四川呷村VHMS矿床：从矿石化学分析到地球化学模型

中国四川呷村矿床是一个典型的含金富银多金属VHMS矿床，其主要成矿金属元素Cu,Zn,Pb,Ag,Au丰度型式均呈非正态分布，多由两重或多重母体构成，揭示矿床经历了两次以上的成矿作用过程。成矿金属元素总体上集中于块状矿带，但贱金属Cu,Zn,Pb没有明显的下部富Cu Zn、上部富Pb Zn的分带，贵金属Ag、Au没有显示明显的层位优选性。矿床构造恢复和化学结构图像显示，金属元素的空间分布和富集机制严格受海底凹陷盆地的基底张性断裂和热水喷口位置控制。至少有4条近SN走向的盆地基底断裂带构成海底下部热水流体的迁移－排泄通道和网脉状成矿带的容矿空间；近EW向断裂与4条SN向断裂的交汇部位，成为上排泄的热水流体在海底的主要喷口，控制了金属元素在海底凹地的空间分布。分别处于凹陷盆地东缘和西缘的热水喷口，因正地形地貌形态而形成山丘堆式矿体（mound-syle)，而处于凹陷盆地中心的热水喷口则积聚大量热水流体，构成卤水池，淀积席状块状矿体（sheet-style)。

The Gacun VHMS Deposit in Sichuan Province: from Chemical Analysis of Ores to Geochemical Model

The Gacun deposit in Sichuan Province is a typical auriferous Ag-rich polymetallic deposit in the intrarifting zone developed in the Triassic Yidun Island-Arc, whose major ore-forming metallic elements such as Cu, Zn, Ph, Ag and An unexceptionally assume nonnormal distributions composed mostly of double or multiple parent bodies, suggesting the existence of more than two times of ore-forming processes. Ore-forming elements are generally concentrated in the massive sulfide ore belt; nevertheless, base metals like Cu, Zn and Ph fail to show obvious zoning characterized by Cu + Zn in the lower part and Ph + Zn in the upper part, and noble metals Ag and An do not display evident horizontal preference. The tectonic reconstruction and chemical structural images of the ore. deposit demonstrate that the spatial distribution and enrichment mechanism of metallic elements are strictly controlled by basement tensional fractures and hydrothermal fluid spouting vents in the submarine depressed basin. There are at least four nearly SN striking basinal basement faulted zones that make up the migration--draining channelways of submarine lower hydrothermal fluids and the host space of stockwork ore belts; the intersections of EW-striking faults with four SN-striking faults serve as the major vents or black smokers of upward draining hydrothermal fluids at the ancient sea floor, which control the spatial distribution of metallic elements at the submarine depression. Due to the positive land form, the hot-water vents at the eastern and western edges of the depressed basin formed mound-style orebodies; in contrast, the hot-water vents in the central part of the depressed basin, having accumulated large quantities of hydrothermal fluids, formed brine pools and precipitated sheet-style massive sUlfide orebodies.