Petrographic Analysis and Total organic content (TOC) of Mudstone Inclusions in Igneous Intrusives in Lower Benue Trough, Nigeria

The lower Benue trough is a linear, intracratonic, graben basin, trending ne-sw. The trough is characterized by an uplifted basement block, flanked by deep basin containing about 6km of sediments. The study area which is part of the lower Benue trough comprises of igneous rock types that are predominantly intermediate to basic in nature. From petrological studies, the rocks are made up of intermediate to high temperature minerals. Total organic carbon (TOC) content tests were conducted on the mudstone inclusions in the pyroclastics, and values range from 0.60%wt- 0.86%wt. The classification of source quality by total organic content (TOC) percent shows that the source quality is fair. This indicates that prior to the eruption, the study area may have had higher organic carbon content but the heat that accompanied the eruption baked the source rock into mudstones thereby reducing the source rock quality. The thermal effect of the igneous intrusions may have increased the temperature above the oil window limit.