Mount Bambouto is a polygenic stratovolcano of the Cameroon Volcanic Line, built between 21 Ma and 4.5 Ma. It is situated approximately 200 km NE of Mount Cameroon, between 09° 55＇ and 10°15＇ longitude eas...Mount Bambouto is a polygenic stratovolcano of the Cameroon Volcanic Line, built between 21 Ma and 4.5 Ma. It is situated approximately 200 km NE of Mount Cameroon, between 09° 55＇ and 10°15＇ longitude east and, 05°25＇ and 05°50＇ latitude north. The volcano covers an area of 500 km^2 and culminates at 2740 m at Meletan dome and bears a collapsed caldera at the summit （13 × 8 km）. Mount Bambouto is characterized by several natural hazards of different origins： meteorological, such as landslides and rock falls; anthropogenic, such as bushfires, tribal wars and deforestation; and volcanological, such as volcanic eruption. The thematic map shows that 55-60% of the caldera has high probability of occurrence of mass movement. The caldera has a high population density （3000 inhabitants）, which increases the level of risk, evaluated at approximately $US3.8 million for patrimony, 3000 civilian deaths and destruction of biodiversity.展开更多
Located southeast of the city of Ngaoundere(Adamawa Plateau)within the continental section of the Cameroon Volcanic Line(CVL),the village of Dibi has been the scene of numerous volcanic manifestations,dominated by thr...Located southeast of the city of Ngaoundere(Adamawa Plateau)within the continental section of the Cameroon Volcanic Line(CVL),the village of Dibi has been the scene of numerous volcanic manifestations,dominated by three types of dynamism(explosive phreatomagmatic,effusive,and Strombolian eruptions);whose rocks,however,are poorly studied.Here,the lavas emitted during those eruptions are analyzed to constrain their origin.Whole rock geochemistry revealed that these rocks consist of basanites and foidites with Mg#varying from 67.3%to 71.2%.They are porphyritic and mainly composed of olivine[(Fo77.28-87.28 in foidites)and(Fo78.92-87.04 in basanites)],diopside[(Wo51En35Fs14 in foidites)and(Wo50-46.18En34.8-41.29Fs10.41-15.92 in basanites)],plagioclase[(labradorite:Ab37.31-39.67An57.43-60.70Or1.99-2.28)in basanites],and alkali feldspar[(anorthoclase:Ab64.45-65.13An6.81-9.15Or26.87-27.08 in foidites and Ab60.92-64.11An8-8.47Or28.45-32.27 in basanite)].Accessory minerals include Al-chromite,Ferrian chromite,titanomagnetite,and apatite.The lavas are silica-undersaturated(SiO_(2):38.9-40.3 wt.%in foidites and SiO_(2):42.5-43.6 wt.%in basanites).They are within-plate basalts with similar features to Oceanic Island Basalt(OIB)magmas,affinity to High-μ(HIMU),Enriched type I(EM1),and recycled component.Their primary melts derived from low degrees of partial melting(3%-5%)of a garnet peridotite mantle source,as shown by the Nb/La(1.30-1.51),Zr/La(4.91-5.85),and Zr/Ce(2.49-2.88)ratios that are consistent with an OIB-like asthenospheric mantle source.Equilibration temperatures have been estimated from the clinopyroxene-liquid thermometer and range between 981.6˚C and 1051.6˚C,at pressures of 0.9-1.6 kbar.展开更多
文摘Mount Bambouto is a polygenic stratovolcano of the Cameroon Volcanic Line, built between 21 Ma and 4.5 Ma. It is situated approximately 200 km NE of Mount Cameroon, between 09° 55＇ and 10°15＇ longitude east and, 05°25＇ and 05°50＇ latitude north. The volcano covers an area of 500 km^2 and culminates at 2740 m at Meletan dome and bears a collapsed caldera at the summit （13 × 8 km）. Mount Bambouto is characterized by several natural hazards of different origins： meteorological, such as landslides and rock falls; anthropogenic, such as bushfires, tribal wars and deforestation; and volcanological, such as volcanic eruption. The thematic map shows that 55-60% of the caldera has high probability of occurrence of mass movement. The caldera has a high population density （3000 inhabitants）, which increases the level of risk, evaluated at approximately $US3.8 million for patrimony, 3000 civilian deaths and destruction of biodiversity.
文摘Located southeast of the city of Ngaoundere(Adamawa Plateau)within the continental section of the Cameroon Volcanic Line(CVL),the village of Dibi has been the scene of numerous volcanic manifestations,dominated by three types of dynamism(explosive phreatomagmatic,effusive,and Strombolian eruptions);whose rocks,however,are poorly studied.Here,the lavas emitted during those eruptions are analyzed to constrain their origin.Whole rock geochemistry revealed that these rocks consist of basanites and foidites with Mg#varying from 67.3%to 71.2%.They are porphyritic and mainly composed of olivine[(Fo77.28-87.28 in foidites)and(Fo78.92-87.04 in basanites)],diopside[(Wo51En35Fs14 in foidites)and(Wo50-46.18En34.8-41.29Fs10.41-15.92 in basanites)],plagioclase[(labradorite:Ab37.31-39.67An57.43-60.70Or1.99-2.28)in basanites],and alkali feldspar[(anorthoclase:Ab64.45-65.13An6.81-9.15Or26.87-27.08 in foidites and Ab60.92-64.11An8-8.47Or28.45-32.27 in basanite)].Accessory minerals include Al-chromite,Ferrian chromite,titanomagnetite,and apatite.The lavas are silica-undersaturated(SiO_(2):38.9-40.3 wt.%in foidites and SiO_(2):42.5-43.6 wt.%in basanites).They are within-plate basalts with similar features to Oceanic Island Basalt(OIB)magmas,affinity to High-μ(HIMU),Enriched type I(EM1),and recycled component.Their primary melts derived from low degrees of partial melting(3%-5%)of a garnet peridotite mantle source,as shown by the Nb/La(1.30-1.51),Zr/La(4.91-5.85),and Zr/Ce(2.49-2.88)ratios that are consistent with an OIB-like asthenospheric mantle source.Equilibration temperatures have been estimated from the clinopyroxene-liquid thermometer and range between 981.6˚C and 1051.6˚C,at pressures of 0.9-1.6 kbar.
