Geochemical characteristics of dolomite: a case study from lower jurassic formations, imbricated zone, Iraqi Kurdistan region

Oct 5, 2024

Journal Springer

Publisher Springer Nature Link

DOI 10.1007/s13146-024-01012-w

Issue 99

Volume 39

The geochemical characteristics and origin of Lower Jurassic dolomites from the Sarki and Sehkaniyan formations in the Imbricated Zone of Northern Iraq were investigated through analysis of major, trace, and rare earth elements, as well as stable isotopes (carbon and oxygen). The consistent CaO and MgO contents, their positive correlation, and elevated Mg/Ca values suggest an early penecontemporaneous sedimentary origin for dolomitization. These dolomites exhibit low Fe, Mn, and Sr contents, along with moderately low Na levels. Furthermore, they display low total rare earth element (ΣREE) contents, indicating low formation temperatures and a lack of light rare earth element (LREE) enrichment, while relatively negative δ18O values dismiss the influence of hydrothermal fluids on dolomitization. The patterns of rare earth elements normalized to the Post-Archean Australian Shale (PAAS) standard reveal a depletion of LREE compared to heavy rare earth elements (HREE), along with distinct negative Ce and positive Eu anomalies in most dolomites. The δ13C and δ18O values of the dolomites exhibit lower values than the contemporaneous seawater of the Lower Jurassic, which suggest the role of organic matter degradation and influence of meteoric water, respectively. Based on the petrographic and geochemical characteristics, the dolomite of the Lower Jurassic formations was mainly formed in the near-surface penecontemporaneous stage with late diagenetic recrystallization especially for Sehkaniyan dolomite.

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