西藏唐格矽卡岩型铜铅锌矿床成矿时代:来自石榴子石U⁃Pb年龄的约束  

The Metallogenic Age of Tangge Skarn-Type Copper-Lead-Zinc Deposit in Xizang:Constraints from Garnet U⁃Pb Geochronology

作　　者：黄倩 吴松[1] 刘晓峰 申亚辉 阿旺旦增 次琼 陈烈 魏守才 Huang Qian;Wu Song;Liu Xiaofeng;Shen Yahui;Danzeng Awang;Ci Qiong;Chen Lie;Wei Shoucai(College of Earth Science and Resources,China University of Geosciences,Beijing 100083,China;No.2 Geological Party,Bureau of Geology and Mineral Exploration and Development,Lhasa 850000,China;No.5 Geological Party,Bureau of Geology and Mineral Exploration and Development,Lhasa 850000,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]西藏自治区地质矿产勘查开发局第二地质大队,西藏拉萨850000 [3]西藏自治区地质矿产勘查开发局第五地质大队,西藏拉萨850000

出　　处：《地球科学》2025年第2期621-638,共18页Earth Science

基　　金：国家自然科学基金(Nos.U22A20572,42072109);西藏自治区中央引导地方科技计划项目(No.XZ202202YD0006C);紫金矿业科技项目“西藏朱诺斑岩铜钼矿床外围找矿靶区优选与资源潜力评价”.

摘　　要：石榴子石原位U-Pb定年是近年来新发展的低U矿物同位素定年方法,目前已在矽卡岩矿床中广泛应用.首次报道了西藏唐格矽卡岩型铜铅锌矿床石榴子石LA-ICP-MS U-Pb年龄及微量元素组成,结合矿床石英斑岩锆石U-Pb年龄结果,对唐格矿床成岩成矿时代及过程进行了探讨.唐格石榴子石U-Pb年龄为65.5±3.9 Ma,石英斑岩锆石U-Pb年龄为68.1±0.9 Ma,限定了其成岩成矿时代为晚白垩世−古新世.唐格石榴子石稀土配分曲线呈轻稀土富集、重稀土亏损,LREE/HREE比值为0.01~12.68,进一步可划分为两期石榴子石(GrtⅠ和GrtII),Eu异常由不明显(Eu/Eu为0.87~0.94)向明显Eu正异常(Eu/Eu为1.49~8.29)再向微弱Eu正异常(Eu/Eu为0.67~1.83)变化,U平均含量先降低(GrtⅠ-1:1.14×10^(−6),GrtⅠ-2:0.65×10^(−6))后升高(GrtⅡ:2.34×10^(−6))都表明氧逸度先升高后降低.第一期石榴子石核部(GrtⅠ-1)的Hf、Ta平均含量(8.84×10^(-6)和0.52×10^(−6))均大于边部(GrtⅠ-2:1.60×10^(−6)和0.23×10^(−6))和第二期石榴子石(GrtⅡ:1.47×10^(−6)和0.37×10^(−6))平均含量,指示成矿过程由封闭状态转为开放、震荡的环境.冈底斯成矿带同碰撞时期矽卡岩型矿床的成岩成矿年龄从西向东呈现由老变新的趋势,揭示了其火山活动具有穿时性,反映了印度−亚洲大陆不均匀碰撞的特征.唐格矿床为在南冈底斯带上新发现的同碰撞期矽卡岩型铜多金属矿床,将会为朱诺矿集区及周边乃至整个南冈底斯带找矿提供新方向.In-situ U-Pb dating of garnet is a newly developed isotope dating method for low-U minerals recently,which has been widely used in skarn deposits study.In this paper,the LA-ICP-MS U-Pb age and trace element compositions of garnet are reported for the first time in the Tangge skarn-type copper-lead-zinc deposit in Xizang.Combining with the results of zircon U-Pb dating of quartz porphyry,this study investigates the timing of magmatism and related mineralization and the ore-forming processes of the Tangge deposit.The garnet U-Pb age is 65.5±3.9 Ma,and the zircon U-Pb age of quartz porphyry is 68.1±0.9 Ma.These ages indicate both the granitic rocks and mineralization of the Tangge deposit were formed at Late Cretaceous-Palaeocene.The rare earth distribution patterns of garnet show an enrichment in light rare earth elements and depleted in heavy rare earth elements in the Tangge deposit with a LREE/HREE ratio is 0.01 to 12.68.Thegarnet can be further divided into two stages(Grt I and Grt II).The different Eu anomalies and average U contents in GrtⅠand GrtⅡindicate that the oxygen fugacity increases at first and then decreases.The average contents of Hf and Ta in the core of the first-stage garnet(GrtI-1)(8.84×10^(−6)and 0.52×10^(−6))are higher than those in the rim(GrtI-2:1.60×10^(−6)and 0.23×10^(−6)),and in the second-stage garnet(GrtII:1.47×10^(−6)and 0.37×10^(-6)),indicating that the metallogenic environment changes from a relatively closed system to an open and oscillating one.The oreforming age of the skarn-type deposits in the syn-collisional Gangdese metallogenic belt is gradually getting older from east to west,which reveals the diachronous volcanic activity and reflects the characteristics of uneven collision between the Indian continent and the Asia continent.The Tangge deposit is a newly discovered syn-collisional skarn-type copper polymetallic deposit in the South Gangdese,which will provide a new direction for mineral prospecting in the Zhunuo ore concentration area and its surround

关 键 词：石榴子石 U-PB定年 矽卡岩矿床 唐格 冈底斯 地球化学 

分 类 号：P597[天文地球—地球化学]