Rates and Mechanisms of Mineral Carbonation in Peridotite: Natural Processes and Recipes for Enhanced, in situ CO2 Capture and Storage

Near-surface reaction of CO2-bearing fluids with silicate minerals in peridotite and basalt forms solid carbonate minerals. Such processes form abundant veins and travertinedeposits, particularly in associationwith tectonically exposed mantle peridotite. This is important in the global carbon cycle, in weathering, and in understanding physical-chemical interaction during retrograde metamorphism. Enhancing the rate of such reactions is a proposed method for geologic CO2 storage, and perhaps for direct capture of CO2 from near-surface fluids. We review, synthesize, and extend inferences from a variety of sources. We include data from studies on natural peridotite carbonation processes, carbonation kinetics, feedback between permeability and volume change via reaction-driven cracking, and proposed methods for enhancing the rate of natural mineral carbonation via in situ processes (“at the outcrop”) rather than ex situ processes (“at the smokestack”). 545 A nn u. R ev . E ar th P la ne t. Sc i. 20 11 .3 9: 54 557 6. D ow nl oa de d fr om w w w .a nn ua lr ev ie w s. or g A cc es s pr ov id ed b y R ic e U ni ve rs ity o n 10 /2 2/ 17 . F or p er so na l u se o nl y. EA39CH19-Kelemen ARI 23 March 2011 23:45 Mineral carbonation: reaction of silicate or oxide minerals with CO2 in fluid to form solid carbonate minerals Olivine: the most abundant mineral in Earth’s upper mantle, (Mg,Fe)2SiO4 Magnesite: the most common magnesium carbonate mineral, MgCO3, with minor Ca and Fe substitution Peridotite: a rock composed of more than 40% olivine and less than 10% plagioclase Plagioclase: one of the feldspar group of minerals, mainly NaAlSi3O8CaAl2Si2O8 Basalt: the most common form of lava on Earth, typically with 48 to 53 wt% SiO2; when fully crystalline, common basalts are a mixture of ∼60% plagioclase, 30% clinopyroxene, and 10% olivine Quartz: a mineral composed of SiO2