Geology, geochronology and geodynamic implications of the Cenozoic magmatic province in W and SE Ethiopia

Berhe, S. M.; Desta, B.; Nicoletti, M.; Teferra, M.

doi:10.1144/gsjgs.144.2.0213

Cited by 117 publications

(60 citation statements)

References 35 publications

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“…The ground mass contains olivine, clinopyroxene, Fe-Ti oxides and plagioclase (An85-An48 range) microlites. The Oligocene volcanism of the northwestern Ethiopian Plateau has been subdivided into three formations (Berhe et al, 1987); the Ashangi and Amba Aiba basaltic units, separated by an angular unconformity (Zanettin, 1992) from the upper ignimbritic Alaji unit. In the Lalibela monumental site, the Amba Aiba basalts are typically overlain by a thick horizon of reddish highly hydrothermally weathered basaltic scoria (commonly referred to as "tuffaceous material").…”

Section: Climatic and Geological Settingmentioning

confidence: 99%

Fourier transform infrared spectroscopic characterization of clay minerals from rocks of Lalibela churches, Ethiopia

Kiros¹,

Gholap²,

Gigante³

2013

Int. J. Phys. Sci.

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This study demonstrates the Fourier transform infrared (FTIR), Raman spectroscopy and scanning electron microscope -energy dispersive X-ray spectrometer (SEM-EDS) techniques which has been applied to characterize decay products and processes occurring at the surface of rock-hewn churches at the UNESCO's World Heritage site of Lalibela, Northern Ethiopia. Spectroscopic analyses comparing the observed frequencies with the available literature, minerals were identified. A special emphasis is devoted to the presence of whewellite/weddellite and kaolinite minerals, never pointed out before this study in the rock hewn churches of Lalibela, and their possible roles on rock decay. The identification of montmorillonite as a weathering product up to 20 mm from the rock/atmosphere interface beyond the level at which kaolinite, whewellite and gypsum are found, suggests that montmorillonite may penetrate even deeper into the rock substrate causing major rock decay. Results indicate that biological attack by green algae and lichens is currently responsible for severe stone surface, physical and chemical weathering leading to considerable weakening of the churches walls. A prompt and careful removal of the biological and other deposits with the non-destructive method (laser cleaning) treatment is therefore recommended.

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Section: Climatic and Geological Settingmentioning

confidence: 99%

Fourier transform infrared spectroscopic characterization of clay minerals from rocks of Lalibela churches, Ethiopia

Kiros¹,

Gholap²,

Gigante³

2013

Int. J. Phys. Sci.

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“…9a). The age distribution of the products of the upper volcanic sequence demonstrates that the volcanic activity started at $10 Ma and developed in three main phases (Miller and Mohr, 1966;Morton et al, 1979;Berhe et al, 1987;Wolde Gabriel et al, 1990, Abebe et al, 1998. Fissure lava flows (e.g., the Anchar and Guraghe basalts, the basal lava flows of the Tullu Wellel Massif) erupted mainly during the oldest phase (10-7 Ma), whilst central volcanoes were formed during the second (6-2 Ma) and third (<1 Ma) phase, with a roughly eastward migration of the foci of volcanism (Fig.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The Afar triple junction, which includes the East African Rift System (EARS) and the Red Sea and Gulf of Aden rifts, is excellent for studying basalt composition as a function of mantle source heterogeneity and degree of melting, and in the last 260 S. Tommasini et al decades a number of models have been proposed to account for its geodynamic evolution (e.g., Baker et al, 1972;Berhe et al, 1987;Hart et al, 1989;Kampunzu and Mohr, 1991;Schilling et al, 1992;Deniel et al, 1994;George and Rogers, 1999;Rogers et al, 2000;Debayle et al, 2001). In this paper we present the result of a study on the geochemical characteristics of mafic lavas outcropping in one sector located in the southern part of the Main Ethiopian Rift (MER) close to Megado, in the Sidamo region, and in two sectors located off-axis the MER, namely, the Yerer-Tullu Wellel Volcano-Tectonic Lineament (YTVL), central Ethiopia, and the southern part of Lake Tana, North Ethiopia (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…5a), have been likely modified during their passage through the shallower domain of the subcontinental mantle, which has different trace element enrichment factors. (Miller and Mohr, 1966;Morton et al, 1979;Berhe et al, 1987;Wolde Gabriel et al, 1990;Abebe et al, 1998). The other two diagrams depict the variation in the depth of melt extraction (b) and Zr=Nb (c) along the volcano-tectonic lineament 274 S. Tommasini et al…”

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The Ethiopian subcontinental mantle domains: geochemical evidence from Cenozoic mafic lavas

et al. 2005

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SummarySince the Cenozoic, Ethiopia was affected by a widespread volcanic activity related to the geodynamic evolution of the Afar triple junction. The plateau building phase was followed by the formation of the Main Ethiopian Rift (MER) accompanied by a bimodal volcanic activity in both the inner parts of the rift and its shoulders. Outside the rift, a concurrent volcanic activity occurred mainly along transversal tectonic lineaments, the most important of which is the Yerer-Tullu Wellel Volcano-Tectonic Lineament (YTVL) developing for $500 km westward of Addis Abeba. Scattered Pliocene -Quaternary volcanoes are reported also inside the plateau such as those outcropping nearby Lake Tana.Here we present the result of a study on carefully screened mafic lavas outcropping in two sectors located off-axis the MER, namely, the YTVL and the southern part of Lake Tana; and in one sector located in the southern tip of the MER close to Megado, in the Sidamo region. The screened samples are petrographically fresh and have SiO 2 <52 wt.% and MgO>4 wt.%, to minimise crystal fractionation effects. Most of the samples belong to the Late Miocene -Quaternary volcanic activity of the East African Rift System (EARS), although a number of samples along the YTVL are representative of the Late Eocene -Early Miocene Ethiopian Volcanic Plateau flood basalts. The selected mafic lavas offer the opportunity to assess the geochemical diversity, if any, Ã Supplementary material to this paper is available in electronic form at http:==dx.doi.org= 10.1007=s00710-005-0081-9 of the subcontinental mantle domains along the MER (Megado and the easternmost part of the YTVL) and in sectors far away from the MER (YTVL and Lake Tana). The samples have a wide compositional range: from basanite to alkali basalt, hy-normative basalt, qz-normative basalt, basaltic andesite, hawaiite, trachybasalt, and trachyandesite. The major and trace element characteristics of the mafic lavas demonstrate an origin from a relatively fertile and trace element enriched lithospheric mantle at pressure variable from $2.0 to 3.5 GPa. Moreover, systematic variations in K=Nb, Ba=Nb, and Ba=Rb demand for the contribution of trace amounts of phlogopite to melt production.The geochemical signature coupled with the geographical distribution of the Late Miocene -Quaternary samples along the YTVL ($500 km) and the Lake Tana and Megado sectors set constraints on a relatively homogenous lateral continuity of the deeper lithospheric mantle domains ($2-3.5 GPa). On the other hand, the trace element characteristics of the Ethiopian Volcanic Plateau samples along the YTVL, demand for a chromatographic process en route to the surface and indicate a shallower lithospheric mantle domain (<2 GPa) with a different geochemical signature. Overall, the selected mafic lavas provide evidence for vertically zoned lithospheric mantle domains: the shallower domain (<2 GPa) consists of an enriched mantle component with a geochemical signature similar to continental crust material (EM II), whilst the de...

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“…In 1990, new hominid remains and major Oldowan and Acheulean occurrences were discovered, and the Bodo cranium and associated artifacts were dated to ca. 0.6 Ma [White et a/., 1993; 100 km Berhe et al [1987]. Clark et al, 1994],nearly doubling the previ ously estimated age.…”

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confidence: 97%

Geoscience methods lead to paleo‐anthropological discoveries in Afar Rift, Ethiopia

WoldeGabriel¹,

Renne²,

Ambrose

et al. 2004

EoS Transactions

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With few exceptions, most of the hominid evolutionary record in Africa is closely associated with the East African Rift System. The exceptions are the South African and Chadian hominids collected from the southern and west‐central parts of the continent, respectively Ethiopia's Middle Awash region stands alone as the most prolific paleo‐anthropological area ever discovered (Figure 1). Its paleontological record has yielded over 13,000 vertebrate fossils, including several hominid taxa, ranging in age from 5.8 Ma to the present. The uniqueness of the Middle Awash hominid sites lies in their occurrence within long, > 6 Ma volcanic and sedimentary stratigraphic records.

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Geology, geochronology and geodynamic implications of the Cenozoic magmatic province in W and SE Ethiopia

Cited by 117 publications

References 35 publications

Fourier transform infrared spectroscopic characterization of clay minerals from rocks of Lalibela churches, Ethiopia

Fourier transform infrared spectroscopic characterization of clay minerals from rocks of Lalibela churches, Ethiopia

The Ethiopian subcontinental mantle domains: geochemical evidence from Cenozoic mafic lavas

Geoscience methods lead to paleo‐anthropological discoveries in Afar Rift, Ethiopia

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