Origin of dolomite in the Late Jurassic platform carbonates, Bolkar Mountains, Central Taurides, Turkey: Petrographic and geochemical evidence

Kırmacı, M. Ziya

doi:10.1016/j.chemer.2012.11.001

Cited by 16 publications

(8 citation statements)

References 51 publications

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“…Fine crystalline (RD1), medium (RD2, RD3) and coarse dense, interlocking (RD4 and RD5) dolomites, typical for the Qal'eh Dokhtar Formation, have been documented from other Jurassic locations worldwide (Reinhold, ; Wierzbicki et al ., ; Adabi, ; Kırmacı, ). Petrographic relationships between dolomite crystals and other diagenetic products in the dolostones of the Qal'eh Dokhtar Formation help to shed a light on the relative timing of dolomitization.…”

Section: Discussionmentioning

confidence: 99%

“…The negative shifts in oxygen isotopes suggested an isotopic fractionation resulting from an increasing temperature during burial condition (Al‐Aasm, ; Mansour and Abd‐Ellatif, ; Barbier et al ., ; Hips et al ., ). On the other hand, some petrographic features such as increasing crystal size in conjunction with increasing burial depth, the presence of irregular contacts between rims and core, inclusion‐rich dirty cores and inclusion‐free clear rims and some geochemical signatures such as depleted oxygen isotope values, and positive covariance between δ 18 O and δ 13 C indicate that replacive dolomites of the Qal'eh Dokhtar Formation were recrystallized by diagenetic solutions at elevated temperatures during subsequent burial (Al‐Aasm and Packard, ; Kırmacı and Akdağ, ; Kırmacı, , ). In comparison with dolomite that would be precipitated in equilibrium with late Jurassic seawater (Kırmacı, ), dolomites of the Qal'eh Dokhtar Formation have quite negative δ 18 O values and positive δ 13 C values.…”

Section: Discussionmentioning

confidence: 99%

“…The carbon isotope values of replacement dolomites in the Qal'eh Dokhtar Formation are between +1.1 and +3.2 ‰ VPDB (mean 2.2 ‰ VPDB). Dolomites precipitated from late Jurassic seawater should have isotopic values of about +1.2 and +2 ‰ VPDB (Kırmacı, ). Carbon isotope values of replacement dolomites in the Qal'eh Dokhtar Formation are comparable with estimated carbon isotope compositions of late Jurassic marine dolomites (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, replacement dolomites, particularly RD4 and RD5, are represented by Sr concentrations lower than those of dolomites precipitating from normal seawater. This finding coupled with depleted δ 18 O values reveals that replacement dolomites were recrystallized at elevated temperatures during the subsequent burial (Land, ; Kırmacı, ). The mean δ 18 O values of these replacement dolomites vary from −4.1 ‰ to −10.1 ‰.…”

Section: Discussionmentioning

confidence: 99%

“…13A and B). The initiation of stylolitization in limestone generally corresponds to a depth of about 500 m (Duggan et al, 2001;Kırmacı, 2008Kırmacı, , 2013. The depth of stylolitization in dolomites is expected to be somewhat higher since dolomites are more resistant to dissolution than limestone (Duggan et al, 2001).…”

Section: Petrography and Cathodoluminescence Characteristicsmentioning

confidence: 99%

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Multistage dolomitization in the Qal'eh Dokhtar Formation (Middle‐Upper Jurassic), Central Iran: petrographic and geochemical evidence

et al. 2016

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The late Jurassic Qal'eh Dokhtar Formation lithologically comprises three parts, from bottom to top, a lower sandstone unit, middle shale unit and an upper carbonate unit, which extend in a N–S direction over a wide area to the east of the Shotori Range and west of the Lut Block (Central Iran). This succession was deposited on a mixed carbonate–siliciclastic ramp. Carbonate rocks of the Qal'eh Dokhtar Formation vary from undolomitized, to partly dolomitized, to completely dolomitized. Field observations from two measured sections (the type section, 955 m thick, and the Sorond section, 639 m thick), combined with detailed petrographic and geochemical analyses, revealed the diverse types of dolomite in this formation. Five types of replacement dolomite and one type of dolomite cement were distinguished. Replacement dolomites (RD) consist of: (1) fine crystalline planar‐s (RD1); (2) medium crystalline planar‐s (RD2); (3) medium crystalline planar‐e (RD3); (4) coarse crystalline planar‐s (RD4); and (5) coarse crystalline planar‐e (RD5). Coarse crystalline planar dolomite cements (DC) were observed in low abundance and filling dissolution voids and fractures. Variation in dolomite types is mainly related to early to late diagenetic processes leading to changes in composition of the dolomitizing fluids. Replacement dolomites are non‐stoichiometric (Ca43‐56–Mg34‐45) with Sr, Mn and Fe concentrations of 41–138 ppm, 168–919 ppm and 5000–21000 ppm, respectively. These dolomites are characterized by δ18O values ranging from 0.0 to –11.8 ‰ VPDB and δ13C values of +1.1 to +3.2 ‰ VPDB. These values are depleted in δ18O relative to the postulated values for late Jurassic dolomites precipitated in equilibrium with seawater, while δ13C values are within the range of Jurassic seawater dolomite values. Fluid inclusion data of RD4, RD5 and DC yield homogenization temperatures of 72 to 118 °C. Based on petrographic, fluid inclusion microthermometric data and geochemical results, the replacement dolomites in the Qal'eh Dokhtar Formation are interpreted to have formed in the subsurface at shallow to intermediate burial depths. These dolomites were then recrystallized at increased burial depths and temperatures. Seawater was the major source of Mg2+ for early diagenetic dolomite (DR1), while Mg2+ for late diagenetic dolomites was provided from diagenesis of clay minerals in shales and mechanical compaction of mudstone in the Qal'eh Dokhtar Formation. The dolomite cement is postdated by coarsely crystalline mosaic calcite cement indicating that diagenetic fluids eventually became undersaturated with respect to dolomite and oversaturated with respect to calcite. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%