滇西北兰坪铅锌银铜矿田含烃富CO_2成矿流体及其地质意义

在流体包裹体显微冷热台系统观测基础上,通过显微激光拉曼探针揭示出兰坪中—新生代盆地内金顶及外围矿床成矿主阶段原生流体包裹体含烃富CO_2,成分变化大。流体成分的耦合关系研究,并配合O、C同位素分析认为成矿流体中部分CO_2来自地幔,部分是沉积地层中碳酸盐岩和有机质分解成因,H_2O和烃主要起源于大气成因盆地卤水和地层有机质。地幔源CO_2对贱金属元素的搬运可能贡献突出,而烃类对金属元素的沉淀意义重大。成矿流体成分具有幔源(富CO_2和金属元素)和壳源(盆地流体富烃类和H_2O)两种流体混合的特征,暗示不同性质流体的混合可能是成矿作用基本方式。

The CO_(2)-rich and Hydrocarbon-bearing Ore-forming Fluid and Their Metallogenic Role in the Lanping Pb-Zn-Ag-Cu Orefield, North-western Yunnan

The CO2-rich fluid inclusion is often seen in the hypometamorphic mineral. Based on the systematical freezing and heating stage observation of fluid inclusions yet, we reveal that the primary fluid inclusion of the main ore-forming stage in the Jinding and periphery deposits are CO2-rich and hydrocarbon-bearing by laser Ro-manor microprobe researches, and the composition variation is evident. The CO2 vs hydrocarbon and CO2 vs H2O are negative-relation in the ore-forming fluid, respectively, and the hydrocarbon vs H2O is positive-rela-tion, and the composition of oxygen- and carbon-isotopes have been analyzed. It is suggested that the partial CO2 was from the mantle and the other from the decomposition of the carbonate rock and the organic matter within the strata, and the water and the hydrocarbon in the ore-forming fluid were mainly from meteorological basin brine and the stratum organic matter. The CO2-rich and hydrocarbon-bearing inclusion formed by selec tion trap of the mineral in the brine of CO2-hydrocarbon that did not dissolve each other completely. The mantle source CO2 may make a remarkable contribution on the transportation of the ore-forming metal from the mant-le , and the hydrocarbon played an important role on the metal precipitation. The ore-forming fluid is character-ized by the mixing of mantle source fluid (CO2- and metal-rich) and crust source fluid (the basin fluid is rich in hydrocarbon and water) , and it may suggest that the mixing of two types of fluids was a basic way of mineral-ization.