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黔西南烂泥沟卡林型金矿床构造岩地球化学特征:对断裂向深部延伸的指示

Tectonic geochemical characteristics of Lannigou Carlin-type gold deposit in southwestern Guizhou: Implications for downward extension of faults

  • 摘要: 烂泥沟金矿床位于滇黔桂“金三角”地区,是中国最大的卡林型金矿床之一,该金矿床的形成与构造具有密切联系,构造是金成矿的重要要素之一。尽管前人对烂泥沟金矿床的构造等开展了大量研究工作,但由于缺少有效方法,控矿断裂在平面上,特别是在剖面上如何向深部延伸,以及流体运移路径和来源等问题还未得到有效解决。针对上述问题,综合运用地球物理勘探数据,对矿区6条主要断裂(烂泥沟—尾怀断裂、边界断裂、板昌断裂、罗顿断裂、新寨断裂及小那井断裂)开展构造岩地球化学系统研究,分析元素迁移富集规律,揭示成矿流体运移轨迹与物质来源。研究取得以下创新性认识:地球化学特征对比显示,边界断裂与烂泥沟—尾怀断裂相较于新寨断裂和罗顿断裂等具有更显著的地球化学异常。主量元素Al2O3、Fe2O3、P2O5含量变化与Sb等成矿元素呈现指示关系。多元统计分析结果表明,Ni、Cd、Tl等元素与Au存在显著正相关,同时Be、Bi、Cu、Cr等微量元素组合可作为Au、Pb、Zn、Sb矿化的有效地球化学指标。地震勘探资料与地表地球化学特征耦合分析表明,烂泥沟—尾怀断裂和边界断裂已切入基底地层,其构造岩中显著的主微量元素异常与深部流体活动特征吻合。相较之下,板昌断裂和罗顿断裂仅发育于浅部盖层,其地球化学异常强度相对较弱。矿体空间分布严格受深大断裂控制,构造岩的Au、Sb异常强度与断裂切割深度呈正相关关系。这一发现为利用地表地球化学勘查替代昂贵的深部地球物理探测提供了新技术思路。

     

    Abstract: The Lannigou Gold Deposit, located in the Yunnan−Guizhou−Guangxi "golden triangle" region, is one of the largest Carlin-type gold deposits in China. The formation of this gold deposit is closely related to tectonic activity, which is one of the key factors in gold mineralization. Although previous studies have extensively investigated the structure of Lannigou Gold Deposits, due to the lack of effective methods, issues such as how the ore-controlling faults extend downward, especially in cross-section, and the pathways and sources of fluid migration remain to be effectively resolved. To address these issues, this study integrated geophysical exploration data to conduct systematic structural-geochemical investigations on six major fault zones (Lannigou−Weihuai, Bianjie, Banchang, Luodun, Xinzhai, and Xiaonajing faults). It deciphered fluid migration trajectories and material provenance through analysis of element migration-enrichment patterns. Innovative findings include: Comparison of geochemical characteristics reveals significantly stronger anomalies along the Bianjie and Lannigou−Weihuai faults than in Xinzhai and Luodun faults. The content variations of major elements such as Al2O3, Fe2O3, and P2O5 show indicative relationships with ore-forming elements including Sb. The results of multivariate statistical analysis show that elements such as Ni, Cd, and Tl exhibit a significant positive correlation with Au. Meanwhile, the trace element assemblage of Be, Bi, Cu, and Cr can serve as effective geochemical indicators for the mineralization of Au, Pb, Zn, and Sb. The coupling analysis of seismic exploration data and surface geochemical characteristics indicates that the Lannigou−Weihuai Fault and the Bianjie Fault have cut into the basement strata. The significant major and trace element anomalies in their tectonites are consistent with the characteristics of deep fluid activity. In contrast, the Banchang Fault and the Luodun Fault only developed within the shallow cover strata, and their geochemical anomalies are relatively weak in intensity. The spatial distribution of orebodies is strictly controlled by deep-seated large faults, and the Au and Sb anomaly intensities in tectonites show a positive correlation with fault incision depth. This finding provides a new technical approach for replacing costly deep geophysical exploration with surface geochemical exploration.

     

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