The Precambrian basement complex in the southernmost part of North-Central Nigeria is underlain by migmatitic banded gneisses, granitic intrusions and dykes of dolerite, rhyolite porphyry and pegmatite. The rocks are ...The Precambrian basement complex in the southernmost part of North-Central Nigeria is underlain by migmatitic banded gneisses, granitic intrusions and dykes of dolerite, rhyolite porphyry and pegmatite. The rocks are generally felsic, containing modal and normative hypersthene, as well as normative corundum. The basement complex has experienced high-grade regional metamorphism as indicated by the presence of hypersthene and plagioclase of andesine composition. Anatectic melting is suggested by the occurrence of ptygmatic folds, folded gneissose foliation, numerous quartzo-feldspathic veins and lenses of dark-colured, micaceous schistose rocks. Geochemically, the rocks have magnesian, calc-alkalic and strongly peraluminous characteristics. Their overall characteristics suggest derivation from progressive (fractional) partial melting of pelitic rocks during high-grade regional metamorphism, possibly associated with intense hydrothermal activities. The magnesian characteristics reflect close affinity to relatively hydrous, oxidizing melts and source regions in settings broadly related to subduction.展开更多
1.Objective Nigeria lies between the West African Craton and the Congo Craton,south of the Tuareg Shield(Ogunmola JK et al.,2015).The Nasarawa pegmatite field mainly comprises of the Precambrian Basement Complex(inclu...1.Objective Nigeria lies between the West African Craton and the Congo Craton,south of the Tuareg Shield(Ogunmola JK et al.,2015).The Nasarawa pegmatite field mainly comprises of the Precambrian Basement Complex(including Archean-Proterozoic migmatite,gneiss,schists and Pan-African “Older Granites”),Mesozoic alkaline ring complexes(“Younger Granites”) and sedimentary basins(Yang QD et al.,2023;Fig.1a).“Older Granites” are part of the Pan-African mobile belt;“Younger Granites” has significant peralkaline characteristics.“Younger Granites” has a wide distribution in the north-central region of Nigeria,including areas such as Kano,Jos-Bauchi,Mada,and Nasarawa,and the emplacement age gradually decreases from north to south from 213 Ma(Dutse complex) to 141 Ma(Afu complex)(Amuda AK et al.,2021).展开更多
文摘The Precambrian basement complex in the southernmost part of North-Central Nigeria is underlain by migmatitic banded gneisses, granitic intrusions and dykes of dolerite, rhyolite porphyry and pegmatite. The rocks are generally felsic, containing modal and normative hypersthene, as well as normative corundum. The basement complex has experienced high-grade regional metamorphism as indicated by the presence of hypersthene and plagioclase of andesine composition. Anatectic melting is suggested by the occurrence of ptygmatic folds, folded gneissose foliation, numerous quartzo-feldspathic veins and lenses of dark-colured, micaceous schistose rocks. Geochemically, the rocks have magnesian, calc-alkalic and strongly peraluminous characteristics. Their overall characteristics suggest derivation from progressive (fractional) partial melting of pelitic rocks during high-grade regional metamorphism, possibly associated with intense hydrothermal activities. The magnesian characteristics reflect close affinity to relatively hydrous, oxidizing melts and source regions in settings broadly related to subduction.
基金funded by the projects of Tianjin North China Geological Exploration Bureau (HK2023–B01,HK2022–B08)China Geological Survey (DD20230576,DD20201152)。
文摘1.Objective Nigeria lies between the West African Craton and the Congo Craton,south of the Tuareg Shield(Ogunmola JK et al.,2015).The Nasarawa pegmatite field mainly comprises of the Precambrian Basement Complex(including Archean-Proterozoic migmatite,gneiss,schists and Pan-African “Older Granites”),Mesozoic alkaline ring complexes(“Younger Granites”) and sedimentary basins(Yang QD et al.,2023;Fig.1a).“Older Granites” are part of the Pan-African mobile belt;“Younger Granites” has significant peralkaline characteristics.“Younger Granites” has a wide distribution in the north-central region of Nigeria,including areas such as Kano,Jos-Bauchi,Mada,and Nasarawa,and the emplacement age gradually decreases from north to south from 213 Ma(Dutse complex) to 141 Ma(Afu complex)(Amuda AK et al.,2021).
