Clog, M. , Lindgren, P., Modestou, S. , McDonald, A., Tait, A., Donnelly, T., Mark, D. and Lee, M. (2024) Clumped isotope and Δ17O measurements of carbonates in CM carbonaceous chondrites: new insights into parent body thermal and fluid evolution. Geochimica et Cosmochimica Acta, 369, pp. 1-16. (doi: 10.1016/j.gca.2024.01.023)
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Abstract
The CM carbonaceous chondrites are key archives for understanding the earliest history of the solar system. Their C-complex asteroid parent body(ies) underwent aqueous alteration, among the products of which are carbonate minerals that can faithfully record the conditions of their formation. In this study we report carbon, triple oxygen and clumped isotope compositions of carbonates in six CM chondrites which span a range in degrees of aqueous alteration (Allan Hills 83100, Cold Bokkeveld, LaPaz Icefield 031166, Lonewolf Nunataks 94101, Murchison, Scott Glacier 06043). Δ¹⁷O values range from −2.6 to −1.0 ‰ (±0.1), and where calcite and dolomite co-exist their Δ¹⁷O differ by 0.6 permil, suggesting precipitation from distinct fluids. Calculated crystallization temperatures range from 5 to 51 °C for calcite (typically ± 10 °C) and 75 to 101(±15) °C for dolomite. The δ¹⁸ᴼVSMOW of the aqueous fluids from which they formed ranges from −6.6 to 2.3 ‰, with no relationship to the δ¹³C of carbonates. As the population of carbonates in any one CM chondrite can include multiple generations of grains that formed at different conditions, these values represent the mode of the temperature of carbonate formation for each meteorite. We observe that in the more altered meteorites carbonate Δ¹⁷O values are lower and formation temperatures are higher. These correlations are consistent with aqueous alteration of the CM chondrites being a prograde reaction whereby the hotter fluids had undergone greater isotope exchange with the anhydrous matrix. Our data are broadly consistent with the closed system model for water/rock interaction, but carbonate mineral formation in the latter stages of aqueous alteration may be linked to fluid movement via fractures.
| Item Type: | Articles |
|---|---|
| Additional Information: | We acknowledge funding from the UK Science and Technology Facilities Council (STFC) through grants ST/W001128/1, ST/T002328/1, ST/G001693/1 and ST/K000942/1. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Modestou, Dr Sevi and Mark, Professor Darren and Donnelly, Mr Terry and Tait, Mr Andrew and Lee, Professor Martin and McDonald, Mr Alex and Lindgren, Dr Paula and Clog, Dr Matthieu |
| Creator Roles: | Clog, M.Investigation, Validation, Visualization, Writing – original draft, Writing – review and editing Lindgren, P.Conceptualization, Resources, Validation, Writing – original draft, Writing – review and editing Modestou, S.Investigation, Validation, Writing – review and editing McDonald, A.Investigation, Validation Tait, A.Investigation, Validation Donnelly, T.Investigation, Validation Mark, D.Funding acquisition, Writing – review and editing Lee, M.Conceptualization, Funding acquisition, Resources, Writing – original draft, Writing – review and editing |
| Authors: | Clog, M., Lindgren, P., Modestou, S., McDonald, A., Tait, A., Donnelly, T., Mark, D., and Lee, M. |
| College/School: | College of Science and Engineering > School of Geographical and Earth Sciences College of Science and Engineering > Scottish Universities Environmental Research Centre |
| Journal Name: | Geochimica et Cosmochimica Acta |
| Publisher: | Elsevier |
| ISSN: | 0016-7037 |
| ISSN (Online): | 1872-9533 |
| Published Online: | 28 January 2024 |
| Copyright Holders: | Copyright © 2024 The Authors |
| First Published: | First published in Geochimica et Cosmochimica Acta 369:1-16 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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