拉萨地体南缘中新世埃达克质斑岩中熔体包裹体特征  

Characteristics of melt inclusions of Miocene adakitic porphyries in the southern margin of Lhasa terrane

作　　者：赵晓燕[1] 杨竹森[1] 董艳蕊 刘畅[2] ZHAO Xiaoyan;YANG Zhusen;DONG Yanrui;LIU Chang(MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质学报》2025年第4期1223-1237,共15页Acta Geologica Sinica

基　　金：中国地质调查项目(编号DD20230008);国家自然科学基金项目(编号42072107);第二次青藏高原综合科学考察研究项目(编号2021QZKK0302)联合资助的成果。

摘　　要：拉萨地体南缘分布大量的中新世埃达克质斑岩体,这些岩体在成矿元素组合及成矿规模上存在明显的差异。为更全面地理解拉萨地体南缘中新世斑岩差异性成矿的制约因素,本文选取带内典型的邦铺成Mo斑岩和甲玛成Cu斑岩为研究对象,开展不同斑岩石英斑晶中的单个熔体包裹体的TIMA扫描及电子探针研究。结果显示,甲玛和邦铺斑岩石英斑晶中的熔体包裹体都以结晶质为主,结晶矿物主要包括石英、钠长石、正长石、斜长石以及云母等;熔体包裹体中SiO_(2)和K_(2)O具有明显的负相关关系,属于高钾钙碱性—钾玄岩系列;相比于邦铺,甲玛含矿斑岩熔体包裹体具有更低的Cl (0~0.03%)和更高的H_(2)O (1.12%~4.35%)含量。研究表明,超钾质岩浆的注入和强烈的钾长石结晶分异作用对碰撞造山背景下的斑岩矿床具有重要的作用;此外,挥发份(包括H_(2)O、Cl等)的含量对成矿的差异性发挥了很大作用。Miocene adakite porphyries are widely distributed along the southern margin of the Lhasa terrane,but they exhibit significant variations in ore-forming element composition and mineralization scale.In order to better understand the constraints of different mineralization of these Miocene porphyries,this study focuses on the ore-bearing porphyries of the Jiama Cu deposit and Bangpu Mo deposit.We carry out TIMA scanning and electron probe analyses of single melt inclusions in quartz phenocrysts from these porphyries.The results show that the melt inclusions in both Jiama and Bangpu are predominantly crystalline,composed mainly of quartz,albite,orthoclase,plagioclase,and mica.A significant negative correlation between SiO_(2) and K_(2O) is observed in these melt inclusions from both deposits,classifying them as high-K calc-alkaline to shoshonite series.The Jiama ore-bearing porphyry has lower Cl(0~0.03%) and higher H_2O(1.12%~4.35%) contents compared to the Bangpu porphyry.Previous research has shown that the injection of ultrapotassic magma and strong crystallization differentiation of potassium feldspar play an important role in the formation of porphyry deposits in collisional environments.In addition,the content of volatiles(including H_(2O) and Cl) significantly influences the differences in metallogenesis.

关 键 词：TIMA扫描 电子探针 熔体包裹体 斑岩矿床 拉萨地体 

分 类 号：P618.41[天文地球—矿床学]