The geology of the Olode area, south-western Nigeria was investigatedpetrographically and geochemically in order to elucidate the mineralisationpotential of the rock units in the area. The area under study is generall...The geology of the Olode area, south-western Nigeria was investigatedpetrographically and geochemically in order to elucidate the mineralisationpotential of the rock units in the area. The area under study is generallychange to underlained by granite gneiss, mica schist and pegmatites.Petrographical studies indicated prevalence of anhedral quartz (30 - 50%),plagioclase (14 - 20%), orthoclase (12 - 15%), muscovite (11 - 15%),tourmaline (6 - 10) and other minerals (8 - 11%) for the pegmatite. Thehigh value of SiO2 and Al2O3 is consistent with the petrographical study.High values and wide range in Ba (34 - 737 ppm) and Zr (3.8 - 132.6 ppm)strongly support a mixture of igneous and sedimentary. The bivariant plotsof Rb vs K/Rb, Zn vs K/Rb and Th vs K/Rb indicated a partial series offractionation, suggesting that the pegmatites are of rare element classeswhile granite gneiss and mica schist belong to the barren muscovite andrare element classes. This was supported by high ratios of K/Cs and K/Babut low Th/U values indicating distinctively low rare metal mineralization.The plot of Na2O/Al2O3 vs K2O/Al2O3 revealed an igneous precursor for allthe rock units. The negative Eu anomalies especially in the pegmatitic rockunit indicates fractionation and point toward a late metasomatic effect andtheir relatively weak negative Ce anomalies, also suggest their rare metalmineralization. The pegmatites, granite gneiss and mica schist of Olodearea considered as barren as all the samples plotted below the Gordiyenkosand Beus’ line of mineralization.展开更多
Combined methods for mineralogical identifications were used to characterise the clay deposits within the Lower Benue Trough of Nigeria to interpret paleo-environmental conditions,the paleoclimatic significance of the...Combined methods for mineralogical identifications were used to characterise the clay deposits within the Lower Benue Trough of Nigeria to interpret paleo-environmental conditions,the paleoclimatic significance of the trough,and effects of weathering on the minerals as factors that favour its deposition/accumulation within the trough which host other important industrial minerals like coal,barite,limestone etc.Bulk-sample random-powder XRD data and data for clay fractions deposited onto zero-background quartz plates were measured.The samples contained kaolinite,vermiculite,and traces of smectite,and the non-clay phases included quartz,microcline,and muscovite.All samples were unaffected after glycolation,confirming the absence of significant smectite.Muscovite was characterized by the nature of its 10Åbasal peak with a width of<0.10°2θ,which was very sharp.DTA/TGA results support the presence of kaolinite,and the characteristic kaolinite O-H,Al-OH,Si-OH and Si-O-Al FTIR bands also confirmed its presence.Vermicular and book-like morphologies were observed under the SEM,typical of kaolinitic clay from in situ alteration.High kaolinite abundance in these sediments is consistent with intense weathering of parent rocks rich in Al under wet/tropical paleo-climatic conditions with fresh and/or brackish water conditions in a continental setting.The variety of observed morphologies suggests that the deposits suffered more of chemical weathering.The clay deposits in Lower Benue Trough are quartz-rich,kaolinitic and derived from the chemical weathering of Al-rich source rocks.展开更多
文摘The geology of the Olode area, south-western Nigeria was investigatedpetrographically and geochemically in order to elucidate the mineralisationpotential of the rock units in the area. The area under study is generallychange to underlained by granite gneiss, mica schist and pegmatites.Petrographical studies indicated prevalence of anhedral quartz (30 - 50%),plagioclase (14 - 20%), orthoclase (12 - 15%), muscovite (11 - 15%),tourmaline (6 - 10) and other minerals (8 - 11%) for the pegmatite. Thehigh value of SiO2 and Al2O3 is consistent with the petrographical study.High values and wide range in Ba (34 - 737 ppm) and Zr (3.8 - 132.6 ppm)strongly support a mixture of igneous and sedimentary. The bivariant plotsof Rb vs K/Rb, Zn vs K/Rb and Th vs K/Rb indicated a partial series offractionation, suggesting that the pegmatites are of rare element classeswhile granite gneiss and mica schist belong to the barren muscovite andrare element classes. This was supported by high ratios of K/Cs and K/Babut low Th/U values indicating distinctively low rare metal mineralization.The plot of Na2O/Al2O3 vs K2O/Al2O3 revealed an igneous precursor for allthe rock units. The negative Eu anomalies especially in the pegmatitic rockunit indicates fractionation and point toward a late metasomatic effect andtheir relatively weak negative Ce anomalies, also suggest their rare metalmineralization. The pegmatites, granite gneiss and mica schist of Olodearea considered as barren as all the samples plotted below the Gordiyenkosand Beus’ line of mineralization.
文摘Combined methods for mineralogical identifications were used to characterise the clay deposits within the Lower Benue Trough of Nigeria to interpret paleo-environmental conditions,the paleoclimatic significance of the trough,and effects of weathering on the minerals as factors that favour its deposition/accumulation within the trough which host other important industrial minerals like coal,barite,limestone etc.Bulk-sample random-powder XRD data and data for clay fractions deposited onto zero-background quartz plates were measured.The samples contained kaolinite,vermiculite,and traces of smectite,and the non-clay phases included quartz,microcline,and muscovite.All samples were unaffected after glycolation,confirming the absence of significant smectite.Muscovite was characterized by the nature of its 10Åbasal peak with a width of<0.10°2θ,which was very sharp.DTA/TGA results support the presence of kaolinite,and the characteristic kaolinite O-H,Al-OH,Si-OH and Si-O-Al FTIR bands also confirmed its presence.Vermicular and book-like morphologies were observed under the SEM,typical of kaolinitic clay from in situ alteration.High kaolinite abundance in these sediments is consistent with intense weathering of parent rocks rich in Al under wet/tropical paleo-climatic conditions with fresh and/or brackish water conditions in a continental setting.The variety of observed morphologies suggests that the deposits suffered more of chemical weathering.The clay deposits in Lower Benue Trough are quartz-rich,kaolinitic and derived from the chemical weathering of Al-rich source rocks.
