The effects of dolomitization on petrophysical properties and fracture distribution within rift-related carbonates (Hammam Faraun Fault Block, Suez Rift, Egypt)

Korneva, Irina; Bastesen, Eivind; Corlett, Hilary; Eker, Anja; Hirani, Jesal; Hollis, Cathy; Gawthorpe, Rob L.; Rotevatn, Atle; Taylor, Rochelle

doi:10.1016/j.jsg.2017.06.005

Cited by 26 publications

(27 citation statements)

References 32 publications

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“…Korneva et al . () describe the distribution of fractures within limestone and stratabound dolostone within the damage zone of, and at 2 km from, the HFF. During formation of the stratabound dolostone, fractures and faults would have been present at the tip of the HFF (Jackson et al ., ), but offset on the HFF was minimal and therefore the damage zone would have been narrow.…”

Section: Discussionmentioning

confidence: 99%

“…The data recorded for each scanline included fracture type, orientation, intensity (number of fractures per metre) and termination and has been detailed in Korneva et al . ().…”

Section: Methodsmentioning

confidence: 97%

“…Fracture density for all lithofacies shows a positive correlation with bed thickness, with the highest density (narrowest fracture spacing) noted in the slope packstones (S1). The matrix‐supported conglomerates (R1) have a fracture density that is only slightly lower than that in the packstones, while the lowest fracture density is noted within the turbidite grainstones (R2) (Korneva et al ., ).…”

Section: Field Observationsmentioning

confidence: 99%

“…The damage zone of the HFF is exposed in the footwall and comprises fabric-destructive, nonstratabound dolostone (massive bodies) that are pervasively dissected by non-stratabound calcite, dolomite, gypsum and iron oxide cemented fractures (Korneva et al, 2017). Hydrobrecciation was not observed, except within a 30 m wide fracture corridor that bounds the massive dolostone body.…”

Section: Geological Settingmentioning

confidence: 99%

“…Hydrobrecciation was not observed, except within a 30 m wide fracture corridor that bounds the massive dolostone body. Away from the damage zone, fracture spacing increases with bed thickness, with a higher fracture density (narrower spacing) in dolostone compared to limestone beds (Korneva et al, 2017).…”

Section: Geological Settingmentioning

confidence: 99%

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Controls on the formation of stratabound dolostone bodies, Hammam Faraun Fault block, Gulf of Suez

et al. 2018

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Dolomitization is commonly associated with crustal‐scale faults, but tectonic rejuvenation, diagenetic overprinting and a fluid and Mg mass‐imbalance often makes it difficult to determine the dolomitization mechanism. This study considers differential dolomitization of the Eocene Thebes Formation on the Hammam Faraun Fault block, Gulf of Suez, which has undergone a simple history of burial and exhumation as a result of rifting. Stratabound dolostone bodies occur selectively within remobilized sediments (debrites and turbidites) in the lower Thebes Formation and extend into the footwall of, and for up to 2 km away from, the Hammam Faraun Fault. They are offset by the north–south trending Gebel fault, which was active during the earliest phases of rifting, suggesting that dolomitization occurred between rift initiation (26 Ma) and rift climax (15 Ma). Geochemical data suggest that dolomitization occurred from evaporated (ca 1·43 concentration) seawater at less than ca 80°C. Geothermal convection is interpreted to have occurred as seawater was drawn down surface‐breaching faults into the Nubian sandstone aquifer, convected and discharged into the lower Thebes Formation via the Hammam Faraun Fault. Assuming a ca 10 Myr window for dolomitization, a horizontal velocity of ca 0·7 m year−1 into the Thebes Formation is calculated, with fluid flux and reactivity likely to have been facilitated by fracturing. Although fluids were at least marginally hydrothermal, stratabound dolostone bodies do not contain saddle dolomite and there is no evidence of hydrobrecciation. This highlights how misleading dolostone textures can be as a proxy for the genesis and spatial distribution of such bodies in the subsurface. Overall, this study provides an excellent example of how fluid flux may occur during the earliest phases of rifting, and the importance of crustal‐scale faults on fluid flow from the onset of their growth. Furthermore, this article presents a mechanism for dolomitization from seawater that has none of the inherent mass balance problems of classical, conceptual models of hydrothermal dolomitization.

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Section: Discussionmentioning

confidence: 99%

“…The data recorded for each scanline included fracture type, orientation, intensity (number of fractures per metre) and termination and has been detailed in Korneva et al . ().…”

Section: Methodsmentioning

confidence: 97%

Section: Field Observationsmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

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Controls on the formation of stratabound dolostone bodies, Hammam Faraun Fault block, Gulf of Suez

et al. 2018

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Mechanisms controlling the localisation of fault‐controlled hydrothermal dolomitisation, Derbyshire Platform, UK

Breislin

Banks

Crowley

et al. 2022

The Depositional Record

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The Derbyshire Platform is a Mississippian aged flat-topped, steep sided platform that forms the westernmost expression of the Derbyshire-East Midlands Platform. On the south-east platform margin, 60 km 2 of Visean limestone has been dolomitised, forming two distinct bodies. One of these bodies forms along a major NW-SE trending basement fault and smaller, associated, N-S trending faults and fractures. This study uses outcrop, petrographic and geochemical analysis to better constrain the timing and mechanism for this fault-controlled dolomitisation. Field relationships demonstrate dolomitisation was multi-phase and initiated after the main phase of matrix pore-occluding calcite cementation on the Derbyshire Platform and terminated prior to the main phase of mineralisation. Fluids are interpreted to have fluxed from adjacent basins, primarily along strike-slip crustal faults that were reactivated during basin inversion at the onset of the Variscan Orogeny. Fluid supply was episodic and progressively confined to fractures as matrix porosity became occluded. The study demonstrates the complex interplay between basin kinematics, host rock permeability and timing of fluid supply through seismic valving along faults that connect the carbonate platform to basin compartments. This ultimately controlled the position of dolomite geobodies along faults and provides a record of fluid flow during the transition from thermal subsidence to post-rift basin inversion. The findings have implications for the exploration of both minerals and hydrocarbon within dolomitised host rocks and can inform studies of fluid transfer and reaction on carbonate platforms within the burial realm.

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Macroscopic Heterogeneity

Tavakoli¹

2019

Carbonate Reservoir Heterogeneity

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The effects of dolomitization on petrophysical properties and fracture distribution within rift-related carbonates (Hammam Faraun Fault Block, Suez Rift, Egypt)

Cited by 26 publications

References 32 publications

Controls on the formation of stratabound dolostone bodies, Hammam Faraun Fault block, Gulf of Suez

Controls on the formation of stratabound dolostone bodies, Hammam Faraun Fault block, Gulf of Suez

Mechanisms controlling the localisation of fault‐controlled hydrothermal dolomitisation, Derbyshire Platform, UK

Macroscopic Heterogeneity

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