Experimental investigations of interactions between saltwater and ultramafic rocks in hydrothermal systems

Abstract

Fluid circulation and serpentinization in ultramafic-hosted hydrothermal systems occurs mostly at slow- spreading mid-ocean ridges, where tectonic processes promote fluid ingress into the crust. This is a fundamental process that impacts transfer of energy and affects the chemical composition of both the ocean lithosphere and the hydrosphere. Experimental investigations of sulfide-bearing serpentinization systems can help further our understanding of the sulfide phase relations at temperature conditions relevant for natural systems. The purpose of the research presented in this dissertation is to simulate fluid-rock interactions in ultramafic-hosted systems and to investigate reaction pathways, hydrogen generation, elemental exchange during reaction progress between rock and fluid, and formation of alteration minerals. The focus lies on the activities of H2 (aq) and H2S (aq) and changes in the assemblages of Fe-Ni-S mineral phases, which had never been tested by experimental work prior to this study.