投稿时间：2023-05-04
修订日期：2023-08-23
网络发布日期：2023-12-29
中文摘要:钨和铜有明显不同的地球化学性质，但钨、铜在矿床中可以共伴生，原因还不清楚。长江中下游成矿带发育典型的斑岩-矽卡岩-层状铜（钨）多金属成矿系统，其中层状铜（钨）矿体成矿时代数据相对较少。作者以该带九瑞矿集区武山铜矿区新发现的钨矿（化）体为研究对象，开展了矿相学、白钨矿原位U-Pb年代学和元素地球化学的研究。研究发现，武山矿床具有层状、矽卡岩型、斑岩型3类铜矿体均有白钨矿矿化，矿床整体由浅至深存在Cu→Cu-W的分带规律。3类矿石中的白钨矿产状类似，充填在粗粒黄铁矿晶体间隙，或呈浸染状分布，被黄铜矿、闪锌矿等交代，产于退化蚀变阶段；其中斑岩中还存在少量晚世代白钨矿，与石英、黄铁矿共生,形成细脉并穿切花岗闪长斑岩，为石英-硫化物阶段产物。通过对退化蚀变阶段白钨矿进行测年和地球化学研究，作者获得了层状矿体含钨黄铜矿矿石中的白钨矿原位LA-ICP-MS U-Pb同位素年龄为（140.6±1.5）Ma，代表层状铜钨矿体成矿时代，在误差范围内与前人获得的斑岩、矽卡岩型矿体的成矿时代基本一致。层状矿体中白钨矿的稀土元素特征和Sr/Mo值符合岩浆热液矿床特征，相比矽卡岩型、花岗岩型白钨矿，层状矿体中白钨矿具有明显较低Mo含量，反映了形成于相对低氧逸度条件；另外，层状矿体中白钨矿具有正Eu异常和与围岩相近的高Y/Ho值的特征，推测其是流体充分交代了含碳围岩地层导致流体性质的明显改变，并且有利于白钨矿和黄铁矿的沉淀，可从深部黄龙组层间部位形成钨品位更富的黄铁矿矿石得到佐证。文章从白钨矿角度证实层状矿体是斑岩-矽卡岩成矿系统的重要组成部分，提出在九瑞矿集区已知铜矿床的深部，尤其是燕山期中酸性侵入岩与含碳质碳酸盐岩的接触带及黄龙组层位，是寻找富钨矿体的新找矿方向。白钨矿的U-Pb同位素定年为长江中下游成矿带层状矿体的成矿时代提供了新的可靠依据。
Abstract:Although there are obvious differences in geochemical behavior for tungsten and copper in magmatic systems, it is able to find large-scale Cu- and W- mineralization in one ore deposits, and the reasons for this occurrence are still under-researched. There are representative porphyry-skarn-stratabound Cu(W) deposits in the Middle-Lower Yangtze River metallogenic belt (MLYRMB), and the timing of formation of stratabound Cu(W) ore bodies is not yet precise. In this study, we present mineralography, laser ablation-inductively coupled plasmamass spectrometry (LA-ICP-MS) U-Pb dating and element geochemistry of scheelite, which is newly found in the Wushan Cu-W deposit, located in the Jiurui ore area, a main component of the MLYRMB. Scheelite mineralization developed among stratabound, skarn and porphyry types copper orebodies. Zoning pattern from shallow to deep is mineralization of Cu transit to Cu-W. The scheelite minerals in the three types of ores are similar characterized by filling in the crystal gap of large pyrite grain or distributing in a disseminated form, replaced by chalcopyrite, sphalerite, and other minerals, and yielded in degenerate alteration stage. There is also a small amount of scheelite yielded in quartz sulfide stage in the granite-type ore, which coexists with quartz and pyrite to form fine veins and cut through granodiorite porphyry. In this timing and geochemistry study to the scheelite of degenerate alteration stage, scheelite grains form stratabound orebody yield U-Pb ages of (140.6±1.5) Ma, representative the timing of Cu-W stratabound ore, and basically consistent with the age of porphyry and skarn-types copper polymetallic ore bodies obtained by predecessors within the error range. The REE patterns and Sr/Mo ratio of scheelite in the stratabound orebody are similar to magmatic hydrothermal tungsten deposits. Stratabound mineralized scheelite has obvious lower Mo content than skarn and granite-types, reflecting its more reduced forming environment, it also has positive Eu anomaly, and high Y/Ho ratio which is similar to wall rock. It is infered that the magmatic fluid had been enough replaced by the carbonaceous wall rock stratum, leading to apparent changes in fluid properties, and being more conducive to the deposition of scheelite and pyrite, thus forming pyrite ore with higher W grade in the stratabound part of Huanglong Formation at the depth of the deposit. This study confirms that Cu-W stratabound orebody is an important part of porphyry-skarn metallogenic system. Proposing the generally zoning pattern of shallow copper and deep tungsten in the Jiurui ore area, can help to W exploration strategies which should focus on the deep part of known copper ore, especially the coupling of Yanshanian intermediate-acid intrusive rock and carbonaceous carbonate rock, and Carboniferous Huanglong Formation. The UPb isotope dating of scheelite provides a new and reliable evidence for the age of stratabound orebodies in the MLYRMB.
keywords:scheelite U-Pb age stratabound orebody Wushan deposit Middle-Lower Yangtze River Metallogenic Belt (MLYRMB)
文章编号：
中图分类号：
文献标志码：
基金项目:本文得到国家自然科学基金项目（编号：41925011）、江西省科学技术厅国家科技奖后备项目培育计划（编号：20203AEI91004）和江西省地质勘查基金项目（编号：20200022）联合资助
引用文本：
高任,谢桂青,冯道水,纪云昊,钟浩,张磊.2023.江西武山铜矿区新发现钨矿（化）体特征和其成因——来自矿相学、白钨矿原位U-Pb年代学和元素地球化学的约束[J].矿床地质,42(6):1139~1158GAO Ren,XIE GuiQing,FENG DaoShui,JI YunHao,ZHONG Hao,ZHANG Lei.2023.Characteristics and genesis of newly discovered W mineralization in Wushan Cu deposit, Jiangxi: Constraints from mineralography, in-situ U-Pb chronology and element geochemistry of scheelite[J].Mineral Deposits42(6):1139~1158
图/表
