GEOLOGY AND GEOCHEMISTRY OF TANTALUM - NIOBIUM MINERALISATION IN EGBE RARE - METAL ENRICHED PEGMATITES, PART OF ISANLU (SHEET 225) SOUTHWEST, NIGERIA
GEOLOGY AND GEOCHEMISTRY OF TANTALUM - NIOBIUM MINERALISATION IN EGBE RARE - METAL ENRICHED PEGMATITES, PART OF ISANLU (SHEET 225) SOUTHWEST, NIGERIA
No Thumbnail Available
Date
2015-09
Authors
USMAN, Jose Adoze
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The pegmatite of Egbe area which has been known to bear valuable economic minerals and associated with other rock types like banded gneiss, schist, amphibolite and granites were investigated with a view to elucidating their petrochemical and geochemical features that may be related to economic rare metal Ta-Nb mineralization in the area
Geological field mapping of the study area was carried out by collecting various rock types, observing their field occurrences, structural components and hand specimen observation.
Thin sections of ten representative rock samples were prepared and studied for petrographic analysis. Twenty whole rock (four pegmatites, five granites, one banded gneiss, one amphibolites, one Schist) samples, five muscovite samples extracted from the pegmatites, One albite and lepidolite were analyzed for major and trace elements including REES using the Inductively Coupled Plasma Mass Spectrometry(ICP-MS) analytical method, Boron- fusion – Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) for Boron and Ion selective Electrode (ISE) for Fluorine at Acme Laboratory, Vancourva, Canada.
Geochemical studies indicated that the pegmatites and the other rock types in the study area are siliceous and peralkaline. The general structural trend in the study area is WNW – ESE direction and foliation with a N – S strike direction was observed in the banded gneiss and schist. Two types of folds, namely, asymmetric and isoclinals were recorded in the banded gneiss and schist respectively. Geochemical analysis revealed that the pegmatites are siliceous and of rare – metal type. The granites are peraluminous and of S – type. Albite, lepidolite and muscovites (extracted from the pegmatites) are significantly enriched in Li, Rb Cs, Nb and Ta compared to the granites, gneiss, schist and amphibolites. The granites showed strong affinity to the sncollisional and volcanic arc granites with an enrichment LREE and a depletion in HREE with a strong negative
vii
Eu anomaly. the rare-metal pegmatites exhibits pronounced negative Ce and Eu anomalies while the barren pegmatites have positive Ce and weak negative Eu anomalies. Rare- metal pegmatites also show weak negative Yb anomaly and the barren ones exhibit weak positive Yb anomaly.
The low K/Rb ratio of the pegmatites indicates fraction accompanied by Rb enrichment and Ba depletion. In Egbe pegmatites, fractionation started from Mn- poor ferrocolumbite towards a slightly Mn- and Nb- enriched manganotantalite and finally to manganotantalite in the more evolved lepidolite. The economic mineral in Egbe area is tantalite.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A MASTER OF SCIENCE DEGREE IN GEOLOGY
DEPARTMENT OF GEOLOGY
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
GEOLOGY,, GEOCHEMISTRY,, TANTALUM - NIOBIUM MINERALISATION,, EGBE RARE - METAL ENRICHED PEGMATITES,, ISANLU,, (SHEET 225),, SOUTHWEST,, NIGERIA,