Ba-Pb mineralization in Ugwuajirija Ishiagu area, lower Benue trough, Southeastern Nigeria: Geochemical evidence

Abstract

Study of rocks of Ugwuajirija Ishiagu area was carried out to determine their mineralization characteristics. This involved 38 samples and elemental ratios, including Ba, Be, Co, Cu, Cs, Nb, Ni, Pb, Sr, Y, Zn and Ba/K2O, Ba/Ni using ICP-MS and ICP-AES techniques. Geological mapping reveals that the area is underlain by four lithostratigraphic formations: Asu River group, Eze-Aku Shale, Nkporo Shale and Mamu Formation. The pre- Santonian formations were affected by magmatic intrusion and emplacement of dolerites, diorites and other diabasic rocks, and hydrothermal solutions leading to mineralization of economic mineral deposits. Modal analysis reveals the dolerite has average plagioclase concentration (41 %), ortho-pyroxene (29 %), clino-pyroxene (7 %), and olivine (9 %). Marly mudstone has quartz (10 %), plagioclase (25 %), orthopyroxene (20 %), clino-pyroxene (8 %) and olivine (8%). Trace and rare earth element analytical results show that all the analyzed samples were depleted in Cs, Sn, and Be < 1.0ppm, but enriched in Ba- 802ppm through 936ppm in the dolerite, to >10,000ppm in the marly-mudstone respectively, which are 2 to 100 times above the average crustal abundance of Ba-400ppm. The mean concentration of Cu, Pb, and Zn increased from 66.2 to 94 ppm in the dolerite at Ugwuele, to 1049ppm in the marly-limestone, to >10,000ppm in the ferruginized mudstones at Ugwuajirija respectively. These enrichments which are above average crustal abundance show that the mudstone and marly limestone in Ugwuajirija Ishiagu area are Ba and Pb mineralized. Further exploration and exploitation are recommended for effective youth empowerment and national development.Keywords: Ba-Pb Mineralization, Ugwuajirija, Lower Benue Trough, Trace Element