| 西秦岭夏河—合作地区早子沟和加甘滩金矿床石英微量元素特征及意义 |
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| 引用本文： | 第鹏飞,汤庆艳,刘聪,宋宏,张家和,刘东晓,王玉玺,蒲万峰.西秦岭夏河—合作地区早子沟和加甘滩金矿床石英微量元素特征及意义[J].现代地质,2021,35(6):1608-1621. |
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| 作者姓名： | 第鹏飞 汤庆艳 刘聪 宋宏 张家和 刘东晓 王玉玺 蒲万峰 |
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| 作者单位： | 1.甘肃省矿产资源储量评审中心,甘肃 兰州 7300002.兰州大学 地质科学与矿产资源学院,甘肃省西部矿产资源重点实验室, 甘肃 兰州 7300003.中国科学院 西北生态环境研究院,甘肃 兰州 7300004.中国科学院大学,北京 1000495.甘肃省矿产资源补偿费征收管理办公室,甘肃 兰州 7300006.甘肃省地质矿产勘查开发局 第三地质矿产勘查院,甘肃 兰州 730050 |
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| 基金项目： | 科技部“第二次青藏高原综合科学考察研究”项目(2019QZKK0704);国家自然科学基金项目(41872073);甘肃省科技计划项目(21JR7RA498);甘肃省科技计划项目(18JR3RA266);兰州大学中央高校基本科研业务费专项资金资助项目(lzujbky-2021-ct07);兰州大学中央高校基本科研业务费专项资金资助项目(lzujbky-2017-77) |
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| 摘 要： | 西秦岭造山带发育有大量三叠纪的金矿床,早子沟和加甘滩金矿床是其中最典型的两个矿床,其金资源量分别为116 t和154 t,均为特大型金矿床。早子沟、加甘滩金矿床均位于夏河—合作区域性逆冲推覆断裂以南。早子沟赋矿地层为三叠统古浪堤组,赋矿岩石为泥质板岩、条带状硅质板岩及粉砂质板岩;加甘滩矿区出露地层为三叠统隆务河组,金矿体赋存于长石石英变砂岩夹粉砂质板岩岩性段内。加甘滩金矿床的研究程度相对较低,属中低温构造蚀变岩型金矿床;早子沟金矿床研究程度较高,但是对它的成因仍有不同的认识。石英的微量元素地球化学特征能够提供成矿流体来源与演化的信息,通过对早子沟和加甘滩金矿床开展石英的微量元素地球化学特征研究,探讨其成矿流体来源、成矿条件以及石英微量元素对金矿床形成的指示,为西秦岭造山带金矿床成因研究提供重要的信息。早子沟和加甘滩金矿床不同类型矿石中石英具有相似的稀土元素球粒陨石标准化配分曲线,总体表现出轻稀土元素相对富集、重稀土元素轻微亏损的特征,而且轻稀土元素与重稀土元素分馏程度高,重稀土元素内部分馏程度弱。 早子沟金矿床成矿期热液石英中Rb与Li呈负相关,Rb与Cs呈正相关,而加甘滩金矿床热液石英中Rb与Li、Cs相关性不明显,表明早子沟金矿床石英中Li含量随流体含量的增加而减少,而Cs含量随流体含量的增加而增加。大多数样品具有Eu负异常和弱的Ce正异常,表明早子沟和加甘滩金矿床形成于还原环境,成矿温度较低。样品的(La/Yb)N较大,反映成矿深度相对较浅。石英的Y/Ho值分别为25.14~30.14和23.40~28.94,指示成矿流体与地壳关系密切。大多数石英样品的Th/La和 Nb/La 值小于1,在大陆地壳标准化图解中具有明显的Sc负异常,Cr、W、Pb和U正异常,表明成矿流体富Cl-,相对富集Cr、W、Pb和U等元素。结合大地构造背景分析,早子沟和加甘滩金矿形成于大陆边缘环境。
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| 关 键 词： | 微量元素 石英 早子沟金矿床 加甘滩金矿床 西秦岭夏河—合作地区 |
| 收稿时间： | 2021-09-10 |
| 修稿时间： | 2021-10-11 |
Trace Element Characteristics of Quartz from the Zaozigou and Jiagantan Gold Deposits in the Xiahe-Hezuo District,West Qinling |
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| DI Pengfei,TANG Qingyan,LIU Cong,SONG Hong,ZHANG Jiahe,LIU Dongxiao,WANG Yuxi,PU Wanfeng.Trace Element Characteristics of Quartz from the Zaozigou and Jiagantan Gold Deposits in the Xiahe-Hezuo District,West Qinling[J].Geoscience——Journal of Graduate School,China University of Geosciences,2021,35(6):1608-1621. |
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| Authors: | DI Pengfei TANG Qingyan LIU Cong SONG Hong ZHANG Jiahe LIU Dongxiao WANG Yuxi PU Wanfeng |
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| Abstract: | There are a large number of Triassic gold deposits in the West Qinling orogenic belt. The gold resources of Zaozigou and Jiagantan gold deposits are 116 t and 154 t, respectively, which are ascribed to superlarge scale. Zaozigou and Jiagantan gold deposits are located in the south of Xiahe-Hezuo regional thrust nappe fault. The ore-bearing stratum of Zaozigou is the Triassic Gulangdi Formation, and the ore-bearing rocks are argillaceous slate, banded siliceous slate and silty slate. The exposed stratum of Jiagantan ore deposit is the Triassic Longwuhe Formation. The gold orebody occurs in the lithologic section of feldspathic quartz metasandstone mixed with silty slate. The Jiagantan gold deposit is ascribed to a medium low-temperature tectonic altered rock type gold deposit, and its research level is relatively low. However, the Zaozigou gold deposit is highly studied, but there are still different views about its genesis. Trace element geochemical characteristics of quartz can reveal the ore-fluid source and evolution of ore-forming fluid, and those from quartz at Zaozigou and Jiagantan were analyzed here to reveal the ore-fluid source and conditions. We also discussed the implication of quartz trace elements on the gold ore formation, which provides important insights for the gold genesis in the West Qinling orogenic belt. Quartz in different types of ores from Zaozigou and Jiagantan has similar chondrite-normalized REE patterns, which generally show the LREE enrichment and HREE depletion, and large LREE/HREE fractionation, but weak internal HREE fractionation. Rubidium is negatively correlated with Li, and positively correlated with Cs in the quartz from Zaozigou; However, the correlation of Rb versus Li and Cs contents in quartz from Jiagantan is not obvious. This shows that the Li content in quartz decreases with the fluid content increasing, while the Cs content increases with the fluid content at Zaozigou. The Rb and Sr contents of quartz at Zaozigou and Jiagantan indicate that the quartz should be hydrothermal. Most samples have negative Eu anomalies and weak positive Ce anomalies, indicating that both gold deposits were formed in a reduced environment with low metallogenic temperature. The (La/Yb)N ratio is relatively high, indicating that the metallogenic depth is relatively shallow. The quartz Y/Ho ratios at Zaozigou and Jiagantan are 25.14-30.14 and 23.40-28.94 respectively, suggesting that the ore-forming fluid should be closely crustal-related. Most quartz samples from Zaozigou and Jiagantan have Th/La and Nb/La values below 1, and shows obvious negative Sc anomalies and positive Cr, W, Pb, and U anomalies, indicating that the ore-forming fluids at Zaozigou and Jiagantan should be Cl-rich. Continental crust-normalized trace element diagram of the quartz samples from Zaozigou and Jiagantan suggest that the ore-forming fluids are relatively rich in Cr, W, Pb, and U. Combined with the geotectonic background, the Zaozigou and Jiagantan gold deposit were formed in a continental margin setting. |
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| Keywords: | trace element quartz Zaozigou gold deposit Jiagantan gold deposit Xiahe-Hezuo district West Qinling |
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