Date of Award
Master of Science (MS)
Dawn M. Cardace
A number of methods of drawing down atmospheric carbon dioxide are being investigated as a result of concerns over the impacts of global warming. Mineral carbonation is a proven manner of sequestering carbon dioxide and functions by binding carbon dioxide with iron-, calcium-, and magnesium-containing minerals—including olivine, pyroxene, and serpentine— to form carbonate minerals. The Coast Range Ophiolite (CRO) in California is a 700 km long body of ultramafic rocks containing vast amounts of olivine and serpentine. By assessing the mineralogical and geochemical characteristics of the minerals in these rocks, I assess the potential quantity of CO2 that could be sequestered in these rocks.
Olivine is the most ideal mineral reactant for carbon sequestration, based on abundance and reactivity. My data show that the first 45 m of surface rocks of the CRO contain very little olivine, but petrography shows olivine at least 110 m below the surface, and olivine has been previously identified in various sections of the CRO. Using energy-dispersive x-ray spectroscopy, I showed that the amount of Mg in olivine in the rocks is 24% and the amount of total Mg + Fe + Ca is 38%. Based on these figures and volume, density, and the percentage of rock reacted with CO2, I calculate that the CRO can sequester ~ 6.9x1013 kg CO2 for Mg-only sequestration and ~9.1x1013 kg CO2 for Mg, Fe, and Ca sequestration, which correspond to 14% and 39% of the amount of atmospheric CO2 that would return us to 350 ppm CO2, Thus the CRO, while not capable of eliminating enough CO2 to halt global warming by itself, still can sequester a considerable amount and should be considered a viable option for mineral sequestration.
Carnevale, Daniel C., "Carbon Sequestration Potential of the Coast Range Ophiolite in California" (2013). Open Access Master's Theses. Paper 46.