Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had be...Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had been recognized among accessory minerals. In the present study, attention is focus on the tourmaline bearing quartzite to the southeast of Kombé II. Structure refinement shows that tourmaline is a Fe-dravite with the formula X(Na<sub>0.95</sub>[]<sub>0.05</sub>)Y(Mg<sub>2.39</sub>Fe<sub>0.61</sub>)Z(Al<sub>5.10</sub>Mg<sub>0.90</sub>)(BO<sub>3</sub>)<sub>3</sub>T[Si<sub>6</sub>O<sub>18</sub>](OH)<sub>3</sub>[(O,OH)<sub>0.88</sub>F<sub>0.12</sub>]. The Fe-dravite is hosted in a Ca-poor quartzite, which is made up, in addition to quartz and tourmaline, of biotite and muscovite. The structure of the dravites shows a low vacancy at the X site, which militates for a crystallization of the tourmaline at a high temperature > 750℃. This is in agreement with previous work which shows that the metamorphic peak in the associated biotite gneiss reaches 825℃. The R1 value of 1.24% means that the crystal structure of the tourmalines is of high quality. The genetical link between gold mineralization and tourmaline should stimulate exploration interest in the study area.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 amphibole biotite gneiss (ABGn) in the Méiganga area forms part of a meta volcano-sedimentary sequence of the Adamawa Yade domain (AYD), Central African Fold Belt (CAFB). This sequence shows affinity with imm...The amphibole biotite gneiss (ABGn) in the Méiganga area forms part of a meta volcano-sedimentary sequence of the Adamawa Yade domain (AYD), Central African Fold Belt (CAFB). This sequence shows affinity with immature sediments (greywackes, arkoses) with intercalation of mafic lavas or tuffs. New 207Pb/206Pb zircon evaporation ages for two ABGn samples range from 1887 - 2339 Ma and from 675 - 889 Ma, respectively. These ages and evidence from internal zircon structures indicate that igneous rocks of Archean to Paleoproterozoic and of early Neoproterozoic age contributed to the detritus of the sedimentary sequence. The deposition of detritus took place prior to 614 - 619 Ma which represent the syntectonic emplacement of the Méiganga metadiorite. Leucogranites north to the Méiganga area were generated by melting of crust identical to that which provided the source of the ABGn. The metasedimentary sequence investigated in this study is similar to that of the southern part of the AYD and in the Borborema Province, NE Brazil. The tectonic and geochronologic characteristics of the AYD in the Méiganga area support the idea that during the Proterozoic, Central Africa and NE Brazil were part of the same continental landmass.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
文摘Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had been recognized among accessory minerals. In the present study, attention is focus on the tourmaline bearing quartzite to the southeast of Kombé II. Structure refinement shows that tourmaline is a Fe-dravite with the formula X(Na<sub>0.95</sub>[]<sub>0.05</sub>)Y(Mg<sub>2.39</sub>Fe<sub>0.61</sub>)Z(Al<sub>5.10</sub>Mg<sub>0.90</sub>)(BO<sub>3</sub>)<sub>3</sub>T[Si<sub>6</sub>O<sub>18</sub>](OH)<sub>3</sub>[(O,OH)<sub>0.88</sub>F<sub>0.12</sub>]. The Fe-dravite is hosted in a Ca-poor quartzite, which is made up, in addition to quartz and tourmaline, of biotite and muscovite. The structure of the dravites shows a low vacancy at the X site, which militates for a crystallization of the tourmaline at a high temperature > 750℃. This is in agreement with previous work which shows that the metamorphic peak in the associated biotite gneiss reaches 825℃. The R1 value of 1.24% means that the crystal structure of the tourmalines is of high quality. The genetical link between gold mineralization and tourmaline should stimulate exploration interest in the study area.
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 amphibole biotite gneiss (ABGn) in the Méiganga area forms part of a meta volcano-sedimentary sequence of the Adamawa Yade domain (AYD), Central African Fold Belt (CAFB). This sequence shows affinity with immature sediments (greywackes, arkoses) with intercalation of mafic lavas or tuffs. New 207Pb/206Pb zircon evaporation ages for two ABGn samples range from 1887 - 2339 Ma and from 675 - 889 Ma, respectively. These ages and evidence from internal zircon structures indicate that igneous rocks of Archean to Paleoproterozoic and of early Neoproterozoic age contributed to the detritus of the sedimentary sequence. The deposition of detritus took place prior to 614 - 619 Ma which represent the syntectonic emplacement of the Méiganga metadiorite. Leucogranites north to the Méiganga area were generated by melting of crust identical to that which provided the source of the ABGn. The metasedimentary sequence investigated in this study is similar to that of the southern part of the AYD and in the Borborema Province, NE Brazil. The tectonic and geochronologic characteristics of the AYD in the Méiganga area support the idea that during the Proterozoic, Central Africa and NE Brazil were part of the same continental landmass.
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.
