地质通报2023，Vol.42Issue(11)：1818-1833,16.DOI:10.12097/j.issn.1671-2552.2023.11.003
滇西北红牛-红山矽卡岩型铜矿床石榴子石原位LA-SF-ICP-MS U-Pb定年及地球化学特征
In-situ LA-SF-ICP-MS U-Pb dating and geochemistry of garnets from Hongniu-Hongshan skarn-type copper deposit in northwestern Yunnan
摘要
Abstract
Hongniu-Hongshan copper deposit is the largest(distal)skarn type deposit discovered in the south section of Yidun Arc.However,there is no direct chronological evidence for the diagenetic age of ore-bearing skarn.The accurate determination of the diagenetic age of skarn is of great significance to the location of this deposit in the two stages of Mesozoic metallogenic events of porphyry in the south section of Yidun Arc.The garnets in skarn of the deposit can be divided into two stages,where the early garnets(Grt Ⅰ)are mostly found in skarn of lean ore with coarse grain structure and isotopic body;and the late garnets(Grt Ⅱ)are mostly found in skarn of rich ore with fine-medium grain structure,oscillatory zoning and heterogeneous and optical anomaly.Based on in-situ LA-SF-ICP-MS U-Pb dating and electron microprobe in-situ concentrations analysis of two stages of garnets in this paper,the U-Pb ages of Grt Ⅰ and GrtⅡ are 84.2±3.0 Ma and 81.7±3.5 Ma,respectively.The contents of major and trace elements suggest that the garnets of the two stages are classified in the andradite and grossularite series,lack of Rb,Ba,K,Sr,etc.and rich in elements Th,U and P,where Grt Ⅰ are characterized by relatively rich in andradite,high LREE/HREE ratio and high positive anomaly of Eu,while Grt Ⅱfeatures relatively rich in grossularite,low LREE/HREE ratio and no abnormal Eu.In combination of the Late Yanshanian mountain metallogenic events of regional collisional porphyry,it is deemed that the diagenetic and metallogenic period of distal skarn in this deposit is at about 80 Ma,when that mineralization is closely related to the acidic porphyry over the same period.The geochemical characteristics of garnets reveal that the dry skarn stage is characterized by a high water/rock ratio and dominated by infiltration metasomatism.The early fluid developed into a relatively closed system of oxidation,high temperature,rich iron and weak alkalinity,and the late stage formed an open system of a relative reduction,relatively low temperature,rich aluminum and acid.关键词
石榴子石/原位LA-SF-ICP-MS U-Pb定年/微区成分/矽卡岩型铜矿/义敦岛弧/滇西北Key words
garnet/In-situ LA-SF-ICP-MS U-Pb dating/micro-area concentrations/skarn-type copper deposit/Yidun Arc/northwestern Yunnan分类
天文与地球科学引用本文复制引用
李守奎,刘学龙,周云满,赵成峰,李方兰,曹振梁,陶兴雄,魏志毅,周杰虎..滇西北红牛-红山矽卡岩型铜矿床石榴子石原位LA-SF-ICP-MS U-Pb定年及地球化学特征[J].地质通报,2023,42(11):1818-1833,16.基金项目
云南黄金集团校企合作项目《滇西北中甸地区红牛-红山铜矿叠加成矿机理及矿床模型研究》(编号:KKF0202121292)、国家自然科学基金项目《滇西北格咱地区红牛-红山铜钼矿床复合成矿系统结构组成及金属来源研究》(批准号:42362010)、昆明理工大学"双一流"科技专项《薄竹山燕山晚期岩浆成矿系统及成矿规律课题》(编号:202202AG050006-2)和云南省高层次科技人才及创新团队选拔专项《Re-PGE等关键金属形成机理课题》(编号:202305AT350004-4) （编号:KKF0202121292）
