滇中楚雄盆地老街子Pb- Ag矿床和白马苴Au(Cu)矿床赋矿岩体对比及成矿模式
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本文受国家重点基础研究发展规划(“973”计划)项目(2015CB452600)、国家自然科学基金项目(41102049)、云岭学者项目(2014)、国家重点研发计划项目(SQ2018YFC06017102)、云南省矿产资源预测评价工程实验室(2010)和云南省地质过程与矿产资源创新团队(2012)联合资助。


Contrast between the ore- bearing syenite porphyry and metallogenic models of the Laojiezi Pb- Ag and the Baimaju Au (Cu) deposits in the Chuxiong basin, central Yunnan, SW China
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    摘要:

    滇中老街子Pb- Ag矿床和白马苴Au(Cu)矿床位于金沙江- 红河富碱斑岩成矿带中段,是楚雄盆地中与喜山期富碱斑岩体时空关系密切的两个矿化中心,二者相距仅2km,但是矿种和矿化类型均不同,金属矿物组合差异显著。两个矿化中心同空间、不同矿化类型的深部结构不清,成因联系不明,制约了姚安富碱斑岩区多金属矿床的理论认识与深部勘查。通过岩石组合、赋矿岩体组构及地球化学特征对比,总结矿化元素空间分布规律,研究认为:①老街子正长斑岩具斑状结构,斑晶为正长石,岩体内发育脉岩;白马苴正长斑岩具似斑状结构,斑晶为正长石和少量斜长石。岩石组合和组构特征差异反映后者形成深度较前者更深;②岩石地球化学特征总体一致,均明显富集大离子亲石元素(K、Rb、Ba和LREE等),相对亏损高场强元素(Ta、Nb、P和Ti等),系中酸性富碱、高钾的正长岩- 石英二长岩钾玄质准铝- 过铝质系列岩石组合,为同源同期岩浆演化的产物。主要差异为老街子正长斑岩稀土总量及Rb/Sr比值整体较白马苴正长斑岩高,反映其岩浆结晶分异演化程度较白马苴正长斑岩高;③对比老街子矿床深部三个中段矿化元素异常分布特征,显示Cu- Mo异常往深部逐渐增强,矿床具有浅部Pb- Ag和深部Cu- Mo- Au的元素组合分带。白马苴矿床由岩体至接触带呈现出Au- Cu矿化/异常→Pb- Ag异常的分带特征。综合上述研究,认为白马苴、老街子矿床及其深部多金属矿化是成因上、时空结构上密切相关的矿床组合,属于浅成低温热液- 斑岩型Pb- Ag- Au(Cu- Mo)多金属成矿系统,深部具斑岩型铜、钼、金成矿潜力。在此基础上,构建了Pb- Ag- Au多金属成矿模式。研究工作对矿区深部及外围找矿预测具实践意义,对区域上同类矿床成矿理论研究和矿产勘查具参考价值。

    Abstract:

    The Laojiezi Pb- Ag andthe Baimaju Au (Cu) deposits, located in the middle section of the Jinshajiang- Honghe alkali- rich porphyry metallogenic belt, are typical mineralization centers thatare associated with the Himalayan stage alkali- rich porphyryin the Chuxiong basin, central Yunnan province. They are only 2 km apart in space, but they are different in mineral species, mineralization types, and metallic mineral assemblages. The deep structure of the two mineralization centers, which occur in the same space and show different types of mineralization, is unclear as is any possible connection between their origins. This limits the theoretical understanding and deep exploration of the polymetallic deposits in the Yao’an alkali- rich porphyry area. In this paper, fabric and geochemical characteristics of ore- bearing syenite porphyry and the rock association in the two deposits were compared,and the spatial distribution of mineralization elements in the deposits was summarized. The results show that: (1) the Laojiezi syenite porphyry is characterized by porphyritic texture with developed vein rocks and orthoclase phenocrysts. The Baimaju syenite porphyry is characterized by porphyaceous texture and the phenocrysts are orthoclase and a small amount of plagioclase. The differences in rock association and fabric features reflect that the formation depth of the Baimaju syenite porphyry was deeper than that of the Laojiezi syenite porphyry; (2) the geochemical characteristics of the two intrusions are consistent. They are both enriched in large- ion lithophile elements, such as K, Rb, Ba and light rare earth elements and depleted in high field strength elements, such as Ta, Nb, P and Ti. Major elements show that both the syenite porphyry belonged to the alkali- rich, high- K and metaluminous- peraiuminous magma series, which are associated with syenite and quartz monzonite. All these characteristics indicate that these two syenite porphyry are the products of homologous and contemporaneous magmatic evolution. However, the ΣREE and the Rb/Sr ratios of the Laojiezi syenite porphyry are higher than that of the Baimaju syenite porphyry, which indicates that the Laojiezi syenite porphyry may have experienced more intensive evolution and differentiation;and (3) the distribution of mineralization elements anomalies at three levels of the Laojiezi Pb- Ag deposit show that the Cu- Mo anomalies gradually increase to the depth; this deposit is characterized by metallic elements zonation from Pb- Ag to Cu- Mo- Au with depth. At the same time, from the intrusions to the exterior contact zone, the Baimaju Au (Cu) deposit shows the zoning characteristics of Au- Cu mineralization/anomaly to Pb- Ag anomaly. Based on the above studies, it is believed that both the Baimaju Au (Cu) and the Laojiezi Pb- Ag deposits, and their deep polymetallic mineralization have closely related genesis and spatial- temporal structures. Therefore, it is suggested that there is an epithermal- porphyry Pb- Ag- Au (Cu- Mo) polymetallic mineralization system in the Laojiezi and Baimaju deposits, indicative of a deeper exploration potential for porphyry- type Cu- Mo- Au deposits. Based on this, a Pb- Ag- Au polymetallic metallogenic model was established. This research is not only significant for prospecting prediction in the deep and periphery of the deposit, but also provides reference for the study of metallogenic theory and mineral exploration in the region.

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杨航,吴鹏,韩润生,姜龙燕,陶琴,江小均,管申进.2020.滇中楚雄盆地老街子Pb- Ag矿床和白马苴Au(Cu)矿床赋矿岩体对比及成矿模式[J].地质学报,94(12):3726-3745.
YANG Hang, WU Peng, HAN Runsheng, JIANG Longyan, TAO Qin, JIANG Xiaojun, GUAN Shenjin.2020. Contrast between the ore- bearing syenite porphyry and metallogenic models of the Laojiezi Pb- Ag and the Baimaju Au (Cu) deposits in the Chuxiong basin, central Yunnan, SW China[J]. Acta Geologica Sinica,94(12):3726-3745.

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  • 收稿日期:2019-09-28
  • 最后修改日期:2020-01-14
  • 录用日期:2020-04-07
  • 在线发布日期: 2020-04-17