Crustal age domains in the Kibaran belt of SW-Uganda: Combined zircon geochronology and Sm–Nd isotopic investigation

Buchwaldt, Robert; Toulkeridis, Theofilos; Todt, W.; Ucakuwun, E. K.

doi:10.1016/j.jafrearsci.2007.11.001

Cited by 33 publications

(19 citation statements)

References 43 publications

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“…Rb-Sr or K-Ar in mica from the Buganda-Toro belt range from 1811 ± 60 (Cahen and Snellling 1966) to 1864 ± 37 Ma (Harper et al 1972). Granite bodies between Fort Portal and Kampala interpreted as syn-to post-tectonic are about 1850 Ma old (1847 ± 6 Ma; Nagudi et al 2003 Koehn et al (2008Koehn et al ( , 2009); Twesigomwe and Ssemmanda (1998); and our own field data 1250 Ma (Buchwaldt et al 2008). These rocks pre-date intrusions emplaced at 1000-970 Ma (Tack et al 2002).…”

Section: Geochronological Informationmentioning

confidence: 60%

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: Geochronological Informationmentioning

confidence: 60%

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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“…Sm‐Nd t DM model ages for Kibaran mafic‐ultramafic to granite intrusions mostly range from 0.9 to 2.5 Ga [ Tack et al ., ; Duchesne et al ., ]. Four Mesoproterozoic granitoid bodies intruding low‐grade Karagwe‐Ankole meta‐sediments in southernmost Uganda yielded more negative εNd (0) between −20 and −35, and older t DM model ages between 3.8 and 2.9 Ga [ Buchwaldt et al ., ].…”

Section: The East African Riftmentioning

confidence: 99%

Weathering geochemistry and Sr‐Nd fingerprints of equatorial upper Nile and Congo muds

Garzanti

Padoan

Setti

et al. 2013

Geochem Geophys Geosyst

162

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[1] This study investigates processes of sediment generation in equatorial central Africa. An original, complete and integrated mineralogical-geochemical database on silt-sized sediments derived from different parent rocks (basalt, granite, gneiss, metapsammite, sandstone) along the East African Rift from 5 S in Tanzania to 5 N in Sudan is presented and used to assess the incidence of diverse factors controlling sediment composition (source-rock lithology, geomorphology, hydraulic sorting, grain size, recycling), with particular emphasis on chemical weathering. [2] Kaolinite abundance, CIA, and a Al values consistently indicate less intense weathering along the steep inner flank and drier axis of the rift hosting Lakes Kivu and Tanganyika than in hot-humid forested highlands east of the Nile-Congo divide, where slopes are gentler and time for weathering longer. The observed order of bulk-sediment mobility (Na ≥ Ca > Sr > Mg > K > Ba ≥ Rb > Cs) roughly corresponds to the degree into which these elements are partitioned in unstable plagioclase versus K-feldspar and phyllosilicates. Weathering-limited erosion characterizes the Rwenzori massif and the Lake Albert

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“…These dates are slightly younger than the climax of the compressional overprint in the KAB as far-field effect of the East African Orogeny, which traditionally has been put around 550 Ma (De Waele et al, 2008;Dewaele et al, 2011;Fernandez-Alonso et al, 2012). This delay possibly reflects the process of aqueous fluxes percolating through underthrust fault systems towards the west as the result of final collision tectonics and associated crustal thickening more to the east (Buchwaldt et al, 2008;Fig. 10).…”

Section: Integration In the Geodynamic Settingmentioning

confidence: 94%

“…During the Mesoproterozoic, dominantly terrigeneous shallow-water sediments were deposited in various sedimentary basins (Buchwaldt et al, 2008;Fernandez-Alonso et al, 2012;Tack et al, 2010). Within the WD, these sediments are grouped into the Akanyaru Supergroup, which contains four groups.…”

Section: Geological Settingmentioning

confidence: 99%

Geochronology of metamorphism, deformation and fluid circulation: A comparison between Rb-Sr and Ar-Ar phyllosilicate and U-Pb apatite systematics in the Karagwe-Ankole Belt (Central Africa)

et al. 2020

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This work presents an integrated geochronology study combining step-heating Ar-Ar and in-situ Rb-Sr phyllosilicate geochronology with EPMA elemental maps and U-Pb apatite geochronology in order to determine the timing and duration of regional deformation and fluid circulation processes in the Karagwe-Ankole Belt in Central Africa. The Kibuye-Gitarama-Gatumba study area (West Rwanda) forms part of the 2 Western Domain of this Mesoproterozoic belt, where the metamorphic and deformation history, geothermometric evolution and mineralization processes (both genesis and geochronology) have been well-documented in previous studies. Our geochronological results and interpretations show the importance of thermal diffusion throughout the elevated temperature regime present in the Neoproterozoic. During the Ediacaran, metamorphism and fluid alteration in the Gatumba area was associated with deformation, as independently demonstrated by U-Pb apatite and Ar-Ar phyllosilicate geochronology. From the end of the Ediacaran until the Late Cambrian, saline fluid activity is recorded and fluid-induced (re)crystallization processes dominate the Gatumba biotite Rb-Sr isotope record. The direct comparison between Rb-Sr and Ar-Ar geochronology suggests a parentless 40 Ar-component is preserved during this fluid-induced (re)crystallization due to its saline, (earth) alkali-rich composition. Additionally, this multi-method approach allows us to place the history of the Western Domain of the Karagwe-Ankole belt in relation to that of the surrounding areas, i.e. the Eastern Domain and the Congo and Tanzania Cratons. Deformation and epidote-amphibolite facies metamorphism (at ~590 -570 Ma), and fluid fluxes (at ~590 -495 Ma) occurred in the Kibuye-Gitarama-Gatumba area after the West Gondwana Orogeny but from the onset of the East African Orogeny onwards till after the culmination of the Gondwana amalgamation, demonstrating the progressively eastwardmoving orogenic front in this supercontinent assembly.

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Crustal age domains in the Kibaran belt of SW-Uganda: Combined zircon geochronology and Sm–Nd isotopic investigation

Cited by 33 publications

References 43 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

Weathering geochemistry and Sr‐Nd fingerprints of equatorial upper Nile and Congo muds

Geochronology of metamorphism, deformation and fluid circulation: A comparison between Rb-Sr and Ar-Ar phyllosilicate and U-Pb apatite systematics in the Karagwe-Ankole Belt (Central Africa)

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