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Brandon Harrison

Bio: Brandon Harrison is an academic researcher from Johns Hopkins University. The author has contributed to research in topics: Gibbs free energy & Lithosphere. The author has an hindex of 2, co-authored 2 publications receiving 298 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the applicability of the revised Helgeson-Kirkham-Flowers (HKF) equations of state for aqueous species was extended to 60kb by developing estimates of ( e H 2 O ).

226 citations

Journal ArticleDOI
TL;DR: It is found that MgCO3 (magnesite)—insoluble in water under ambient conditions—becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon and the Earth’s deep carbon could possibly be recycled through aqueous transport through subduction zones.
Abstract: Water is a major component of fluids in the Earth’s mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties greatly limits our ability to model water–rock interactions and, in general, our understanding of aqueous fluids below the Earth’s crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earth’s upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)—insoluble in water under ambient conditions—becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. Our results suggest that aqueous carbonates could leave the subducting lithosphere during dehydration reactions and could be injected into the overlying lithosphere. The Earth’s deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones.

157 citations


Cited by
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Journal ArticleDOI
TL;DR: Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments.
Abstract: Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5–10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory.

484 citations

Journal ArticleDOI
TL;DR: In this paper, the balance between carbonate subduction into the deep Earth and CO2 release through degassing at volcanoes is critical for the carbon cycle, and fluid-mediated reactions could liberate significant amounts of carbon from the subducting slab for later release at arc volcanoes.
Abstract: The balance between carbonate subduction into the deep Earth and CO2 release through degassing at volcanoes is critical for the carbon cycle. Geochemical analyses of an exhumed subduction zone complex in Greece show that fluid-mediated reactions could liberate significant amounts of carbon from the subducting slab for later release at arc volcanoes.

268 citations

Journal ArticleDOI
TL;DR: In this paper, the applicability of the revised Helgeson-Kirkham-Flowers (HKF) equations of state for aqueous species was extended to 60kb by developing estimates of ( e H 2 O ).

226 citations

Journal ArticleDOI
TL;DR: In this article, a large-scale mantle low δ26Mg anomaly in eastern China has been delineated, suggesting the contribution of sedimentary carbonates recycled into the upper mantle, but limited into the lower mantle.
Abstract: Although deep carbon recycling plays an important role in the atmospheric CO2 budget and climate changes through geological time, the precise mechanisms remain poorly understood. Since recycled sedimentary carbonate through plate subduction is the main light-δ26Mg reservoir within deep-Earth, Mg isotope variation in mantle-derived melts provides a novel perspective when investigating deep carbon cycling. Here, we show that the Late Cretaceous and Cenozoic continental basalts from 13 regions covering the whole of eastern China have low δ26Mg isotopic compositions, while the Early Cretaceous basalts from the same area and the island arc basalts from circum-Pacific subduction zones have mantle-like or heavy Mg isotopic characteristics. Thus, a large-scale mantle low δ26Mg anomaly in eastern China has been delineated, suggesting the contribution of sedimentary carbonates recycled into the upper mantle, but limited into the lower mantle. This large-scale spatial and temporal variation of Mg isotopes in the mantle places severe constraints on deep carbon recycling via oceanic subduction.

220 citations

Journal ArticleDOI
01 Jan 2016-Lithos
TL;DR: In this article, the authors consider records of fluid and mass transfer at localities representing various depths and structural expressions of evolving paleo-interfaces, ranging widely in structural character, the rock types involved, and the rheology of these rocks.

182 citations