On the penetration of a hot diapir through a strongly temperature-dependent viscosity medium

Daly, Steven; Raefsky, A.

doi:10.1111/j.1365-246x.1985.tb04331.x

Cited by 44 publications

(35 citation statements)

References 16 publications

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“…According to GROUT'S (1932) suggestion (see also SCHMELLING et al, 1988 andCRUDER, 1990), rock flow around the diapirs should occur within a narrow zone in response to warming by the magma and could permit their rise. This problem, which has come to be known as the hot Stoke's model (MARSH, 1982) has been approached in the PaSt using analytic, numerical and experimental methods (MARSH, 1982;MORRIS, 1982;RIBE, 1983;AINSARI & MOR-RIS, 1985;DALY & RAEFSKY, 1985;MAHON et al, 1988). They yield remarkably consistent results.…”

Section: Ascentmentioning

confidence: 89%

Kinematics of large syn-orogenic intrusions: example of the Lower Proterozoic Saraya batholith (Eastern Senegal)

1992

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ZusammenfassungDer groge Saraya Batholith intrudierte in die unterproterozoischen Schichten des 6stlichen Senegals. Die Geftigeanalyse zeigt, dag dieger groge, granitische Batholith einem zusammengesetzten K6rper entspricht, der aug mehreren zusammengewachsenen Plutonen mit zwischengeschalteten Diapiren besteht. Die Interpretation des strukturellen Geftigemusters in diesen Plutonen und in den umgebenden Gesteinen liefert die Basis ftir ein hypothetisches Modell ftir den Beginn, den Aufstieg und die Platznahme des Plutons wie folgt: 1. Entwicklung eines tiefen N-S orientierten Rtickens in Abhfingigkeit von einer wichtigen Krustenfraktur, welche aug einer frtiheren Dehnungsphase durch eine Horizontalverschiebung reaktiviert wurde. Diese hat wahrscheinlich die Absonderung, Ansammlung und den Aufstieg des Magmas erleichtert. 2. Die Intrusion und das Aufsplittern des Rtickens in einige Diapire, erm6glichte dag simultane und separate Aufsteigen, in einer Anordnung von N-S gerichteten sinistralen Transversalverschiebungen, die eine NW-SE Verengung und eine verstfirkte Platznahme der Plutone initiierte. 3. Die endgtiltige Platznahme wird charakterisiert durch dag Wechselspiel zwischen regionaler Deformation und plutonischer ,,Aufblfihung~<. Letztere ftihrte zu einem Zusammenwachsen der Intursionen, und zur Bildung eines gr6geren, scheinbar homogenen K6rpers. Dieses Modell kann erweitert werden auf die anderen gr6geren Birimian Batholithe des Unteten Proterozoikums im 6stlichen Senegal. AbstractThe large Saraya batholith intruded the Lower Proterozoic sequences of Eastern Senegal. Structural analysis indicates that this large granitic batholith corresponds to a composite body consisting of several coalescent plutons and interfering diapirs. Interpretation of the structural fabric patterns in these plutons and in the host-rocks constitutes the basis of a hypothetical model of initiation, ascent and emplacement as follows: (1.) development of a deep N-S granitic ridge controled by a major crustal fracture generated by an earlier extensional phase re-activated by a strike-slip fault which, probably, would facilitate segregation, collection and ascent of magmas; (2.) intrusion and splitting up of the ridge into several diapirs which ascended simultaneously and separately in a setting of a N-S sinistral transcurrent deformation inducing a transverse NW-SE shortening and forceful emplacement of plutons and (3.) final emplacement characterized by interference between regional deformation and pluton 'ballooning', the latter leading to the coalescence of intrusions and to the formation of a larger, apparently homogeneous body.This model could be extended to the other large Birimian batholiths of the Lower Proterozoic in Eastern Senegal.

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Section: Ascentmentioning

confidence: 89%

Kinematics of large syn-orogenic intrusions: example of the Lower Proterozoic Saraya batholith (Eastern Senegal)

1992

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“…We use a finite element numerical method to model the flow with a simple three layer viscosity structure for the upper mantle (Hughes et al, 1979;Daly and Raefsky, 1985). The numerical method is discussed in detail in the appendix.…”

Section: This Thesismentioning

confidence: 99%

“…These equations are solved using a velocity based finite element method (Daly and Raefsky, 1985). Although the incompressibility equation:…”

Section: The Numerical Model Of the Flowmentioning

confidence: 99%

“…These equations are solved using a velocity based finite element method with explicit time stepping (Daly and Raefsky, 1985), which has been modified to solve the heat equation with a finite difference method. Although the incompressibility equation:…”

Section: The Convective Flowmentioning

confidence: 99%

“…We solved these equations using a velocity based finite element method, which has been modified to solve the heat equation on finite difference grid, and followed the flow in time with an explicit time stepping method (Daly and Raefsky, 1985). Although the incompressibility equation:…”

Section: The Numerical Modelmentioning

confidence: 99%

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The effect of a shallow low viscosity zone on mantle convection and its expression at the surface of the earth

Robinson¹

1987

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Many features of the oceanic plates cannot be explained by conductive cooling with age. A number of these anomalies require additional convective thermal sources at depths below the plate: mid-plate swells, the evolution of fracture zones, the mean depth and heat flow relationships with age and the observation of small scale (150-250 km) geoid and topography anomalies in the Central Pacific and Indian oceans.Convective models are presented of the formation and evolution of these features.In particular, the effect of a shallow low viscosity layer in the uppermost mantle on mantle flow and its geoid, topography, gravity and heat flow expression is explored. A simple numerical model is employed of convection in a fluid which has a low viscosity layer lying between a rigid bed and a constant viscosity region.Finite element caiculations have been used to determine the effects of (1) the viscosity contrast between the two fluid layers, (2) the thickness of the low viscosity zone, (3) the thickness of the conducting lid, and (4) the Rayleigh number of the fluid based on the viscosity of the lower layer.A model simple for mid-plate swells is that they are the surface expression of a convection cell driven by a heat flux from below.The low viscosity zone causes the top boundary layer of the convection cell to thin and, at high viscosity contrasts and Rayleigh numbers, it can cause the boundary layer to go unstable.The low viscosity zone also mitigates the transmission of normal stress to the conducting lid so that the topography and geoid anomalies decrease.The geoid anomaly decreases faster than the topography anomaly, however, so that the depth of compensation can appear to be well within the conducting lid.Because the boundary layer is thinned, the elastic plate thickness also decreases and, since the low viscosity allows the fluid to flow faster in the top layer, the uplift time decreases. as well. We have compared the results of this modeling to data at the Hawaii, Bermuda, Cape Verde and Marquesas swells, and have found that it can reproduce their 3 observed anomalies. The viscosity contrasts that are required range from 0.2-0.01, which are in agreement with other estimates of shallow viscosity variation in the upper mantle. Also, the estimated viscosity contrast decreases as the age of the swell increases. This trend is consistent with theoretical estimates of the variation of such a low viscosity zone with age.Fracture zones juxtapose segments of the oceanic plates of different ages and thermal structures. The flow induced by the horizontal temperature gradient at the fracture zone initially downwells immediately adjacent to the fracture zone on the older side, generating cells on either side of the plume. The time scale and characteristic wavelength of this flow depends initially on the viscosity near the largest temperature gradient in the fluid which, in our model, is the viscosity of the low viscosity layer. They therefore depend on .both the Rayleigh number and the viscosity contrast between the laye...

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Influence of a West Antarctic mantle plume on ice sheet basal conditions

Seroussi

Ivins

Wiens³

et al. 2017

JGR Solid Earth

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The possibility that a deep mantle plume manifests Pliocene and Quaternary volcanism and potential elevated heat flux in West Antarctica has been studied for more than 30 years. Recent seismic images support the plume hypothesis as the cause of Marie Byrd Land (MBL) volcanism and geophysical structure. Mantle plumes may more than double the geothermal heat flux above nominal continental values. A dearth of in situ ice sheet basal data exists that samples the heat flux. Consequently, we examine a realistic distribution of heat flux associated with a possible late Cenozoic mantle plume in West Antarctica and explore its impact on thermal and melt conditions at the ice sheet base. We use a simple analytical mantle plume parameterization to produce geothermal heat flux at the base of the ice sheet. The three‐dimensional ice flow model includes an enthalpy framework and full‐Stokes stress balance. As both the putative plume location and extent are uncertain, we perform broadly scoped experiments to characterize the impact of the plume on geothermal heat flux and ice sheet basal conditions. The experiments show that mantle plumes have an important local impact on the ice sheet, with basal melting rates reaching several centimeters per year directly above the hotspot. In order to be consistent with observations of basal hydrology in MBL, the upper bound on the plume‐derived geothermal heat flux is 150 mW/m2. In contrast, the active lake system of the lower part of Whillans Ice Stream suggests a widespread anomalous mantle heat flux, linked to a rift source.

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On the penetration of a hot diapir through a strongly temperature-dependent viscosity medium

Cited by 44 publications

References 16 publications

Kinematics of large syn-orogenic intrusions: example of the Lower Proterozoic Saraya batholith (Eastern Senegal)

Kinematics of large syn-orogenic intrusions: example of the Lower Proterozoic Saraya batholith (Eastern Senegal)

The effect of a shallow low viscosity zone on mantle convection and its expression at the surface of the earth

Influence of a West Antarctic mantle plume on ice sheet basal conditions

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