The aim of this study of the spatial dispersion of tin, niobium and tantalum mineralization associated with the Mayo Darlé granitoids was to produce prospecting guides through predictive maps of Sn, Nb and Ta in ...The aim of this study of the spatial dispersion of tin, niobium and tantalum mineralization associated with the Mayo Darlé granitoids was to produce prospecting guides through predictive maps of Sn, Nb and Ta in the region. It was based on a database (in appendix) obtained after analysis of rock samples (greisens and quartz veins) collected in the field, using a portable X-ray fluorescence (XRF) spectrometer. Two approaches were used: 1) structural studies in the field using the directions of veins and fractures 2) the use of variographic maps, an essential element in geostatistics for determining directional anisotropies. A joint synthesis of the modelling results shows that tin, tantalum and niobium mineralization at Mayo Darlé is concentrated along strike intervals N315E to N320E, with mineralization also occurring along strike N35E for high-grade Sn, medium-grade Ta and low-grade Nb. In short, mineral concentrations disperse progressively in space: positively from east to west for tantalum and niobium, and inversely for tin.展开更多
The Baïbokoum-Touboro-Ngaoundaye area is located in the Adamoua-Yade domain of the Pan-African Fold Belt in Central Africa. The present work concerns the petrographic and geochemical study. The study area is ...The Baïbokoum-Touboro-Ngaoundaye area is located in the Adamoua-Yade domain of the Pan-African Fold Belt in Central Africa. The present work concerns the petrographic and geochemical study. The study area is made up of plutonic rocks including two amphibole granites, four biotite and muscovite granites, two syenites and one monzonite sample. These rocks have a granular porphyroid texture, with a mylonitic tendency. The primary paragenesis consists of Opx + Cpx + Amp + Bt + Pl + Or + Mic + Qtz + Ap + Sph + Zr and the secondary paragenesis consisting of Ch + Op. Plutonic rocks are shoshonitic to calc-alkaline with a strong potassic affinity. The REE profiles of these rocks show a negative anomaly of Eu in the granites and no Eu anomaly in syenites and monzonite (syeno-diorite). Multielement spectra of plutonic rocks present a negative anomaly in Nb-Ta and Ti. Fractional crystallization is the process that made these rocks of study area. These rocks are placed in a subduction to syn-collisional (VAG + Syn-COLG) and of intraplate granitoids (WPG) environment.展开更多
The border of Cameroon and Chad is characterized by a Precambrian basement straddling the Touboro-Ba?bokoum area;this basement is made up of gneiss, amphibolite and granitoids (granite, syenite, granodiorite). The stu...The border of Cameroon and Chad is characterized by a Precambrian basement straddling the Touboro-Ba?bokoum area;this basement is made up of gneiss, amphibolite and granitoids (granite, syenite, granodiorite). The studied rocks display high-K calk-alcalcaline to shoshonitic characteristic. Granitoids are metaluminous. Rocks under study derived from partial melts from metabasaltic to metatonalitic sources, and partial melts from metagreywackes. They shear the same origin as many granitoids describe westward in the Meiganga area and west Cameroon. This shows that the basement straddling the Touboro-Ba?bokoum area belongs to the Adamawa-Yadé Domain of the Central African Fold Belt.展开更多
Hangloa granitoids form part of the wide range calc-alkaline Pan-African granitic suites within the Adamawa Yade Domain(AYD)in Cameroon.There are several reports on metaluminous granitoids within this domain.The peral...Hangloa granitoids form part of the wide range calc-alkaline Pan-African granitic suites within the Adamawa Yade Domain(AYD)in Cameroon.There are several reports on metaluminous granitoids within this domain.The peraluminous suite has been locally reported and their petrogenesis is not fully understood.Petrography and whole-rock geochemistry were used to study the petrogenesis/formation of granitic rocks within this area.The results show that the granitoids are composed of quartzo-feldspathic,made up of granites,monzonites and quartz monzonites which were intruded in the Paleoproterozoic orthogneissic basement.The major and trace element compositions show that they are high-K calc-alkaline to shoshonites,with S-type affinity.The molar ratio A/CNK is>1.1,while the ratio of CaO+Na_(2)O/Al_(2)O_(3) is generally<1 making them strongly peraluminous.The REE shows enrichment in the LREE over the HREE,with(La/Yb)N varying from 11.9 to 53.32,(Dy/Yb)N from 0.77 to 2.13 and moderately negative Eu anomaly((Eu/Eu^(*))N range from 0.42 to 0.93).Most granite samples show depletion in P,with CaO/Na_(2)O<0.3 and Rb/Sr≤1 indicative of clay-poor metapelitic source,while the others show clay-rich metagreywackes sources.The strong peraluminosity,S-type affinity,high Ba/Sr,Ba/Rb and low Rb/Sr indicate they are crustal-derived.The compositional variation might be induced by the partial melting of different source materials followed by fractional crystallization of the granitic magma.The source nature requires fragments of Paleoproterozoic metasedimentary and metaigneous rocks derived from the collision between the north-central Cameroon block and the Congo Craton during the Pan-African.展开更多
文摘The aim of this study of the spatial dispersion of tin, niobium and tantalum mineralization associated with the Mayo Darlé granitoids was to produce prospecting guides through predictive maps of Sn, Nb and Ta in the region. It was based on a database (in appendix) obtained after analysis of rock samples (greisens and quartz veins) collected in the field, using a portable X-ray fluorescence (XRF) spectrometer. Two approaches were used: 1) structural studies in the field using the directions of veins and fractures 2) the use of variographic maps, an essential element in geostatistics for determining directional anisotropies. A joint synthesis of the modelling results shows that tin, tantalum and niobium mineralization at Mayo Darlé is concentrated along strike intervals N315E to N320E, with mineralization also occurring along strike N35E for high-grade Sn, medium-grade Ta and low-grade Nb. In short, mineral concentrations disperse progressively in space: positively from east to west for tantalum and niobium, and inversely for tin.
文摘The Baïbokoum-Touboro-Ngaoundaye area is located in the Adamoua-Yade domain of the Pan-African Fold Belt in Central Africa. The present work concerns the petrographic and geochemical study. The study area is made up of plutonic rocks including two amphibole granites, four biotite and muscovite granites, two syenites and one monzonite sample. These rocks have a granular porphyroid texture, with a mylonitic tendency. The primary paragenesis consists of Opx + Cpx + Amp + Bt + Pl + Or + Mic + Qtz + Ap + Sph + Zr and the secondary paragenesis consisting of Ch + Op. Plutonic rocks are shoshonitic to calc-alkaline with a strong potassic affinity. The REE profiles of these rocks show a negative anomaly of Eu in the granites and no Eu anomaly in syenites and monzonite (syeno-diorite). Multielement spectra of plutonic rocks present a negative anomaly in Nb-Ta and Ti. Fractional crystallization is the process that made these rocks of study area. These rocks are placed in a subduction to syn-collisional (VAG + Syn-COLG) and of intraplate granitoids (WPG) environment.
文摘The border of Cameroon and Chad is characterized by a Precambrian basement straddling the Touboro-Ba?bokoum area;this basement is made up of gneiss, amphibolite and granitoids (granite, syenite, granodiorite). The studied rocks display high-K calk-alcalcaline to shoshonitic characteristic. Granitoids are metaluminous. Rocks under study derived from partial melts from metabasaltic to metatonalitic sources, and partial melts from metagreywackes. They shear the same origin as many granitoids describe westward in the Meiganga area and west Cameroon. This shows that the basement straddling the Touboro-Ba?bokoum area belongs to the Adamawa-Yadé Domain of the Central African Fold Belt.
基金the financial and technical support received from the Geoscience Laboratories in Toulouse(LGT)France under L’Agence Universitaire de la Francophonie(AUF)project during the analysis of the samples and thin section preparation。
文摘Hangloa granitoids form part of the wide range calc-alkaline Pan-African granitic suites within the Adamawa Yade Domain(AYD)in Cameroon.There are several reports on metaluminous granitoids within this domain.The peraluminous suite has been locally reported and their petrogenesis is not fully understood.Petrography and whole-rock geochemistry were used to study the petrogenesis/formation of granitic rocks within this area.The results show that the granitoids are composed of quartzo-feldspathic,made up of granites,monzonites and quartz monzonites which were intruded in the Paleoproterozoic orthogneissic basement.The major and trace element compositions show that they are high-K calc-alkaline to shoshonites,with S-type affinity.The molar ratio A/CNK is>1.1,while the ratio of CaO+Na_(2)O/Al_(2)O_(3) is generally<1 making them strongly peraluminous.The REE shows enrichment in the LREE over the HREE,with(La/Yb)N varying from 11.9 to 53.32,(Dy/Yb)N from 0.77 to 2.13 and moderately negative Eu anomaly((Eu/Eu^(*))N range from 0.42 to 0.93).Most granite samples show depletion in P,with CaO/Na_(2)O<0.3 and Rb/Sr≤1 indicative of clay-poor metapelitic source,while the others show clay-rich metagreywackes sources.The strong peraluminosity,S-type affinity,high Ba/Sr,Ba/Rb and low Rb/Sr indicate they are crustal-derived.The compositional variation might be induced by the partial melting of different source materials followed by fractional crystallization of the granitic magma.The source nature requires fragments of Paleoproterozoic metasedimentary and metaigneous rocks derived from the collision between the north-central Cameroon block and the Congo Craton during the Pan-African.
