Le manteau supérieur à l’aplomb de la plaine de Kumba (ligne du Cameroun), d’après les enclaves de péridotites à spinelles dans les laves basaltiques

Teitchou, Merlin Isidore; Grégoire, Marilaure; Dantas, C.; Tchoua, Félix M.

doi:10.1016/j.crte.2006.12.006

Cited by 34 publications

(17 citation statements)

References 25 publications

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“…The upper parts of the ascending diapirs would have been laminated as evidenced by the texture of the NK14 sample (transitional porphyroclastic to equigranular, Figure 3(C)). These results would thus confirm the existence of asthenospheric diapirs directly below the upper mantle of Nyos as suggested by Teitchou et al [44]:…”

Section: Discussionsupporting

confidence: 90%

Upper Mantle Dynamic and Evolution beneath Lake Nyos Volcano (Cameroon Volcanic Line), Documented by Peridotite Xenoliths Enclosed in Alkali Basalts

Teitchou¹,

Tchop²,

Grégoire³

et al. 2022

IJG

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Volcanic deposits from the lake Nyos contain ultramafic xenoliths: lherzolites, harzburgites and wehrlites, sometimes containing amphiboles and phlogopites. The lithospheric mantle beneath Nyos, as inferred from chemical diagrams, has experienced partial melting and variably cryptic and modal metasomatism of the two groups of samples that have been distinguished: Group 1 samples are characterized by spoon-shaped REE patterns, and Group 2 samples show light (L) REE-enriched patterns. Metasomatic events were associated with pervasive infiltration of volatile (Ti, CO 2 , H 2 O) or alkali-rich small melts fractions and fluids. Later on, hydrous phases, Ti-rich Cpx, CaO-rich Ol, Ti-rich Ol, Cr poor and low values of NiO and F O (%) in wehrlite compared to other xenoliths, precipitated from alkali enrichments due to the percolation of the mantle by basaltic magmas. The metasomatic liquid which percolates the Nyos mantle column was a dense alkaline silicate rich in volatile, displaying low HFSE abundances in the metasomatic hydrous melts compared to the LILE. It is suggested that 1) cryptic metasomatism affected Group 1 samples, 2) the spinel-free wehrlite is a Group 2 sample corresponding to a cumulate of a similar melt and 3) amphibole may be a potassiumbearing mineral in addition to phlogopite at shallower levels of Nyos upper mantle. P-T estimated indicates that xenoliths were initially equilibrated in the garnet stability field, at depth of 85 Km, and then they were re-equilibrated in the spinel field owing to isobaric heating up to 1000˚C. Adiabatic decompressions occur from 85 to 50 Km materialized by sample NK14 showing transitional porphyroclastic to equigranular texture and displaying pyroxene-Cr How to cite this paper: Teitchou, M.I.,

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Section: Discussionsupporting

confidence: 90%

Upper Mantle Dynamic and Evolution beneath Lake Nyos Volcano (Cameroon Volcanic Line), Documented by Peridotite Xenoliths Enclosed in Alkali Basalts

Teitchou¹,

Tchop²,

Grégoire³

et al. 2022

IJG

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“…8, #7). Similarly, in the Kumba Plain, a south-western extension of the Tombel Graben, a dozen of cinder cones and maars may have a recent Quaternary age (Cornen et al, 1992;Tamen et al, 2007;Teitchou et al, 2007). The Mount Cameroon and the Bioko Island have present-day eruptions (Déruelle et al, 1991(Déruelle et al, , 2000Suh et al, 2003) (Fig.…”

Section: The South Cameroon Line Activitymentioning

confidence: 94%

The discovery of late Quaternary basalt on Mount Bambouto: Implications for recent widespread volcanic activity in the southern Cameroon Line

Dongmo

Nkouathio

Pouclet³

et al. 2010

Journal of African Earth Sciences

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“…In contrast to the Tombel graben where volcanic activity was dominantly Strombolian type and build several scoria cones (e.g., Nkouathio et al, 2002), the KVF is characterised by several volcanic features, including old basaltic lava flows that covered almost the entire field, with short basaltic lava flows outcropping in the north of the volcanic field. The KVF has about forty-seven scoria cones, and four maars: the BMM, the Kotto Barombi, the Mbwadong and the Dissoni maars (Tamen et al, 2007;Teitchou et al, 2007). It is thought that volcanic activity in the KVF began probably in the Eocene (Dumort, 1968) and the latest event occurred probably about 0.05 ka ago at the Barombi Kotto Maar .…”

Section: Geological Settingmentioning

confidence: 97%

Towards the reconstruction of the shallow plumbing system of the Barombi Mbo Maar (Cameroon) Implications for diatreme growth processes of a polygenetic maar volcano

Tchamabé

Ohba

Keresztúri

et al. 2015

Journal of Volcanology and Geothermal Research

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a b s t r a c tUnderstanding the mechanisms involved in the formation of maars and their diatreme growth processes has been a subject of contention. While there is no direct evidence of the presence of diatremes beneath most of the young maars, their existence is inferred based on the amount and type of country rocks excavated at different depths and deposited as pyroclastic ejecta around their craters. Properly tracing fragmented country rocks in ejecta to interpret their depths of origin and thus the depths of phreatomagmatic explosions require good and detailed information on the substrate geology that is generally lacking at many maars. As an alternative, this paper explores the role of juvenile components in deposits of a maar for understanding the cratering and growth of diatremes during maar-forming eruptions. Based on field investigations, pyroclast distribution, componentry and grain morphology examinations this study reports on the eruptive mechanisms that led to the formation of the Barombi Mbo Maar (BMM), a polygenetic maar volcano in Cameroon. The BMM consists of three diatremes that formed during distinct eruptive events and coalesced to produce an "amalgamated maar-diatreme". Two end-member types of eruption styles from the "dry" magmatic to the "wet" phreatomagmatic explosions governed the formation of the maar. In total, a minimum of~0.0658 km 3 of magma (Dense Rock Equivalent corrected) was ejected based on calculation by applying interpolation techniques on digital elevation models obtained from SRTM30m data corrected by rock textural data collected from the field. The distribution of juvenile clasts throughout the stratigraphic sequence suggests a complex subsurface eruptive process, which originated probably within the uppermost part of the diatreme. From the distribution and morphology of juvenile clasts in the deposits, it is inferred that cratering and country rock excavation during the growth of each of the small diatremes developed mainly from shallow level explosions, sometimes with lateral and vertical variations in the position of the explosion loci. A prospective juvenile-based conceptual model is proposed for the formation of the BMM. The model suggests that, during maar-forming eruptions, explosions taking place at a deeper position might entrain extensive amount of lithics from the mostly lithic-dominated upper crater infill to deposit juvenile-poor (b10 vol.%) tephra beds. Layers with a juvenile content of 10-60 vol.%, for example, might result from deep to shallow-seated explosions, with a common entrainment of lithics from the crater infill region, and with much of the remobilized tephra being transported to the ejecta ring sequence. In contrast, explosions occurring at shallower positions will produce mainly juvenile-rich beds (juvenile N 90 vol.%).

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Le manteau supérieur à l’aplomb de la plaine de Kumba (ligne du Cameroun), d’après les enclaves de péridotites à spinelles dans les laves basaltiques

Cited by 34 publications

References 25 publications

Upper Mantle Dynamic and Evolution beneath Lake Nyos Volcano (Cameroon Volcanic Line), Documented by Peridotite Xenoliths Enclosed in Alkali Basalts

Upper Mantle Dynamic and Evolution beneath Lake Nyos Volcano (Cameroon Volcanic Line), Documented by Peridotite Xenoliths Enclosed in Alkali Basalts

The discovery of late Quaternary basalt on Mount Bambouto: Implications for recent widespread volcanic activity in the southern Cameroon Line

Towards the reconstruction of the shallow plumbing system of the Barombi Mbo Maar (Cameroon) Implications for diatreme growth processes of a polygenetic maar volcano

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