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Dual carbonate clumped isotope (Δ47-Δ48) measurements constrain different sources of kinetic isotope effects and quasi-equilibrium signatures in cave carbonates

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dc.contributor.author Parvez, Zeeshan A
dc.contributor.author El-Shenawy, Mohammed I
dc.contributor.author Lucarelli, Jamie K
dc.contributor.author Sang-Tae, Kim
dc.contributor.author Johnson, Kathleen R
dc.contributor.author Wright, Kevin
dc.contributor.author Gebregiorgis, Daniel
dc.contributor.author Montanez, Isabel P
dc.contributor.author Wortham, Barbara
dc.contributor.author Asrat, Asfawossen
dc.contributor.author Reinhardt, Eduard
dc.contributor.author Christensen, John N
dc.contributor.author Matamoros, Irvin W
dc.contributor.author Rubi, Joshua
dc.contributor.author Miguel, Kevin
dc.contributor.author Elliott, Ben M
dc.contributor.author Flores, Randy
dc.contributor.author Kovacs, Shawn
dc.contributor.author Eagle, Robert A
dc.contributor.author Tripati, Aradhna
dc.date.accessioned 2025-11-25T14:29:24Z
dc.date.available 2025-11-25T14:29:24Z
dc.date.issued 2024-11-27
dc.identifier.citation Parvez, Zeeshan A .,El-Shenawy, Mohammed.,Lucarelli, Jamie. K.,Sang-Tae, Kim.,Johnson, Kathleen. R.,Wright, Kevin., Gebregiorgis, Daniel., Montanez, Isabel. P., Wortham, Barbara., Asrat, Asfawossen., Reinhardt, Eduard., Christensen, John. N., Matamoros, Irvin. W., Rubi, Joshua., Miguel, Kevin., Elliott, Ben. M., Flores, Randy., Kovacs, Shawn., Eagle, Robert .A., Tripati, Aradhna. (2024) Dual carbonate clumped isotope (Δ47-Δ48) measurements constrain different sources of kinetic isotope effects and quasi-equilibrium signatures in cave carbonates. Geochimica et Cosmochimica Acta, 366, 95-112. https://doi.org/10.1016/j.gca.2023.11.017 en_US
dc.identifier.issn 1872-9533
dc.identifier.uri https://repository.biust.ac.bw/handle/123456789/719
dc.description.abstract Cave carbonate minerals are an important terrestrial paleoclimate archive. A few studies have explored the potential for applying carbonate clumped isotope thermometry to speleothems as a tool for constraining past temperatures. To date, most papers utilizing this method have focused on mass-47 clumped isotope values (Δ47) at a single location and reported that cave carbonate minerals rarely achieve isotopic equilibrium, with kinetic isotope effects (KIEs) attributed to CO2 degassing. More recently, studies have shown that mass-47 and mass-48 CO2 from acid digested carbonate minerals (Δ47 and Δ48) can be used together to assess equilibrium and probe KIEs. Here, we examined 44 natural and synthetic modern cave carbonate mineral samples from 13 localities with varying environmental conditions (ventilation, water level, pCO2, temperature) for (dis)equilibrium using Δ47-Δ48 values, in concert with traditional stable carbon (δ13C) and oxygen (δ18O) isotope ratios. Data showed that 19 of 44 samples exhibited Δ47-Δ48 values indistinguishable from isotopic equilibrium, and 18 (95 %) of these samples yield Δ47-predicted temperatures within error of measured modern temperatures. Conversely, 25 samples exhibited isotopic disequilibria, 13 of which yield erroneous temperature estimates. Within some speleothem samples, we find Δ47-Δ48 values consistent with CO2 degassing effects, however, the majority of samples with KIEs are consistent with other processes being dominant. We hypothesize that these values reflect isotopic buffering effects on clumped isotopes that can be considerable and cannot be overlooked. Using a Raleigh Distillation Model, we examined carbon and oxygen isotope exchange trajectories and their relationships with dual clumped isotope disequilibria. Carbon isotope exchange is associated with depletion of both Δ47 and Δ48 relative to equilibrium, while oxygen isotope exchange is associated with enrichment of both Δ47 and Δ48 relative to equilibrium. Cave rafts collected from proximate locations in Mexico exhibit the largest average departures from equilibrium (ΔΔ47¯ = −0.032 ± 0.007, ΔΔ48¯ = −0.104 ± 0.035, where ΔΔi is the measured value – the equilibrium value). This study shows how the Δ47-Δ48 dual carbonate clumped isotope framework can be applied to a variety of tcave carbonate mineral samples, enabling identification of isotopic equilibria and therefore quantitative application of clumped isotope thermometry for paleoclimate reconstruction, or alternatively, constraining the mechanisms of kinetic effects. en_US
dc.description.sponsorship U.S. Department of Energy (DOE), BES – Grant DE-FG02-83613ER16402 Heising-Simons Foundation – Grant 2022-3314 Natural Sciences and Engineering Research Council of Canada (NSERC) – Discovery Grants 386188-2010, 2015-04413, 2020-05810 Center for Diverse Leadership in Science (supported by the Packard Foundation, Sloan Foundation, Silicon Valley Community Foundation, and NSF) National Science Foundation (NSF) – Grants ICER-2039462, RISE-2232606, 5K12GM106996 (IRACDA), 2002509, 1405472, 1603056, 1806090, 2103129 STARTPACOM – Support acknowledged en_US
dc.language.iso en en_US
dc.publisher Elsevier Ltd en_US
dc.subject Speleothems en_US
dc.subject Clumped isotopes en_US
dc.subject Cave carbonates en_US
dc.title Dual carbonate clumped isotope (Δ47-Δ48) measurements constrain different sources of kinetic isotope effects and quasi-equilibrium signatures in cave carbonates en_US
dc.description.level phd en_US
dc.description.accessibility unrestricted en_US
dc.description.department mge en_US


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