Mineralogy and Geochemistry of Mud Rock Units of the Late Cretaceous Kanawa and Gulani Formations, Eastern Gongola Basin, North-Eastern Nigeria: Implications for Provenance Studies

摘要

The clay mineralolgy and geochemistry of the mud rock units of the Late Cretaceous Kanawa and Gulani formations in the eastern Gongola Basin were investigated with the sole aim of unravelling the provenance. The distinctive clay minerals and other accessories minerals identified from XRD analysis included; dioctahedral smectite, partially ordered and well ordered kaolinites, illite, and glauconite, palygorskite, sepiolite (found only in the glauconitic horizon) etc, and quartz, microcline, anatase, muscovite, phosphate, hematite etc, respectively. The elemental composition within the same mud rocks unit analysed using XRF revealed the presence of the following major elements: Al 2 O 3 , Fe 2 O 3 , SiO 2 , K 2 O, CaO and TiO 2 in virtually all samples and P 2 O 5 in only two samples. Additionally, trace elements identified from some of the samples are; V 2 O 5 , Cr 2 O 3 , BaO, MoO 3 etc. The major elements are consistent with the chemical composition of the clay minerals and other non-clay minerals present. The presence of Illite or/and smectite, and well ordered kaolinite suggest intense climatic fluctuations between warm and dry, to hot and humid tropical condition. From the geochemical evaluation of the mudrock units within the Late Cretaceous Kanawa and Gulani formations shows that they were probably derived from mafic (basaltic) rocks.