In this paper we reported the 40 Ar 39 Ar dating results of hornblendes in Grt Pl bearing amphibolite from the Larsemann Hills, East Antarctica. Their apparent ages respectively are 1586 Ma, 1011...In this paper we reported the 40 Ar 39 Ar dating results of hornblendes in Grt Pl bearing amphibolite from the Larsemann Hills, East Antarctica. Their apparent ages respectively are 1586 Ma, 1011 1080 Ma, 761 Ma, 529 582 Ma. Their plateau ages of 1036 Ma and 554 Ma as well as an Ar Ar isochron age of 1010 Ma have also been obtained respectively. These isotopic dating results for the first time by the Ar Ar method for hornblendes completely record almost all the structural metamorphic thermal events that this region experienced, and provide an answer to the controversial question on the structural metamorphic thermal events of this region in recent several years, namely, which one is more important, the late Proterozoic 1000 Ma event (Grenvillian) or the early Palaeozoic 500 Ma event ( Pan African), as well as whether the former exists or not. The 40 Ar 39 Ar dating results of hornblendes show that the Larsemann Hills experienced a complicated poly metamorphic evolutionary history, and their protoliths were probably formed in early to mid Proterozoic. The late Proterozoic 1000 Ma event (Grenvillian) has been confirmed to be a predominant tectonothermal event whilst the early Palaeozoic 500 Ma event (Pan African) has been confirmed just to be the last strong tectonothermal event in this region.展开更多
This study is aimed at evaluating groundwater potential of Ipinsa-Okeodu area, near Akure, Southwestern Nigeria. A multi-criteria model was developed for achieving this aim;the GRT model which is based on geology of e...This study is aimed at evaluating groundwater potential of Ipinsa-Okeodu area, near Akure, Southwestern Nigeria. A multi-criteria model was developed for achieving this aim;the GRT model which is based on geology of each sounding point, resistivity, and thickness of the aquifer across the study area was successfully used to evaluate the aquifer potential of the area for future groundwater development programme in the area. Geophysical investigation involving vertical electrical sounding was carried out across the study area. A total of one hundred and two (102) vertical electrical soundings (VES) data were acquired using Schlumberger array with maximum half-current electrode separation of 150 m. Three to five geoelectric layers were delineated across the study area. The predominant curve types are KH, H, K and A. The maps of aquifer layer resistivity and aquifer layer thickness were generated and synthesized with the geology of the study area in producing the GRT model map/groundwater potential map. The groundwater potential map shows that the area is characterized by five groundwater potential zones;poor, low, moderate, good and high. The northwestern regions, north central and part of the southwestern regions are high groundwater potential zones, the northern and most part of southeastern zone are of moderate potential, while small portion in the southeastern and northern zones are of low groundwater potential.展开更多
文摘In this paper we reported the 40 Ar 39 Ar dating results of hornblendes in Grt Pl bearing amphibolite from the Larsemann Hills, East Antarctica. Their apparent ages respectively are 1586 Ma, 1011 1080 Ma, 761 Ma, 529 582 Ma. Their plateau ages of 1036 Ma and 554 Ma as well as an Ar Ar isochron age of 1010 Ma have also been obtained respectively. These isotopic dating results for the first time by the Ar Ar method for hornblendes completely record almost all the structural metamorphic thermal events that this region experienced, and provide an answer to the controversial question on the structural metamorphic thermal events of this region in recent several years, namely, which one is more important, the late Proterozoic 1000 Ma event (Grenvillian) or the early Palaeozoic 500 Ma event ( Pan African), as well as whether the former exists or not. The 40 Ar 39 Ar dating results of hornblendes show that the Larsemann Hills experienced a complicated poly metamorphic evolutionary history, and their protoliths were probably formed in early to mid Proterozoic. The late Proterozoic 1000 Ma event (Grenvillian) has been confirmed to be a predominant tectonothermal event whilst the early Palaeozoic 500 Ma event (Pan African) has been confirmed just to be the last strong tectonothermal event in this region.
文摘This study is aimed at evaluating groundwater potential of Ipinsa-Okeodu area, near Akure, Southwestern Nigeria. A multi-criteria model was developed for achieving this aim;the GRT model which is based on geology of each sounding point, resistivity, and thickness of the aquifer across the study area was successfully used to evaluate the aquifer potential of the area for future groundwater development programme in the area. Geophysical investigation involving vertical electrical sounding was carried out across the study area. A total of one hundred and two (102) vertical electrical soundings (VES) data were acquired using Schlumberger array with maximum half-current electrode separation of 150 m. Three to five geoelectric layers were delineated across the study area. The predominant curve types are KH, H, K and A. The maps of aquifer layer resistivity and aquifer layer thickness were generated and synthesized with the geology of the study area in producing the GRT model map/groundwater potential map. The groundwater potential map shows that the area is characterized by five groundwater potential zones;poor, low, moderate, good and high. The northwestern regions, north central and part of the southwestern regions are high groundwater potential zones, the northern and most part of southeastern zone are of moderate potential, while small portion in the southeastern and northern zones are of low groundwater potential.
