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Title: Diamond formation due to a pH drop during fluid–rock interactions

Journal Article · · Nature Communications
DOI:https://doi.org/10.1038/ncomms9702· OSTI ID:1239809

Diamond formation has typically been attributed to redox reactions during precipitation from fluids or magmas. Either the oxidation of methane or the reduction of carbon dioxide has been suggested, based on simplistic models of deep fluids consisting of mixtures of dissolved neutral gas molecules without consideration of aqueous ions. The role of pH changes associated with water–silicate rock interactions during diamond formation is unknown. Here we show that diamonds could form due to a drop in pH during water–rock interactions. We use a recent theoretical model of deep fluids that includes ions, to show that fluid can react irreversibly with eclogite at 900 °C and 5.0 GPa, generating diamond and secondary minerals due to a decrease in pH at almost constant oxygen fugacity. Overall, our results constitute a new quantitative theory of diamond formation as a consequence of the reaction of deep fluids with the rock types that they encounter during migration. Diamond can form in the deep Earth during water–rock interactions without changes in oxidation state.

Research Organization:
Johns Hopkins Univ., Baltimore, MD (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
FG02-96ER14616
OSTI ID:
1239809
Journal Information:
Nature Communications, Vol. 6; ISSN 2041-1723
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 64 works
Citation information provided by
Web of Science

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Cited By (9)

Immiscible hydrocarbon fluids in the deep carbon cycle journal June 2017
Diamond growth from organic compounds in hydrous fluids deep within the Earth journal October 2019
Carbon sequestration during core formation implied by complex carbon polymerization journal February 2019
Uncovering and quantifying the subduction zone sulfur cycle from the slab perspective journal January 2020
Thermodynamic modelling of fluids from surficial to mantle conditions journal February 2019
Highly oxidising fluids generated during serpentinite breakdown in subduction zones journal September 2017
Diamond Growth from Organic Compounds in Hydrous Fluids Deep within the Earth conference January 2020
Uncovering and quantifying the subduction zone sulfur cycle from the slab perspective text January 2020
The lower pT limit of deep hydrocarbon synthesis by CaCO3 aqueous reduction journal July 2017

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