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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. Plain Language Summary: The sequestration of CO2 through mineralization has been a widely debated potential method for coping with rising levels of anthropogenic CO2 emissions. The C‐O stable isotope compositions of carbonates from the Barzaman Formation in Oman have been used to estimate the amount of atmospheric CO2 stored in them. These samples have geochemical signatures that suggest they are closely related to the oceanic crust, which is a precursor to the Oman Ophiolite. Based on the carbon and oxygen isotope model, we estimate that atmospheric CO2 contributed approximately 78% ± 11% (sd) of the overall carbon budget in a calcite sample at the time of its formation. The remaining 22% ± 9% (sd) of the carbon, on the other hand, is most likely contributed by DIC acquired by water after interacting with different carbonate lithofacies and soil. Additional research on local groundwater is needed to fully evaluate the C‐budget in the Barzaman Formation, as DIC may contain atmospheric CO2 previously stored by the carbonate lithofacies. Key Points: First reporting of the geochemical and isotopic data sets of carbonates from the Barzaman Formation, OmanC‐O isotope model is used to calculate the amount of atmospheric CO2 stored in carbonates as a result of carbonation of ultramafic clastsCarbonate growth temperatures in various water types are estimated using their corresponding δ18OVPDB and δ18OVSMOW values [ABSTRACT FROM AUTHOR]

The Dhofar 1673, Dhofar 1983, and Dhofar 1984 meteorites are three lunar regolith breccias classified based on their petrography, mineralogy, oxygen isotopes, and bulk chemistry. All three meteorites are dominated by feldspathic lithic clasts; however, impact melt rock clasts and spherules are also found in each meteorite. The bulk chemistry of these samples is similar to other feldspathic highland meteorites with the Al2O3 content only slightly lower than average. Within the lithic clasts, the Mg # of mafic phases versus the anorthite content of feldspars is similar to other highland meteorites and is found to plot intermediate of the ferroan‐anorthositic suite and magnesian suite. The samples lack any KREEPy signature and have only minor indications of a mare basalt component, suggesting that the source region of all three meteorites would have been distal from the Procellarum KREEP Terrane and could have possibly been the Feldspathic Highland Terrane. All three meteorites were found within 500 m of each other in the Dhofar region of Oman. This, together with their similar petrography, stable isotope chemistry, and geochemistry indicates the possibility of a pairing. [ABSTRACT FROM AUTHOR]

We report the equilibration temperatures derived from the oxygen isotope thermometry of pyroxene-olivine pair from the Dar al Ghani (DaG) 476 (1200 +105/-90 °C) and Sayh al Uhaymir (SaU) 008 (1430 +220/-155 °C) meteorites showing a difference of over 200 °C at the face values. Regardless of the large associated uncertainties, contrasting geochemical and isotopic characteristics such as oxygen fugacities, hydrogen isotopic compositions (referred to as the D/H ratios), olivine abundances, presence of merrillite and/or apatite, and their chlorine contents between the two meteorites are observed in the literature. These opposing features lend support to the idea that the relative difference observed in the estimated temperatures is probably real and significant, thus providing insights into the Martian mantle magmatism. Based on our temperature estimation and previous magmatic models, we propose that SaU 008 could have been originated from a deeper depleted mantle source. However, DaG 476 may have been produced by the partial melting of the entrained pockets of the depleted mantle similar to that of the SaU 008's source at a relatively shallower depth. Both meteorites erupted as a relatively thick lava flow or a shallow intrusion at approximately the same time followed by a launch initiated by a single meteoritic impact 1.1 million years (Ma) ago. [ABSTRACT FROM AUTHOR]