Grant: Discovery Grants Program - Individual

Ultramafic rocks form a large part of the Earth accessible to water and are subject to hydration metamorphism, commonly at low pressure and temperature. Under appropriate physico-chemical conditions, this can lead to formation of serpentinites (rocks essentially composed of serpentine minerals such as chrysotile asbestos) in various tectonic settings. During serpentinization, a number of important reactions take place. Of particular interest are; 1) the generation of large amounts of hydrogen; 2) the increase in pH and lowering in dissolved silica with decreasing temperature of the fluids, which may induce calc-silicate alteration at the interface between silica-rich rocks and their ultramafic host; and 3) the formation of metallic ore deposits such as nickel. During serpentinization, conditions can become sufficiently reducing to stabilize iron-nickel alloys and native iron, and transform solid or dissolved forms of carbon into hydrocarbons. However, very few studies have attempted to correlate the mineral assemblages in serpentinites with the nature of the serpentinizing fluids. Under what conditions are fluids gas-like or liquid-like? Establishing the latter within the range of pressure and temperature conditions found within the Earth's crust is an essential first step to further evaluation of the generation of hydrocarbon gases, the hydrolysis of hydrocarbons and the mobility of ore metals. Detailed studies of the mineralogy and of fossil fluids that were trapped into minerals that grew during serpentinization episodes can provide clues to solving these outstanding issues and forms the body of this proposed research program. An understanding of the processes outlined above will provide the tools for evaluating the global abiogenic hydrocarbon budget to oceans, the efficiency of metal mass transfer for the formation of economic deposits, and the input of primary food source for bacterial organism in extreme environments.