Les laves du mont Bangou : une première manifestation volcanique éocène, à affinité transitionnelle,de la Ligne du Cameroun     

Jacob Fosso  Jean-Jacques Ménard  Jacques-Marie Bardintzeff  Pierre Wandji  Félix M. Tchoua  Hervé Bellon 《Comptes Rendus Geoscience》2005,337(3):315-325

Mount Bangou, an Eocene volcano (⁴⁰K–⁴⁰Ar ages between 44.7 and 43.1 ± 1 Ma) is the oldest dated volcano of the Cameroon Line. In this region, two magmatic series, evolving by fractional crystallization, show transitional affinities that are exceptionally known in this sector. Mineral compositions of basaltic rocks (scarce modal olivine and occurrence of normative hypersthene) as well as geochemical characteristics (low Ba, La, Ta contents and high Y/Nb ratios) are in agreement with this trend. The succession of magmas evolving in time from transitional to more typical alkaline compositions is evidenced in a continental setting. To cite this article: J. Fosso et al., C. R. Geoscience 337 (2005).  相似文献   

Evolution of volcanism in graben and horst structures along the Cenozoic Cameroon Line (Africa): implications for tectonic evolution and mantle source composition   总被引：2，自引：0，他引：2  

D. G. Nkouathio  A. Kagou Dongmo  J. M. Bardintzeff  P. Wandji  H. Bellon  A. Pouclet 《Mineralogy and Petrology》2008,94(3-4):287-303

Tombel graben and Mounts Bambouto are two volcanic fields of the typical system of alternating graben and horst structure of the Cameroon Volcanic Line. Tombel graben is a young volcanic field, whereas Mounts Bambouto horst is an old stratovolcano with calderas. Volcanic products in both settings have a signature close to that of Ocean Island Basalt implying a major role of FOZO (focal zone) component and varied contribution of depleted mantle (DMM) and enriched mantle (EM) components. The Cameroon Volcanic Line is a hot line essentially resulting from passive rifting. Eocene to Recent intraplate basaltic volcanism in the study area was probably a result of mantle upwelling coupled with lithospheric extension. The olivine basaltic magma of horst volcanoes evolved in a large-scale, steady-state magmatic reservoir via crystal fractionation and limited contamination to highly differentiated alkaline lavas (trachyte and phonolite). Conversely, rapid ascent of lavas along multiple fault lines of graben structures produced less evolved lavas (hawaiite) within small reservoirs. This model, evaluated for the study area, involves mantle upwelling inside zones of weakness in the lithosphere after intra-continental extension. It can be applied to other parts of the Cameroon Volcanic Line as well, and is similar to that described in other intra-continental rift-related areas in Africa.  相似文献   

Baossi–Warack monogenetic volcanoes,Adamawa Plateau,Cameroon: petrography,mineralogy and geochemistry     

Tiabou  Anicet Feudjio  Temdjim  Robert  Wandji  Pierre  Bardintzeff  Jacques-Marie  Che  Vivian Bih  Bate Tibang  Edith Ekatah  Ngwa  Caroline Neh  Mebara  François Xavier Onana 《中国地球化学学报》2019,38(1):40-67

Acta Geochimica - Three monogenetic cones in the Baossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line (CVL) are documented in this study....  相似文献   

Xenoliths of dunites, wehrlites and clinopyroxenites in the basanites from Batoke volcanic cone (Mount Cameroon, Central Africa): petrogenetic implications     

P. Wandji  J. P. F. Tsafack  J. M. Bardintzeff  D. G. Nkouathio  A. Kagou Dongmo  H. Bellon  H. Guillou 《Mineralogy and Petrology》2009,96(1-2):81-98

The lavas of the Mount Cameroon, a Plio-Quaternary stratovolcano and the most important volcano along the Cameroon Volcanic Line (CVL), constitute a weakly differentiated alkaline series: mainly comprising basanites as well as alkaline basalts, hawaiites and mugearites. Ultramafic xenoliths (1–5?×?0.5–4 cm) of dunites, wehrlites and clinopyroxenites have been discovered in the basanites of a strombolian cone, located near Batoke on the South flank of the massif at an elevation of 500 m. K-Ar whole rock dating of the basanitic host rock has yielded an age of 0.73?±?0.08 Ma. This result falls within the range of the seven new K-Ar age determinations of mafic lavas, between 2.83 Ma and the Present. These are the first K-Ar data on this massif. The ⁸⁷Sr/⁸⁶Sr ratios of basic lavas are low (0.703198–0.703344), and ¹⁴³Nd/¹⁴⁴Nd ratios are intermediate (0.512851–0.512773). These ratios are typical of a mantle origin. The main characteristics of the xenoliths are: (a) total FeO contents are 15.1 to 19.1 wt.% in olivines (chrysolite, Mg# ranging from 79 to 84) of xenoliths, and 4.7 to 6.9 wt.% in diopsides of xenoliths, (b) diopsides of the clinopyroxenites have up to 7.2 wt.% Al₂O₃ and 2.3 wt.% TiO₂, (c) spinels occur as interstitial grains between chrysolite and diopside grains, i.e. Cr₂O₃-rich magnetites (19 to 21 wt.% Cr₂O₃) in the dunites as well as (22 to 25 wt.% Cr₂O₃) in the wehrlites and titanomagnetites (14 to 15 wt.% TiO₂) in the clinopyroxenites. Mineralogical analyses show an important re-equilibration between the chrysolite xenocrysts and the host basanitic magma. We observed a decrease in Mg and Ni towards the rim, and an enrichment in all others cations like Fe, Mn, Ca, Si. The changes of Fe²⁺ / Mg²⁺ are the most important. The xenoliths are interpreted as cumulates: clinopyroxenite xenoliths have probably crystallized and fractionated at an early stage from the mafic (host basanitic) magma, while dunite and wehrlite xenoliths seem to have crystallized from a previous more primitive batch of magma. These alkaline liquids could have been derived from partial melting of a garnet- rich lherzolite in the upper mantle beneath the Cameroon Volcanic Line. The Al^IV/Al^VI ratios remain high (1.2 to 4.9) in the clinopyroxenes of the xenoliths. This suggests crystallization under a lower pressure than that of equilibration of the clinopyroxenes (ratios 0.6 to 0.8) found in typical mantle xenoliths from the CVL.  相似文献   

Tchabal Gangdaba massif in the Cameroon Volcanic Line: a bimodal association     

Zénon Itiga  Jacques-Marie Bardintzeff  Pierre Wotchoko  Pierre Wandji  Hervé Bellon 《Arabian Journal of Geosciences》2014,7(11):4641-4664

Tchabal Gangdaba (TG) volcanic massif, which is a part of the continental sector of the Cameroon Volcanic Line (CVL), is dated between 34.4 and 25.1 Ma. It displays mafic lavas (picrobasalt and basanite, 41–43 wt % SiO₂) and felsic lavas (rhyolite, 68–73 wt % SiO₂). The lack of intermediate rocks evidences a pronounced Daly gap between 43 and 68 wt % SiO₂, which corresponds to an important time span of 3.4 Ma. It is interpreted as due to extensive fractional crystallization under peculiar thermodynamical conditions. Felsic lavas yield strong negative anomalies in Ba, Sr and Eu (0.1?206Pb/²⁰⁴Pb?207Pb/²⁰⁴Pb?208Pb/²⁰⁴Pb?相似文献