云南马厂箐多金属矿床地质地球化学特征及成矿机制探讨

云南马厂箐多金属矿床是金沙江-哀牢山构造带上与喜马拉雅期富碱斑岩有关的Cu、Mo、Au 成矿的典型代表之一。矿体（脉）的产出与富碱斑岩体（脉）在空间上共存、时间上相近或稍晚、成因上密切相关, 蚀变和成矿分带明显。岩体内产出斑岩型Mo、Cu 矿化, 以Mo 矿化为主; 岩体与围岩接触带产出接触交代型Cu、Mo、Au、Fe 矿化, 以Cu、Fe 矿化为主, Au 矿化较弱; 而距接触带稍远的围岩地层中则产出Au、Pb、Zn 矿化。流体包裹体研究表明, 从马厂箐矿段→乱硐山矿段→人头箐-金厂箐矿段, 流体包裹体具有相态组合逐渐简单, 温度、盐度逐渐降低, 成矿压力逐渐减小, 成矿深度逐渐变浅的趋势。同位素地球化学研究表明, 马厂箐Cu、Mo、Au 多金属矿属于同一个岩浆和流体成矿系统在不同物理化学条件下的产物, 表现出随流体成矿作用的进行, 矿化由斑岩体内部向接触带和围岩地层推进, 富碱岩浆和地幔流体作用逐渐减弱, 而围岩地层的影响则逐渐增强, 流体性质由幔源向壳幔混合直至壳源为主演化。最后探讨了马厂箐Cu、Mo、Au 多金属矿的成矿机制, 并初步预测该矿床具有较好的深部成矿潜力。

Geologic, geochemistry characteristics and ore-forming mechanism of Machangqing polymetallic deposit,Yunnan Province

Machangqing polymetallic deposit is one of the typical copper-molybdenum deposits, which are related to alkaline-rich porphyry in Himalaya period in the tectonic belt of Jingshajiang-Ailaoshan, Yunnan Province. Ore bodies （lodes） coexist with alkaline-rich porphyry （vein） in space, are similar to or slightly younger than but are genetically related to the latter. The zonations of alteration type and ore-formation are clear： porphyry-type copper-molybdenum, mainly molybdenum mineralization in the rock body; contact-metasomatism-type copper-olybdenum-gold-iron, mainly copper-iron and weak gold mineralization in the contact between surrounding rock and the rock body; gold-lead-zinc mineralization in the wallrock far from the contact. The phase assemblage of inclusions becomes gradually simpler, with decreasing temperatures, salinity and ore-forming
pressures from the Machangqing ore segment→Luandongshan→Rentouqing→Jinchangqing （ore segment）,
indicating gradually shallower mineralization depths. Isotope geochemistry reveals that polymetallic deposits,
such as copper, molybdenum and gold, are the products of the same mineralizing system of magma and fluid in
different physicochemical conditions, and that with the process of fluid ore-formation, mineralization took place from the inner porphyry body, through the contact zone to the wallrock. Consequently, the role of alkaline-rich magma and mantle fluid decrease with increasing effect from wallrock, and the component of fluid evolved from mantle-derived, crust-mantle-mixed to crust-dominant. Finally, this paper discusses the ore-forming mechanism of the Machangqing copper-molybdenum-gold polymetallic deposit, and preliminary predict that the ore-forming potentiality in deeper depths is promising.