Flood and Shield Basalts from Ethiopia: Magmas from the African Superswell

Kieffer, Bruno; Arndt, Nicholas; Lapierre, Henriette; Bastien, Florence; Bosch, Delphine; Pêcher, Arnaud; Yirgu, Gezahegn; Ayalew, Dereje; Weis, Dominique; Jerram, Dougal A.; Keller, Francine; Meugniot, Claudine

doi:10.1093/petrology/egg112

Cited by 412 publications

(333 citation statements)

References 73 publications

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“…In fact, the incompatible trace element patterns of the Hronicum basaltic rocks are likely to be related to a lithosphere mantle source and are dissimilar to the patterns of the oceanic basalts or plume-related basalts, also described by Dostal et al (2003). These patterns are typical of many continental flood basalt provinces, such as Paraná, Columbia River plateau, Ethiopia, Siberian and Emeishan CFBs (Piccirillo et al 1988;Dostal & Greenough 1992;Hooper & Hawkesworth 1993;Arndt et al 1993;Sharma 1997;Kieffer et al 2004;Reichow et al 2009;He et al 2010 and references therein). The good correlation with the Siberian traps is shown by the Siberian traps normalized patterns of the Hronicum basic rocks (Fig.…”

Section: Discussionmentioning

confidence: 94%

Geochemistry and Sr, Nd isotopic composition of the Hronic Upper Paleozoic basic rocks (Western Carpathians, Slovakia)

Vozár¹,

Spišiak²,

Vozárová³

et al. 2015

Geologica Carpathica

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The paper presents new major and trace element and first Sr-Nd isotope data from selected lavas among the Permian basaltic andesite and basalts of the Hronicum Unit and the dolerite dykes cutting mainly the Pennsylvanian strata. The basic rocks are characterized by small to moderate mg # numbers (30 to 54) and high SiO 2 contents (51-57 wt. %). Low values of TiO 2 (1.07-1.76 wt. %) span the low-Ti basalts. Ti/Y ratios in the dolerite dykes as well as the basaltic andesite and basalt of the 1 st eruption phase are close to the recommended boundary 500 between high-Ti and low-Ti basalts. Ti/Y value from the 2 nd eruption phase basalt is higher and inclined to the high-Ti basalts. In spite of this fact, in all studied Hronicum basic rocks Fe 2 O 3 * is lower than 12 wt. % and Nb/La ratios (0.3-0.6) are low, which is more characteristic of low-Ti basalts. The basic rocks are characterized by Nb/La ratios (0.56 to 0.33), and negative correlations between Nb/La and SiO 2 , which point to crustal assimilation and fraction crystallization. The intercept for Sr evolution lines of the 1 st intrusive phase basalt is closest to the expected extrusions age (about 290 Ma) with an initial 87 Sr/ 86 Sr ratio of about 0.7054. Small differences in calculated values I Sr document a partial Sr isotopic heterogeneity source (0.70435-0.70566), or possible contamination of the original magma by crustal material. For Nd analyses of the three samples, the calculated values εCHUR (285 Ma) are positive (from 1.75 to 3.97) for all samples with only subtle variation. Chemical and isotopic data permit us to assume that the parental magma for the Hronicum basic rocks was generated from an enriched heterogeneous source in the subcontinental lithospheric mantle.

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Section: Discussionmentioning

confidence: 94%

Geochemistry and Sr, Nd isotopic composition of the Hronic Upper Paleozoic basic rocks (Western Carpathians, Slovakia)

Vozár¹,

Spišiak²,

Vozárová³

et al. 2015

Geologica Carpathica

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“…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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“…The Lake Tana basin mainly constitutes lavas that erupted during the Plio-Oligocene through fissures and later through shield volcanoes (Kieffer et al, 2004). During the Pliocene -Holocene, Aden series lavas erupted and formed a volcanic barrier to the south of Lake Tana, which helped to form the present lake (Mohr, 1964).…”

Section: Introductionmentioning

confidence: 99%

Geomorphology of the Lake Tana basin, Ethiopia

et al. 2013

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The geomorphological map of the Lake Tana basin (15,077 km 2 , Nile basin, Ethiopia) presented in this paper was prepared from fieldwork data, maps and satellite data that were processed with a geographic information system (GIS). It contains four major components: (i) hydrography, (ii) morphology and morphometry, (iii) materials and (iv) processes at a scale of 1:500,000. The geomorphological setting of the basin consists of lavas that erupted from fissures or (shield) volcanoes during the Tertiary and Quaternary eras, were uplifted and eroded primarily by water. Lake Tana emerged through a combination of a lava barrier blocking the Blue Nile to the south and by epirogenetic subsidence. When the lake reached its maximum extent, extensive lacustrine plain (e.g. Fogera and Dembia plains) were created, river valleys and basins were filled with sediment and higher lying topography was eroded. Today, the lake plays a lesser role in landscape formation because of a decreased extent (3041 km 2 ) compared to the ancient maximum (6514 km 2 ). Dominant processes today are fluvial and subaerial. Recent (1886Recent ( -2010 changes in the lake coastline are small with the exception of the delta formed by Gilgel Abay, which has increased disproportionally over the last 15 years. This indicates a large input of sediment which is mainly due to rivers flowing through Quaternary lavas. The recent sediment input increase is most probably related to human induced land-use changes.

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Flood and Shield Basalts from Ethiopia: Magmas from the African Superswell

Cited by 412 publications

References 73 publications

Geochemistry and Sr, Nd isotopic composition of the Hronic Upper Paleozoic basic rocks (Western Carpathians, Slovakia)

Geochemistry and Sr, Nd isotopic composition of the Hronic Upper Paleozoic basic rocks (Western Carpathians, Slovakia)

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

Geomorphology of the Lake Tana basin, Ethiopia

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