Kolosjoki Sedimentary Formation: A record in the aftermath of the Paleoproterozoic global positive delta 13C excursion in sedimentary carbonates

The Kolosjoki Sedimentary Formation of the Pechenga Greenstone Belt, north eastern Fennoscandia, records the aftermath of the Paleoproterozoic global positive delta 13C excursion in sedimentary carbonates (the Lomagundi-Jatuli isotope excursion). The goals of this research were to provide detailed n...

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Bibliographic Details
Published in:Chemical geology 2013-12, Vol.362, p.165-180
Main Authors: Salminen, Paula E, Karhu, Juha A, Melezhik, Victor A
Format: Article
Language:English
Subjects:
Belts
Carbonates
Formations
Isotopes
Limestone
Magnesium
Rocks
Trends
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Summary:The Kolosjoki Sedimentary Formation of the Pechenga Greenstone Belt, north eastern Fennoscandia, records the aftermath of the Paleoproterozoic global positive delta 13C excursion in sedimentary carbonates (the Lomagundi-Jatuli isotope excursion). The goals of this research were to provide detailed new data on the delta 13C trend in the Kolosjoki Sedimentary Formation and generate a secular delta 13C curve for the time period immediately succeeding the Lomagundi-Jatuli isotope excursion. For these purposes, sedimentary carbonate samples from two new drillcores representing the Kolosjoki Sedimentary Formation were collected. In total 88 whole-rock samples and 67 micro-drilled subsamples (ca. 1-3mg) were analyzed for the isotope composition of C and O, the whole-rock elemental abundances, and for the composition of the acid-soluble fraction. The Kolosjoki carbonate rocks are dolostone or calcitic dolostone (Mg/Ca=0.50-0.67) with minor limestone (Mg/Ca=0.04-0.06). Only weak correlation was observed between the Mn/Sr ratios and the delta 13C and delta 18O values, and the carbonate samples have likely retained their near-primary delta 13C values. The sedimentary carbonate rocks show first low delta 13C values at -2 to -1ppt and then a subtle, upward increasing delta 13C trend from ca. 1 to 3ppt. The increasing delta 13C trend is interpreted to record a recovery from a delta 13C minimum following the Lomagundi-Jatuli isotope excursion.
ISSN:0009-2541
DOI:10.1016/j.chemgeo.2013.10.018