Experimental investigation of metals behavior in magmatic-hydrothermal fluids
E001
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Abstract
Magmatic-hydrothermal ore deposits refer to a wide variety of anomalous metallic concentration that form in or around igneous rock units (e.g., Cu-Au-Mo porphyries or epithermals, W skarns, etc…). In these complex systems, metals may be scavenged directly from the magmatic source through degassing, or from surrounding rocks that are more efficiently leached out thanks to the heat provided by the close-by magmas. Determining the composition and transport properties of the different fluids potentially present in these systems has been a matter of debate for years.
The partitioning of metals in magmatic fluids/gas is also known to contribute to the release of consequent and sometimes toxic amounts of metals at active volcanic centers, with recent estimates of metal emissions from Masaya, Etna or Iceland even suggesting that short-term metal release associated with volcanic activity may be comparable to anthropogenic emissions from rich industrial countries [Edmonds et al., 2018]. Yet, how metals are dissolved and transported in high-temperature fluids remains poorly constrained as these elusive phases cannot be sampled as such in nature.
In this team talk, we will present the different technics used at ISTO to characterize metals behavior in high-T fluids down to the molecular state. After a brief introduction on the challenges encountered when studying magmatic-hydrothermal fluids and how we can tackle them experimentally, Tom Chatelin (PhD) will present the basics of synchrotron technics for Earth Sciences and the preliminary results from his first synchrotron XAS experiments investigating the speciation of Zn in hydrothermal fluids. Then, Cordula Haupt (Postdoctoral researcher) will tell us about her IHPV experiments designed to constrain the fluid-melt partitioning of metals. Finally, Marion Louvel (PI) will conclude with a presentation of the recent technical developments of X-ray radiography, XRD and SAXS at ISTO and the new opportunities they may provide to study and model the effects of vapor-brine separation or hydrothermal alteration during ore formation.