地学前缘 ›› 2025, Vol. 32 ›› Issue (5): 326-344.DOI: 10.13745/j.esf.sf.2024.11.27

• 成矿系统解码 • 上一篇    下一篇

青海省祁漫塔格牛苦头铅锌矿床年代学与矿物微量元素特征研究

王新雨1(), 王书来1,*(), 刘明2, 祝新友1, 刘家军3, 杨新雨1, 王幻1, 王玉往1, 吴锦荣2   

  1. 1.北京矿产地质研究院有限责任公司, 中国地质调查局矿产资源绿色评价研究中心, 北京 100012
    2.青海鸿鑫矿业有限公司, 青海 格尔木 816099
    3.中国地质大学(北京), 北京 100083
  • 收稿日期:2024-08-15 修回日期:2024-11-01 出版日期:2025-09-25 发布日期:2025-10-14
  • 通信作者: 王书来
  • 作者简介:王新雨(1991—),男,博士,高级工程师,从事矿产勘查与矿床成矿规律研究工作。E-mail: wxyu1991@126.com
  • 基金资助:
    中国铜业重点科技项目“青海省格尔木牛苦头及外围铅锌成矿规律研究与潜力评价(QHHX-KZ-JF2020-001)”

Study on the chronology and trace element characteristics of skarn mineral in the Niukutou deposit, Qimantag region, Qinghai Province

WANG Xinyu1(), WANG Shulai1,*(), LIU Ming2, ZHU Xinyou1, LIU Jiajun3, YANG Xinyu1, WANG Huan1, WANG Yuwang1, WU Jinrong2   

  1. 1. Beijing Institute of Geology for Mineral Resources Co., Ltd., Research Center for Green Evaluation of Mineral Resources, CGS, Beijing 100012, China
    2. The Qinghai Hongxin Mining Co., Ltd, Golmud 816099, China
    3. China University of Geosciences (Beijing), Beijing 10083, China
  • Received:2024-08-15 Revised:2024-11-01 Online:2025-09-25 Published:2025-10-14
  • Contact: WANG Shulai

摘要:

青海省祁漫塔格牛苦头矿床是东昆仑地区近年来探明的大型夕卡岩铅锌多金属矿床,其成矿时代和矿物成因研究方面存在争议。本文以牛苦头M1矿段西南侧斑状花岗岩和与该岩体相关的夕卡岩矿物为研究对象,通过野外调研、LA-ICP-MS矿物U-Pb测年、LA-ICP-MS矿物原位微量元素分析技术,试图厘定成矿岩体与夕卡岩矿物成岩成矿时代,揭示成矿物理化学条件,进而查明成矿流体演化与成矿之间的关系。LA-ICP-MS锆石U-Pb年代学研究结果表明,牛苦头矿床M1采坑西南侧与夕卡岩化密切相关的斑状花岗岩形成于(222.7±2.2) Ma,与之相关的石榴子石结晶时代为219 Ma,二者耦合于印支期晚三叠世,表明牛苦头矿床M1采坑西南侧存在印支期成矿作用。根据野外综合研究和LA-ICP-MS矿物原位微量元素分析结果,自成矿岩体向外,依次形成石榴子石夕卡岩带、钙铁辉石夕卡岩带、(黑柱石)锰钙铁辉石夕卡岩带和(锰质黑柱石)锰钙辉石夕卡岩带。成矿流体演化过程中,石榴子石等矿物稀土元素特征由轻稀土富集、重稀土亏损向轻稀土亏损、重稀土富集转变,其U、Nd等含量降低,指示成矿流体温度降低,氧逸度降低,pH增高;上述成矿流体物理化学条件的变化,导致靠近成矿岩体形成磁黄铁矿、磁铁矿、黄铜矿和贫锰夕卡岩矿物组合,而远离成矿岩体形成闪锌矿、方铅矿和富锰夕卡岩矿物组合。

关键词: 晚三叠世成矿作用, 锆石和石榴子石U-Pb年代学, 夕卡岩矿物LA-ICP-MS原位微量元素, 祁漫塔格

Abstract:

The Niukutou deposit is a large-scale skarn Pb-Zn polymetallic deposit discovered in recent years in the Qimantag region, East Kunlun orogenic belt, Qinghai Province. The study of its mineralization age and ore genesis remains highly controversial. This paper presents a study of the porphyritic granite on the southwest side of the Niukutou M1 ore district and the associated skarn minerals. Through field research, LA-ICP-MS zircon U-Pb dating, and LA-ICP-MS mineral in-situ trace element analysis, this study aims to determine the chronology of the ore-related intrusion and the ore-forming ages of skarn minerals, reveal the physical and chemical conditions of mineralization, and further clarify the relationship between the evolution of ore-forming fluids and mineralization. LA-ICP-MS U-Pb geochronology results indicate that the porphyritic granite closely related to skarn on the southwest side of the Niukutou deposit was emplaced at (222.7±2.2) Ma, alignand the crystallization age of the associated garnet is 219 Ma. Both ages fall within the Late Triassic (Indosinian period), indicating Indosinian mineralization on the southwest side of the Niukutou deposit, distinct from the previously known Devonian event. Comprehensive field research and LA-ICP-MS mineral in-situ trace element analysis reveal a distinct skarn zonation sequence outward from the ore-forming intrusive: garnet skarn zone→hedenbergite skarn zone→(ilvaite-bearing) Mn-hedenbergite skarn zone→(ilvaite-bearing) johannsenite skarn zone. During the evolution of the ore-forming fluid, the REE patterns of these minerals change from LREE-enriched and HREE-depleted to LREE-depleted and HREE-enriched. Concurrently, δEu values, ΣREE contents, and U and Nd concentrations decrease. These geochemical trends indicate declining temperature and oxygen fugacity (f(O2)), alongside increasing Mn content and pH of the fluid. The aforementioned changes in the physicochemical conditions of the ore-forming fluids resulted in the formation of a mineral assemblage comprising pyrrhotite, magnetite, chalcopyrite, and Mn-poor skarn minerals proximal to the ore-forming intrusive, whereas sphalerite, galena, and Mn-rich skarn minerals precipitated distal to it.

Key words: Late Triassic mineralization, U-Pb geochronology of zircon and garnet, LA-ICP-MS in-situ trace elements of skarn minerals, Qimantag

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