Abstract
The dolerites in some parts of southern Benue Trough were studied petrographically. The results show that most of the dolerites in the Anambra and Afikpo basins are olivine dolerites except Umuchieze LokpaUkwu that host mostly quartz porphyry dolerites. The thin section results show that the dolerite rocks in Umuchieze LokpaUkwu has mineral paragenesis of plagioclase feldspar+quartz +pyroxene + biotite + hornblende + and hematite. The pore spaces and fractures in the rocks are healed by the infilling of quartz. The porphyritic texture of the dolerite in the study area show variable temperatures of the crystallized magma that formed the dolerite. The sharp contacts of the dolerites and the host rocks could play roles in the alteration of the crystallizing magma. Hydrothermal interaction, contamination and assimilation played major roles in the evolutionary processes of the magma that formed the quartz-porphyry dolerite. Key word : Quartz, Dolerites, Benue Trough, Magma DOI: 10.7176/JEES/10-2-09 Publication date: February 29 th 2020
Highlights
Benue Trough is one of the sedimentary basins in Nigeria in which the sediment thickness is estimated to be about 6,500m in some places and was formed by several transgressive and regressive sedimentary cycles (Onwualu-John and Ukaegbu, 2009)
The results show that most of the dolerites in the Anambra and Afikpo basins are olivine dolerites except Umuchieze LokpaUkwu that host mostly quartz porphyry dolerites
The tectonism that occurred in Benue Trough was accompanied with magmatism and the magmatism resulted to the emplacement of two groups of dolerite (Olivine dolerites and quartz porphyry dolerite) in the study area
Summary
Benue Trough is one of the sedimentary basins in Nigeria in which the sediment thickness is estimated to be about 6,500m in some places and was formed by several transgressive and regressive sedimentary cycles (Onwualu-John and Ukaegbu, 2009). The Santonian deformation produced the Abakaliki Anticlinorium. The origin and geology of Benue Trough have been discussed by Etuk et al (2008), Reyment (1965), Wright et al (1985), Nwajide (1990), Onwualu-John and Ukaegbu (2009), Kogbe (1976). The study area (LokpaUkwu) is within the Southern Benue Trough and lies within the Anambra Basin. The Abakaliki Anticlinorium forms the high relief in the study area while the dolerites form a moderate domal height that has intruded the sedimentary sequences. Though much work has been done on the geology of Benue Trough but the study of the quartz porphyry dolerite of this basin is scarce. The scope of this work is to determine the geologic processes that resulted to the Formation of the peculiar quartz - dolerite rock in the study area
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