title: Enhanced olivine carbonation within a basalt as compared to single-phase experiments: reevaluating the potential of CO2 mineral sequestration.
abstract: Batch experiments were conducted in water at 150 °C and PCO2 = 280 bar on a Mg-rich tholeiitic basalt (9.3 wt % MgO and 12.2 wt % CaO) composed of olivine, Ti-magnetite, plagioclase, and clinopyroxene. After 45 days of reaction, 56 wt % of the initial MgO had reacted with CO2 to form Fe-bearing magnesite, (Mg0.8Fe0.2)CO3, along with minor calcium carbonates. The substantial decrease in olivine content upon carbonation supports the idea that ferroan magnesite formation mainly follows from olivine dissolution. In contrast, in experiments performed under similar run durations and P/T conditions with a San Carlos olivine separate (47.8 wt % MgO) of similar grain size, only 5 wt % of the initial MgO content reacted to form Fe-bearing magnesite. The overall carbonation kinetics of the basalt was enhanced by a factor of ca. 40. This could be explained by differences in the chemical and textural properties of the secondary silica layer that covers reacted olivine grains in both types of sample. Consequently, laboratory data obtained on olivine separates might yield a conservative estimate of the true carbonation potential of olivine-bearing basaltic rocks.
authors.affiliation: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS , 1 rue Jussieu, F-75005 Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Sissmann
authors.forename: Fabrice
authors.initials: F
authors.lastname: Brunet
authors.forename: Isabelle
authors.initials: I
authors.lastname: Martinez
authors.forename: François
authors.initials: F
authors.lastname: Guyot
authors.forename: Anne
authors.initials: A
authors.lastname: Verlaguet
authors.forename: Yves
authors.initials: Y
authors.lastname: Pinquier
authors.forename: Damien
authors.initials: D
authors.lastname: Daval
mesh_terms: D000535:Aluminum / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry*; D000077215:Clay; D058085:Iron Compounds / Q000737:chemistry*; D017616:Magnesium Compounds / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008903:Minerals / Q000737:chemistry*; D016062:Porosity; D017640:Silicates / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry; D012996:Solutions; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D002254:Carbonates; D058085:Iron Compounds; D017616:Magnesium Compounds; D008903:Minerals; D017640:Silicates; D012996:Solutions; C060346:basalt; D002245:Carbon Dioxide; C034475:olivine; D000535:Aluminum; D000077215:Clay; D012825:Silicon