Earliest magmatism in Ethiopia: Evidence for two mantle plumes in one flood basalt province

George, Rhiannon; Rogers, Nick; Kelley, S. P.

doi:10.1130/0091-7613(1998)026<0923:emieef>2.3.co;2

Cited by 339 publications

(292 citation statements)

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“…Due to their locations on the rift shoulders, neither area was affected by reheating related to subsidence and sedimentation within a sag basin. Thermal impacts of a mantle plume beneath the Tanzanian Craton since the Eocene-Oligocene [Ebinger and Sleep, 1998;George et al, 1998;Pik et al, 2008] remain a possibility, but clearly did not strongly influence the thermal evolution of the area as recorded in our samples.…”

Section: Eocene Through Middle Miocene Monotonic Slow Cooling or Rehementioning

confidence: 82%

“…Thermo-chronological and geophysical evidence for protracted subsidence in this sag basin is corroborated by regional pinch-outs of fluvial and organic-rich lacustrine sediments exposed along the Elgeyo Escarpment [Morley et al, 1992;Mugisha, 1997;Ego, 1994;Renaut et al, 1999] and the regional extent and thickness of the overlying <14.5 Ma phonolites that cover the present-day eastern and western rift shoulders [Lippard, 1973]. Alternatively, reheating could have been associated with the thermal impact of a mantle plume beneath the Tanzanian Craton since the Eocene-Oligocene [Ebinger and Sleep, 1998;George et al, 1998;Pik et al, 2008].…”

Section: Eocene Through Middle Miocene Monotonic Slow Cooling or Rehementioning

confidence: 99%

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Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

et al. 2015

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Key points: Data and modeling show Paleogene and middle Miocene cooling episodes  Cooling episodes separated by stable conditions, slow exhumation or subsidence  Extension pattern is compatible with random rift initiation above a plume This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/2015TC003949 ©2015 American Geophysical Union. All rights reserved. AbstractThe cooling history of rift shoulders and the subsidence history of rift basins are cornerstones for reconstructing the morphotectonic evolution of extensional geodynamic provinces, assessing their role in paleoenvironmental changes, and evaluating the resource potential of their basin fills. Our apatite fission-track and zircon (U-Th)/He data from the Samburu Hills and the Elgeyo Escarpment in the northern and central sectors of the Kenya Rift indicate a broadly consistent thermal evolution of both regions. Results of thermal modeling support a three-phased thermal history since the early Paleocene. The first phase (~65-50 Ma) was characterized by rapid cooling of the rift shoulders and may be coeval with faulting and sedimentation in the Anza Rift basin, now located in the subsurface of the Turkana depression and areas to the east in northern Kenya. In the second phase, very slow cooling or slight reheating occurred between ~45 and 15 Ma as a result of either stable surface conditions, very slow exhumation, or subsidence. The third phase comprised renewed rapid cooling starting at ~15 Ma. This final cooling represents the most recent stage of rifting, which followed widespread flood-phonolite emplacement and has shaped the present-day landscape through rift shoulder uplift, faulting, basin filling, protracted volcanism, and erosion. When compared with thermochronologic and geologic data from other sectors of the East African Rift System, extension appears to be diachronous, spatially disparate, and partly overlapping, likely driven by interactions between mantle-driven processes and crustal heterogeneities, rather than the previously suggested north-south migrating influence of a mantle plume.

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Section: Eocene Through Middle Miocene Monotonic Slow Cooling or Rehementioning

confidence: 82%

Section: Eocene Through Middle Miocene Monotonic Slow Cooling or Rehementioning

confidence: 99%

Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

et al. 2015

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“…Zones of thinned lithosphere then channeled buoyant asthenosphere up to~1000 km laterally to the evolving African-Arabian rift system in the Horn of Africa. George et al (1998) and Rogers et al (2000), on the other hand, cited petrological differences between Afar and Kenyan lavas as evidence that two Cenozoic plumes may have existed, one rising and dispersing beneath southern Ethiopia~45 Ma and the other rising beneath the Afar depression.…”

Section: The Ethiopian Mantlementioning

confidence: 99%

“…Physical state of the Ethiopian mantle: evidence from the geological record The~2 km thick sequences of flood basalts and rhyolites that erupted onto the Ethiopian plateau (e.g., Baker et al, 1996;Hofmann et al, 1997) prior to or concomitant with the 29-31 Ma onset of extension in the Red Sea and Gulf of Aden rift systems (e.g., Wolfenden et al, 2004), have frequently been cited as evidence for one or more traditional mantle plumes beneath the region. The location and number of plumes or upper mantle convective cells are debated, however (e.g., Beccaluva et al, 2009;Burke, 1996;Courtillot et al, 1999;Ebinger and Sleep, 1998;Furman et al, 2006;George et al, 1998;Kieffer et al, 2004;Rogers, 2006;Rogers et al, 2000;Rooney et al, 2012a,b;Schilling et al, 1992). Ebinger and Sleep (1998), for example, suggested that one large plume spread beneath the African Plate near Turkana at~45 Ma, with melt production minimal until lithospheric thinning commenced in the Red Sea and Gulf of Aden.…”

Section: The Ethiopian Mantlementioning

confidence: 99%

The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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Despite the importance of continental breakup in plate tectonics, precisely how extensional processes such as brittle faulting, ductile plate stretching, and magma intrusion evolve in space and time during the development of new ocean basins remains poorly understood. The rifting of Arabia from Africa in the Afar depression is an ideal natural laboratory to address this problem since the region exposes subaerially the tectonically active transition from continental rifting to incipient seafloor spreading. We review recent constraints on along-axis variations in rift morphology, crustal and mantle structure, the distribution and style of ongoing faulting, subsurface magmatism and surface volcanism in the Red Sea rift of Afar to understand processes ultimately responsible for the formation of magmatic rifted continental margins. Our synthesis shows that there is a fundamental change in rift morphology from central Afar northward into the Danakil depression, spatially coincident with marked thinning of the crust, an increase in the volume of young basalt flows, and subsidence of the land towards and below sea-level. The variations can be attributed to a northward increase in proportion of extension by ductile plate stretching at the expense of magma intrusion. This is likely in response to a longer history of localised heating and weakening in a narrower rift. Thus, although magma intrusion accommodates strain for a protracted period during rift development, the final stages of breakup are dominated by a phase of plate stretching with a shift from intrusive to extrusive magmatism. This late-stage pulse of decompression melting due to plate thinning may be responsible for the formation of seaward dipping reflector sequences of basalts and sediments, which are ubiquitous at magmatic rifted margins worldwide.

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“…Detailed studies of Icelandic magmas show a complex picture of melt evolution, mixing, and assimilation in the crust [e.g., (Shorttle et al 2013;Winpenny and Maclennan 2011)], and this points to both the heterogeneity of the mantle source and the varied evolutionary paths that a single magma may take within the crust. The Afar region bears comparison with Iceland, in that it is a subaerial spreading centre influenced by at least one mantle plume (George et al 1998;Hofmann et al 1997;Pik et al 2006;Schilling 1973).…”

Section: Regional Backgroundmentioning

confidence: 99%

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Donovan

Blundy

Oppenheimer

et al. 2017

Contrib Mineral Petrol

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The 2011 eruption of Nabro volcano, Eritrea, produced one of the largest volcanic sulphur inputs to the atmosphere since the 1991 eruption of Mt. Pinatubo, yet has received comparatively little scientific attention. Nabro forms part of an off-axis alignment, broadly perpendicular to the Afar Rift, and has a history of large-magnitude explosive silicic eruptions, as well as smaller more mafic ones. Here, we present and analyse extensive petrological data obtained from samples of trachybasaltic tephra erupted during the 2011 eruption to assess the pre-eruptive magma storage system and explain the large sulphur emission. We show that the eruption involved two texturally distinct batches of magma, one of which was more primitive and richer in sulphur than the other, which was higher in water (up to 2.5 wt%). Modelling of the degassing and crystallisation histories demonstrates that the more primitive magma rose rapidly from depth and experienced degassing crystallisation, while the other experienced isobaric cooling in the crust at around 5 km depth. Interaction between the two batches occurred shortly before the eruption. The eruption itself was likely triggered by recharge-induced destabilisation of vertically extensive mush zone under the volcano. This could potentially account for the large volume of sulphur released. Some of the melt inclusions are volatile undersaturated, and suggest that the original water content of the magma was around 1.3 wt%, which is relatively high for an intraplate setting, but consistent with seismic studies of the Afar plume. This eruption was smaller than some geological eruptions at Nabro, but provides important insights into the plumbing systems and dynamics of off-axis volcanoes in Afar.

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Earliest magmatism in Ethiopia: Evidence for two mantle plumes in one flood basalt province

Cited by 339 publications

References 0 publications

Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

The development of extension and magmatism in the Red Sea rift of Afar

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

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