Melezhik, V.A. and Fallick, A.E. (2003) δ13C and δ18O variations in primary and secondary carbonate phases: several contrasting examples from Palaeoproterozoic 13C-rich metamorphosed dolostones. Chemical Geology, 201(3-4), pp. 213-228. (doi: 10.1016/j.chemgeo.2003.07.003)
Full text not currently available from Enlighten.
Publisher's URL: http://dx.doi.org/10.1016/j.chemgeo.2003.07.003
Abstract
The Palaeoproterozoic Kuetsjarvi Sedimentary Formation from the Pechenga Greenstone Belt, NW Russia, has been studied with the purpose of determining δ<sup>13</sup>C<sub>carb</sub> and δ<sup>18</sup>O<sub>carb</sub> values in various carbonate phases from genetically different <sup>13</sup>C-rich dolostones sampled by micro-coring techniques. Samples were collected from quarries and drillholes. This avoids the influence of recent weathering on isotopic composition, and allows rocks from different metamorphic facies intersected by deep drillholes to be sampled. In the low-grade greenschist facies conditions, distinct textural components from the same parental impure dolostones have yielded δ<sup>13</sup>C values ranging within 1‰, and showing no statistical differences between early dolomicrite and late void- and fenestra-filling dolospar. No significant differences have been observed between analyses of the whole-rock and microcored samples. Genetically different dolomites, however, retain their primary isotopic peculiarities and show δ<sup>13</sup>C differences exceeding 30‰. No external isotopically light carbon has been introduced during diagenesis, and therefore there is no evidence of soil-derived CO<sub>2</sub> which commonly shifts δ<sup>13</sup>C to more negative values. δ<sup>18</sup>O values show 2–6‰ fluctuations in distinct textural components from the same parental dolostones which were caused by syn-depositional/early diagenetic processes. Genetically different dolomites largely retain their syn-depositional/early diagenetic δ<sup>18</sup>O values ranging from 9‰ (mantle-influenced) to 30‰ (evaporation-induced). The high-grade greenschist facies metamorphism, marked by the reaction dolomite+quartz+H<sub>2</sub>O→tremolite+calcite<sub>2</sub>+CO<sub>2</sub>, significantly reset δ<sup>13</sup>C (by 3‰) in the metamorphic calcite<sub>2</sub> and δ<sup>18</sup>O (by 6‰) in all carbonate components. In such cases, the best proxy for depositional δ<sup>13</sup>C values of impure dolostones can only be provided by microcored samples of the dolomite phase.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Fallick, Professor Anthony |
| Authors: | Melezhik, V.A., and Fallick, A.E. |
| Subjects: | Q Science > QE Geology |
| College/School: | College of Science and Engineering > Scottish Universities Environmental Research Centre |
| Journal Name: | Chemical Geology |
| ISSN: | 0009-2541 |
University Staff: Request a correction | Enlighten Editors: Update this record
Deposit and Record Details
Deposit and Record Details