Origin and regional significance of late Precambrian and early Palaeozoic granitoids in the Pan-African belt of Somalia

Lenoir, J.-L.; Li�geois, J.-P.; K�ster, D.; Utke, A.; Matheis, G.; Haider, A.

doi:10.1007/bf00194167

Cited by 8 publications

(10 citation statements)

References 34 publications

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“…1 The East African rift system, indicating the position of the Toro-Ankole, Virunga and South Kivu volcanic fields in the western branch (modified after Milesi et al 2004). Note the gap between the northern end of the western branch and the northern branch Morley 1999, Lenoir et al 1994Rainaud et al 2005;McConnell 1972;De Waele et al 2008). The Rwenzori Mountains are at the junction of the Toro (green) and Kibaran (blue) belts belt (Cahen et al 1984) that borders the southern end of the Tanzania craton.…”

Section: Regional Basement Geology Of the Western And Branch Of The Earsmentioning

confidence: 96%

Continuous cratonic crust between the Congo and Tanzania blocks in western Uganda

Link¹,

Koehn²,

Barth³

et al. 2010

Int J Earth Sci (Geol Rundsch)

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Western Uganda is a key region for understanding the development of the western branch of the East African rift system and its interaction with pre-existing cratonic lithosphere. It is also the site of the topographically anomalous Rwenzori Mountains, which attain altitudes of [5000 m within the rift. New structural and geochronological data indicate that western Uganda south and east of the Rwenzori Mountains consists of a WSW to ENE trending fold and thrust belt emplaced by thickskinned tectonics that thrust several slices of Proterozoic and Archaean units onto the craton from the south. The presence of Archaean units within the thrust stack is supported by new Laser-ICP-MS U-Pb age determinations (2637-2584 Ma) on zircons from the Rwenzori foothills. Repetition of the Paleoproterozoic units is confirmed by mapping the internal stratigraphy where a basal quartzite can be used as marker layer, and discrete thrust units show distinct metamorphic grades. The thrust belt is partially unconformably covered by a Neoproterozoic nappe correlated with the Kibaran orogenic belt. Even though conglomerates mark the bottom of the Kibaran unit, intensive brittle fault zones and pseudotachylites disprove an autochthonous position. The composition of volcanics in the Toro-Ankole field of western Uganda can be explained by the persistence of a cratonic lithosphere root beneath the northwardly thrusted Archaean and Palaeoproterozoic rocks of westernmost Uganda. Volcanic geochemistry indicates thinning of the lithosphere from [140 km beneath Toro-Ankole to ca. 80 km beneath the Virunga volcanic field about 150 km to the south. We conclude that the western branch of the East African rift system was initiated in an area of thinner lithosphere with Palaeoproterozoic cover in the Virunga area and has propagated northwards where it now abuts against thick cratonic lithosphere covered by a thrust belt consisting of gneisses, metasediments and metavolcanics of Neoarchaean to Proterozoic age.

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Section: Regional Basement Geology Of the Western And Branch Of The Earsmentioning

confidence: 96%

Continuous cratonic crust between the Congo and Tanzania blocks in western Uganda

Link¹,

Koehn²,

Barth³

et al. 2010

Int J Earth Sci (Geol Rundsch)

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“…The relationships between Madagascar and surrounding regions of Gondwana. Tight-fit Gondwana reconstruction after Lawver et al (1992Lawver et al ( , 1998 Lenoir et al 1994;Shiraishi et al 1994;Krö ner and Sassi 1996;Shackleton 1996;Krö ner et al 1997;Bartlett et al 1998;Jacobs et al 1998;Teklay et al 1998;Tucker et al 1999aTucker et al , 1999bde Wit et al 2001;Muhongo et al 2001;Whitehouse et al 2001;Yibas et al, in press. morphosed to upper amphibolite to granulite facies at 560-510 Ma (Bartlett et al 1998). The Moyar, Bhavani, and Palghat-Cauvery shear zones were active in late Neoproterozoic times (Meissner et al 2002).…”

Section: Relationship To Surrounding Gondwanan Terrainsmentioning

confidence: 99%

The Tectonic Evolution of Central and Northern Madagascar and Its Place in the Final Assembly of Gondwana

Collins

Windley²

2002

The Journal of Geology

263

148

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A B S T R A C TRecent work in central and northern Madagascar has identified five tectonic units of the East African Orogen (EAO), a large collisional zone fundamental to the amalgamation of Gondwana. These five units are the Antongil block, the Antananarivo block, the Tsaratanana sheet, the Itremo sheet, and the Bemarivo belt. Geochronological, lithological, metamorphic, and geochemical characteristics of these units and their relationships to each other are used as a type area to compare and contrast with surrounding regions of Gondwana. The Antananarivo block of central Madagascar, part of a broad band of pre-1000-Ma continental crust that stretches from Yemen through Somalia and eastern Ethiopia into Madagascar, is sandwiched between two suture zones we interpret as marking strands of the Neoproterozoic Mozambique Ocean. The eastern suture connects the Al-Mukalla terrane (Yemen), the Maydh greenstone belt (northern Somalia), the Betsimisaraka suture (east Madagascar), and the Palghat-Cauvery shear zone system (south India). The western suture projects the Al-Bayda terrane (Yemen) through a change in crustal age in Ethiopia to the region west of Madagascar. Our new framework for the central EAO links the Mozambique belt with the Arabian/Nubian Shield and highlights the power of tectonic analysis in unraveling the complex tectonic collage of the EAO.

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“…FC, along with limited contamination by middle to upper crustal material, has been found to be a plausible process for the generation of high-silica potassic (A-type) leucogranites in many parts of north-east Africa (e.g. Küster et al 1990;Lenoir et al 1994;NØdØlec et al 1995).…”

Section: Petrogenesis Of the Konso Plutonmentioning

confidence: 99%

Petrology, geochronology and Sr?Nd isotopic geochemistry of the Konso pluton, south-western Ethiopia: implications for transition from convergence to extension in the Mozambique Belt

Asrat

Barbey²

2003

International Journal of Earth Sciences

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Granites were shown to be excellent geochronological, structural and geodynamic markers. Among several generations of granites described in the Neoproterozoic of Ethiopia, we studied the post-tectonic Konso pluton to characterise the post-Pan-African evolution of the Mozambique Belt (MB) of southern Ethiopia. The Konso pluton is a composite intrusion of slightly peraluminous and ferro-potassic, bt (biotite)-leucogranites, bt-hbl (hornblende)-granites and subordinate coeval metaluminous monzodiorites, intruded into high-grade gneiss-migmatite associations of the MB. The whole suite displays chemical features of A-type granites. It is LIL-and HFS-elements enriched with Y/Nb and Yb/ Ta!1.2. The granites and leucogranites show nonfractionated to fractionated REE patterns [(La/ Yb) N =0.3-9.4] with strong negative Eu anomalies. The monzodiorites show fractionated REE patterns [(La/ Yb) N =5.5-7.4] with negligible negative Eu anomaly. The low initial ( 87 Sr/ 86 Sr) 450 ratios (0.70113-0.70441) and positive eNd (450) values (+1.8 to +3.3) suggest an isotopically primitive source. The Konso granites are likely to be derived from a basaltic parent, with minor contamination by crustal material with high Y/Nb and low Sr initial isotopic ratios. Age of pluton emplacement is constrained by a Rb-Sr isochron and zircon U-Pb data at 449€2 Ma. The Konso pluton is, therefore, the witness of an Ordovician A-type magmatic event, which marks a change from convergence, related to the Pan-African collision, to extension in the Mozambique Belt of southern Ethiopia.

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Origin and regional significance of late Precambrian and early Palaeozoic granitoids in the Pan-African belt of Somalia

Cited by 8 publications

References 34 publications

Continuous cratonic crust between the Congo and Tanzania blocks in western Uganda

Continuous cratonic crust between the Congo and Tanzania blocks in western Uganda

The Tectonic Evolution of Central and Northern Madagascar and Its Place in the Final Assembly of Gondwana

Petrology, geochronology and Sr?Nd isotopic geochemistry of the Konso pluton, south-western Ethiopia: implications for transition from convergence to extension in the Mozambique Belt

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