| 勉略宁矿集区铜厂铜-铁矿床成因:黄铜矿Re-Os定年和硫化物原位硫同位素制约 |
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| 引用本文： | 栾燕,王瑞廷,钱壮志,孙晓辉,郑崔勇,张天运,丁坤.勉略宁矿集区铜厂铜-铁矿床成因:黄铜矿Re-Os定年和硫化物原位硫同位素制约[J].地球科学,2022,47(1):259-276. |
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| 作者姓名： | 栾燕 王瑞廷 钱壮志 孙晓辉 郑崔勇 张天运 丁坤 |
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| 作者单位： | 1.长安大学地球科学与资源学院, 陕西西安 710054 |
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| 基金项目： | 国家自然科学基金项目(No.41603040);陕西省自然科学基础研究计划项目(No.2019JM-160);中央高校基本科研业务费专项资金资助项目(Nos.300102271201,300102270203)。 |
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| 摘 要： | 铜厂铜-铁矿床在成矿时代、成矿物质来源及矿床成因等方面存在较大争议，限制了其成矿模式的建立以及进一步的找矿实践. 利用黄铜矿Re-Os同位素对该矿床进行定年，并利用LA-MC-ICP-MS技术对黄铜矿、黄铁矿及磁黄铁矿等硫化物开展原位硫同位素研究. 分析结果显示，5件黄铜矿Re-Os同位素等时线年龄为484±34 Ma（MSWD=8.7），表明铜厂铜-铁矿床形成于早古生代加里东期. 铜厂铜-铁矿床上部铜矿床中黄铜矿（+9.75‰~+13.1‰）和黄铁矿（+9.22‰~+13.9‰）的δ34S值略高于下部铁矿床中黄铜矿（+8.66‰~+10.9‰）、黄铁矿（+8.85‰~+11.0‰）和磁黄铁矿（+7.93‰~+9.28‰）. 计算得到早期成矿热液的δ34S∑S值约为+10.6‰，晚期成矿热液的δ34S∑S值约为+12.3‰，说明矿床硫是地幔硫混染海水硫形成的，热化学还原在海水硫酸盐还原过程中起到关键作用. 铜厂铜-铁矿床的形成可分为两期:新元古代晋宁期，Rodinia超大陆裂解导致勉略宁地区发生海底火山喷发形成富含Fe、Cu的初始矿源层；早古生代加里东期，大陆边缘持续的裂解和裂陷形成勉略海槽并导致强烈的岩浆活动，富含挥发分及硫的岩浆热液混合海水硫，并从细碧岩中萃取Fe、Cu等成矿物质，早期成矿热液在铜厂地区深部形成铁矿床，随着磁铁矿和硫化物的沉淀，成矿热液演化到晚期阶段并沿断裂构造带向上运移，在铜厂地区浅部形成铜矿床.
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| 关 键 词： | 勉略宁 铜厂铜-铁矿床 Re-Os同位素定年 LA-MC-ICP-MS 原位硫同位素 成矿模式 矿床学 |
| 收稿时间： | 2021-04-23 |
Genesis of Tongchang Copper-Iron Deposit in Mian-Lue-Ning Area:Constraints from Re-Os Isotopic Dating of Chalcopyrite and In-Situ Sulfur Isotope Compositions of Sulfides |
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| Luan Yan,Wang Ruiting,Qian Zhuangzhi,Sun Xiaohui,Zheng Cuiyong,Zhang Tianyun,Ding Kun.Genesis of Tongchang Copper-Iron Deposit in Mian-Lue-Ning Area:Constraints from Re-Os Isotopic Dating of Chalcopyrite and In-Situ Sulfur Isotope Compositions of Sulfides[J].Earth Science-Journal of China University of Geosciences,2022,47(1):259-276. |
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| Authors: | Luan Yan Wang Ruiting Qian Zhuangzhi Sun Xiaohui Zheng Cuiyong Zhang Tianyun Ding Kun |
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| Institution: | (School of Earth Science and Resources,Chang’an University,Xi’an 710054,China;Northwest Nonferrous Metals Geological Mining Group Company Limited,Xi’an 710054,China;711 Team of Hanzhong Northwest Nonferrous Metals Company Limited,Hanzhong 723000,China;Shannxi Railway Institute,Weinan 714099,China) |
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| Abstract: | There are great disputes about the metallogenic age,source of ore-forming material and genesis of the Tongchang copper-iron deposit,which limits the establishment of its metallogenic model and further prospecting practice.Re-Os isotope of chalcopyrite is used to date the ore-forming age,and the S isotope compositions of chalcopyrite,pyrite and pyrrhotite are systematically studied by LA-MC-ICP-MS.The Re-Os isotopic isochron age of the five chalcopyrite samples is 484±34 Ma(MSWD=8.7),indicating that the Tongchang copper-iron deposit was formed in the Early Paleozoic Caledonian period.Theδ34S values of chalcopyrite(+9.75‰-+13.1‰)and pyrite(+9.22‰-+13.9‰)in the upper part of Tongchang copper-iron deposit are slightly higher than those of chalcopyrite(+8.66‰-+10.9‰),pyrite(+8.85‰-+11.0‰)and pyrrhotite(+7.93‰-+9.28‰)in the lower part.Theδ34SΣS value in the early ore-forming hydrothermal solution is about+10.6‰,and that in the late ore-forming hydrothermal solution is about+12.3‰,showing that the sulfur source of the deposit is from mixture of mantle sulfur and seawater sulfur.Thermochemical sulfate reduction(TSR)plays an important role in the process of seawater sulfate reduction.The formation of the Tongchang copper-iron deposit can be divided into two stages.In Neoproterozoic Jinning period,Rodinia supercontinent breakup event leads to submarine volcanic eruption and the formation of initial source bed which was enriched in Fe and Cu.During the Caledonian period of Early Paleozoic,the continuous cracking and rifting of the continental margin formed the Mian-Lue trough and led to intense magmatic activity.The magmatic hydrothermal solution enriched in volatile and sulfur,mixed with seawater sulfur,and extracted Fe,Cu and partial sulfur source from the spilite of the Guojiagou Formation.The early ore-forming hydrothermal solution formed the iron ore body in the deep part of the Tongchang area.With the precipitation of magnetite and sulfide,the ore-forming hydrothermal solution evolved to the late stage and migrated upward along the fault to form the copper deposit in the upper part of the Tongchang area. |
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| Keywords: | Mian-Lue-Ning Tongchang copper-iron deposit Re-Os isotopic dating LA-MC-ICP-MS in-situ S isotope metallogenetic model mineral deposit |
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