Petrogenesis of silicic peralkaline rocks in the Ethiopian rift: Geochemical evidence and volcanological implications

Peccerillo, Angelo; Donati, Carmelita; Santo, Alba Patrizia; Orlando, Andrea; Yirgu, Gezahegn; Ayalew, Dereje

doi:10.1016/j.jafrearsci.2006.06.010

Cited by 99 publications

(62 citation statements)

References 42 publications

(75 reference statements)

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“…This contradicts the previous works on felsic lavas along the CVL (e.g. Franz et al 1999;Ngounouno et al 2000;Peccerillo et al 2007) reporting low Ba (10-107 ppm) and Zr/Nb (2.4-4.5).…”

Section: Crustal Contamination and Magma Minglingcontrasting

confidence: 94%

Petrology and geochronology of felsic volcanics in the Sabga area (Bamenda Highlands): implications for age variation along the Cameroon Volcanic Line

Tibang¹,

Suh²,

Cottle³

et al. 2018

J. Geosci.

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The textural characteristics of felsic lavas and ignimbrites in the Sabga area along the continental segment of the Came roon Volcanic Line (CVL) are documented in this study. Two rhyolitic lava flows separated by mafic and rhyodacitic lava flows were dated by zircon LA-ICP-MS technique in order to constrain the timescales of successive flow emplace ment as well as magma chamber processes in this volcanic field. The studied samples have rheomorphic characteristics such as eutaxitic textures defined by elongated fiamme as well as deformed and welded glass shards. They exhibit flow banding and contain spherulitic groundmass. Rhyolitic autobreccias and ignimbrites are widespread in the Sabga area, are peralkaline in nature and their ages are broadly similar at ~23.0 ± 0.3 Ma (23.34 ± 0.34 Ma for the ignimbrite and 22.98 ± 0.28 Ma for the rhyolitic autobreccia unit). These ages suggest rapid recharge of magma into a periodically replenished and open chamber. The felsic rocks in the Sabga area and around the Bamenda Highlands are also younger compared to other felsic units along the CVL (29 Ma to 69.4 ± 0.4 Ma).

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“…This contradicts the previous works on felsic lavas along the CVL (e.g. Franz et al 1999;Ngounouno et al 2000;Peccerillo et al 2007) reporting low Ba (10-107 ppm) and Zr/Nb (2.4-4.5).…”

Section: Crustal Contamination and Magma Minglingcontrasting

confidence: 94%

Petrology and geochronology of felsic volcanics in the Sabga area (Bamenda Highlands): implications for age variation along the Cameroon Volcanic Line

Tibang¹,

Suh²,

Cottle³

et al. 2018

J. Geosci.

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“…Fractional crystallization of basaltic magma rather than anatexis of continental crust was the major source for the silicic magmas of the Afar and rift valley margins Peccerillo et al, 2003;Peccerillo et al, 2007;Ayalew and Gibson, 2009;Rooney et al, 2012b). A lessened magma supply rate, resulting in magmatic intrusion at greater depths and slower cooling (Behn et al, 2006), fostered crystal fractionation processes together with lithospheric assimilation.…”

Section: Stage 2: Tectonic Stretchingmentioning

confidence: 99%

Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin

Rooney

Mohr

Dosso

et al. 2013

Geochimica et Cosmochimica Acta

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evidence of mantle reservoir evolution during progressive rifting along the western Afar margin. Geochimica et Cosmochimica Acta, Elsevier, 2013Elsevier, , 102, pp.65-88. 10.1016Elsevier, /j.gca.2012 Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin AbstractThe Afar triple junction, where the Red Sea, Gulf of Aden and African Rift System extension zones converge, is a pivotal domain for the study of continental-to-oceanic rift evolution. The western margin of Afar forms the southernmost sector of the western margin of the Red Sea rift where that margin enters the Ethiopian flood basalt province. Tectonism and volcanism at the triple junction had commenced by $31 Ma with crustal fissuring, diking and voluminous eruption of the EthiopianYemen flood basalt pile. The dikes which fed the Oligocene-Quaternary lava sequence covering the western Afar rift margin provide an opportunity to probe the geochemical reservoirs associated with the evolution of a still active continental margin. 40 Ar/ 39 Ar geochronology reveals that the western Afar margin dikes span the entire history of rift evolution from the initial Oligocene flood basalt event to the development of focused zones of intrusion in rift marginal basins. Major element, trace element and isotopic (Sr-Nd-Pb-Hf) data demonstrate temporal geochemical heterogeneities resulting from variable contributions from the Afar plume, depleted asthenospheric mantle, and African lithosphere. The various dikes erupted between 31 Ma and 22 Ma all share isotopic signatures attesting to a contribution from the Afar plume, indicating this initial period in the evolution of the Afar margin was one of magma-assisted weakening of the lithosphere. From 22 Ma to 12 Ma, however, diffuse diking during continued evolution of the rift margin facilitated ascent of magmas in which depleted mantle and lithospheric sources predominated, though contributions from the Afar plume persisted. After 10 Ma, magmatic intrusion migrated eastwards towards the Afar rift floor, with an increasing fraction of the magmas derived from depleted mantle with less of a lithospheric signature. The dikes of the western Afar margin reveal that magma generation processes during the evolution of this continental rift margin are increasingly dominated by shallow decompressional melting of the ambient asthenosphere, the composition of which may in part be controlled by preferential channeling of plume material along the developing neo-oceanic axes of extension.

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“…Numerous studies have examined the geochemical characteristics of Quaternary magmatism within the WFB, focusing on the issue of assimilation and fractional crystallisation of the basalts and the magmagenesis of the silicic products in the rift (Cole, 1969;Dickinson and Gibson, 1972;Weaver et al, 1972;Brotzu et al, 1974;Gibson, 1975;Brotzu et al, 1981;Gasparon et al, 1993;Webster et al, 1993;Boccaletti et al, 1995;Boccaletti et al, 1999a;Trua et al, 1999;Peccerillo et al, 2003;Peccerillo et al, 2007;Rampey et al, 2010;Ronga et al, 2010). A full review is beyond the scope of this paper, though basalts erupted in the WFB are among the least crustally contaminated in the region (e.g.…”

Section: Magmatic Fractionation Systems -Wfbmentioning

confidence: 99%

Insights into extensional processes during magma assisted rifting: Evidence from aligned scoria cones

Rooney

Bastow

Keir

2011

Journal of Volcanology and Geothermal Research

125

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Mechanical and magmatic processes exert first-order control on the architecture and evolution of rifts. As a continental rift develops towards a new oceanic spreading centre, extension that is initially accommodated in a broad zone of faulting and ductile stretching must transition towards a narrow zone of focused magmatic intrusion. The Main Ethiopian Rift (MER), part of the East African Rift System, is an ideal location to study this transition because it captures rifting processes during continental breakup. In this contribution we synthesise geochemical data from scoria cones in the Wonji Fault Belt (WFB) and Silti-Debre Zeyit Fault Zone (SDFZ) in the MER to provide new constraints on the development of mantle melting columns and magmatic plumbing systems since the onset of rifting. We utilize the extensive geophysical and geochemical databases, collected in the Ethiopian Rift, to show that geochemical evidence of heterogeneity in the depth of the mantle melting column which produced Quaternary rift basalts correlates with lithospheric structure. When combined with existing observations of asymmetry across the rift in terms of depth of melting column and magmatic plumbing systems, it is evident that the mechanical structure of the rift, defined during the initial stages of breakup, has played a dominant role in the initial development of magma assisted rifting in the MER. Surface structures and crustal-scale geophysical studies have suggested the WFB is analogous to a sea-floor spreading centre. However, the geochemical characteristics of rift basalts are consistent with mantle tomography that shows no evidence beneath the MER for passive magmatic upwelling beneath discrete rift segments as is observed in the ocean basins. Collectively, the Ethiopian data show that the distribution of mantle melts during the initiation of magma assisted rifting is fundamentally influenced by lithospheric structures formed during earlier syn-rift stretching.

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Petrogenesis of silicic peralkaline rocks in the Ethiopian rift: Geochemical evidence and volcanological implications

Cited by 99 publications

References 42 publications

Petrology and geochronology of felsic volcanics in the Sabga area (Bamenda Highlands): implications for age variation along the Cameroon Volcanic Line

Petrology and geochronology of felsic volcanics in the Sabga area (Bamenda Highlands): implications for age variation along the Cameroon Volcanic Line

Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin

Insights into extensional processes during magma assisted rifting: Evidence from aligned scoria cones

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