滇西“碱质热液型”金多金属矿床地质特征与找矿模型

滇西地区地质构造演化复杂,成矿地质条件优越,经历了多期次、多类型成矿作用,形成了多条各具特色的金多金属成矿带。文章通过对区内金沙江-哀牢山金多金属成矿带内北衙、马厂箐、姚安、长安等典型矿床的解剖和对比研究,发现带内金多金属矿床与经典的斑岩型矿床相比具有显著的差异性,主要表现是：成矿岩体岩性以碱性系列为特征,w(K₂O+Na₂O)超过8%;成矿流体碱质含量偏高,流体阳离子（K⁺+Na⁺）含量约占流体总量的87%~95%;成矿过程中,除岩浆热液参与成矿外,岩浆气水热液与围岩间的水岩反应,是导致矿质沉淀的主体;自成矿岩体向外依次发育裂隙脉型、矽卡岩型、构造破碎带型和石英硫化物脉型矿化,组成多位一体。文章基于典型矿床特征的系统总结,提出了“碱质热液型”金多金属矿床的概念,并对其成矿作用过程进行了初步探讨。最终,文章构建了滇西地区碱质热液型金多金属矿地物化遥综合找矿模型,并指导相关矿床找矿勘查取得了重要进展。

Geological characteristics and exploration model of "alkaline hydrothermal type" gold polymetallic deposits in western Yunnan

The evolution of geological structure in western Yunnan has a long and complex history. It has experienced many stages and various types of mineralization. The gold polymetallic metallogenic belt with prominent characteristics was formed in the area. According to the summary and comparative study of the characteristics of typical deposits, such as Beiya, Machangqing, Yao''an, Chang''an, etc. It is found that the gold polymetallic deposits in the belt are significantly different from the classical porphyry and hydrothermal deposits. For example, the rock properties of the ore-forming intrusion are characterized by alkaline series, with w(K₂O+Na₂O) content exceeds to 8%. The alkali content of ore-forming fluid is also high, (K⁺+Na⁺) accounts for 87%~95% of the total number of fluid cations. The water rock reaction between magmatic gas hydrothermal solution and surrounding rock is the key to mineral precipitation during the process of mineralization. In terms of mineralization assemblage, fracture vein type, skarn type, structural fracture zone type and quartz sulfide vein type mineralization assemblage are successively developed from the metallogenic rock mass outward, which form a multi type metallogenic system. Based on the systematic summary of the characteristics of typical deposits, the paper put forward to the concept of "alkaline hydrothermal" gold polymetallic deposit, and discussed its metallogenic process. Furthermore, a geophysical, geochemical and remote comprehensive prospecting model for "alkaline hydrothermal" gold polymetallic deposits in western Yunnan has been constructed to guide the prospecting and exploration of related deposits and made important progress. Finally, the prospecting model of geology, geophysics, geochemistry and remote sensing has been constructed. The model is applied to the prospecting and exploration of "alkaline hydrothermal" gold polymetallic deposits in western Yunnan, and make the obvious effect of exploration.