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Silica sources of Lower Carboniferous cherts from the Rhenohercynian basin from petrography and silicon isotopes

Cherts are robust geological archives, yet the multitude of factors controlling silicon isotope fractionation still limit interpretations of silicon isotope signatures (δ30Si). In this work, we compare petrographic features of cherts with bulk rock δ30Si and major element ratios to assess the paleo-environmental significance of δ30Sichert and to investigate the possible origins of silica of Lower Carboniferous cherts from the Rhenohercynian basin. For this investigation, we selected a section on a paleo-high position in the basin that was mostly shielded from the influence of detrital material. Variations in the abundance of radiolarian molds do not appear to influence the silicon isotope signatures of the bulk chert, indicating that the original δ30Si signature of radiolarians is overprinted. Instead, we observe decreasing δ30Si values with increasing Al/Si, suggesting an influence of interbedded layers of metabentonites on the δ30Si in chert. We tentatively suggest that the pure cherts attain a Si isotope signature that is set during equilibration of siliceous ooze with paleo-seawater.

Details

Author
Finja Groth1, Michael Tatzel1
Institutionen
1Geoscience Center, University of Göttingen, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/h1qd-gw26