Genetic understanding of hydrothermal ore deposits demands knowledge of solubility and speciation of ore metals. Solubility determines the transport of appropriate amount of ore-forming metals. Accordingly, the solubility of metals and their precipitation as ore minerals are prerequisites for the formation of hydrothermal ore deposits. This chapter is devoted to results of experimental solubility studies of various metals, along with thermodynamic assessment of solubility and speciation involved. While solubility is a measure of total concentration of a given metal in hydrothermal fluid when in equilibrium with an ore mineral or mineral assemblage, speciation is a measure of amount of various metal species in the fluid as a function of temperature, pressure, and fluid composition. The term solubility refers to the maximum limit for transportation of dissolved metal species in the hydrothermal fluid at equilibrium condition. Equilibrium solubility proceeds in the direction of the system approaching the state of chemical equilibrium. The extent to which the hydrothermal fluid is saturated in a given ore mineral can be determined by comparing the fluid ion activity product (IAP) with the mineral solubility product (KSP). The factor speciation controls both equilibrium solubility and precipitation mechanism of ore minerals from the hydrothermal fluid. Thus, it is necessary to identify dominant species and their relative concentrations in the hydrothermal fluid. Literature on solubility of metals and precipitation of ore minerals is exhaustive. Some of the excellent and extensive reviews are by Seward and Barnes (1997), Wood and Samson (1998), Reed and Palandri (2006), and Seward et al. (2014). Solubility of ore minerals has been studied by different approaches. These include experimental solubility measurements, UV/VIS and X-ray absorption spectroscopy, thermodynamic predictions, and other numerical simulations involving ab initio, ab initio/molecular dynamics (MD) computations. All these studies provided thermodynamic data and molecular insight into energetics of complexation, metal-ligand bond lengths, parameters that are crucial to understand metal transport, metal (+ complex) partitioning during boiling and fluid phase separation, and most importantly various causative factors behind precipitation ore minerals in hydrothermal systems. We first deal with simple ionic solubility, followed by effect of metal-ligand complexation on solubility, and result of complexation on precipitation mechanisms. This will be followed by examples of solubility of some important ore-forming metals and the causative factors behind precipitation of ore minerals from hydrothermal fluids.

Solubility of Ore Minerals in Hydrothermal Fluid

章节
发表日期：

2026年

查看全文

Biswajit Mishra,
Dewashish Upadhyay

摘要

Genetic understanding of hydrothermal ore deposits demands knowledge of solubility and speciation of ore metals. Solubility determines the transport of appropriate amount of ore-forming metals. Accordingly, the solubility of metals and their precipitation as ore minerals are prerequisites for the formation of hydrothermal ore deposits. This chapter is devoted to results of experimental solubility studies of various metals, along with thermodynamic assessment of solubility and speciation involved. While solubility is a measure of total concentration of a given metal in hydrothermal fluid when in equilibrium with an ore mineral or mineral assemblage, speciation is a measure of amount of various metal species in the fluid as a function of temperature, pressure, and fluid composition. The term solubility refers to the maximum limit for transportation of dissolved metal species in the hydrothermal fluid at equilibrium condition. Equilibrium solubility proceeds in the direction of the system approaching the state of chemical equilibrium. The extent to which the hydrothermal fluid is saturated in a given ore mineral can be determined by comparing the fluid ion activity product (IAP) with the mineral solubility product (KSP). The factor speciation controls both equilibrium solubility and precipitation mechanism of ore minerals from the hydrothermal fluid. Thus, it is necessary to identify dominant species and their relative concentrations in the hydrothermal fluid. Literature on solubility of metals and precipitation of ore minerals is exhaustive. Some of the excellent and extensive reviews are by Seward and Barnes (1997), Wood and Samson (1998), Reed and Palandri (2006), and Seward et al. (2014). Solubility of ore minerals has been studied by different approaches. These include experimental solubility measurements, UV/VIS and X-ray absorption spectroscopy, thermodynamic predictions, and other numerical simulations involving ab initio, ab initio/molecular dynamics (MD) computations. All these studies provided thermodynamic data and molecular insight into energetics of complexation, metal-ligand bond lengths, parameters that are crucial to understand metal transport, metal (+ complex) partitioning during boiling and fluid phase separation, and most importantly various causative factors behind precipitation ore minerals in hydrothermal systems. We first deal with simple ionic solubility, followed by effect of metal-ligand complexation on solubility, and result of complexation on precipitation mechanisms. This will be followed by examples of solubility of some important ore-forming metals and the causative factors behind precipitation of ore minerals from hydrothermal fluids.