PETROGENESIS AND STRUCTURAL CONTROL OF PEGMATITES AROUND KWARRA AREA: IMPLICATIONS ON RARE METAL MINERALIZATION, PART OF KURRA SHEET 189 SW, NORTH CENTRAL NIGERIA

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Date
2019-10
Authors
SUNDAY, Adedeji Ebenezer
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Abstract
The study area is underlain by Basement Complex rocks and Younger Granites. The Basement Complex rocks comprise amphibolite, migmatite gneiss, banded gneiss, granite gneiss and albitised granite, while the Younger Granite rock is alkali granite. Pegmatites and dolerites represent the minor rocks types in the study area. The pegmatites are grouped into two types; the quartzmuscovite- pegmatite and quartz-feldspar-pegmatite. The principal stress directions in the study area are N-S, NE-SW, and NNE-SSW with minor ENE-WSW, E-W trends. The quartz-muscovitepegmatites are relatively rich in HFS elements such as Zr, Ga, and Nb and Ta, having values above the average crustal abundance of 165ppm, 17ppm, 25ppm and 2.2 ppm respectively. It is highly concentrated in lithophile element Rb but depleted in Sr and Ba. By contrast, the quartz-feldspar pegmatite is depleted in HFS elements namely Zr, Ga, and Nb and Ta and the LILE Sr and Ba but enriched in Rb although not up to the level of the quartz-muscovite-pegmatites. The quartzmuscovite- pegmatite is of the rare metal class akin to the LCT typeand has higher concentration of Be, Cu, Ga, Nb, Sn, Ta, Ti, V, W, Y, Zn and Zr compared to the quartz-feldspar-pegmatite which is of the barren class.The pegmatites and albitized granite have been affected to varying degrees by sodic metasomatism which led to the replacement of K by Na in the feldspars and increase in the uranium concentration. The albitized rock types have low ΣREE, Sr and Ba while Rb is progressively depleted with increasing degree of albitisation.Although the rare metal pegmatites lack clearly defined development of Ta and Cs minerals and columbite-tantalite series, it is relatively high Sn concentration (up to 798 ppm), amounts high enough to be associated with a cassiterite mineralization. Based on the trace element concentration of the pegmatites, the petrogenesis of the rare metal pegmatite can be taken to be as a result of the partial melting of a deeply buried S-type fertile granite while the barren one (quartz-feldspar-pegmatite) is simply derived from late stage residual melts of less evolved granitic parent and trace element leached due to the intense effect of metasomatism.
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A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL AHMADU BELLO UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN GEOLOGY (MINERAL EXPLORATION) DEPARTMENT OF GEOLOGY FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY, ZARIA NIGERIA
Keywords
PETROGENESIS,, STRUCTURAL CONTROL,, PEGMATITES AROUND KWARRA AREA,, IMPLICATIONS ON RARE METAL MINERALIZATION,,, PART OF KURRA SHEET 189 SW,, NORTH CENTRAL NIGERIA
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