- Tytuł:
- The dolomite problem : evidence from 3D modeling, XRD and geochemical data of Zechstein reefs (Upper Permian, Germany)
- Autorzy:
- Blendinger, Wolfgang
- Powiązania:
- https://bibliotekanauki.pl/articles/2060255.pdf
- Data publikacji:
- 2020
- Wydawca:
- Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
- Tematy:
-
Zechstein
dolomite
limestone
isotopes
3D modeling
fluid flow - Opis:
- Three-dimensional modeling of the limestone and dolomite distribution in an Upper Permian (Zechstein) stromatolite-bryozoan reef, ~500 m in diameter and 35 m thick (77 borehole cores, 172 data points), shows that dolomite occurs as laterally and vertically discontinuous intervals. The prevailing mineral phases are near-stoichiometric dolomite and Mg-free calcite (370 XRD and 274 XRF analyses). Both δ13C and δ18O (526 analyses) show a spread of ~10‰ and co-vary with the mineralogy; the heaviest dolomite and calcite δ13C differ by ~1.5‰. Diagenetic modifications caused by flowing meteoric fluids could account for the observed “inverted J” trend of stable and the radiogenic signature of 87Sr/86Sr (23 analyses), but neither vertical nor horizontal gradients occur in the reef modeled. Because the dolomite geometries are incompatible with those predicted by fluid flow models, and the limestone-dolomite difference in δ13C overlaps estimates of isotope fractionation associated with Mg content, the dolomite studied was a depositional Very High Mg Calcite recrystallized to dolomite in a semi-closed diagenetic system rather than a Low Mg Calcite transformed by a dolomitization process. The isotope pattern suggests biogenic fractionation and/or loss of heavy stable C and O and light Sr isotopes during diagenesis.
- Źródło:
-
Geological Quarterly; 2020, 64, 3; 692--710
1641-7291 - Pojawia się w:
- Geological Quarterly
- Dostawca treści:
- Biblioteka Nauki
Artykuł