川西北马脑壳金矿床构造-流体-金成矿作用系统演化模式

基于对马脑壳金矿床构造变形分析及流体包裹体研究,探讨了马脑壳金矿床形成过程和热液成矿机制,认为自印支运动以来,该区先后经历了韧性、韧-脆性及脆性等多期构造变形演化过程,并伴有多次热液活动。热液的来源及性质与构造变形作用密切相关,早期韧性构造变形期,热液来源以地层建造水和变质水为主,而韧-脆性变形期以来大气降水不断加入并逐渐占据优势。由韧性→韧-脆性和韧-脆性→脆性构造变形机制的转变,引起热液发生混合及相分离作用,并导致热液体系T、pH、fo₂、fs₂等物化条件降低变化,造成热液中含金络合物溶解度大幅度下降而发生沉淀成矿作用。概括总结了马脑壳金矿床构造-流体-金成矿作用系统演化模式。

A SYSTEMATIC EVOLUTION MODEL OF STRUCTURE-FLUIDGOLD MINERALIZATION FROM MANAOKE GOLD DEPOSIT, NORTHWEST SICHUAN

By analysis of tectonic deformation and study on fluid inclusions, the ore forming processes and hydro-thermal mineralization mechanism of the Manaoke gold deposit were discussed. The studied region, namely, northwest Sichuan, experienced a multi phase of deformations through ductile, ductile-brittle to brittle ones from the Indosinian orogeny, accompanying multi-stage of hydro-thermal activities successively. A sources of the hydro-thermal fluids related with tectonism intimately, that is during the phase of ductile deformation, in which the solutions mainly originated from connate water and metamorphic water. From the phase of ductile-brittle deformation, meteoric water joined and predominated gradually. The changes of tectonic deformation mechanism from ductile to ductile-brittle and ductile-brittle to brittle deformation, resulted in fluid mixing and phase separation processes of the hydro thermal solutions, which caused, in turn, the reductions of T、pH、fo₂ and fs₂ etc. The physico chemical conditions of fluid systems, as a result, the solubilities of the gold bearing complexes lowered sharply and gold deposition created. The systematic evolution model of structure fluid gold mineralization from the Manaoke gold deposit was summarized.