Chemical responses to hydraulic fracturing and wolframite precipitation in the vein-type tungsten deposits of southern China
Chemical responses to hydraulic fracturing and wolframite precipitation in the vein-type tungsten deposits of southern China
复制标题
华南脉状钨矿床水力压裂和黑钨矿沉淀的化学响应
DOI：
10.1016/j.oregeorev.2018.08.027
复制
发表时间：
2018-11
影响因子：
3.3
通讯作者：
张德会
中科院分区：
文献类型：
--
作者：
刘向冲;马跃;邢会林;张德会
黑钨矿是我国南方脉状钨矿床的主要矿石矿物。成矿流体的研究取得了很大进展，但黑钨矿沉淀的机制仍然知之甚少。高压流体驱动的水力压裂是岩浆-热液转换过程中常见的力学过程，但这种力学过程是否以及如何影响化学平衡并导致黑钨矿沉淀尚不确定。本文探讨了如何水力压裂过程中影响钨在CO2饱和的NaCl溶液中的溶解度使用流体力学数值模型耦合多组分热力学模型。本文提出的热力学模型为Fe-W-Cl-Na-C-O-H体系。模拟结果表明，流体压力对CO2在NaCl溶液中的溶解度随流体压力的降低而降低，pH值随流体压力的降低而升高的化学平衡有显著影响。pH值的增加会降低流体中主要含铁物质（FeCl 20）和主要含钨物质（HWO 4 −）的浓度。钨在流体中的溶解度达到几十ppm。在水力压裂数值试验中，识别出了十余种流体压力波动。这些压力波动导致钨的溶解度降低超过最大溶解度的30%。水力压裂过程中流体压力的反复下降导致CO2损失，可能是从成矿流体中沉淀黑钨矿的有效过程。这些发现也可能提供了一个深入了解其他金属的沉淀机制，从含CO2的热液流体。
Wolframite is the main ore mineral in the vein-type tungsten deposits of southern China. Much progress has been made on the characteristics of the mineralizing fluids, but the mechanisms of wolframite precipitation remain poorly understood. Hydraulic fracturing driven by high-pressure fluids is a common mechanical process during magmatic-hydrothermal transition, but it is uncertain whether and how this mechanical process may affect chemical equilibrium and cause wolframite precipitation. This paper examines how a hydraulic fracturing process affects solubility of tungsten in CO2-saturated NaCl solutions using a hydro-mechanical numerical model coupled with a multi-component thermodynamic model. The thermodynamic model presented here is in the system of Fe-W-Cl-Na-C-O-H. The modeling results indicate that fluid pressure exerts a significant influence on chemical equilibrium where CO2solubility in NaCl solutions decreases with decreasing fluid pressure and pH increases with decreasing fluid pressure. An increase in pH reduces the concentrations of the dominant iron-bearing species (FeCl20) and the dominant tungsten-bearing species (HWO4−) in fluids. Tungsten solubility in fluids reaches tens of ppm. Over ten fluctuations of fluid pressure are identified in the numerical experiments of hydraulic fracturing. These pressure fluctuations cause a decrease in solubility of tungsten by over 30% of the maximum solubility. Repeated drops of fluid pressure during hydraulic fracturing processes cause CO2loss and could be efficient processes for precipitating wolframite from mineralizing fluids. These findings may also offer an insight into the precipitation mechanisms of other metals from CO2-bearing hydrothermal fluids.
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影响因子：
3.5
作者：
J. Cosgrove
通讯作者：
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矿化计算流体动力学的一些基本问题：综述
影响因子：
3.9
作者：
Zhao, Chongbin;Reid, L. B.;Regenauer-Lieb, R.
通讯作者：
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影响因子：
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作者：
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影响因子：
5.3
作者：
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通讯作者：
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影响因子：
4.8
作者：
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通讯作者：
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