ore genises

introduction to deposit formation and transformation


The formation of most of the earth’s mineral resources requires the presence of a fluid phase to extract the ore elements from their hosts by dissolution, to promote transport (mechanical and/or chemical) and ultimately to deposit them in suitable locales. Therefore, the knowledge and understanding of the fluid phase are critical to the development of any model of ore genesis. These fluids, which may vary widely in terms of composition, temperature, physical state, and flow characteristics, represent a state of matter in which the molecules are able to flow past one another without any limit or without any fracture or dislocation. Their state as gas, vapour, or liquid exhibits a progressively closer association of molecules and is characterised by different mechanical and thermodynamic properties.

Understanding the genesis of ores through their characterization and obtaining the precise information of magmatic, hydrothermal, tectonic, and sedimentary events that produce the ore-forming crustal fluids and metal sources that form these economic mineral deposits is a basic approach in ore genetic studies. Thus many ore deposits are produced at depth in the endogenous environment, characterized by the earth’s internal heat and its dissipation. They are eventually exhumed or brought close to the surface either by erosion of the cover or by tectonic uplift or both. A large number of economically important mineral deposits also form in the exogenous environment where weathering and sedimentation are major geological processes in water-dominant systems that are driven by the solar heat flux and where biological mediation is common. Between these two end members, there are also processes which in various combinations contribute to the formation of ore deposits or their transformation.

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