The geology of the angareb ring dike complex, northwestern ethiopia

Hahn, Gregory A.; Raynolds, Robert G.; Wood, Raymond

doi:10.1007/bf02599825

Cited by 34 publications

(8 citation statements)

References 8 publications

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“…The highest values of subsidence concentrate immediately north of the Lake Tana in correspondence with the Angareb ring complex. This region probably represented one of the main feeding areas of the system [ Hahn et al ., ]. Filtering the isostatic and the postflood basalt contributions from the topography, we infer the preflood basalt configuration (Figures a and e). This surface has an average elevation of ~750 m asl and presents two topographic highs in the present Lake Tana region and in the southernmost portion of the study area (Figures a and e).…”

Section: Discussionmentioning

confidence: 99%

“…In particular, the highest values fall around the Angareb ring complex, immediately north of the lake (Figure c). This region most probably represented one of the main feeding areas of the system [ Hahn et al ., ]. Thick deposits (1200–1500 m) fill the Desse‐Tana Depression and are located in correspondence of the lower Blue Nile River valley (Figure c). By considering the actual Trap distribution (Figure c) and thickness (Figure c) we estimate a minimum total Trap volume of ~9 · 10 5 km 3 (84% in the Ethiopian Plateau, 10% in the Somalian Plateau, and 6% in the Yemen Plateau).…”

Section: Geometry Of the Flood Basaltsmentioning

confidence: 99%

“…The highest values are found immediately north of the Lake Tana in correspondence with the Angareb ring complex which, according to Hahn et al . [], represented one of the most active flood basalt eruption centers. From the erosional unloading model, we determine a maximum flexural uplift between 47 and 156 m (see supporting information Table S3 and Figure S5).…”

Section: Restoring Topography Back In Timementioning

confidence: 99%

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Long-term, deep-mantle support of the Ethiopia-Yemen Plateau

et al. 2016

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Ethiopia is a key site to investigate the interactions between mantle dynamics and surface processes because of the presence of the Main Ethiopian Rift (MER), Cenozoic continental flood basalt volcanism, and plateau uplift. The role of mantle plumes in causing Ethiopia's flood basalts and tectonics has been commonly accepted. However, the location and number of plumes and their impact on surface uplift are still uncertain. Here we present new constraints on the geological and topographic evolution of the Ethiopian Plateau (NW Ethiopia) prior to and after the emplacement of the large flood basalts (40-20 Ma). Using geological information and topographic reconstructions, we show that the large topographic dome that we see today is a long-term feature, already present prior to the emplacement of the flood basalts. We also infer that large-scale doming operated even after the emplacement of the flood basalts. Using a comparison with the present-day topographic setting, we show that an important component of the topography has been and is presently represented by a residual, nonisostatic, dynamic contribution. We conclude that the growth of the Ethiopian Plateau is a long-term, probably still active, dynamically supported process. Our arguments provide constraints on the processes leading to the formation of one of the largest igneous plateaus on Earth.

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Section: Discussionmentioning

confidence: 99%

Section: Geometry Of the Flood Basaltsmentioning

confidence: 99%

Section: Restoring Topography Back In Timementioning

confidence: 99%

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Long-term, deep-mantle support of the Ethiopia-Yemen Plateau

et al. 2016

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“…Geochemistry, Geophysics, Geosystems been coeval with the eruption of the Alaje/upper flood basalts (Hahn et al, 1976), which is now dated at the end of the main flood basalt event at ca. 29 Ma (Abbate et al, 2014;Hofmann et al, 1997).…”

Section: 1029/2018gc007724mentioning

confidence: 99%

Constraining the Magmatic Plumbing System in a Zoned Continental Flood Basalt Province

Rooney

Krans

Mège

et al. 2018

Geochem Geophys Geosyst

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The geographic heterogeneities in lava composition observed in continental flood basalt provinces could provide a probe of material upwelling from the deep mantle and their length scales, but their utility is limited by uncertainties in the locus of magmatism. We examine the magma plumbing system for the Oligocene Ethiopian flood basalts. The province, which exhibits domains defined by the eruption of low‐Ti (LT) and high‐Ti (HT) lavas, requires a magmatic plumbing system that facilitates the transit of compositionally distinct magmas through the crust without mixing. Here we present a geochemical and geochronological study of a suite of 43 dikes from western Ethiopia. We find that the dikes were dominantly emplaced contemporaneously with the Oligocene flood basalt phase of activity. The composition of the dikes is overwhelmingly LT in character, typified by an overall flat rare earth element pattern (median value of La/LuCN = 2.6), and a lack of enrichment in incompatible trace elements in comparison to the HT lavas. These observations confirm the western Ethiopian dike swarm as a source for the LT flood basalts in the Ethiopian flood basalt province. We also present tentative evidence for an eastward migration in the LT dike system over time. These observations are consistent with the terminal stages of the LT magmatism being centered on the Simien shield volcano. We conclude that the apparent separation of ~400 km between the LT and HT magma plumbing systems allowed for the development of a strongly geochemically zoned continental flood basalt province.

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“…Most outflow lag breccias seem associated with high-energy but small-volume eruptions (greater than 100 km 3) of relatively mafic tuff (dacite, rhyodacite); many largevolume quartz latitic and rhyolitic tuffs, as in the San Juan field, contain sparse lithic fragments in the outflow sheet, even when coarse collapse breccias accumulated within the source caldera. [Oftedahl, 1978], Glen Coe in Scotland [Roberts, 1966;Taubeneck, 1967;Bailey, 1969], the Angareb ring complex in western Ethiopia [Hahn et al, 1977], and the Conway-Moat Mountain area, New Hampshire [Noble and Billings, 1967].…”

Section: Lenses Of Landslide Debris a Few Tens Of Meters Thick Occur mentioning

confidence: 99%

The Roots of Ash Flow Calderas in Western North America: Windows into the Tops of Granitic Batholiths

Series

1984

Collected Reprint Series

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Large-volume ash flow eruptions and associated caldera collapses provide a direct link with subvolcanic granitic plutons of batholithic dimensions. The eruptive history, structural features, and petrologic evolution of ash flow calderas provide data on early stages of the evolution of an associated subvolcanic magmatic system. Broadly cogenetic, erosionally unroofed granitic plutons provide a record mainly of the late stages of emplacement and crystallization of silicic magmas. This review summarizes features of well-studied calderas and ash flow volcanic fields in western North America, exposed at advantageous levels where both remnants of a volcanic sequence and upper parts of the cogenetic intrusion are preserved, in comparison with similar rocks elsewhere in the world. Primary examples include San Juan, Mogollon-Datil, Marysvale, Latir-Questa, Chiricahua-Turkey Creek, Challis, and Boulder Batholith-Elkhorn Mounfains. Most ash flows have erupted from sites of preceding volcanism that records shallow accumulation of caldera-related magma. Structural boundaries of calderas are single ring faults or composite ring fault zones that dip vertically to steeply inward' outward dipping boundary faults favored by some models have not been identified in North American calderas. The area and volume of caldera collapse are roughly proportional to the amount of erupted material. Pyroelastic eruptions of relatively small volume (less than 50-100 km 3) may cause incomplete hinged caldera subsidences or structural sags; larger systems are bounded by complete ring faults. Few ash flow vent structures have been related to major calderas' vent geometry, as determined by size analyses of pyroelastic materials, may shift complexly during 9aidera collapse. Scalloped topographic walls beyond the structural boundaries of most calderas are due to secondary gravitational slumping during subsidence. Most exposed floors are a structurally coherent plate or cylinder bounded by a ring fault or dike, indicating pistonlike caldera collapse' chaotically brecciated floors predicted by models of piecemeal collapse have not been identified. Deviations from circular shape commonly reflect influence of regional structures; some calderas in extensional terranes are elongate in the direction of extension. Large calderas (greater than 100 km 3 of erupted material) collapse concurrently with eruption, as indicated by thick intracaldera ash flow fill and interleaved collapse slide breccias. Volumes of intracaldera an d outflow tuff tend to be subequal' correlation between them is commonly complicated by contrasts in abundance and size of phenocrysts and lithie fragments, degree of welding, devitrification, alterati øn, and even chemical composition of magmatic material. Postcollapse volcanism may occur from varied vent geometries within ash flow calderas' ring vent eruptions are most common in resurgent calderas, reflecting renewed magmatic pressure. Large intrusions related to resurgence are exposed centrally within some calderas; ring dikes and other ...

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The geology of the angareb ring dike complex, northwestern ethiopia

Cited by 34 publications

References 8 publications

Long-term, deep-mantle support of the Ethiopia-Yemen Plateau

Long-term, deep-mantle support of the Ethiopia-Yemen Plateau

Constraining the Magmatic Plumbing System in a Zoned Continental Flood Basalt Province

The Roots of Ash Flow Calderas in Western North America: Windows into the Tops of Granitic Batholiths

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