Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology

Ferguson, David; Calvert, Andrew T.; Pyle, David M.; Blundy, Jon; Yirgu, Gezahegn; Wright, Tim

doi:10.1038/ncomms2410

Cited by 18 publications

(18 citation statements)

References 37 publications

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“…[19] The linear correlation between K-Ar ages and distance to the axial rift [e.g., De Chabalier and Avouac, 1994;Ferguson et al, 2013] defines a mean spreading rate of 2.9 6 0.2 cm yr À1 . However, anomalous young age for one sample outside the rift indicate an off-axis volcanism on the northern shoulder and suggest that eruptions occurred 66 kyr ago within a zone 3 km wide (subrift Dankalelo, Figures 2a and 2b) [Manighetti et al, 1998].…”

Section: Age/distance Relationship In the Asal Riftmentioning

confidence: 99%

“…[3] The East African Rift System is a classic example of continental breakup, where the deformation of the continental crust is located along magmatic segments [e.g., Manighetti et al, 1998;Manighetti et al, 2001;Doubre et al, 2007aDoubre et al, , 2007bEbinger et al, 2008;Ferguson et al, 2013]. The central Main Ethiopian Rift marks the transition between rifting of thick continental crust in the southern and central East African Rift System and incipient seafloor spreading in the northern Afar, into the Afar Depression [e.g., Hayward and Ebinger, 1996;Rooney et al, 2007].…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Age/distance Relationship In the Asal Riftmentioning

confidence: 99%

Section: Introductionmentioning

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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“…The segment is transitional between continental rifting and oceanic seafloor spreading Ferguson et al 2013), and consists of a rifted central valley with a mid-segment central high containing a large collapse structure, and a significant stratovolcano, Dabbahu, at the northern end (Field et al 2012a, b;Medynski et al 2013). The segment can be considered transitional between the axial volcanic range morphology of the northern Afar rift segments (Erta 'Ale, Tat Ali, Alayta) and the rift valley graben morphology of southern Afar and the Main Ethiopian Rift (Bizouard et al 1980;Hayward & Ebinger 1996;Field et al 2012a, b).…”

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confidence: 99%

A multidisciplinary study of the final episode of the Manda Hararo dyke sequence, Ethiopia, and implications for trends in volcanism during the rifting cycle

Barnie

Keir

Hamling

et al. 2015

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The sequence of dyke intrusions between 2005 and 2010 in the Manda Hararo rift segment, Ethiopia, provided an opportunity to test conceptual models of continental rifting. Based on trends up to dyke 13 in the sequence, it was anticipated that, should magma supply continue, dykes would shorten in length and eruptions would increase in size and decrease in distance from the segment centre as extensional stress was progressively released. In this paper we revisit these predictions by presenting a comprehensive overview of the May 2010 dyke and fissure eruption, the 14th and last in the sequence, from InSAR, seismicity, satellite thermal data, ultraviolet SO 2 retrievals and multiple LiDAR surveys. We find the dyke is longer than other eruptive dykes in the sequence, propagating in two directions from the segment centre, but otherwise fairly typical in terms of opening, propagation speed and geodetic and seismic moment. However, though the eruption is located closer to the segment centre, it is much smaller than previous events. We interpret this as indicating that either the Manda Hararo rifting event was magma limited, or that extensional stress varies north and south of the segment centre.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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“…This structural map extends primarily over the neovolcanic zone (<0.6 Myr) and also over the Gulf Basalt series (1.1–0.6 Myr) composing the rift flanks including the AVC (Kidane et al, ; Stab et al, ). The oldest dating of fault scarp available on the rift eastern flank goes back to ~200 kyr (Ferguson et al, ), a time interval we tackle with this study. Our fault mapping includes the most recent magmato‐tectonic events up to May 2007, the date of the latest optical images used for this map (Figure b; Dumont et al, ).…”

Section: Methodsmentioning

confidence: 99%

Rifting Processes at a Continent‐Ocean Transition Rift Revealed by Fault Analysis: Example of Dabbahu‐Manda‐Hararo Rift (Ethiopia)

et al. 2019

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Analyses of fault attributes have contributed to unraveling fault growth processes in diverse tectonic settings. By integrating such analysis at the scale of a fault population, we propose to investigate the characteristics of a rift that has evolved up to a stage typical of a continent-ocean transition. We address this problem by considering Dabbahu-Manda-Hararo (DMH) rift segment (Central Afar, Ethiopia), recognized for being in a late rifting stage. We quantify fault azimuth, length, and throw attributes for 668 normal faults. Along DMH rift, the mean fault density is 0.87 ± 0.7 km/km 2 and the median tectonic strain ranges from 1.8% to 3.1% assuming a fault dip of 60°and 45°, respectively. Maximum tectonic strain (>10%) is found where the rift azimuth changes. Along-rift variations in fault azimuth, length, and scaling relationships suggest a different stage of rifting in the northern part of the rift. We show that this difference can be attributed to the influence of the Dabbahu volcano located at the northern tip of the rift, which captured the propagating Manda-Hararo rift in the last~100 kyr. The morpho-tectonic analysis reveals numerous common features with slow-spreading ridge segments, such as the Lucky Strike segment located along the Mid-Atlantic ridge (segment length, spreading rate, associated magmatic system) but also with intermediate and fast ones (axial valley, fault throws, and diking). This study reveals that a rift at the continent-ocean transition may be characterized by a transient and evolutionary behavior that shares features with oceanic ridges from slow-to fast-spreading rates.Plain Language Summary East Africa forms one of the best locations around the world for studying rifting processes. In the Afar depression, three limits of tectonic plates meet to break up the African continent. Faults and volcanism shape rift morphology, and they both participate in the continental breakup. We study 668 faults along the Dabbahu-Manda-Hararo rift that is close to give birth to an ocean. We focus on how faults develop by measuring their length, their height, orientation, and number in a given area. Our analysis shows that in the northern part of the rift, faults develop in a singular way, illustrated by their unusual great length at the rift axis. We gather evidences of the specificity of faults located in this area, and we link them to the presence of Dabbahu volcano that developed~100 kyr ago in this area. We also compare our rift to a slow oceanic ridge located in Atlantic with which it shares numerous features (spreading rate, morphology, and magmatic system). This comparison leads us to discuss how different these extensional systems are and to better understand the transition between a continent and an ocean.

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Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology

Cited by 18 publications

References 37 publications

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

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

A multidisciplinary study of the final episode of the Manda Hararo dyke sequence, Ethiopia, and implications for trends in volcanism during the rifting cycle

Rifting Processes at a Continent‐Ocean Transition Rift Revealed by Fault Analysis: Example of Dabbahu‐Manda‐Hararo Rift (Ethiopia)

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