Volcanism in the Afar Rift sustained by decompression melting with minimal plume influence

Rychert, C.; Hammond, James; Harmon, Nicholas; Kendall, J.‐M.; Keir, Derek; Ebinger, C. J.; Bastow, I. D.; Ayele, Atalay; Belachew, M.; Stuart, G. W.

doi:10.1038/ngeo1455

Cited by 108 publications

(164 citation statements)

References 28 publications

(34 reference statements)

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“…24), where melting occurs according to the geodynamic model for Afar of ref. 13 with the onset of melting between depths of 70 km and 80 km and melt production continues until a depth of 40 km. The compositions of melts generated from these regimes (Fig.…”

Section: Conventional Rifting Modelsmentioning

confidence: 99%

“…However, the response of the lower part of the Ethiopian lithosphere to extension remains unclear and it is debated whether the lower plate has been preferentially thinned 14 , effectively compensating for the modest net crustal attenuation, or whether a significant thickness of the lithospheric mantle remains intact 17 . A related controversy concerns the temperature of the Afar mantle 13,19 , which exerts a fundamental control on the depth and extent of melting and is therefore a key parameter in understanding the ongoing magmatism and thermal structure of the upper mantle.…”

Section: Conventional Rifting Modelsmentioning

confidence: 99%

“…However, it is unclear whether the cause of voluminous melt production at volcanic rifts is primarily increased mantle temperature or plate thinning 1,2,[8][9][10][11][12] . Also disputed is the extent to which plate stretching or thinning is uniform or varies with depth with the entire continental lithospheric mantle potentially being removed before plate rupture [13][14][15][16] . Here we show that the extensive magmatism during rifting along the southern Red Sea rift in Afar, a unique region of sub-aerial transition from continental to oceanic rifting, is driven by deep melting of hotterthan-normal asthenosphere.…”

mentioning

confidence: 99%

“…14) to almost zero at the point of plate rupture. Some models propose that the lower-mantle lithosphere is preferentially removed at an early stage of breakup 13 , possibly by stretching 14 or detachment 16 ; others suggest that a significant portion of the lithospheric mantle remains until the final stage of plate thinning 16 . Ethiopia offers an excellent opportunity to understand how mantle temperature and plate thinning covary during rifting because it exposes several stages of rift development, including the final stages of transition to oceanic spreading in northern Afar 17 .…”

mentioning

confidence: 99%

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Melting during late-stage rifting in Afar is hot and deep

Ferguson

Maclennan

Bastow

et al. 2013

Nature

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Section: Conventional Rifting Modelsmentioning

confidence: 99%

Section: Conventional Rifting Modelsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Melting during late-stage rifting in Afar is hot and deep

Ferguson

Maclennan

Bastow

et al. 2013

Nature

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“…[11] Deep structure of the Afar depression is constrained by seismic refraction and seismological data [Ruegg, 1975;Berckhemer et al, 1975;Makris and Ginsburg, 1987;Knox et al, 1998;Nyblade et al, 2000;Rychert et al 2012]. Knox and et al [1998] localized a pronounced negative S wave velocity gradient beneath Afar Depression between 60 and 110 km, which is characteristic of the upper mantle.…”

mentioning

confidence: 99%

Petrological constraints on melt generation beneath the Asal Rift (Djibouti) using quaternary basalts

Pinzuti

Humler

Manighetti

2013

Geochem Geophys Geosyst

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[1] The temporal evolution of the mantle melting processes in the Asal Rift is evaluated from the chemical composition of 56 new lava flows sampled along 10 km of the rift axis and 9 km off-axis (i.e., erupted within the last 620 kyr). Petrological and primary geochemical results show that most of the samples of the inner floor of the Asal Rift are affected by plagioclase accumulation. Trace element ratios and major element compositions corrected for mineral accumulation and crystallization show a symmetric pattern relative to the rift axis and preserved a clear signal of mantle melting depth variations. While FeO, Fe 8.0 , Zr/Y, and (Dy/Yb) N decrease from the rift shoulders to the rift axis, SiO 2 , Na/Ti, Lu/Hf increase and Na 2 O and Na 8.0 are constant across the rift. These variations are qualitatively consistent with shallow melting beneath the rift axis and deeper melting for off-axis lava flows. Na 8.0 and Fe 8.0 contents show that beneath the rift axis, melting paths are shallow, from 81 6 4 to 43 6 5 km. These melting paths are consistent with adiabatic melting in normal-temperature fertile asthenosphere, beneath an extensively thinned mantle lithosphere. On the contrary, melting on the rift shoulders (from 107 6 7 to 67 6 8 km) occurred beneath thicker lithosphere, requiring a mantle solidus temperature 100 6 40 C hotter. In this geodynamic environment, the calculated rate of lithospheric thinning appears to be 4.0 6 2.0 cm yr À1 , a value close to the mean spreading rate (2.9 6 0.2 cm yr À1 ) over the last 620 kyr.

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Seismic images of magmatic rifting beneath the western branch of the East African rift

Jakovlev

Rümpker

Schmeling

et al. 2013

Geochem Geophys Geosyst

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[1] We have performed a tomographic study using a joint data set that includes local and teleseismic events, recorded by a temporary network in the western branch of the East African rift system. From the travel time residuals, we derive a three-dimensional model of seismic P-wave velocity anomalies for the crust and upper mantle down to a depth of 80 km. Particular attention is paid to the verification of the inversion results by various resolution tests. The results show that the eastern rift shoulder is characterized by relatively high seismic velocities. Lower velocities are obtained beneath the entire length of the rift valley and the Rwenzori Mountains. A prominent feature is observed north-east of the mountain range: here we detected a vertically oriented, cylindrical low-velocity anomaly with maximum amplitudes in the middle crust and the upper mantle lithosphere. We suggest that this anomaly indicates reservoirs of molten material related to the ongoing rifting process within this segment of the rift. Just above this anomaly, at depths between 5 and 16 km, earthquake swarms exist. The observed reduction in P-wave velocity is used to provide constraints on the possible melt content and temperature anomaly in the uppermost mantle. The observed 3-5% P-velocity decrease can be explained by melt fraction up to 2%-3.3% or alternatively by a temperature increase of at least 248 to 376 K and even higher-temperature anomalies are possible if lower ambient temperatures in the reference mantle are assumed. Probably, the two effects act in combination.Components: 7,941 words, 8 figures.

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Volcanism in the Afar Rift sustained by decompression melting with minimal plume influence

Cited by 108 publications

References 28 publications

Melting during late-stage rifting in Afar is hot and deep

Melting during late-stage rifting in Afar is hot and deep

Petrological constraints on melt generation beneath the Asal Rift (Djibouti) using quaternary basalts

Seismic images of magmatic rifting beneath the western branch of the East African rift

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