In the Mangodara area within the Banfora greenstone belts (Baoulé-Mossi domain of the West African Craton), our study focused on geochemical assessment of the mobility of major and trace elements. Gold and base m...In the Mangodara area within the Banfora greenstone belts (Baoulé-Mossi domain of the West African Craton), our study focused on geochemical assessment of the mobility of major and trace elements. Gold and base metal occurrences are hosted in highly metamorphic felsic (metarhyolite) and intermediate (metadacite and metaandesite) formations. Common mineral assemblages made up of staurolite - kyanite - pyrophyllite are interpreted to represent the metamorphosed equivalent of aluminous hydrothermal alteration. Associated felsic and intermediate volcanic rocks are enriched in Fe<sub>2</sub>O<sub>3</sub>, K<sub>2</sub>O (metaandesite, metarhyolite) and depleted in MgO, Al<sub>2</sub>O<sub>3</sub>, CaO, P<sub>2</sub>O<sub>5</sub>, Na<sub>2</sub>O (metarhyolite) and Fe<sub>2</sub>O<sub>3</sub>, MgO, CaO (metaandesite). Al<sub>2</sub>O<sub>3</sub> depletion in mineralized kyanite-staurotide bearing metarhyolites suggests corroded minerals. Mineralized metarhyolites show enrichment in Au, Ag, Ba, Bi, Cr, Cu, Eu, La, Mo, Ni, Pb, S, Sc, V and depletion in As Sb Co, Sn, Zn while mineralized metaandesites show enrichment in Au, Ag, As, Mo, S, Sb and depletion in Co, Sn, Zn, Bi, Cr, Cu, Eu, Ni, Pb, Sc. Ba, La, V are immobile in metaandesites. Finally, Ag, As, Sn appear as geochemical vectors for gold exploration in the study area since gold mineralization is characterized by Au + Ba + Cu + Eu + La + Mo + Ni + S association in metarhyolites and Au + S + Sb + As + Ag + Bi in metaandesites.展开更多
Central Asian and Pacific mobile belts are the two geological superstructures of Eastern Asia. They keep many geological secrets. There is a region of the interaction of the structures in the frames of the margin ofEa...Central Asian and Pacific mobile belts are the two geological superstructures of Eastern Asia. They keep many geological secrets. There is a region of the interaction of the structures in the frames of the margin ofEast Asia. The region is ambiguous. It is denominated in tectonic superposition or covering (interference) of the segments of the structures. The main goal of the research work is to establish the boundary line of the jointing of two superstructures. Here we show the role of the Mesozoic tectonic restructuring and magmatism in the interaction of the structures. The region of their jointing is the boundary line between Bureja-Jziamusy and Badzhal terrains. The boundary line in the frames of Mongol-Okhotsk orogenic belt is disputable. Geochronological and paleomagnetic data and chemical composition of the volcano-plutonic rocks of the eastern margin of Mongol-Okhotsk belt and of the structures of Central-Asian mobile belt were recently obtained. The data allow us to review the region of the joint of the two structures of easternAsia. It was suggested to draw the boundary line of the joint (in this case-interference) of Central Asian mobile belt and Pacific mobile belt in the frames of the eastern margin of Mongol-Okhotsk orogenic belt along the margin of the disappearance of late Mesozoic oversubductional volcano-plutonic complexes in the western direction. The structure of Bureja-Jziamusy superterrain was related to the structures of the Pacific mobile belt. The proposed model of the region of jointing of two East Asian superstructures enables us to reconsider the tectonic and geodynamical and metallogeny schemes of evolution of the Eastern margin ofAsia.展开更多
In the eastern part of the Indian shield,late PaleozoiceMesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt(EGMB)and ...In the eastern part of the Indian shield,late PaleozoiceMesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt(EGMB)and amphibolite facies rocks of the Rengali Province.At present,the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin,and in the Rengali Province to the north.Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB(wt15 mGal),through the basin(w 10 mGal),into the Rengali Province(w 15 mGal).The data are consistent with the reportedly uncompensated nature of the EGMB,and indicate that the crust below the Rengali Province has a cratonic gravity signature.The contact between the two domains with distinct sub-surface structure,inferred from gravity data,coincides with the North Orissa Boundary Fault(NOBF)that defnes the northern boundary of the Talchir Basin.Post-Gondwana faults are also localized along the northern margin of the basin,and present-day seismic tremors also have epicenters close to the NOBF.This indicates that the NOBF was formed by reactivation of a Neoproterozoic terrane boundary,and continues to be susceptible to seismic activity even at the present-day.展开更多
文摘In the Mangodara area within the Banfora greenstone belts (Baoulé-Mossi domain of the West African Craton), our study focused on geochemical assessment of the mobility of major and trace elements. Gold and base metal occurrences are hosted in highly metamorphic felsic (metarhyolite) and intermediate (metadacite and metaandesite) formations. Common mineral assemblages made up of staurolite - kyanite - pyrophyllite are interpreted to represent the metamorphosed equivalent of aluminous hydrothermal alteration. Associated felsic and intermediate volcanic rocks are enriched in Fe<sub>2</sub>O<sub>3</sub>, K<sub>2</sub>O (metaandesite, metarhyolite) and depleted in MgO, Al<sub>2</sub>O<sub>3</sub>, CaO, P<sub>2</sub>O<sub>5</sub>, Na<sub>2</sub>O (metarhyolite) and Fe<sub>2</sub>O<sub>3</sub>, MgO, CaO (metaandesite). Al<sub>2</sub>O<sub>3</sub> depletion in mineralized kyanite-staurotide bearing metarhyolites suggests corroded minerals. Mineralized metarhyolites show enrichment in Au, Ag, Ba, Bi, Cr, Cu, Eu, La, Mo, Ni, Pb, S, Sc, V and depletion in As Sb Co, Sn, Zn while mineralized metaandesites show enrichment in Au, Ag, As, Mo, S, Sb and depletion in Co, Sn, Zn, Bi, Cr, Cu, Eu, Ni, Pb, Sc. Ba, La, V are immobile in metaandesites. Finally, Ag, As, Sn appear as geochemical vectors for gold exploration in the study area since gold mineralization is characterized by Au + Ba + Cu + Eu + La + Mo + Ni + S association in metarhyolites and Au + S + Sb + As + Ag + Bi in metaandesites.
文摘Central Asian and Pacific mobile belts are the two geological superstructures of Eastern Asia. They keep many geological secrets. There is a region of the interaction of the structures in the frames of the margin ofEast Asia. The region is ambiguous. It is denominated in tectonic superposition or covering (interference) of the segments of the structures. The main goal of the research work is to establish the boundary line of the jointing of two superstructures. Here we show the role of the Mesozoic tectonic restructuring and magmatism in the interaction of the structures. The region of their jointing is the boundary line between Bureja-Jziamusy and Badzhal terrains. The boundary line in the frames of Mongol-Okhotsk orogenic belt is disputable. Geochronological and paleomagnetic data and chemical composition of the volcano-plutonic rocks of the eastern margin of Mongol-Okhotsk belt and of the structures of Central-Asian mobile belt were recently obtained. The data allow us to review the region of the joint of the two structures of easternAsia. It was suggested to draw the boundary line of the joint (in this case-interference) of Central Asian mobile belt and Pacific mobile belt in the frames of the eastern margin of Mongol-Okhotsk orogenic belt along the margin of the disappearance of late Mesozoic oversubductional volcano-plutonic complexes in the western direction. The structure of Bureja-Jziamusy superterrain was related to the structures of the Pacific mobile belt. The proposed model of the region of jointing of two East Asian superstructures enables us to reconsider the tectonic and geodynamical and metallogeny schemes of evolution of the Eastern margin ofAsia.
文摘In the eastern part of the Indian shield,late PaleozoiceMesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt(EGMB)and amphibolite facies rocks of the Rengali Province.At present,the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin,and in the Rengali Province to the north.Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB(wt15 mGal),through the basin(w 10 mGal),into the Rengali Province(w 15 mGal).The data are consistent with the reportedly uncompensated nature of the EGMB,and indicate that the crust below the Rengali Province has a cratonic gravity signature.The contact between the two domains with distinct sub-surface structure,inferred from gravity data,coincides with the North Orissa Boundary Fault(NOBF)that defnes the northern boundary of the Talchir Basin.Post-Gondwana faults are also localized along the northern margin of the basin,and present-day seismic tremors also have epicenters close to the NOBF.This indicates that the NOBF was formed by reactivation of a Neoproterozoic terrane boundary,and continues to be susceptible to seismic activity even at the present-day.
