Geochemical and C-O Isotopic Study of Ophiolite-Derived Carbonates of the Barzaman Formation, Oman: Evidence of Natural CO2 Sequestration Via Carbonation of Ultramafic Clasts

Arshad Ali, Iftikhar Ahmed Abbasi*, Leonardo Brandão Nogueira, Osman Salad Hersi, Sumaiya A.N. Al Kindi, Mohamed A.K. El-Ghali, Sobhi Jaber Nasir

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Carbonate precipitation through atmospheric CO2 uptake by alkaline-hyperalkaline waters offers a potential approach to mitigating anthropogenic CO2 emissions. The Oman Ophiolite produces high-pH water characterized by continuous sequestration of CO2 at the air-water interface. The geochemical and isotopic data of carbonates from the Barzaman Formation is used to assess the amount of atmospheric CO2 stored in the dolomite-calcite assemblage. Post Archean Australian Shale -normalized rare earth elements patterns, with the exception of La and Ce anomalies, are similar to those of the bulk oceanic and lower crusts, with increasing LREE and flat HREE trends, and a positive Eu anomaly. The δ13CVPDB and δ18OVSMOW isotope values of the analyzed samples show two distinct end-members, in which dolomite (−7.77‰ and +27.3‰) is isotopically heavier than calcite (−9.93‰ and +21.5‰). The estimated carbonate growth temperatures (18°C–56°C) are indistinguishable from the previously reported range (18°C–66°C). The C-O isotope model for calcite, groundwater, and atmospheric CO2 shows that an ophiolite-derived calcite sample absorbed an unequivocal amount of atmospheric CO2 (78% ± 11%) during precipitation. At the same time, dissolved inorganic carbon (DIC) in water accounts for the remaining carbon contribution (22% ± 9%). DIC is closely associated with different carbonate lithofacies and ophiolite-derived soil, exhibiting large variations in C-O isotopic compositions caused by isotopic disequilibrium. Taken together, geochemical and isotopic properties confirm that the carbonates were formed under oxic conditions triggered by the water-rock interaction. For a reliable estimate of CO2 sequestered by carbonates of the Barzaman Formation, a systematic groundwater analysis is recommended to determine the contribution of CO2 in DIC.

Original languageEnglish
Article numbere2020JB021290
JournalJournal of Geophysical Research: Solid Earth
Volume126
Issue number10
DOIs
Publication statusPublished - Oct 2021
Externally publishedYes

Keywords

  • Barzaman Formation
  • C-O isotopes
  • carbonates
  • carbonation
  • CO sequestration
  • Oman Ophiolite

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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