| 广东河台金矿硫化物地球化学特征及地质意义 |
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| 引用本文：焦骞骞,张露,张胜印,朱平平,戴家润,龚朝阳.2024.广东河台金矿硫化物地球化学特征及地质意义[J].地球学报,45(4):609-622. |
| DOI：10.3975/cagsb.2024.051402 |
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| 基金项目:云南省科技计划项目高层次科技人才及创新团队选拔专项(编号: 202305AT350004);云南省科技计划项目(编号: 202202AG050006);国家自然科学基金项目(编号: 41902086) |
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| 中文摘要:河台金矿是广东省最大的金矿, 被认为是典型的剪切带型金矿。尽管矿床产于云开群变质岩中, 但是在产出时间和空间展布上又与云楼岗和伍村岩体有密切关系, 再加上成矿的多阶段性, 导致对成矿流体及物质来源一直存在争议。河台金矿的金主要以自然金形式产出, 与黄铁矿、黄铜矿、磁黄铁矿等矿石矿物紧密共生。本文对河台金矿田热液成矿期金-硫化物阶段的黄铁矿、磁黄铁矿进行了微量元素和Sr-Nd同位素分析, 以进一步示踪成矿流体及物质来源。两种硫化物Co/Ni比值为0.36~3.33, 显示主要为热液成因。Hf/Sm、Nb/La、Th/La值<1, 暗示成矿热液是以富Cl–的流体为主; Y/Ho比值为12.0~33.0, 与糜棱岩有明显区别; (87Sr/86Sr)i值为0.707 078~0.713 545, εNd(t)为–19.36 ~ –15.12, 位于华夏板块元古代基底和EM1富集地幔之间。这些特征暗示成矿流体的多源性。黄铁矿∑LREE/∑HREE值介于5.53~15.4, 在球粒陨石标准化图中呈明显右倾, δEu值为0.48~0.75, 具有明显的Eu负异常, 与糜棱岩特征相似, 暗示成矿物质主要来自围岩。结合前人年代学研究结果, 推测印支期在混合岩化和韧性剪切作用下, 变质流体将云开群中的成矿物质运移到剪切带中, 使Au初步富集; 燕山期地壳深部华夏板块中—古元古代基底重熔产生的岩浆流体混入少量地幔流体, 为剪切带中成矿物质发生活化迁移提供载体和动力, 并在局部再次富集形成工业矿体。 |
| 中文关键词:黄铁矿 微量元素 Sr-Nd同位素 成矿物质及流体来源 广东河台金矿 |
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| Geochemical Characteristics and Geological Implications of Sulfides in the Hetai Goldfield, Guangdong Province |
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| Abstract:Hetai goldfield, the largest gold-concentration district in Guangdong Province, is a typical example of gold mineralization related to ductile-shear deformation. Deposits in the goldfield occurred in the Yunkai metamorphic series, however, the close spatial and temporal association with the Yunlougang and Wucun granitoids, and the multi-stage mineralization resulted in long-term controversy regarding the source of ore-forming fluids and metals. The Au mineralization in the goldfield predominantly occurs as native gold intimate intergrowth with ore minerals that including pyrite, chalcopyrite, and pyrrhotite. We analyzed the trace elements and Sr-Nd isotopes of pyrite and pyrrhotite that present at the gold-sulfide substage of hydrothermal mineralization stage to further constrain the origin of the ore-forming fluids and metals. Two types of sulfides had Co/Ni ratios in range of 0.36 to 3.33, indicating a mainly hydrothermal genesis. The ratios of Hf/Sm, Nb/La, and Th/La of the sulfides are less than 1, suggesting that ore-forming fluids were enriched in Cl–; Y/Ho ratio of this study varied from 12.0 to 33.0, significantly different from that of mylonite; and (87Sr/86Sr)i and εNd(t) values in the range of 0.707 078 to 0.713 545 and –19.36 to –15.12, respectively, between the HuaXia Plate basement and EM-1 enriched mantle. The above results suggested the multi-origin of the ore-forming fluids. Pyrite with ∑LREE/∑HREE values ranging from 5.53 to 15.4 and obviously negative Eu anomaly with δEu values from 0.48 to 0.75, had remarkable similarity to the mylonite in the chondrite-normalized diagram with right incline pattern, suggesting that the ore-forming metals were mainly derived from the surrounding metamorphic series. Combined with previous geochronological result, we proposed that during the Indosinian period, the metamorphic fluids that derived from the migmatization and ductile shearing drove the ore-forming metals from the Yunkai Group to initially concentrate in the shear zones. In the Yanshanian period, magmatic fluids that derived from the remelting of the Paleo-Proterozoic HuaXia Plate basement mixed with some mantle-derived fluids, playing a role as the carrier and driving force for the activation and migration of ore-forming metals, resulted in the formation of economic orebodies at the favorable place within the shear zones. |
| keywords:pyrite trace elements Sr-Nd isotopes sources of ore-forming fluids and metals Hetai goldfield in Guangdong Province |
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