Polyphase dolomitization of the Wuchiapingian Zechstein Limestone (Ca1) isolated reefs (Wolsztyn Palaeo-Ridge, Fore-Sudetic Monocline, SW Poland)

Authors

  • Marek Jasionowski Polish Geological Institute – National Research Institute, Rakowiecka 4, 00-975 Warszawa, Poland
  • Tadeusz Marek Peryt Polish Geological Institute – National Research Institute, Rakowiecka 4, 00-975 Warszawa, Poland
  • Tomasz Durakiewicz Mass Spectrometry Laboratory, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland; Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

DOI:

https://doi.org/10.7306/gq.1194

Keywords:

Zechstein Limestone, reefs, diagenesis, dolomitization, carbon and oxygen isotopes

Abstract

Dolomitisation was the main diagenetic process in the Upper Permian Zechstein Limestone of the Wolsztyn High-dolomite cementation (“over-dolomitisation”) also occurred. The rocks studied usually have a mixed mineralogy and represent a continuous spectrum from pure limestone to pure dolomite. This is due to varying degrees of dolomitisation, dolomite cementation and dedolomitisation. There are two main types of dolomite: replacement dolomite (mostly planar unimodal dolosparite mosaics that are mainly fabric-destructive) and cement dolomite (planar isopachous rims and pore-filling non-planar saddle-dolomite crystals). The timing of dolomitisation and dolomite cementation is difficult to ascertain, but comparing petrographical and geochemical data indicates that the reef carbonates were dolomitised shortly after deposition in a near-surface sabkha/seepage-reflux and then in burial systems. It seems that many of the dolomites gain their present isotopic composition when buried in relatively high-temperature conditions, as shown by low oxygen isotopic ratios ( δ18O as low as –9‰ PDB) and the presence of saddle dolomite. No isotopic support for a water-mixing mechanism is documented.

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Published

2014-09-30

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Section

Thematic issue