The Ethiopian Flood Basalt Province

Mohr, Paul; Zanettin, B.

doi:10.1007/978-94-015-7805-9_3

Cited by 162 publications

(45 citation statements)

References 56 publications

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“…In order to refine models of the impact of large igneous provinces on climate change events, we must first provide better constraints on the MVD component, which until now has been neglected. 31-25 [3][4] 0.6 [5] 0.35 [5] Minor North Atlantic 62-55 [6] 1.3 [7] 6.6 [7] Locally imp.…”

Section: -Summary and Conclusionmentioning

confidence: 99%

“…60 [2] Ferrar Dolerite 150 [3] 450 [4] 110 [5] 170 [5] Kirkpatrick Basalt ? 195 [6] .8 [5] 70 [5] Prebble Fm (CTM) ? .8 [7] ?…”

Section: Northern Skyementioning

confidence: 99%

“….1 [7] Mawson Fm (SVL) .07 [8] 4.1 [9] .02 [8] .25 [10] Exposure Hill Fm (NVL) ? figure 6a; [4] length 3000 km and mean width 150 km, as assumed by [5]; [5] Fleming et al (1997); [6] length 1300 km (Otway Massif to Mesa Range) and mean width 150 km (mean width probably too large); [7] rough calculation from published sketches and thickness (Hanson and Elliot, 1996;Elliot and Hanson, 2001), with interpolation between measured sections within specific regions, but no interpolation between regions; [8] calculated from digitised, georeferenced maps and sketches from Grapes et al (1974), Korsch (1984), Isaac et al (1996), Elliot et al (1997), andMcClintock (2001);[9] interpolation between exposures from Prince Albert Mountains to Shapeless Mountain (195 km); [10] assumes a mean thickness of 60 m, which is a minimum;…”

Section: Northern Skyementioning

confidence: 99%

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Mafic volcaniclastic deposits in flood basalt provinces: A review

Ross

Ukstins

McClintock

et al. 2005

Journal of Volcanology and Geothermal Research

137

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Flood volcanic provinces are assumed generally to consist exclusively of thick lavas and shallow intrusive rocks (mostly sills), with any pyroclastic rocks limited to silicic compositions. However mafic volcaniclastic deposits (MVDs) exist in many provinces, and the eruptions that formed such deposits are potentially meaningful in terms of potential atmospheric impacts and links with mass extinctions. The province where MVDs are the most voluminousthe Siberian Traps -is also the one temporally associated with the greatest Phanerozoic mass extinction. A lot remains to be learned about these deposits and eruptions before a convincing genetic link can be established, but as a first step, this contribution reviews in some detail the current knowledge on MVDs for the provinces in which they are better known, i.e. the North Atlantic Igneous Province (including Greenland, the Faeroe Islands, the British Isles, and tephra layers in the North Sea basin and vicinity), the Ontong Java plateau, the Ferrar, and the Karoo. We also provide a brief overview of what is known about MVDs in other provinces such as the Columbia River Basalts, the Afro-Arabian province, the Deccan Traps, the Siberian Traps, the Emeishan, and an Archean example from Australia. The thickest accumulations of MVDs occur in flood basalt provinces where they underlie the lava pile (Faeroes: >1 km, Ferrar province: ≥400 m, Siberian Traps: 700 m). In the Faeroes case, the great thickness of MVDs can be attributed to accumulation in a local sedimentary basin, but in the Ferrar and Siberian provinces the deposits are widespread (>3 x 10 5 km 2 for the latter). On the Ontong Java plateau over 300 m of MVDs occur in one drill hole without any overlying lavas. Where the volcaniclastic deposits are sandwiched between lavas, their thickness is much less. In most of the cases reviewed, primary MVDs are predominantly of phreatomagmatic origin, as indicated by the clast assemblage generally consisting of basaltic clasts of variable vesicularity (dominantly non-to poorly-vesicular) mixed with abundant country rock debris. The accidental lithic components often include loose quartz particles derived from poorly consolidated sandstones in underlying sedimentary basins (East Greenland, Ferrar, Karoo). These underlying sediments or sedimentary rocks were not only a source for debris but also aquifers that supplied water to fuel phreatomagmatic activity. In the Paraná-Etendeka, by contrast, the climate was apparently very dry when the lavas were emplaced (aeolian sand dunes) and no MVDs are reported. Volcanic vents filled with mafic volcaniclastic material, a few tens of metres to about 5 km across, are documented in several provinces (Deccan, North Atlantic, Ferrar, Karoo); they are though to have been excavated in relatively soft country rocks (rarely in flood lavas) by phreatomagmatic activity in a manner analogous to diatreme formation.

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Section: -Summary and Conclusionmentioning

confidence: 99%

“…60 [2] Ferrar Dolerite 150 [3] 450 [4] 110 [5] 170 [5] Kirkpatrick Basalt ? 195 [6] .8 [5] 70 [5] Prebble Fm (CTM) ? .8 [7] ?…”

Section: Northern Skyementioning

confidence: 99%

Section: Northern Skyementioning

confidence: 99%

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Mafic volcaniclastic deposits in flood basalt provinces: A review

Ross

Ukstins

McClintock

et al. 2005

Journal of Volcanology and Geothermal Research

137

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“…DATA AND SOURCES FOR FIGURE 2Area and volume fromReidel et al (2013).Only for Africa; area and volume fromMohr and Zanettin (1988).Area and volume fromJay and Widdowson (2008).Area and volume fromEldholm and Grue (1994).Area fromErnst (2014) and volume fromMarks et al (2014).…”

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confidence: 99%

North America’s Midcontinent Rift: When rift met LIP

et al. 2015

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Rifts are segmented linear depressions that are filled with sedimentary and igneous rocks; they form by extension and often evolve into plate boundaries. Flood basalts, a class of large igneous provinces (LIPs), are broad regions of extensive volcanism formed by sublithospheric processes. Typical rifts are not filled with flood basalts, and typical flood basalts are not associated with significant crustal extension and faulting. North America's Midcontinent Rift (MCR) is an unusual combination, because its 3000-km length formed during a continental breakup event 1.1 Ga, but it contains an enormous volume of igneous rocks that are mostly flood basalt. We show that MCR volcanic rocks are significantly thicker than other flood basalts, due to their deposition in a narrow rift rather than across a broad region, giving the MCR a rift's geom etry but a LIP's magma volume. Structural modeling of seismic-reflection data shows that LIP volcanics were deposited during two phases-an initial rift phase where flood basalts filled a fault-controlled extending basin and a postrift phase where LIP volcanics and sediments were deposited in a thermally subsiding sag basin without associated faulting. The crust thinned during the initial rifting phase and then rethickened during the postrift phase and later compression, yielding the present thicker crust observed seismologically. The restriction of extension to a single normal fault in each rift segment, steeply inward-dipping rift shoulders with sharp hinges, and persistence of volcanism after rifting ended gave rise to a deep flood basalt-filled rift geometry not observed in other presently active or ancient rifts. The unusual coincidence of a rift and LIP arose when a new rift associated with continental breakup interacted with a mantle plume or overrode anomalously hot or fertile upper mantle.

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“…The former are subaqueous, transitional basalts with enriched 'plume-type' characteristics which erupted between the continental volcanism of the Eskimo Formation and the formation of the ocean basin. As such, they can be compared with volcanism in opening rifts, like, for example, the volcanism in the Afar area in northern Ethiopia (Mohr 1983). The spinifex basalts overlie the Mg-basalts and therefore erupted after the opening of the ocean basin.…”

Section: Tectonic Interpretationmentioning

confidence: 99%

Geochemistry, Petrogenesis and Tectonic Environment of Circum-Superior Belt Basalts, Canada

Arndt¹,

Brügmann²,

Lehnert³

et al. 1987

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S U M M A RY: The Circum-Superior Belt of Proterozoic basalts and sedimentary rocks surrounds, and in some places, unconformably overlies the Archaean Superior Craton in northern Quebec, Canada. Four main groups of volcanic rocks are recognized. The oldest unit, the Eskimo Formation on the Belcher Islands, consists of subaerial massive continental tholeiites with 4-7% MgO, relatively high SiO 2 and K20, enriched LREE and other incompatible elements, negative Nb and Ta anomalies, and eNd (T = 1.8 Ga) of -7 to -8. The overlying Flaherty Formation contains largely subaqueous, massive or pillowed, mildly alkaline (transitional) basalts with relatively low SiO2, high alkalis and TiO2, enriched incompatible trace elements (including Nb and Ta), and eNa of + 3. Stratigraphically higher units (on the Ottawa Islands and the Chukotat Formation, Cape Smith Belt) contain subaqueous, massive or pillowed flows, and layered gabbro-peridotite flows with compositions ranging from MgO-rich ol-phyric basalt and evolved cpx-plag-phyric basalt to ol-cpx cumulate. Maximum MgO in noncumulate samples reaches 17 wt%, and trace element characteristics are MORB-like: LREE and other incompatible elements are depleted, and end is + 4 to + 5. The highest units, exposed on the Ottawa Islands, consist of komatiitic basalts and include unusual spinifex-textured layered flows. Although maximum noncumulate MgO contents are about 16 wt%, olivine xenocrysts in cumulate layers have the composition Fo92, and provide evidence of a komatiite (MgO = ,,-22%) precursor magma. Komatiitic basalts are less depleted than the underlying Mg-basalts, with flat to enriched LREE, negative Nb and Ta anomalies, and eNd = 0.The chemical features of Eskimo Formation basalts and spinifex basalts can be explained by crustal contamination of parental magmas derived from depleted mantle with end = + 5 : the continental tholeiites by 20-30% contamination of parental basalt and the spinifex basalts by about 7% contamination of parental komatiite. The Mg-basalt series results from partial melting of depleted mantle followed by low pressure fractional crystallization, whileFrom PHARAOH, T.

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The Ethiopian Flood Basalt Province

Cited by 162 publications

References 56 publications

Mafic volcaniclastic deposits in flood basalt provinces: A review

Mafic volcaniclastic deposits in flood basalt provinces: A review

North America’s Midcontinent Rift: When rift met LIP

Geochemistry, Petrogenesis and Tectonic Environment of Circum-Superior Belt Basalts, Canada

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