Dolomite: occurrence, evolution and economically important associations

Warren, John K.

doi:10.1016/s0012-8252(00)00022-2

Cited by 1,157 publications

(868 citation statements)

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“…(70 mme1 mm), compared with D1 (dolomicrite), suggest a later stage of replacive dolomitization that likely started with increased temperature and pressure (Warren, 2000). The cloudy core with clear rims of D2 crystals indicate replacement of a precursor carbonate (cloudy core) and cementation (clear rim) whereas zoned CL images reflect chemical variations within the crystal (Warren, 2000).…”

Section: Fluid-inclusion Gas Analysismentioning

confidence: 98%

“…The cloudy core with clear rims of D2 crystals indicate replacement of a precursor carbonate (cloudy core) and cementation (clear rim) whereas zoned CL images reflect chemical variations within the crystal (Warren, 2000). Undulose extinction in dolomites is caused by distorted crystal lattice that results from crystal growth at high temperatures (e.g., Warren, 2000;Rameil, 2008;Kırmacı, 2008). This is consistent with the mean Th (126.6 ± 12.8 o C, n ¼ 97) value of D2 and suggests crystallization at higher temperatures and deeper burial conditions relative to D1.…”

Section: Fluid-inclusion Gas Analysismentioning

confidence: 99%

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Origin of Lower Ordovician dolomites in eastern Laurentia: Controls on porosity and implications from geochemistry

Azomani

Azmy

Blamey

et al. 2013

Marine and Petroleum Geology

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a b s t r a c tThe Catoche Formation of the St. George Group in eastern Laurentia (western Newfoundland) consists of early Ordovician (Arenigian) shallow marine platform carbonates (w160 m thick), which were extensively dolomitized during the course of their diagenetic history. The dolomites occur as both replacement and pore-filling cements and are a major control on porosity distribution in the formation. The origin and diagenetic history of the Catoche dolomites at Daniel's Harbour (western Newfoundland) were analysed in comparison to equivalent successions at Port au Choix (PaC) and Port au Port Peninsula (PaP) to assay the reservoir potential of these dolomites in eastern Laurentia. Petrographic examination identified at least three generations of dolomites in the Catoche Formation, which are: (1) an early replacement sub-to eu-hedral micritic dolomite (<4 mme30 mm, D1), (2) eu-to sub-hedral dolomite (70 mme1 mm) often with cloudy cores and clear rims (D2), and (3) subhedral to anhedral saddle dolomite cement (200 mme3 mm, D3). The micritic dolomite (D1) exhibits a dull cathodoluminescence (CL) under cathodoluminoscope, whereas dolomite D2 exhibits consistent concentric CL zonation. Some subhedral crystals of D3 appear zoned both in plane polarized light and cathodoluminoscope, otherwise D3 exhibits a dull CL. Stoichiometric dolomite occurs in all three generations with D2 as the dominant dolomite by abundance.The low strontium (47 ± 25 ppm) content coupled with depleted d 18 O value of dolomitizing fluids (-10 to -11.2& VSMOW) and near-micritic grain size, suggests an early precipitation of dolomite D1 at low temperatures of near-surface conditions from solutions likely formed by mixing of early Ordovician sea and meteoric waters. In contrast, microthermometric measurements of primary two-phase fluid inclusions in dolomite D2 (homogenization temperatures of 102e168 o C with a salinity range of 19.8e25 eq wt% NaCl) and dolomite D3 (homogenization temperatures of 158e190 o C with a salinity range of 20.2e22.2 eq wt% NaCl), suggest that both dolomite generations were generated in mid to deep burial settings from high salinity, low temperature (<200 o C) hydrothermal fluids likely under suboxic conditions. This is consistent with the low Sr concentrations for D2 (36.4 ± 8 ppm) and D3 (38.7 ± 9 ppm), d 18 O values of dolomitizing fluids for D2 (þ2.1 to þ8.1&, VSMOW) and D3 (þ6 to þ8.1& VSMOW), coupled with Fe contents of D2 (1684 ± 1096 ppm) and D3 (1783.7 ± 618 ppm) as well as the respective Mn (D2 ¼ 131.2 ± 50 and D3 ¼ 197.5 ± 55 ppm) concentrations.SREE and shale normalized (REESN) values of Catoche carbonates indicate enrichment in rare earth element (REE) composition of the earliest calcite (C1) relative to those of Arenig seawater, whereas the REESN profiles of the dolomite generations mimic that of calcite C1. The Ce (Ce/Ce*)SN and La (La/La* ¼ Pr/Pr*)SN anomalies of the Catoche dolomites are consistent with precipitation in equilibrium with source fluids in slightly oxic to suboxic conditions whereas Eu...

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Section: Fluid-inclusion Gas Analysismentioning

confidence: 98%

Section: Fluid-inclusion Gas Analysismentioning

confidence: 99%

Origin of Lower Ordovician dolomites in eastern Laurentia: Controls on porosity and implications from geochemistry

Azomani

Azmy

Blamey

et al. 2013

Marine and Petroleum Geology

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“…The fine-crystalline D1 is petrographically and geochemically different to the fault- (Warren, 2000). In addition, the dolomitizing fluids must have obtained Fe and Mn from a non-carbonate source, i.e.…”

Section: Stratabound Dolomitementioning

confidence: 99%

Linking process, dimension, texture, and geochemistry in dolomite geobodies: A case study from Wadi Mistal (northern Oman)

Vandeginste¹,

John²,

Flierdt³

et al. 2013

Bulletin

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Understanding the distribution and geometry of reservoir geobodies is crucial for netto-gross estimates and to model subsurface flow. This paper focuses on the process of dolomitization and resulting geometry of diagenetic geobodies in an outcrop of Jurassic host rocks from northern Oman. Field and petrographic data show that a first phase of stratabound dolomite is crosscut by a second phase of fault-related dolomite. The stratabound dolomite geobodies are laterally continuous for at least several hundreds of meters (~1000 ft) and probably regionally and are half a meter (1.6 ft) thick. Based on petrography and geochemistry, a process of seepage reflux of mesosaline or hypersaline fluids during the early stages of burial diagenesis is proposed for the formation of the stratabound dolomite. In contrast, the fault-related dolomite geobodies are trending along a fault that can be followed for at least 100 Running head:Linking process, dimension, texture and geochemistry in dolomite geobodies

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“…and Pitman. 1 998 ) and it is considered as a useful geothermometer, indicating minimum burial temperatures of 60 to 150 cC (Warren, 2000). Thus, the very similar petrographic and geochemical data of dolomite in the three studied sections, along with the combined occurrence of saddle dolomite in the Henarejos section and the lower 5 18 0 values of dolomite in this site compared to those obtained at Landete and Talayuelas, reinforce the hypothesis that dolomite in the three sections precipitated from similar fluids but at different temperatures.…”

Section: Dolomitementioning

confidence: 99%

“…Moller, 1989;Pohl, 1990;Warren, 2000;Deelman, 2008 and references therein). Specifically, dolomite and magnesite precipitation in siliciclas tic continental deposits have been previously described in other Permian and Triassic basins as relatively early diagenetic phases (e.g.…”

Section: Introductionmentioning

confidence: 99%

Shallow burial dolomitisation of Middle–Upper Permian paleosols in an extensional tectonic context (SE Iberian Basin, Spain): Controls on temperature of precipitation and source of fluids

Benito¹,

Horra²,

López-Gómez³

et al. 2011

Sedimentary Geology

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This work is forused on carbonate paleosols developed in three stratigraphic sections (Landete, Talayuelas and Henarejos) of the Middle-Late Permian Alcotas Formation in the SE Iberian Basin. The A1cotas Fonnation, of alluvial origin, was deposited in semi-connected half-grabens developed during the early stages of the Pennian-Triassic rifting stage that affected the Iberian Basin. The studied sections were located in two of these half-grabens, the Henarejos section being much closer to the basin boundary fault than the other two sections. The mineralogy and texture of the carbonate precursor of paleosols in the three studied sections are not preserved because original carbonate is replaced by coarse crystals of dolomite and/or magnesite. Dolomite crystals are typically euhedral, displaying rhombohedral shapes and reddish luminescence, although in the Henarejos section dolomite displays non-planar boundaries and frequently saddle habit. Micas are defonned and adapted to dolomite aystals, which, in turn, are affected by stylolites, suggesting that dolomite precipitated before mechanical and chemical compaction. Magnesite crystals are af f ected mean values are -6.5 and -6.0%0 and the &180VPDB mean values are -6.7 and -7.8%0, in the Landete and Talayuelas sections, respectively. The 87Srf�r ratios of magnesite are similar in both sections yielding values between 0.71258 and 0.72508. This suggests that they probably precipitated from similar fluids during progressive burial and at higher temperatures than dolomites at the same sections. Assuming that magnesite precipitated from a fluid with similar &180 values in both sections, then it had to precipitate at a temperature around 8 QC higher in Talayuelas than in the Landete section. Dolomitisation and magnesite predpitation probably occurred via reflux of saline to hypersaline brines from the overlying Mid-Late Triassic Muschelkalk and/or Keuper facies. The temperatures inferred for dolomite predpitation, however, are too high for shallow burial if a normal geothermal gradient is applied. Thus, it can be inferred that saline fluids were heated as they flowed through the syn-sedimentary extensional faults that controlled Middle Pennian to Middle Triassic sedimentation; consequently fluids would have been at higher temperatures near the Henarejos area, which was closer to the basin boundary fault than at the Talayuelas and Landete areas, which were situated further away. This contention is in agreement with recent studies which demonstrate that an important thennal event took place during Late Triassic-Early Jurassic times in the Iberian Peninsula.

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Dolomite: occurrence, evolution and economically important associations

Cited by 1,157 publications

References 140 publications

Origin of Lower Ordovician dolomites in eastern Laurentia: Controls on porosity and implications from geochemistry

Origin of Lower Ordovician dolomites in eastern Laurentia: Controls on porosity and implications from geochemistry

Linking process, dimension, texture, and geochemistry in dolomite geobodies: A case study from Wadi Mistal (northern Oman)

Shallow burial dolomitisation of Middle–Upper Permian paleosols in an extensional tectonic context (SE Iberian Basin, Spain): Controls on temperature of precipitation and source of fluids

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