Hydrothermal dolomite—a product of poor definition and imagination

Machel, Hans G.; Lonnee, Jeff

doi:10.1016/s0037-0738(02)00259-2

Cited by 217 publications

(132 citation statements)

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“…at least 5 to 10ºC warmer than the surrounding rocks (Machel and Lonnee, 2002), based on 1) the high trapping temperatures (average of 220ºC +/-20ºC) derived from fluid inclusions (after applying a minimum pressure correction for 4 km depth, Zhang and Frantz, 1987) and 2) the fact that the rocks underwent deep high temperature diagenesis, also referred to as deep anchizone metamorphism with temperature not exceeding 200ºC during deepest burial in Early Campanian (Breton et al, 2004).…”

Section: Conceptual Model For the Genesis Of Fault-related Dolomite Gmentioning

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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Section: Conceptual Model For the Genesis Of Fault-related Dolomite Gmentioning

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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“…Hydrothermal dolomite (HTD) forms when dolomitization occurs from fluids that are significantly hotter than the ambient rock (Machel and Lonnee, 2002). HTD has become common parlance for dolomite formed proximal to faults, with a non-stratabound core and stratabound margin, commonly localized around normal and strike-slip faults, with little consensus on the source of fluid or Mg 2+ or the process for dolomitization (Davies and Smith, 2006).…”

Section: Introduction and Geological Settingmentioning

confidence: 99%

Fault-controlled dolomitization in a rift basin

Hollis¹,

Bastesen²,

Boyce³

et al. 2017

Geology

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There are numerous examples of fault-controlled, so-called hydrothermal dolomite (HTD), many of which host economic mineral deposits or hydrocarbons, but there remains a lack of consensus as to how they form. In particular, multiple phases of diagenetic overprinting can obscure geochemical fingerprints. Study of a Cenozoic succession with a relatively simple burial history here provides new insights into the development of differentially dolomitized beds. The Hammam Faraun fault (HFF) block within the Suez Rift, Egypt, hosts both massive and stratabound dolostone bodies. Non-fabric-selective massive dolostone is limited to the damage zone of the fault, while fabric-selective stratabound dolostone bodies penetrate nearly 2 km into the footwall. Oligo-Miocene seawater is interpreted to have been drawn down discrete faults into a deep aquifer and convected upwards along the HFF. Escape of fluids from the incipient HFF into the lower Thebes Formation led to differential, stratabound dolomitization. Once the HFF breached the surface, fluid circulation focused along the fault plane to form younger, massive dolostone bodies. This study provides a snapshot of dolomitization during the earliest phases of extension, unobscured by subsequent recrystallization and geochemical modification. Contrary to many models, stratabound dolomitization preceded non-stratabound dolomitization. Fluids were hydrothermal, but with little evidence for rapid cooling and brecciation common to many HTD bodies. These results suggest that many of the features used to interpret and predict the geometry of HTD in the subsurface form during later phases of structural deformation, perhaps overprinting less structurally complex dolomite bodies.

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“…• C) relative to the host limestone (Machel and Lonnee, 2002), and are usually structurally controlled. HTD bodies can have a patchy and localised distribution around sub-seismic scale faults (Machel, 2004;Wilson et al, 2007;Lopez-Horgue et al, 2010), but can also occur as stratabound bodies extending laterally for several tens of kilometres away from the faults proposed to have sourced the hydrothermal fluids (Davies and Smith, 2006;Corbella et al, 2014;Dewit et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Reactive transport modelling of hydrothermal dolomitisation using the CSMP++GEM coupled code: Effects of temperature and geological heterogeneity

et al. 2017

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University of Bristol -Explore Bristol Research General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Reactive transport modelling of hydrothermal dolomitisation using the CSMP++GEM coupled code:Effects of temperature and geological heterogeneity AbstractReactive transport simulations using our CSMP++GEM coupled code were applied to study the major controls on replacement dolomitisation and the development of dolomite geobodies in a hydrothermal setting. A series of 2D simulations show how elevated temperature and reactive surface area increase the rate of dolomitisation, and result in a dolomite replacement front that is both sharper and inclined at a higher angle from vertical. This inclination, an effect of gravity segregation, is apparent in thick homogeneous units, but in layered systems the lithological contrast determines the shape of the dolomite front. The increase in permeability resulting from porosity generation upon replacement of calcite by dolomite has a major effect on accelerating the overall progress of dolomitisation. In contrast, the changes in fluid density due to chemical reactions and the pressure dependence of thermodynamic data have a minor influence under simulated conditions. Primary dolomite forms slowly after complete replacement of host calcite, leading to porosity decrease, and is only locally important around the source of the hydrothermal fluid.For a simple layered system, our model results are in excellent agreement * Corresponding author. Present address: ETH Zurich, Institute of Geochemistry and Petrology. E-mail address: alina.yapparova@gmail.comPreprint submitted to Chemical Geology July 6, 2017with those obtained using TOUGHREACT code. They do, however, show the advantage of unstructured triangular over structured rectangular meshes for resolving complex curved/inclined front shapes. Such meshes also offer benefits in simulating fault-controlled hydrothermal dolomitisation. Our simulations predict dolomite geobodies comparable in scale and morphology to natural examples documented at outcrops, and underline the importance of understanding the permeability structure within and around the fault zone.

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Hydrothermal dolomite—a product of poor definition and imagination

Cited by 217 publications

References 9 publications

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

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

Fault-controlled dolomitization in a rift basin

Reactive transport modelling of hydrothermal dolomitisation using the CSMP++GEM coupled code: Effects of temperature and geological heterogeneity

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