羌塘南缘青草山斑岩铜矿床地质特征与岩浆属性  

Geological characteristics and magmatic properties of the Qingcaoshan porphyry copper deposit in the southern margin of Qiangtang

作　　者：董艳蕊 赵晓燕[1,2] 杨竹森 刘畅[3] DONG Yan-rui;ZHAO Xiao-yan;YANG Zhu-sen;LIU Chang(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China;SinoProbe Laboratory of the Ministry of Natural Resources,Beijing 100094,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,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]自然资源部深地科学与探测技术实验室,北京100094 [3]中国地质科学院地质研究所,北京100037

出　　处：《岩石矿物学杂志》2024年第6期1531-1552,共22页Acta Petrologica et Mineralogica

基　　金：第二次青藏高原综合科学考察研究(2021QZKK0302);中国地质调查局深部地质调查项目(DD20230008,DD20230230)。

摘　　要：青草山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,发育斑岩型铜矿化,但岩浆岩的地球化学特征和起源演化过程尚不明确,制约了该矿化区找矿潜力进一步的评价。为此,对青草山矿化区出露的岩浆岩进行了详细的锆石U-Pb年代学、锆石微量元素、岩石地球化学、Sr-Nd同位素和角闪石电子探针分析,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,为进一步评价区域找矿潜力提供支撑。研究显示,青草山矿化区成矿期岩浆岩主要包括花岗闪长斑岩、闪长玢岩和二长花岗斑岩,成岩年龄集中在120~118 Ma,成矿期后细晶岩的锆石U-Pb年龄为114 Ma,均为早白垩世岩浆活动的产物。通过锆石中Ti含量计算出成矿期的花岗闪长斑岩、闪长玢岩、二长花岗斑岩中锆石的结晶温度平均值分别为604、689、684℃,氧逸度lg(fO_(2))平均值分别为-18.58、-15.77、-14.18,ΔFMQ变化范围分别为ΔFMQ-0.46~ΔFMQ+2.38、ΔFMQ-5.66~ΔFMQ+4.28、ΔFMQ-1.32~ΔFMQ+6.24。闪长玢岩和花岗闪长斑岩属于高钾钙碱性-钾玄岩系列,为准铝质-弱过铝质岩浆岩,具有弧岩浆岩属性;(^(87)Sr/^(86)Sr)i值介于0.7074~0.7093之间,ε_(Nd)(t)值介于-7.1~-5.3之间,处于亏损地幔与下地壳演化线之间的区域,显示出壳幔混源的特征。角闪石的电子探针结果显示,闪长玢岩含水量平均值为7.4%。研究表明,青草山白垩纪岩浆岩起源于俯冲板片交代地幔楔部分熔融,并受到了地壳物质的混染,同时显示出高氧逸度高含水量的特点,指示青草山矿化区具有良好的斑岩铜矿成矿潜力。The Qingcaoshan mineralization area is located on the northwest side of the Duolong mining area,with a large area of magmatic rocks exposed on the surface and developed porphyry-type copper mineralization.However,the geochemical characteristics and origin and evolution of the magmatic rocks are not yet clear,which restricts further evaluation of the prospecting potential of this mineralization area.For this purpose,detailed zircon U-Pb geochronology,zircon trace elements,rock geochemistry,Sr-Nd isotopes,and hornblende electron microprobe analyses were conducted on the exposed magmatic rocks in the Qingcaoshan mineralization area to explore the source area and evolution process of the magmatic rocks,determine their temperature and pressure conditions,magma oxygen fugacity,and water content,and provide support for further evaluating the regional prospecting potential.The study shows that the ore-forming magmatic rocks in the Qingcaoshan mineralized area mainly consist of granodiorite porphyry,diorite porphyry,and monzonitic granite porphyry,with diagenetic ages concentrated between 120~118 Ma.The zircon U-Pb age of the postmineralization aplite is 114 Ma,all of which are products of Early Cretaceous magmatic activity.The average crystallization temperatures of zircons in granodiorite porphyry,diorite porphyry,and monzonitic granite porphyry during the mineralization period were calculated based on the Ti content in zircons,which were 604,689 and 684℃,respectively.The average oxygen fugacity lg(fO_(2))was-18.58,-15.77 and-14.18,respectively.The range ofΔFMQ variation wasΔFMQ-0.46~ΔFMQ+2.38,ΔFMQ-5.66~ΔFMQ+4.28 andΔFMQ-1.32~ΔFMQ+6.24.The diorite porphyry and granodiorite porphyry belong to the high-potassium calcium alkaline-potassium basalt series,and quasi aluminum-weak peraluminous magmatic rocks,with arc magmatic rock properties;The(^(87)Sr/^(86)Sr)i value ranges from 0.7074 to 0.7093,and theε_(Nd)(t)value ranges from-7.1 to-5.3,located in the region between the depleted mantle and the lower crust evolut

关 键 词：地球化学 矿物学特征 岩浆属性 青草山矿化区 羌塘南缘 

分 类 号：P618.41[天文地球—矿床学] P588.1[天文地球—地质学]