Dolomitization of middle miocene buildups, Um Gheig area, Red Sea coast, Egypt

Shaaban, Mohamed N.; Holail, Hanafy; Rashed, Mohamed

doi:10.1007/bf03175422

Cited by 13 publications

(7 citation statements)

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“…Since the criticisms of the mid‐1980s, interpretations of mixing‐zone dolomitization have generally involved just recrystallization of an existing dolomite body (Coniglio et al. , 1988; Land, 1991; Shaaban et al. , 1997) or the generation of dolomite cements either in small amounts throughout an area (e.g.…”

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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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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“…5 (Qing and Mountjoy 1989) and the field ofArbuckle dolomite, Oklahoma is from (Gao et al 1995). Purser et al 1994;Sibley et al 1994;Shaaban et al 1997).…”

Section: Stable Isotopesmentioning

confidence: 99%

“…The origin of ancient massive and stratal dolomite has been regarded as equivocal and problematic (Land 1980;Banner et al 1988;Gao 1990;Sun 1994;Gao et al 1995;Shaaban et al 1997;Warren 2000;Haas and Demeny 2002). Initial dolomite deposits usually undergo a potential multiple episodes of diagenetic modifications (i.e.…”

Section: Introductionmentioning

confidence: 99%

Multiple dolomitization events of the Lower Carboniferous Um Bogma Formation, west central Sinai, Egypt

Shaaban

Holail

Sedeik

et al. 2005

Carbonates Evaporites

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The Lower Carboniferous Urn Bogma Formation in west-central Sinai , Egypt displays extensive and pervasive dolomitization. The combined petrographic/isotopic/stratigraphic investigations of the dolomite succession in the studied area reveal the presence of two distinct dolomite types: dolomite type (1) is confined to the basal part of the succession being associated with economic ferro-manganese deposits, and dolomite type (II) is located near the upper part of the succession. Silt, clay and marl beds vertically separate the two dolomitic units .The dominance of ooid and benthic fossil ghosts in the basal dolomite type (1) supports the suggestion that the CaCO J precursor has been formed under shallow agitated subtidal setting. The terrigenous beds that overlie this basal unit indicate that that the area has been brought into a meteoric realm during a subsequent lowstand period even before the emplacement of the upper part of the formation . During this period considerable stabilization of the initial metastable CaCO J phases into diagenetic low-Mg calcites has presumably took place.The persistent stratigraphic distribution of dolomite type (II) throughout the entire area and the typical marine 8 nC values (+ 1.1 and 2.9%0 POB) are consistent with platform-wide pumping system within a subtidal setting. Early stabilization of the initial CaCO J fabrics of the basal carbonate unit impeded their dolomitization during this stage. Subsequent shallow burial stabilization of dolomite type (II) is assessed from the well-developed stylolites, the non-planar crystal boundaries, the undulose extinction, the low porosity and the relatively depleted 8 180 (-5 .1 to -7%0 POB ) values. The initiation of dolomite type (I) was a post-burial process as indicated from the euhedral planar crystal boundaries, the high intercrystalline porosity and the absence of any compaction fabrics. The oxygen (3.3 to 4.7%0 POB) and carbon (+ 1.9 to 3.40/00 POB) isotopic values of this type of dolomite are possibly inherited from the CaCO J precursor where dolomitization took place from more or less unmodified marine water during period of minimum sea level fluctuations.

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“…In the NW Red Sea and Gulf of Suez area, dolomitization is considered one of the major and largest diagenetic processes that affected the Neogene carbonate platforms. This phenomenon was dealt with by some authors, most of them focusing on middle Miocene dolomitization of certain areas along the NW Red Sea and the Gulf of Suez (e.g., Aissaoui et al, 1986;Coniglio et al, 1988;Sun, 1992;Shaaban et al, 1997;Clegg et al, 1998). Other studies dealt with the problem in a general manner (e.g., Purser, 1998;El-Haddad, 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Purser (1998) believed in heated basinal sea waters for dolomitization, whereas El-Haddad (2004) believed in the mixing of meteoric water and sea water together with formation water in the rocks for the regional dolomitization of the middle Miocene carbonates in the Red Sea, which was extensively active during the evaporative sea level drawdown. On the other hand, Shaaban et al (1997), in their work at the Um Gheig area, suggested that the middle Miocene dolomitization took place within a zone of circulating marine pore fluids ahead of a mixing zone.…”

Section: Introductionmentioning

confidence: 99%

The impact of eustasy, tectonics, and paleoclimate on the dolomitization of the syn-rift Neogene carbonate platforms in the Red Sea coastal area, Egypt

Hassan¹

2017

Turkish J Earth Sci

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A very significant quantity of dolomites and dolomitic limestones of variable origins occurs in the syn-rift Neogene carbonate platforms of the NW Red Sea coast and the Gulf of Suez. These are more common in the Um Diheisi Member of the Ranga Formation (early Miocene), the Um Mahara Formation (middle Miocene), the Um Gheig Formation (late Miocene), and the Dashet El Dabaa Member of the Shagra Formation (Pliocene). Based on their stratigraphic distribution, petrography, and cathodoluminescent characteristics, as supported by geochemical data, syn-rift irregular morphotectonic relief, and the eustasy, four distinct types of dolomites have been identified and were interpreted as follows: 1) Syndepositional stratiform dolomicrite of the Um Diheisi Member occurred in structurally half graben restricted basins favoring structural sites of cyclic peritidal dolomitization that developed in response to sea transgression and then short-term sea level fall of each cycle period. 2) Regional replacive dolomite of the Um Mahara Formation involved mixing meteoric, marine, and hypersaline waters associated with the highstand sea level and then the repeated emergence of the platform and the temporal drowning with restricted marine waters. 3) Mixed syndepositional, replacive, and void-filling cement dolomites of the Um Gheig Formation, which suggest three dolomitization events:-i-an early, penecontemporaneous dolomite associated with highstand phases; ii-diagenetic dolomites formed by mixing meteoric and hypersaline reflux waters during lowstands and falling sea level, and iii-the latest dolomitization phase that occurred as dolomite cement involving hydrothermal fluids during the exposure periods. 4) Replacive dolomite of the Dashet El Dabaa Member, which involved mixtures of hypersaline and marine waters. Paleoclimate played an important role in the dolomitization of the Neogene sediments. An arid climate prevailed during the dolomite of the Um Diheisi Member and the early dolomitization phases of the Um Gheig Formation. A humid climate predominated in the replacive dolomite of the Um Mahara Formation, in which the meteoric groundwater allowed the dissolution of precursor limestones and subsequent formation of extensive bodies of dolomites. Arid conditions also prevailed during the dolomitization of the Dashet El Dabaa Member, as evidenced by the lack of dissolution and the abundance of well-preserved unstable feldspars.

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Dolomitization of middle miocene buildups, Um Gheig area, Red Sea coast, Egypt

Cited by 13 publications

References 31 publications

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

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

Multiple dolomitization events of the Lower Carboniferous Um Bogma Formation, west central Sinai, Egypt

The impact of eustasy, tectonics, and paleoclimate on the dolomitization of the syn-rift Neogene carbonate platforms in the Red Sea coastal area, Egypt

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