Heat flow variations in continental rifts

Lysak, S.V.

doi:10.1016/0040-1951(92)90352-7

Cited by 61 publications

(8 citation statements)

References 30 publications

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“…[10] High Moho temperatures and partial melt in the upper mantle and lower crust have been inferred on the basis of anomalous Vp/Vs ratios [Dugda et al, 2007;Keranen et al, 2009], shear wave splitting delays , and low resistivity [Whaler and Hautot, 2006] in the CMER. Surface heat flow measurements in the Afar [Lysak, 1992] of 150-250 mWm À2 , compared to values $100 mWm À2 to the south, imply further elevation of the geotherm toward the Afar.…”

Section: Elevated Moho Temperaturesmentioning

confidence: 89%

Lithospheric strength and strain localization in continental extension from observations of the East African Rift

et al. 2012

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[1] GPS observations along three profiles across the Ethiopian Rift and Afar triple junction record differences in the length scale over which extension is accommodated. In the Afar region, where the mantle lithosphere is nearly or entirely absent, measurable extension occurs over $175 km; in the northern Ethiopian Rift, where the mantle lithosphere is anomalously thin and hot, extensional strain occurs over $85 km, extending beyond the structural rift valley; in the southern Ethiopian Rift, where the mantle lithosphere approaches standard continental thickness, extensional strain occurs over <10 km. This trend of increasingly distributed deformation contrasts with the standard model where continental rifts become mid-ocean spreading centers through strain localization.

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Section: Elevated Moho Temperaturesmentioning

confidence: 89%

Lithospheric strength and strain localization in continental extension from observations of the East African Rift

et al. 2012

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“…Studies of contemporary continental extension have shown that surface heat flow measurements are locally variable, but they rapidly decrease to normal values a few tens of kilometers away from the extension zone [ Nyblade , 1997]. This may not be the case for the geotherms in the shallow crust as they are influenced by the regional thermal regime rather than by local fluid circulation that greatly affect the surface heat flow measurements [ Lysak , 1992]. Thus the correlation between surface heat flow and geothermal gradient may not be straightforward as the geothermal gradient may vary in a much more regular manner than supposed by measuring the surface heat.…”

Section: Landscape Evolutionmentioning

confidence: 99%

Deciphering continental breakup in eastern Australia using low‐temperature thermochronometers

et al. 2005

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[1] First-order topographical features at high-elevation passive margins have the potential to store information about the early stages of continental rifting, which are usually lost in the sediment record. In this study we present a new combination of apatite fission track and (U-Th)/He analyses from two coast-perpendicular traverses to decipher the time of formation and evolution of the escarpment at the southeastern Australian margin. A combination of inverse and forward modeling of the apatite fission track (AFT) and He data indicates that the coast experienced a rapid denudational event starting at 110 ± 10 Ma, at least 15 Myr before seafloor spreading (85 Ma), in agreement with the hypothesis that rifting at magma-poor margins evolves slowly. Thus the enhanced denudation is not related to the synbreakup base level drop, but it may have been related to a thermally driven transient surface uplift. Considerations on isostatic flexure and rigidity of the lithosphere indicate that unless significant synrift brittle movements are assumed to have occurred along margin-parallel faults that are no more visible, the coast must have experienced a higher geothermal gradient than normal. The evolution of the rest of the coastal plain may have taken up to $90 Myr, in agreement with numerical models of passive margins evolution. The (U-Th)/He ages across the coastal plain are consistent with an in-place-excavation scenario of a high rift shoulder, and they rule out the possibility of a constant retreat of the escarpment. AFT + He data from the plateau indicate that the highlands remained stable throughout continental breakup, experiencing rates of erosion of 5-10 m/Myr since, at least, 200 Ma.

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“…Anomalously high surface heat flux as the result of a regionally elevated geotherm has been reported within central Afar [Lysak, 1992] and has been attributed either to enhanced magmatic activity associated with localized asthenospheric upwellings and decompressional melting or to the proposed Afar plume [Oppenheimer and Francis, 1997;Cochran and Karner, 2007]. Surface eruptions hence only occur where localization of strain is sufficient to provide conduits for flow, which is constrained to axial rift segments.…”

Section: Strain Localization and Upper-lower Crustal Decouplingmentioning

confidence: 99%

Receiver function constraints on crustal seismic velocities and partial melting beneath the Red Sea rift and adjacent regions, Afar Depression

et al. 2014

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The Afar Depression is an ideal locale for the investigation of crustal processes involved in the transition from continental rifting to oceanic spreading. To provide relatively high resolution images of the crust beneath the Red Sea rift (RSR) represented by the Tendaho graben in the Afar Depression, we deployed an array of 18 broadband seismic stations in 2010 and 2011. Stacking of about 2300 receiver functions from the 18 and several nearby stations along the ∼200 km long array reveals an average crustal thickness of 22 ± 4 km, ranging from ∼17 km near the RSR axis to 30 km within the overlap zone between the Red Sea and Gulf of Aden rifts. The resulting anomalously high V p ∕V s ratios decrease from 2.40 in the southwest to 1.85 within the overlap zone. We utilize theoretical V p and melt fraction relationships to obtain an overall highly reduced average crustal V p of ∼5.1 km/s. The melt percentage is about 10% beneath the RSR while the overlap zone contains minor quantities of partial melt. The observed high V p ∕V s values beneath most of the study area indicate widespread partial melting beneath the southwest half of the profile, probably as a result of gradual eastward migration of the RSR axis. Our results also suggest that the current extensional strain in the lower crust beneath the region is diffuse, while the strain field in the upper crust is localized along narrow volcanic segments. These disparate styles of deformation imply a high degree of decoupling between the upper and lower crust.

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Heat flow variations in continental rifts

Cited by 61 publications

References 30 publications

Lithospheric strength and strain localization in continental extension from observations of the East African Rift

Lithospheric strength and strain localization in continental extension from observations of the East African Rift

Deciphering continental breakup in eastern Australia using low‐temperature thermochronometers

Receiver function constraints on crustal seismic velocities and partial melting beneath the Red Sea rift and adjacent regions, Afar Depression

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