Whole-rock geochemistry of basic and intermediate intrusive rocks in the Ishiagu area: further evidence of anorogenic setting of the Lower Benue rift, southeastern Nigeria

Abstract

IntroductionThe Lower Benue rift is the southern part of the intracontinental Benue rift-basin, which extends from the Niger Delta northeast towards the southern part of Cameroun, a distance of about 1000 km long and 80 km wide. Its evolutionary history was traced to the opening of the Gulf of Guinea and the South Atlantic during the separation of the South American plate from the African plate in the Mesozoic era (Burke et al., 1971;Grant, 1971) (Figure 1), accompanied by magmatic activities that span the Jurassic (Bajocian) to the Tertiary (Umeji, 2000).The first report of the existence of intrusive rocks in the Lower Benue rift was by Wilson and Bain (1928), who described the rocks exposed at Lokpanta during the construction of the Port Harcourt-Enugu railway line as intrusions (Obiora and Charan, 2010). The intrusive and volcanic rocks in the Lower Benue rift have been described as intermediate to basic in composition and associated with lead-zinc mineralization (Farrington, 1952;Gunthert and Richards, 1960;Cratchley and Jones, 1965; Nwachukwu, 1972), as cited by Obiora and Charan (2010). Burke et al. (1971) described the rocks (volcanic and intrusive) around the Abakaliki area (Figure 1) as andesite lavas and tuffs and proposed a subduction origin for the rocks in the Benue rift. However, Olade (1978, 1979) reported alkali basalts and tuffs with spilite using petrographic and geochemical data and concluded that the rocks were within plate 'hotspot' basalts. Some others

Assessment of Activity Concentration of Radionuclides in Soil and Cassava Food Crop from Solid Mineral Mining Site in Ishiagu, Ivo L.G.A of Ebonyi State, Nigeria

“…The average level of radioisotope present in the food specimen were calculated to be 21.01 Bq/Kg(mung beans), 25.6 Bq/Kg ( maize) for 226 Ra , 62.6 Bq/kg (mung beans), 72.9 Bq/kg (maize) for 228 Th and 542.9 Bq/kg (mung beans), 434. 6 Bq/kg (maize) for 40 K. The radionuclide content of the maize and mung beans from Minjingu area and that of Bukombe zone in Geita Region both in Tanzania were compared, and the results shows that the radioactivity of the specimen in Minjingu area were higher. The sum of annual effective dose of 2.003 ± 0.044 mSv/year for intake of 226 Ra and 228 Th by adults was determined.…”

“…The representative gamma index is given as . (6) This gamma index is also used to correlate the annual dose rate due to the excess external gamma radiation caused by superficial materials [1]. This is a tool used to find out materials that might portray health problem when used for construction.…”

Geochemical Characterization of Mineralized Pegmatites around Wowyen Areas, Akwanga, Northcentral Nigeria

“…*Data for fertile peg. from [48] *UCC is average upper-continental crust after [47] Normalizing factors from [41] . Symbols are as shown in Figure 3.…”

Petrology and Geochemistry of Rocks of Ishiagu and Environs Southeastern Nigeria Using Ed-Xrf Method

“…The geochemical data expressed in weight percent of the representative oxides were plotted in various discriminatory diagrams (Figs. 5,6,7,8). Table 2 shows that all the rocks are enriched in SiO 2 , Al 2 O 3 , Fe 2 O 3 , and TiO 2 with average values of 48.367.…”

“…The petrology and geochemistry of rocks of Ishiagu and environs in the Anambra Basin and Afikpo Syncline had been studied by some scholars, for example Reyment [3], Ezepue [4], Obi [5], Obioha, et al [6], Obioha [7], Chukwu and Obiora [8], and many others. However, more systematic work covering adjacent/rural areas of Ishiagu and environs is still needed to be done to properly elucidate the complex petrological, geochemical and mineralogical characteristics of the area, using integrated geological mapping, petrological and analytical geochemical approach.…”