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

Ferguson, David; Maclennan, John; Bastow, I. D.; Pyle, David M.; Jones, S. M.; Keir, Derek; Blundy, Jon; Plank, Terry; Yirgu, Gezahegn

doi:10.1038/nature12292

Cited by 94 publications

(98 citation statements)

References 42 publications

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“…Tomographic studies in northern Afar also show a region of low seismic velocity from 50 to 400 km depth, which is interpreted as a region of elevated temperature and partial melt Stork et al, 2013;Civiero et al, 2015). This interpretation is further corroborated by modeling geochemical data that suggest an elevated mantle temperature of 1450°C (Ferguson et al, 2013;Armitage et al, 2015). The elevated mantle temperature will promote partial melting, even at relatively low rates of extension.…”

Section: Geological Settingsupporting

confidence: 63%

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Illsley‐Kemp¹,

Keir²,

Bull³

et al. 2017

Bulletin of the Seismological Society of America

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The Danakil region of northern Afar is an area of ongoing seismic and volcanic activity caused by the final stages of continental breakup. To improve the quantification of seismicity, we developed a calibrated local earthquake magnitude scale. The accurate calculation of earthquake magnitudes allows the estimation of b-values and maximum magnitudes, both of which are essential for seismic-hazard analysis. Earthquake data collected between February 2011 and February 2013 on 11 three-component broadband seismometers were analyzed. A total of 4275 earthquakes were recorded over hypocentral distances ranging from 0 to 400 km. A total of 32,904 zero-to-peak amplitude measurements (A) were measured on the seismometer's horizontal components and were incorporated into a direct linear inversion that solved for all individual local earthquake magnitudes (M L ), 22 station correction factors (C), and 2 distance-dependent factors (n, K) in the equation M L logA− logA 0 C. The resultant distance correction term is given by − logA 0 1:274336 logr=17 − 0:000273r − 17 2. This distance correction term suggests that attenuation in the upper and mid-crust of northern Afar is relatively high, consistent with the presence of magmatic intrusions and partial melt. In contrast, attenuation in the lower crust and uppermost mantle is anomalously low, interpreted to be caused by a high melt fraction causing attenuation to occur outside the seismic frequency band. The calculated station corrections serve to reduce the M L residuals significantly but do not show a correlation with regional geology. The cumulative seismicity rate produces a b-value of 0:9 0:06, which is higher than most regions of continental rifting yet lower than values recorded at midocean ridges, further supporting the hypothesis that northern Afar is transitioning to seafloor spreading.Electronic Supplement: List of all local earthquakes used in the study with calculated local magnitudes and associated magnitude error.

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Section: Geological Settingsupporting

confidence: 63%

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Illsley‐Kemp¹,

Keir²,

Bull³

et al. 2017

Bulletin of the Seismological Society of America

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“…Despite the importance of the magma intrusion process during continental break-up, it remains unclear how molten rock is delivered into the lower crust and how it is transported through the crust to sometimes erupt at the surface. The southern Red Sea rift of Afar is the ideal study locale to address this problem as it sub-aerially exposes late-stage magmatic rifting caused by extension above anomalously warm (Ferguson et al 2013) and seismically slow (Stork et al 2013) mantle.…”

mentioning

confidence: 99%

Use of a high-precision gravity survey to understand the formation of oceanic crust and the role of melt at the southern Red Sea rift in Afar, Ethiopia

Lewi

Keir

Birhanu

et al. 2015

Self Cite

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Abstract:The Red Sea arm of the triple junction in northeastern Ethiopia provides an opportunity to investigate rift-forming processes at divergent boundaries. In an attempt to study the subsurface, especially the distribution and role of melt in the rifting process, we carried out a high-precision gravity survey with a mean-square error of 0.011 mgal, assisted by differential global positioning system measurements. The profile is 162 km long and strikes ENE-WSW across the southern part of the Red Sea rift at a latitude of approximately 11.758 N. Modelling of the Bouguer anomaly, constrained by a priori information, showed detailed in-rift variations in the crustal structure and the distribution of melt beneath the rift axis. Our interpretation suggested that the process of continental break-up is governed by crustal stretching and rifting accompanied by the emplacement of melt into the lower crust above a lower density upper mantle. In addition, we interpreted the thickness of the crust beneath this part of the rift axis to be 25 km. The subsurface distribution of density beneath the profile shows that the south-central part of the Red Sea rift has modified thinned crust, intruded by high-density material, which resembles the crust formed during seafloor spreading.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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“…Wang et al, , 2014Heinonen et al, 2013). Zn/Fe and Fe/Mn ratios are promising proxies for discriminating a pyroxenite from a peridotite source (Le Roux et al, 2010;Ferguson et al, 2013;Zhang et al, 2015). Most of our samples have Zn/Fe and Fe/Mn ratios similar to peridotite melts (Fig.…”

Section: Origin Of the Early Jurassic Basaltsmentioning

confidence: 99%

Petrogenesis of early Jurassic basalts in southern Jiangxi Province, South China: Implications for the thermal state of the Mesozoic mantle beneath South China

Cen

Wang

et al. 2016

Lithos

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

Cited by 94 publications

References 42 publications

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Use of a high-precision gravity survey to understand the formation of oceanic crust and the role of melt at the southern Red Sea rift in Afar, Ethiopia

Petrogenesis of early Jurassic basalts in southern Jiangxi Province, South China: Implications for the thermal state of the Mesozoic mantle beneath South China

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