化的结果。含矿的花岗闪长岩浅成侵位,富含角闪石,具有高氧逸度高含水量的特�The Lemaca mineralization area is situated in the northwest of the Duolong ore cluster,characterized by a vast expanse of exposed igneous rocks on the surface and hosting porphyry and skarn type Cu-Fe mineralization.However,the source and evolution of magmatic rocks of this area remain unclear,necessitating further exploration to assess the mineralization potential of this area.A detailed study of zircon U-Pb dating,whole-rock major and trace elements,as well as Sr-Nd isotopic analysis on the magmatic rocks exposed in the Lemaca prospecting area,together with EPMA and LA-ICP-MS analysis on the hornblendes in the magmatic rocks were conducted in this paper to explore the origin and evolution process of the magmatic rocks,and determine the mineralization factors such as temperature and pressure conditions,magmatic oxygen fugacity,and water content of them.The findings of these studies provide support for further evaluating the ore-forming potential of this region.The Lemaca mineralization area primarily consist of diorite cumulate(DC),diorite porphyry(DP),quartz diorite porphyry(QDP),granodiorite(GD),and granite porphyry(GP).The zircon U-Pb ages of the measured samples are concentrated between 122Ma and 118Ma,representing an Early Cretaceous magmatism.The DC presents a cumulate structure,with SiO 2 content(44.97%~45.91%)close to the range of basaltic primary magma.The rare earth element distribution curve exhibits a right-leaning gentle style.DP,QDP and GD belong to high K calcium alkaline and metaluminous to peraluminous magmatic rocks.These rocks have the properties of arc magmatic rocks and possess consistent Sr-Nd isotopic compositions.The(^(87)Sr/^(86)Sr)_(i)andε_(Nd)(t)values range within 0.7058~0.7063 and-3.7~-2.8,both located on the mixed line between MORB and the lower crust.Based on the number of hornblende cations,the calculated average crystallization temperatures of GC,DP,QDP and GD are 923℃,873℃,847℃and 763℃,respectively,whose intrusion depths corresponding to crystallization pressures are 12

关 键 词：地球化学 矿物学特征 岩浆属性 勒玛擦矿化区 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学] P618.41