Chemistry and Environments of Dolomitization —A Reappraisal

Machel, Hans G.; Mountjoy, Eric W.

doi:10.1016/0012-8252(86)90017-6

Cited by 309 publications

(139 citation statements)

References 47 publications

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“…After 31 years of continued experiments, dolomite has never been found to form inorganically at 25°C (Land,1998). There is agreement that dolomite formation is rare under environmental conditions due to thermodynamic constraints (Machel and Mountjoy, 1986). However, some catalysts (Land, 1998) might allow for the easy low temperature laboratory synthesis of dolomite.…”

Section: Discussionmentioning

confidence: 99%

Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain

Alonso-Zarza

Martín-Pérez

2008

Sedimentary Geology

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Dolomite is a common mineral in the rock record but rare in recent superficial environments. Where it does occur, it is related to anoxic, sulfate-rich environments and microbial activity. The occurrence of some dolomite deposits in caves, however, indicates that dolomite formation is also possible in oxic, non-sulfate settings. Dolomite is forming at 17°C and in oxic-vadose conditions on the host rocks and aragonite speleothems of the Castañar Cave, Cáceres, Spain. It appears as spheroids and dumbbells 50-300 μm in diameter that internally consist of micron-sized rhombic to rounded crystals. Initially this dolomite is Carich, non-stoichiometric and poorly ordered. Mg-rich solutions allow the precipitation of metastable Mg-rich carbonates, such as huntite. This soon transforms into this Ca-rich dolomite, which later "ages" to form a more stoichiometric dolomite. These dolomites show similarities to those grown under anoxic, sulfate-rich conditions and their presence in caves provides a different setting that may contribute to the understanding of the "dolomite problem", including their initial formation and later recrystallization processes.

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Section: Discussionmentioning

confidence: 99%

Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain

Alonso-Zarza

Martín-Pérez

2008

Sedimentary Geology

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“…There is a statistically significant correlation between the percentage of dolomite and the δ 13 C of the bulk rock (r=0.64, n>500, p<<0.01), a correlation that can be accounted for as a result of the approximate 1 ‰ enrichment in the δ 13 C relative to co-genetic calcite (Sheppard and Schwarz, 1970). Under normal circumstances, diagenesis under the influence of meteoric fluids (Matthews and Allan, 1978;Allan and Matthews, 1982) results in the formation of carbonates with highly negative δ Strontium.-The concentration of Sr was analyzed in the dolomite separates in order to help constrain the nature of the fluids responsible for the dolomitization (Land, 1980;Machel and Mountjoy, 1986;Budd, 1997). Based on previous work (Vahrenkamp and Swart, 1990;Banner, 1995;Malone et al, 1996) it is known that stoichiometric dolomites, when formed from fluids with Sr/Ca ratios close to seawater, have a Sr concentration of approximately 100 ppm.…”

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confidence: 99%

Origin of Dolomite in the Arab-D Reservoir from the Ghawar Field, Saudi Arabia: Evidence from Petrographic and Geochemical Constraints

Swart

Cantrell

Westphal

et al. 2005

Journal of Sedimentary Research

108

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“…reduction of Fe increases pore water alkalinity (Machel & Mountjoy, 1986;Curtis, 1978). The microbial-produced carbon is suggested as the source for carbonate cements .…”

Section: +mentioning

confidence: 99%

“…However, oil within the Eocene reservoir shows no sign of biodegradation (Gratzer et al, 2011). Bacterial activity triggered alkaline conditions and carbonate precipitation especially at the OWC (Machel & Mountjoy, 1986;Watson et al, 1995). A Karpatian/ Badenian westward tilting and an uplift especially in the eastern part during late Miocene of the NAFB is evident (Gusterhuber, 2012), which may have induced a displacement of primary OWCs.…”

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confidence: 99%

Carbonate cementation in Upper Eocene clastic reservoir rocks from the North Alpine Foreland Basin (Austria)

Grundtner¹,

Groß²,

Gratzer³

et al. 2017

AJES

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A strong relationship between carbonate precipitation and microbial gas generation is evident for the Upper Eocene reservoir rocks of the North Alpine Foreland Basin. To achieve a better understanding of this relationship, 40 samples of limnic to shallow marine, gas-, oil-and water-bearing sandstones were studied to determine mineralogy and diagenetic history. The specific mineral parageneses were used to reconstruct changes in the hydrogeochemical conditions over time. Thus, authigenic mineral phases within reservoir rocks are an important archive for the reconstruction of pore fluid composition changes.The eogenetic pore space evolution of investigated Eocene sandstones is influenced by their primary mineralogy, which is strongly controlled by (i) depositional environment, (ii) detrital input and (iii) transport distances. Thus, a low compositional maturity is associated with high feldspar and high clay mineral content. Authigenic clay minerals, formed during several stages of diagenesis, play an important role for reservoir quality, due to pore space reduction.During eogenesis, authigenic micritic and sparitic carbonate phases are precipitated, which decreases the pore space. These eogenetic carbonate cements exhibit isotope values of about δ C: -5.9 to +2.2‰ and O: -8.3 to -4.3‰ [VPDB]. Some of these sam- 18ples indicate a trend towards lighter δ O values (-17.2‰), which is attributed to meteoric flush.Within the Eocene sandstones, two types of strongly cemented zones with low permeabilities can be differentiated: (i) extraordi- 13nary light δ C (-28.4‰) carbonates, which formed due to degradation of organic matter at the stage of advanced sulfate reduc- 13tion and (ii) heavy δ C (δ C: +8.7‰), which precipitated at the fermentation zone. Within the reservoir sandstones telogenesis is characterized by mineral destabilization (e.g. carbonate and feldspar corrosion) and kaolinite precipitation. The formation of authigenic kaolinite booklets resulted into a decrease in porosity.

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Chemistry and Environments of Dolomitization —A Reappraisal

Cited by 309 publications

References 47 publications

Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain

Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain

Origin of Dolomite in the Arab-D Reservoir from the Ghawar Field, Saudi Arabia: Evidence from Petrographic and Geochemical Constraints

Carbonate cementation in Upper Eocene clastic reservoir rocks from the North Alpine Foreland Basin (Austria)

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