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Introduction
Published in Sukumar Laik, Offshore Petroleum Drilling and Production, 2018
Diapiric trap – Diapiric movement within rocks is mainly controlled by the buoyant forces owing to density differences of the different rock layers. A less dense rock layer has more buoyancy force underlain within the high density bearing rock layers. Thus, less dense rocks move upward vertically and form a diaper. These sorts of traps are genetically different from true structural traps as no tectonic force is acting here. However, structure associated with this trap may be similar to the structure as originated by tectonic movement. Associated structures generated with diapiric traps are domal trap, field trap, fault trap, pinchout trap and truncation trap. All these structures are described in a salt diaper. A diapiric trap may be of either salt diaper or mud diaper.
Igneous activity and landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Magma intruded into the earth’s crust or extruded upon its surface appears to have been mobilized at relatively shallow depths. For example, basalt which erupts at the surface at a temperature of 1200°C probably became molten at a depth of less than 100 km – at a depth of 500 km the confining pressure of 150,000 bar (1 bar ≏ surface atmospheric pressure) would impose a pressure melting point in excess of 2000°C on this rock. Under atmospheric pressure solidification of lava occurs between 600°C and 900°C, depending on the chemical composition and gas content. The melting of magma within the earth is the result of a complex interaction of increases of temperature, decreases of pressure and addition of water. Volcanic heat contributes only about one-hundredth of the total terrestrial heat loss but it is very localized along belts of rising convective currents or at the more than 120 hot spots associated with the rising ‘plumes’ which will be described later. As was suggested earlier, the convecting layer probably occurs at depths of less than 700 km and contains a hierarchy of different convection cell sizes. About half of the heat in the convecting layer is generated within the layer itself and half comes from the mantle below, the latter source explaining why localized volcanic activity can continue at a given location despite the movement of a lithospheric plate over it. Magma rises within the earth as coherent through-piercing blobs or diapirs (Greek: diapeiro - ‘pierce through’), or as columns of partly molten rock by a complex set of processes including the ‘elbowing aside’ of superincumbent rocks by mechanisms of slow creep and their partial ‘digestion’ (anatexis). At shallow depths a combination of diapir pressure, thermal expansion and gas pressure (partly from groundwater turned to steam) may lead to surface eruptions.
Geological Structures
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
The term diapir (= through-piercing) is used for structures produced by materials such as rock-salt or mobile granite which have moved upwards and pierced through the overlying strata. Material ascends as a diapir when it is weak enough to flow and less dense than the overlaying strata.
Formation of Cu–Au porphyry deposits: hydraulic quartz veins, magmatic processes and constraints from chlorine
Published in Australian Journal of Earth Sciences, 2023
G. N. Phillips, J. R. Vearncombe, J. D. Clemens, A. Day, A. F. M. Kisters, B. P. Von der Heyden
In the broader igneous literature, thick batholiths dominated by silicate melt are not favoured (Lundstrom & Glazner, 2016). Instead, for felsic intrusions, small pipes or dykes are modelled as feeding relatively thin sheets of granitic rocks (Clemens & Mawer, 1992). The perception of enormous volumes of granitic magma forming batholiths is, to some extent, a legacy of the view that granitic magmas rise through the crust as huge, buoyant magma globules (diapirs). In reviews of this subject, Clemens and Mawer (1992) and Petford et al. (2000) have shown that neither small nor large diapirs can effectively transport magmas through the crust. Magmas generally fracture their own channels upward, forming dykes. Recently, Phillips et al. (2022) demonstrated that at least one large pluton, the Strathbogie batholith, of approximately 2000 km2, is remarkably thin, with an aspect ratio (width to thickness) of the order of several hundred. A similar conclusion has been drawn from the even larger Donkerhuk batholith of southern Africa (Hall & Kisters, 2016). If this pizza shape is a common feature, then we would have no good reason to hypothesise the existence of the sorts of voluminous batholithic parent bodies to porphyry systems, as required by the igneous fractionation model for the concentration of metals in residual magmas and magmatic hydrothermal fluids.
Characteristics of features formed by gas hydrate and free gas in the continental slope and abyssal plain of the Middle Caspian Sea
Published in Marine Georesources & Geotechnology, 2021
H. Gerivani, V.A. Putans, L.R. Merklin, M.H. Modarres
Due to many similarities between the mud diapirs and gas chimneys, it is difficult to distinguish them from each other on seismic profile 4 as experienced in previous studies around the world. Zhang et al. (2018) discussed that the appearance, shape, and size of these features (diapirs and chimneys) are similar and vary widely. Moreover, both of these features are characterized by vertical columnar fuzzy or chaotic zones on seismic sections. The mud diapir is a geologic body mainly formed by upward intrusion of muddy sediments usually accompanied by the natural gas and water. The activity of mud diapir is under high temperature and overpressure driving forces and causes disturbances in sediments as the attitude of original geological structure of sediments are really changed (Lüdmann and Wong 2003; Liu, Lu, and Zhang 2015). In addition, the top of mud diapir generally shows mounded anticline appearance formed by upward force of diapir movement. Gas chimneys appear because of upward migration of gas originating from deeper formations (Heggland 1997; Løseth, Gading, and Wensaas 2009). Unlike to mud diapirs, the original geological structure and the attitude of stratum are not deformed in gas chimneys. Here, on profile 4, upward force curved sedimentary beds without changing their general geological texture inside the Chimney/Diapir features. Hence, it seems that these features should be categorized as chimneys made by high-pressure gas-rich fluids as the fluids curved the beds upward in some places.