Fluid mixing forms basement-hosted Pb-Zn deposits: Insight from metal and halogen geochemistry of individual fluid inclusions
Fluid mixing forms basement-hosted Pb-Zn deposits: Insight from metal and halogen geochemistry of individual fluid inclusions
复制标题
DOI：
10.1130/g34092.1
复制
发表时间：
2013-06
期刊：
影响因子：
5.8
通讯作者：
T. Fusswinkel;T. Wagner;M. Wälle;T. Wenzel;C. Heinrich;G. Markl
中科院分区：
文献类型：
--
作者：
T. Fusswinkel;T. Wagner;M. Wälle;T. Wenzel;C. Heinrich;G. Markl
结晶基底和上覆沉积盆地之间的不整合面上的流体混合通常被认为是成矿的有效化学机制，但基底卤水的起源和成矿过程很少有直接的证据。采用激光烧蚀-电感耦合等离子体质谱显微分析单个流体包裹体的阴离子成分的改进的检测方法，我们同时确定了矿石金属浓度和Cl/Br比的纹理良好约束的包裹体组合从基底托管石英-萤石-重晶石-铅锌脉系统。流体包裹体中Pb + Zn浓度和Cl/Br质量比之间的负相关性为基底来源的富金属卤水和贫金属地层水的混合提供了明确的证据，该地层水的盐度来自三叠纪沉积盖层中的岩盐溶解。这两个不同的盐水具有可比的盐度的混合过程中记录的个别石英晶体含有小方铅矿夹杂物的生长，证明矿物沉积过程中的流体混合的瞬态和情节的性质。
Fluid mixing across unconformities between crystalline basement and overlying sedimentary basins is commonly invoked as an efficient chemical mechanism for ore deposition, but the origin of basement brines and the process of ore formation have rarely been linked by direct evidence. Using laser ablation–inductively coupled plasma–mass spectrometry microanalysis of individual fluid inclusions with an improved detection approach for anion components, we determined simultaneously the ore metal concentrations and the Cl/Br ratio in texturally well constrained inclusion assemblages from a basement-hosted quartz-fluorite-barite-Pb-Zn vein system. An inverse correlation between the Pb + Zn concentrations and the Cl/Br mass ratios in the fluid inclusions provides clear evidence for mixing of a basement-derived metal-rich brine and a metal-poor formation water that acquired its salinity from halite dissolution in Triassic evaporites of the sedimentary cover. This mixing of two distinct brines with comparable salinity is recorded during the growth of individual quartz crystals containing small galena inclusions, demonstrating the transient and episodic nature of fluid mixing during mineral deposition.