Quantitative constraints on the interplay of fluid properties and rock mechanics in the formation of magmatic-hydrothermal ore deposits
Abstract
Porphyry copper and epithermal gold are among the most abundant types of ore deposits worldwide. There is evidence that both might form in a common type of magmatic-hydrothermal system related to the crystallization of subduction-related hydrous magmas in the upper crust. Our recent numerical modelling quantitatively shows that the implementation of real non-linear fluid properties and transient feedbacks with rock mechanics are key to explain some first-order controls on their formation. The salinity of the volatiles released from the solidifying magma extends the pressure-temperature range of two- or three-phase coexistence of vapour, liquid and solid halite to significantly higher pressures and temperatures as compared to pure water, and fluid inclusion analyses and theoretical models show the importance of these phase relations for metal transport and ore precipitation. Many magmatic-hydrothermal systems like porphyry-type ore deposits have dense quartz-vein networks that were formed by hydrofracturing of the rock and that are clearly associated with ore formation. In order to quantitatively constrain the hydrology of these systems in a physically rigorous way, we developed a numerical magmatic-hydrothermal simulator that can combine an accurate model of saltwater and a transient pressure- and temperature-dependent permeability model with a transport scheme that can handle the expulsion of magmatic fluids. Generic simulations demonstrate the role of fluid and rock properties in self-organizing and stabilizing fluid flow at conditions favourable for metal enrichment to economic grades in the porphyry and epithermal environments.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.V11A2746W
- Keywords:
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- 1034 GEOCHEMISTRY / Hydrothermal systems;
- 1847 HYDROLOGY / Modeling;
- 1859 HYDROLOGY / Rocks: physical properties;
- 8424 VOLCANOLOGY / Hydrothermal systems