Mississippian Non-Supratidal Dolomite, Ste, Genevieve Limestone, Illinois Basin: Evidence for Mixed-Water Dolomitization

Choquette, Philip W.; Steinen, Randolph P.

doi:10.2110/pec.80.28.0163

Cited by 44 publications

(8 citation statements)

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“…Therefore, even if early meteoric cementation existed, the positive d 13 C values indicate that calcite growth during burial and/or telogenesis was important enough to control the final isotopic signal. The covariant trend of d 13 C and d 18 O observed in micrites of HPFs is typical of precipitation in mixed meteoric groundwaters and subsurface brines in a deep aquifer (Moshier 1989a;Choquette and Steinen 1980). However, oxygen-isotope compositions of micrites that range from -6.1% to -3.0% are higher than those of burial and telogenetic calcites (Fig.…”

Section: Origin Of Rounded Micritesmentioning

confidence: 89%

Origin of Micropores In Late Jurassic (Oxfordian) Micrites of the Eastern Paris Basin, France

Carpentier

Ferry

Lécuyer

et al. 2015

Journal of Sedimentary Research

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Porous micritic facies, either primary chalks or resulting from secondary destructive micritization, can constitute important hydrocarbon or water reservoirs. Characterization of reservoir properties and the understanding of factors which controlled the distribution of porosity are of primary interest to evaluate the prospective reserves. Middle and late Oxfordian limestones of the eastern Paris Basin show several horizons with porosities higher than 20%. The porosity is mainly microporous and located either within secondary micritized grains or in the micritic matrix. Using SEM, cathodoluminescence, as well as confocal microscopy, stable oxygen and carbon isotope ratios, and petrophysical measurements, a scenario for the evolution of the micropores is proposed. Lime mudstones to packstones constitute the majority of the high-porosity facies (HPFs). Inner lagoonal deposits are more micritized and thus more porous than grainstones, and facies rich in leiolitic oncoids and echinoid clasts are less impacted by micritization. Micritization was responsible for an increase of the intragranular porosity in most grain types. During both eogenesis and shallow burial, mineralogical stabilization dissolved aragonitic particles and allowed precipitation of calcite rhombs. This process was probably enhanced below surfaces of subaerial exposure. During burial, Ostwald ripening allowed the growth of larger micrite crystals at the expense of smaller ones during early Berriasian and late Aptian recharges of deep aquifers when the northern margin of the basin was exposed. Overgrowths on micrite crystals were more important in intervals strongly affected by chemical compaction, which favored oversaturation of waters with respect to calcite. In low-porosity horizons (LPFs), the dense micritic texture of oncoids and the monocrystalline architecture of echinoid clasts prevented an intense micritization, while the strong chemical compaction enhanced poronecrosis. Telogenetic fracturing created new fluid pathways that favored inputs of meteoric fluid in porous micrite and allowed the continuation of Ostwald ripening during Cenozoic times. As a whole, mesogenetic inputs of waters undersaturated with respect to calcite in deep aquifers during exposure of basin margins are a more efficient process than early subaerial exposure for enhancing aggrading neomorphism and appearance of microporous micrites. Initial mineralogical heterogeneities also impact the intensity of chemical compaction and thus the stratigraphical distribution of microporous limestones.

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Section: Origin Of Rounded Micritesmentioning

confidence: 89%

Origin of Micropores In Late Jurassic (Oxfordian) Micrites of the Eastern Paris Basin, France

Carpentier

Ferry

Lécuyer

et al. 2015

Journal of Sedimentary Research

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“…To avoid the possibility that sulphides present in the samples might react with the phosphoric acid to give hydrogen sulphide and carbon dioxide, evolving gasses were passed through silver phosphate, which removed hydrogen sulphide as silver sulphide. Because it proved impossible to separate dolomite stages physically, bulk crystals were analysed following Choquette and Steinan (1980), Gawthorpe (1987) and Wilson et al (1990). All P O and 613C data are reported in parts per thousand (%) relative to the Pee Dee Belemnite (PDB) standard.…”

Section: Methodsmentioning

confidence: 99%

The geometry and petrogenesis of hydrothermal dolomites at Navan, Ireland

Braithwaite

Rizzi²

1997

Sedimentology

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The dolomites at Navan, Ireland, formed in Courceyan peritidal and shallow‐shelf limestones. The dolomite body has a plume‐like geometry, cross‐cutting both lithological boundaries and diagenetic barriers generated by sea‐floor cementation and emergence. The dolomitizing fluids rose parallel to major faults to diffuse laterally through the succession, controlled by variations in permeability that reflect both facies variation on deposition and pre‐dolomitization diagenesis. Cathodoluminescent zones reveal three principal stages of dolomite emplacement, separated by dissolution surfaces, with each stage reflecting several changes in the character of dolomitizing solutions. The predominance of dull zones indicates burial rather than surface conditions. The dolomites formed some time after burial in response to an areally limited hydrothermally‐driven flow. Isotope values (σ18O of — 6σ6 to — 10.4%δ and σ13C of — 0σ2 to +2σ5%δ PDB), and fluid inclusion data, suggest that these fluids had compositions similar to those of Carboniferous seawater. However, these became hotter with time, with temperature increasing from 60 to 160δC. The Navan dolomites are closely associated with Europe's largest zinc‐lead deposit. The distribution of the ores follows the same trend as that of the dolomites and paragenetic relationships indicate that dolomitization and mineralization were temporally and genetically related.

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“…Land et al. , 1975; Choquette & Steinen, 1980; Dunham & Olson, 1980; Magaritz et al. , 1980; Churnet et al.…”

Section: Introductionmentioning

confidence: 99%

The role and impact of freshwater–seawater mixing zones in the maturation of regional dolomite bodies within the proto Floridan Aquifer, USA

Gaswirth¹,

Budd²,

Farmer³

2007

Sedimentology

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Palaeogene dolostones from the sub-surface of Florida are ideal for the study of dolomite maturation because they record the early stages of a secondary dolomite overprint without destruction by later diagenetic overprints. Two distinct dolomite textures occur in the dolostones of the Upper Eocene Ocala and Lower Oligocene Suwannee limestones in west-central Florida: a porous and permeable sucrosic dolomite and a less porous and relatively impermeable indurated non-sucrosic dolomite. In both textures, the initial matrix dolomite is dully luminescent, whereas the secondary overprint is dominantly luminescent cement in the Suwannee and only neomorphic luminescent dolomite in the Ocala. The abundance of luminescent dolomite ranges from 2% to 38%, which translates to 1AE6 km 3 of material in the Suwannee and 13AE5 km 3 in the Ocala. Extrapolated trace-element contents (Sr and Na) and d 18 O values for the matrix and luminescent end-members indicate a marine origin for the matrix dolomite in both units, and a freshwater-seawater mixingzone origin for the secondary luminescent dolomites. The d 18 O values indicate that a saline, middle mixing-zone environment overprinted the Suwannee but a more dilute mixing zone affected the Ocala. Fluid-fluid mixing models constrained by modern Floridan aquifer hydrochemistry and extrapolated 87 Sr/ 86 Sr values of the luminescent phases indicate that the mixing zones operated during the Late Miocene to Pliocene in the Ocala and affected the Suwannee in the Pliocene. The luminescent Suwannee mixing-zone cement reduced porosity up to threefold and permeability up to 100-fold, which converted many sucrosic dolomites to indurated dolomites. By contrast, the neomorphic luminescent Ocala dolomite did not have an appreciable impact on the maturations. Although freshwater-seawater mixing zones were not the sites of the initial dolomitization, the mixing-zone environment did dramatically overprint and mature the regionally widespread dolomites of the Ocala and Suwannee limestones. This maturation occurred shortly after formation of the proto-Floridan aquifer; the timing suggests the matrix dolomites were 'ripe' for alteration and that the only prerequisite for mixingzone dolomite is pre-existing dolomite substrates to reduce kinetic barriers. In contrast to recent claims, the results of this study demonstrate that mixing zones can be effective in forming regionally significant amounts of secondary dolomite and influencing the petrophysical maturation of dolomite bodies.

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Mississippian Non-Supratidal Dolomite, Ste, Genevieve Limestone, Illinois Basin: Evidence for Mixed-Water Dolomitization

Cited by 44 publications

References 0 publications

Origin of Micropores In Late Jurassic (Oxfordian) Micrites of the Eastern Paris Basin, France

Origin of Micropores In Late Jurassic (Oxfordian) Micrites of the Eastern Paris Basin, France

The geometry and petrogenesis of hydrothermal dolomites at Navan, Ireland

The role and impact of freshwater–seawater mixing zones in the maturation of regional dolomite bodies within the proto Floridan Aquifer, USA

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