Petrographic Studies of Yolde Formation Exposed at Gombe, Gongola Basin, N E Nigeria

Abstract

Geological mapping carried out in Gombe area revealed the presence of Yolde, Pindiga and Gombe Sandstone Formations. But in the case of this study, only the silicalstics of Yolde Formation are used for the Petrographic investigation. Petrographic analysis results indicate that Quartz is the dominant mineral in all the studied slides followed by potassium feldsper (Orthoclase), Iron oxide, altered feldspers, whereas Limonite and Zircon appear thrice each. Quartz framework grain is abundant due its greatest resistant to chemical decomposition and mechanical abrasion, Orthoclase is the only feldspers mineral present due to resistant than most of them. Altered feldspers is an opaque mineral visible only under cross-polar, it is believed to have been formed due to alteration of ferro- magnesian minerals. Zircon is the only non-stable opaque mineral present due to ability to withstand abrasion weathering, it is found in recycled sedimentary facies. Stable opaque present are Iron oxide and Limonite. Limonite results from dissolution of hematite and sometimes it is referred to as goethite or Iron ore. Iron oxide in this study is undifferentiated, because in theory, it represents both hematite and magnetite, then to a lesser extent, the rarer oxide mineral maghemite. It was observed in all the slides and this suggests that the Yolde Formation of the study area have been intensely weathered and most have travel some distance from source rock. Its provenance can be said to be from