Geophysical imaging of metacratonizaton in the northern edge of the Congo craton in Cameroon

Ngalamo, Jeannot F. Goussi; Bisso, Dieudonné; Abdelsalam, Mohamed G.; Atekwana, Estella A.; Katumwehe, Andrew; Ekodeck, Georges Emmanuel

doi:10.1016/j.jafrearsci.2016.12.010

Cited by 45 publications

(12 citation statements)

References 68 publications

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“…Similar tectonic setting was recently proposed by Ngamy Kamwa et al (2019) in the Yoro‐Yamben area and by Hamdja Ngoniri et al (2021) in the Ngazi Tina area. The findings of this study conform to the N‐S geodynamic collision model between the AYD and the northern border of the Congo Craton, resulting in crustal thickening, sub‐crustal lithospheric mantle delamination, and upwelling of the asthenosphere (Goussi Ngalamo et al, 2017, and references therein).…”

Section: Discussionsupporting

confidence: 87%

Zircon trace element geochemistry and Ti‐in‐zircon thermometry of the Linté Pan‐African granitoids, Central Cameroon: Constraints on the genesis of host magma and tectonic implications

et al. 2021

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The Linté area belongs to the central part of the Adamawa‐Yadé Domain (AYD) within the Pan‐African Central African Fold Belt (CAFB) in Cameroon. This area is dominated by Neoproterozoic high‐K calc‐alkaline syenite and monzonite intruding Archean to Palaeoproterozoic gneisses. In this contribution, trace element compositions of zircon obtained using laser ablation inductively coupled plasma mass spectrometry are used to constrain the petrogenesis and tectonic setting of Linté area. The analysed zircon grains display restricted ranges of Hf contents with an average of 8,197 ppm in syenite, 8,220 ppm in alkali‐feldspar syenite, and 9,026 ppm in monzonite. They display high Th/U ratios (>0.5) typical of magmatic zircons. The monzonite zircons have a higher ∑REE content (483.42 ppm) than the syenite zircons (237.70 ppm). The chondrite‐normalized rare‐earth element (REE) diagram of Linté samples shows very similar patterns, characterized by a steeply rising slope due to important heavy rare‐earth element enrichment relative to light rare‐earth element, with distinctive positive Ce and negative Eu anomalies. The application of the Ti‐in‐zircon thermometer reveals a wide range of crystallization temperatures (574–1,137°C for syenites and 713–1,008°C for monzonite), implying a deep level of melting, likely within the lower continental crust of the CAFB. The integration of geochemical behaviours of some trace elements (U, Hf, Zr, Ce, Th, and Nb), together with discrimination diagrams, suggests the crystallization of a continental crust‐derived magma under variable oxidation states and emplacement in a magmatic‐arc setting. This finding represents and adds on to the N‐S geodynamic convergence model between the AYD and the northern border of the Congo Craton.

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Section: Discussionsupporting

confidence: 87%

Zircon trace element geochemistry and Ti‐in‐zircon thermometry of the Linté Pan‐African granitoids, Central Cameroon: Constraints on the genesis of host magma and tectonic implications

et al. 2021

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“…15 out of the 32 broadband seismic stations deployed between 2005 January and 2007 February in Cameroon have been selected to make the comparison. From the comparison of our crustal thickness estimate with those obtained by recent gravity studies of [34,35], it is noticed that most of our results by tectonic provinces in terms of terrain average join those of [34]. As seen from this comparison, our results closely match the Moho model of [34] in the most tectonic provinces of the study area; differences are mainly within ± 1:5 km.…”

Section: Gravity Moho Depth and Comparison With Previoussupporting

confidence: 84%

“…[21] discussed the compensation mechanisms in the North China Craton by comparing the gravity Moho and the isostatic Moho. The authors concluded that most of the earthquakes (M L > 4) occurred beneath areas [34]). WAC: West Africa Craton; CC: Congo Craton; KC: Kalahari Craton; PAB: Pan-African Belt; CCL: Congo Craton Limit; KCSZ: Kribi Campo Shear Zone; CCSZ: Central Cameroon Shear Zone; SSZ: Sanaga Shear Zone.…”

Section: Introductionmentioning

confidence: 99%

“…Several authors have also used the satellite gravimetric model to provide a more accurate result on the estimation of the crustal density and thickness variation. More recently, [34] analyzed the WGM 2012 gravity model to compute the Moho depth of the Mobile belt and the CC through 2D spectral analysis. Their study allowed us to relate the continental collision between the CC and the PAB to the metacratonization processes due to the dense lower crust presence under the southern part of the Adamawa-Yade domain.…”

Section: Introductionmentioning

confidence: 99%

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Crustal Thickness Variations and Tectonic Settings in the Southwest Cameroon Inferred from Gravity and Topography Data

et al. 2022

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EIGEN 6C4 gravity anomalies are interpreted to determine the lateral and vertical variations in the crust and upper mantle structure and their influence on the isostasy of the coastal plain, transition zone between the Congo Craton (CC), the Pan-African Belt (PAB), and adjacent areas. The regional gravity anomalies have been inverted in an attempt to provide a Moho depth map. The inversion process was based on the Parker-Oldenburg method with a density contrast of 0.55 g/cm3 and an average depth reference of 39 km. In addition, various tests have been performed to validate the resulting Moho model and estimate the efficiency of the 3D gravity inversion by varying the density contrast for a fixed Moho reference depth. Inversion results reveal that the Moho depths generally agree with those obtained from previous geophysical studies. The computation of the isostatic models using the ETOPO1 digital elevation model (DEM) and its comparison with the Moho models obtained from gravity induce the following main conclusions: (1) an overcompensated crust beneath the coastal plain and the Yaounde Domain, (2) the crust beneath areas located in the southern end of the Adamawa-Yade Domain is thin and undercompensated, and (3) main volcanoes of the Southwestern Cameroon Volcanic Line (CVL) are isostatically undercompensated. This study also revealed that the local isostatic compensation law is not satisfied for most of the tectonic provinces of the study area, and we suggest alternative tectonic mechanisms to support topography below these tectonic features. Additionally, most seismic events (M>3.5) occurred in areas marked by abrupt changes in compensation amplitude. Thus, we concluded from this study that the northern limit of the CC, the Mount Cameroon, and its surroundings are tectonic extension areas that may play a crucial role in the occurrence of future earthquakes.

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“…To reduce and to quantify the uncertainty of the Moho and LAB calculations, we adopted the procedure of Emishaw et al (), Goussi Ngalamo et al (, ), and Fletcher et al (). First, we used three first‐order polynomial fits for the segments of the spectral curve representing the Moho and LAB.…”

Section: Methodsmentioning

confidence: 99%

Lithospheric Structure Beneath the Cretaceous Chilwa Alkaline Province (CAP) in Southern Malawi and Northeastern Mozambique

et al. 2019

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We used aeromagnetic and satellite gravity data to investigate lithospheric structure beneath the Cretaceous Chilwa Alkaline Province (CAP) in southern Malawi and adjacent Mozambique. The CAP consists of granites, syenites, nepheline syenites, basanites, phonolite dikes, and minor carbonatite bodies. The intrusions were emplaced in the Precambrian (Mesoproterozoic-Neoproterozoic) terranes of the Southern Irumide and Mozambique orogenic belts. Aeromagnetic data show the CAP as overlapping circular anomalies typical of nested igneous ring complexes formed through caldera collapse mechanism. We used gravity data to infer that: (1) the CAP was sourced from~30-km wide igneous bodies now preserved in the upper crust at~5-km depth.(2) the CAP is underlain by up to~45-km thick crust (due to mafic magmatic underplating) and a lithosphere as thin as~90 km. These data suggest that mafic magmatic underplating and lithospheric thinning occurred during a Cretaceous rifting event. We propose, based on these results and taking into account previous petrographic, geochemical, geochronological, and isotopic studies, that the silica undersaturated magmatic phase of the CAP was due to flux melting of the asthenosphere. This was followed by silica-rich magmatic phase due to decompression melting of the asthenosphere as a result of lithospheric thinning. Lithospheric thinning and ascendance of the asthenospheric melt might have been facilitated by the presence of late Neoproterozoic to early Cambrian suture zone. The heat provided by the mafic magmatic underplating resulted in partial melting of the lower crust to form the silica-saturated CAP intrusions from mixed magma sources.

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Geophysical imaging of metacratonizaton in the northern edge of the Congo craton in Cameroon

Cited by 45 publications

References 68 publications

Zircon trace element geochemistry and Ti‐in‐zircon thermometry of the Linté Pan‐African granitoids, Central Cameroon: Constraints on the genesis of host magma and tectonic implications

Zircon trace element geochemistry and Ti‐in‐zircon thermometry of the Linté Pan‐African granitoids, Central Cameroon: Constraints on the genesis of host magma and tectonic implications

Crustal Thickness Variations and Tectonic Settings in the Southwest Cameroon Inferred from Gravity and Topography Data

Lithospheric Structure Beneath the Cretaceous Chilwa Alkaline Province (CAP) in Southern Malawi and Northeastern Mozambique

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