Lithosphere-Asthenosphere Interactions Below Rifts

Keen, C. E.; Boutilier, R.

doi:10.1007/978-94-011-0043-4_2

Cited by 39 publications

(34 citation statements)

References 18 publications

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“…In order to investigate transient mantle dynamics, an initial-value approach must be adopted as done in the studies of rifting-related convection Keen and Boutilier, 1995;Boutilier and Keen, 1999].…”

Section: Discussionmentioning

confidence: 99%

“…The influence of a sharp spatial variation in boundaries on a convective system is a highly nonlinear problem. It has been considered with some specific model geometries, such as for convection due to slab cooling [Rabinowicz et al, 1980;Nataf et al, 1981;Christensen, 1983], and for convection due to cratonic lithosphere or rifting-g&nerated lithospheric necking [e.g., Richter, 1973;Elder, 1976;Keen and Boutilier, 1995;King and Anderson, 1998]. Because these studies focus on specific geological problems, it is difficult to extract the general effects of a heterogeneous top boundary.…”

Section: Introductionmentioning

confidence: 99%

“…Because these studies focus on specific geological problems, it is difficult to extract the general effects of a heterogeneous top boundary. Moreover, an initial-value approach is common in these convection studies Keen and Boutilier, 1995;Boutilier and Keen, 1999], so their results critically depend on a particular choice of initial conditions.…”

Section: Introductionmentioning

confidence: 99%

“…A lithospheric lid such as preexisting continental lithosphere and cold oceanic lithosphere imposes the 131 MYII lIhI upper limit of a mantle melting zone, and its importance is probably greatest during continental breakup [e.g., Fram and Lesher, 1993;Kelemen and Holbrook, 1995]. In addition, the mantle upwelling rate is not necessarily equal to the surface divergence rate, and it can be much higher than passive upwelling in the presence of either a mantle plume [e.g., Ribe et al, 1995;Ito et al, 1996], or a sharp lateral temperature gradient in the lithospheric lid Keen and Boutilier, 1995;Boutilier and Keen, 1999].Adiabatically upwelling mantle, if not too cold, eventually intersects its solidus and begins to melt. We adopt the following solidus of dry peridotite [Takahashi and Kushiro, 1983],…”

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Magmatism and dynamics of continental breakup in the presence of a mantle plume

Korenaga¹

2000

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This thesis studies the dynamics of mantle melting during continental breakups by geophysical, geochemical, and numerical analyses. The first part focuses on the mantle melting and crustal accretion processes during the formation of the Southeast Greenland margin, on the basis of deep-crustal seismic data. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a compressional velocity structure, and a long-wavelength structure with strong lateral heterogeneity is successfully recovered, including 30-to 15-km-thick igneous crust within a 150-km-wide continent-ocean transition zone. A nonlinear Monte Carlo analysis is also conducted to establish the absolute uncertainty of model parameters. The derived crustal structure is first used to resolve the origin of a margin gravity high, with new inversion schemes using both seismic and gravity constraints. Density anomalies producing the gravity high seem to be confined within the upper crust, not in the lower crust as suggested for other volcanic margins. A new robust framework is then developed for the petrological interpretation of the velocity structure of igneous crust, and the thick igneous crust formed at the continentocean transition zone is suggested to have resulted from vigorous active upwelling of mantle with only somewhat elevated potential temperature. In the second part, the nature of mantle melting during the formation of the North Atlantic igneous province is studied on the basis of the major element chemistry of erupted lavas. A new fractionation correction scheme based on the Ni concentrations of mantle olivine is used to estimate primary melt compositions, which suggest that this province is characterized by a large degree of major element source heterogeneity. In the third part, the nature of preexisting sublithospheric convection is investigated by a series of finite element analyses, because the strength of such convection is important to define the "normal" state of mantle, the understanding of which is essential to identify any anomalous behavior of mantle such as a mantle plume. The results suggest that small-scale convection is likely in normal asthenosphere, and that the upwelling velocity in such convection is on the order of 1-10 cm/yr. 271 Introductory NotesThis thesis is composed of three parts, all of which are related to the dynamics of mantle melting during continental breakups. In the first part, rifting magmatism associated with the opening of the North Atlantic (at -60 Ma) is investigated on the basis of deep-crustal seismic data collected across the Southeast Greenland continental margin. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a two-dimensional velocity structure (Chapter 1). Several key issues in travel time tomography such as velocity-depth ambiguity and absolute parameter uncertainty are identified, and a practical strategy is presented to resolve them. The derived crustal velocity structure is the...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Magmatism and dynamics of continental breakup in the presence of a mantle plume

Korenaga¹

2000

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“…thenosphere has a lower density then the mantle lithosphere. In the following, it will be shown that the first order features of the Pannonian basin can be explained by a first phase of passive extension followed by a second phase of active smallscale convective upwelling of the asthenosphere beneath the rift zone induced by the previous rifting history (Buck, 1985;Keen and Boutilier, 1995;Huismans et al, 2001a,b).…”

Section: Introductionmentioning

confidence: 95%

The Pannonian basin: Dynamic modelling of the transition from passive to active rifting

Huismans¹,

Podladchikov²,

Cloetingh³

2002

Stephan Mueller Spec. Publ. Ser.

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Abstract. We examine a number of first order features of Pannonian basin evolution in terms of the feedback relation between passive far-field induced extension and active Raleigh-Taylor instable upwelling of the asthenosphere. We show that active mantle upwelling following a phase of passive extension are viable mechanisms explaining the Pannonian basin formation. The dynamic interplay between far-field driven passive extension and active thinning of the mantle lithosphere by convective upwelling beneath the rift zone is modelled using thermo-mechanical finite element methods. Our modelling results predict a first phase of passive lithospheric thinning which is followed by a second phase of late syn-rift to post-rift active mantle lithosphere thinning due to buoyancy induced flow beneath the rift zone. The pattern of coeval extension in the thinning region and compression in the flanking regions, predicted by the numerical model, may be explained by the buoyancy forces due to lithosphere thinning. It is demonstrated that time scales of and stresses generated by both processes are comparable. The model might also explain the occurrence of late shallow mantle related decompression melts in the Pannonian region and late regional doming.

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The role of long‐term rifting history on modes of continental lithosphere extension

et al. 2016

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Continental lithosphere extension results in complex basin types with differing structural styles, subsidence, thermal histories, and melt production. Many studies have examined the role of initial rheological layering, geothermal gradients, and extension rates during a single rifting event. This approach neglects the tectonic history of many basins that are marked by multiple rifting events. Here we address the role of repeated extension on long‐term lithospheric strain modes and the resulting basins, highlighting cases most affected by previous rifting events. We use numerical models of a lithosphere undergoing two rifting events of differing extension rates and separated by cooling, to show the effect of early events on subsequent evolution. The combination of boundary displacement velocity in both events leads to the formation of various rift basin types, ranging from narrow to wide to hyperextended and with variation of subsidence patterns, degrees of symmetry, and melt yield. We show that basin type, subsidence, and melt production might be strongly affected by previous rifting events, illustrating cases in which the previous rifting history cannot be neglected. Our models reproduce the first‐order features of Earth's sedimentary basins and propose a classification to guide the interpretation of extensional basins and their evolution.

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Lithosphere-Asthenosphere Interactions Below Rifts

Cited by 39 publications

References 18 publications

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Magmatism and dynamics of continental breakup in the presence of a mantle plume

The Pannonian basin: Dynamic modelling of the transition from passive to active rifting

The role of long‐term rifting history on modes of continental lithosphere extension

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