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https://doi.org/10.4154/GC.2014.05

Dinaride evaporite mélange: Diagenesis of the Kosovo polje evaporites

Anita Kulušić ; University of ZagrebFaculty of Mining Geology and Petroleum Engineering
Sibila Borojević Šostarić ; University of ZagrebFaculty of Mining Geology and Petroleum Engineering

Sažetak

Permian to Triassic age and floored by the various Adriatic carbonate platform units. The tectonic history of the Dinaridic evaporite mélange is related to long term burial and Palaeogene to Neogene exhumation processes. Evaporiterocks of the Kosovo polje deposits are associated with carbonates, clastic and minor albitized, subvolcanic, neutralto basic rocks. They are capped by a clayey Quaternary cover of variable thickness, and a several metres thick cavernouscarbonate breccia – rauhwacke. Evaporite rocks show two distinct facies: laminated evaporite-carbonate, composed of evaporite and dolomicrite (± organic matter, pyrite, halite) intercalations, and evaporite-carbonate breccia, composed of fragments of laminated evaporites, carbonate and siltite, cemented by massive gypsum ± sulfur, occurringat the shallower levels and related to the emplacement. The Quaternary cover is composed of 47-88% clayey material, comprising illite, kaolinite and most likely vermiculite, 9-49 % carbonate and 3-4% evaporite minerals. The thickness of the evaporite rehydration zone correlates negatively with the thickness of the overlying Quater nary cover and with the amount of clayey material within it. Rauhwacke are composed of partly dedolomitized dolostone and leachedgypsum fragments, cemented with late stage calcite. Diagenetic processes are related to early diagenesis and the burialphase began with the formation of diagenetic halite from an oversaturated subsurface or surface (lagoon) brine, and was followed by the biochemical reduction of evaporite sulphate to sulfide and formation of pyrite within organic-richcarbonate laminae. These processes triggered early dolomitization (in a shallow burial realm), and the formation of idiomorphic planar-e type of dolomite crystals at temperatures below 50-60°C. Planar dolomite suppressed diagenetichalite. With an increase in burial depth, gypsum dehydrates to anhydrite and when temperatures exceed ~50 °C, precipitation of fine grained non-planar –a type of dolomite began. Halite molds are partly replaced with non-planar-atype of dolomite. During regional uplift and exhumation, anhydrite rehydrated to gypsum under the influence of low-temperature undersaturated fluid (meteoric water), whereas hydrogen-sulfide oxi dized to elementary sulfur, observed as cement in the evaporite-carbonate breccia. Rauhwacke at the uppermost part of the deposit are formed by severe tectonic movements associated with the gypsum-driven dedolomitization process.

Ključne riječi

evaporite melange; burial; emplacement; diagenesis; Kosovo polje evaporites; Dinarides

Hrčak ID:

124275

URI

https://hrcak.srce.hr/124275

Datum izdavanja:

21.3.2014.

Posjeta: 1.459 *