Existence de dykes doléritiques anciens à composition de tholéiites continentales au sein de la province alcaline de la ligne du Cameroun. Implication sur le contexte géodynamique

Vicat, Jean-Paul; Ngounouno, Ismaı̈la; Pouclet, André

doi:10.1016/s1251-8050(01)01526-9

Cited by 9 publications

(19 citation statements)

References 17 publications

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“…Alkali-earth element Sr (430-700 ppm) and Ba (800-1300 ppm) contents are high and close to those of Biden dolerites in the Adamawa plateau, Cameroon [12] which exhibit very high Ba contents (up to 1802 ppm). Rb contents (28-76 ppm) show a wide range and are higher than in Mayo Oulo-Léré dolerites, Cameroon (10 ppm, [13]) and the Neoproterozoic flood basalts (≈ 4 ppm) of the lower Dja, Yokadouma and Nola, Cameroon [14].…”

Section: Geochemistrymentioning

confidence: 67%

“…Zr/Nb ratios in Group 1 (12.3-13.8) are nearly constant, whereas they are fairly higher in Group 2 (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Ratios in both groups are similar to E-MORB (between 10 and 20, La/Nb ratios are between 1 and 3 ( Figure 8) and range between ocean basalts (MORB and OIB) and arc basalts.…”

Section: Geochemistrymentioning

confidence: 84%

“…Thus, dolerite compositions ( Figure 6B) exhibit an array from active margin to late/post orogenic intra-continental fields when plotted in an La-Y-Nb diagram (after [20]). [12], Mayo Oulo-Léré [13] and Obudu [24] dyke swarms.…”

Section: Geochemistrymentioning

confidence: 99%

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The dolerite dyke swarm of Mongo, Guéra Massif (Chad, Central Africa): Geological setting, petrography and geochemistry

et al. 2017

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Dolerite dykes are widespread in the Mongo area within the granitic Guéra Massif (Chad, Central Africa). Dykes are several hundred metres to several kilometres long, a metre to decametre thick, and vertical, crosscutting the Pan-African granitic basement rocks. They are controlled by major Pan-African NNE-SSW, NE-SW and ENE-WSW faults. Rocks constituting the dykes exhibit typical doleritic textures (i.e. intergranular, ophitic or subophitic). They are mainly composed of phenocrysts, microcrysts and microlites of clinopyroxene, amphibole, plagioclase, alkali feldspar and Fe-Ti oxides. Mongo dolerites are classified into two groups: Group 1 of basalt and trachybasalt and Group 2 of basaltic trachyandesite, which follow a trend with continental tholeiite affinities, and are differentiated through fractional crystallization. Trace element enrichment and REE contents show the high melting degree at shallow depths of enriched sub-continental lithospheric mantle, whose composition is intermediate between OIB and MORB, contaminated by small amounts of sediment during older subduction. Mongo dolerites are interpreted as imprints of either the final stage of stabilization of ancient continental crust, or the initiation of tectonic activity related to Pan-African mobile belts.

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Section: Geochemistrymentioning

confidence: 67%

Section: Geochemistrymentioning

confidence: 84%

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The dolerite dyke swarm of Mongo, Guéra Massif (Chad, Central Africa): Geological setting, petrography and geochemistry

et al. 2017

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“…The lamprophyres have high incompatible element contents and contain hydrous (kaersutite, biotite) and/or carbonate minerals and are interpreted to originate from a volatile-rich metasomatized lithospheric mantle [20]. In the Adamawa region, however, dykes are mainly doleritic [21]. Although undated, these dolerites with continental tholeiitic affinities are thought to be older since they were never found to crosscut the 51 Ma plateau basalts of the early CVL units.…”

Section: Geological Settingmentioning

confidence: 99%

“…Clinopyroxenes are diopside to augite in composition (Fig. 4d, 5) according to the classification of [23] with compositions in the range Wo 49-43 Ens 32-43 Fs [12][13][14][15][16][17][18][19][20][21][22][23][24] . Clinopyroxenes in the Bangangte and Dschang areas are augites and diopside in the Manjo area.…”

Section: Mineral Chemistrymentioning

confidence: 99%

Petrology, Geochemistry, and Geodynamic Implications of Basaltic Dyke Swarms from the Southern Continental Part of the Cameroon Volcanic Line, Central Africa

Tchouankoue¹

2012

TOGEOJ

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Basaltic dyke swarms in the southern continental part of the Cameroon Volcanic Line (Bangangte, Dschang, Manjo areas) are tholeiitic in composition with 46 to 50 wt.% SiO 2 and have moderate Mg-numbers (53-59), medium TiO 2 contents (1.48-2,05 wt.%), and flat to mildly enriched incompatible trace element patterns. Comparison with trace element patterns of representative Cenozoic basaltic rocks of the Cameroon Volcanic Line (Bana anorogenic complex, Mt. Bambouto, Adamawa Plateau basalts) indicates that these dykes are less enriched in light REE and show different incompatible trace element ratios (La/Yb: 5.7 to 8.6; Zr/Nb: 7.6 to 12.0; Ba/Th: 87.7 to 93.3). The trace element patterns of the dykes and their Sr-and Nd-isotope compositions, however, are similar to those of the pre-Cenozoic volcanic rocks of the Benue Trough in Nigeria. Our data therefore suggest that these dykes represent the magmatic history related to the break-up of Africa and South America and are unrelated to the Tertiary volcanism of the Cameroon Line.

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Major, trace elements and Sr–Nd–Pb isotopes systematics of mafic dykes from the Figuil (northern Cameroon) and Léré (southwestern Chad) areas

Gountié Dedzo,

Klamadji,

Zangmo Tefogoum

et al. 2023

Geological Journal

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In this study, field descriptions of the dolerite dykes cross‐cutting the Pan‐African basement (DPB) and the dolerite and gabbroic dykes cross‐cutting the Cretaceous sedimentary basin (DGCSB) are used together with petrographic, bulk‐rock geochemistry, as well as Sr–Nd–Pb isotopic data to constrain the geodynamic setting and origin of these mafic (basanite, basalt and basaltic andesite in composition) rocks that outcrop in the Figuil–Léré area. The DPB dykes are alkaline with SiO2 of 46.63–49.03 wt% and MgO of 3.93–7.11 wt%. In contrast, the DGCSB dykes are subalkaline with SiO2 ranging between 50.24 and 53.16 wt% and MgO fluctuating between 5.22 and 7.90 wt%, comparable to dykes described in other regions of the Cameroon Line (CL). The rocks studied belong to the tholeiitic series and were emplaced in within‐plate basalts (WPB) and mid‐ocean ridge basalts (MORBs) setting. The variations in major and trace elements from the basanite to basaltic andesite compositions are dependable with fractional crystallization (FC) of different mineral phases such as opaque minerals, olivine, clinopyroxene, amphibole and alkali feldspar. Most samples exhibit negative Nb–Ta and positive Sr anomalies, which together with the negative correlation between MgO and 87Sr/86Sr, and isotopic ratio of 206Pb/204Pb <19.5 (18.27–19.49) suggests interactions of crustal components. Nevertheless, this contamination seems limited because there is a positive correlation between SiO2 and 143Nd/144Nd plot and low Ba contents (72–210 ppm) of the samples compared to the mid‐continental crust (259–628 ppm). Trace element modelling proposes a derivation of the Figuil–Léré dykes from parental melts generated by 4%–15% partial melting of a source containing garnet peridotite in the mixed lithospheric–asthenospheric mantle. The isotopic data of the dykes studied with hybrid magma composition are characterized by more radiogenic 87Sr/86Sr, 143Nd/144Nd and 206Pb/204Pb isotopic ratios with a dominant mixing of depleted MORB mantle (DMM)–enriched mantle 1 (EM1)–enriched mantle 2 (EM2), like those of other mafic dykes of the CL.

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Existence de dykes doléritiques anciens à composition de tholéiites continentales au sein de la province alcaline de la ligne du Cameroun. Implication sur le contexte géodynamique

Cited by 9 publications

References 17 publications

The dolerite dyke swarm of Mongo, Guéra Massif (Chad, Central Africa): Geological setting, petrography and geochemistry

The dolerite dyke swarm of Mongo, Guéra Massif (Chad, Central Africa): Geological setting, petrography and geochemistry

Petrology, Geochemistry, and Geodynamic Implications of Basaltic Dyke Swarms from the Southern Continental Part of the Cameroon Volcanic Line, Central Africa

Major, trace elements and Sr–Nd–Pb isotopes systematics of mafic dykes from the Figuil (northern Cameroon) and Léré (southwestern Chad) areas

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