GEOLOGY, GEOCHEMISTRY AND GENESIS OFAMETHYST MINERALIZATION AND ASSOCIATED ROCKS IN DUTSEN BAKURA HILL, NORTHCENTRAL NIGERIA
GEOLOGY, GEOCHEMISTRY AND GENESIS OFAMETHYST MINERALIZATION AND ASSOCIATED ROCKS IN DUTSEN BAKURA HILL, NORTHCENTRAL NIGERIA
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Date
2014-05
Authors
Rose, SOLOMON Anche
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Abstract
Dutsen Bakura Hill is located within the North-Central part of the Nigeria Pan-African Orogenic belt. The Dutsen Bakura Hill is an example of an amethyst bearing vein mineralization in an uplifted faulted metamorphic terrain. The host rock is sheared gneiss that has been affected by Pan African tectonism. These tectonic events resulted into fracturing, faulting, folding and metamorphism of the rocks in the area. The host rocks of the amethyst veins are marked by considerable shearing and breciation attributed to brittle deformation.The vein is a late stage epithermal deposits with a NE-SW trend consistent with the Pan-African structural trend. Mineralization in the vein consists of bands of milky quartz and amethyst formed in a two stage sequence considered as a gneissic makeover of quartz. Major element distribution indicates an increase in SiO2 content from the granite gneiss host to the core of the vein. Incompatible trace and lithophile elements ratio Ba/Nb, Nb/Ta, Zr/Hf and Pb/Nd values in granite gneiss and sheared gneiss are similar but differ from that of milky quartz and amethyst. There is a decrease in concentration of some trace elements such as the lanthanides from the gneissic host to the core of the vein as the SiO2 content increases. The REE distribution pattern in the hostrock is marked by enrichments of LREE, depletion of HREE and marked Eu anomaly with slight positive Ce anomalies. On the other hand, the mineralized vein shows no pronounced negative Eu anomaly and it REE pattern is irregular, with the characteristic REE tetrad effect. The oxygen isotope data of the quartz extracted from the granite gneiss and that of the milky quartz and amethyst is 7.1‰, 12.1‰, 17.1‰ respectively. There is a trend from low to high oxygen isotope values from the granite gneiss to the milky quartz and amethyst within a single filling phase. The oxygen isotope signature constrained the source of the vein material to greywackes and siliciclastics rocks. Furthermore, the oxygen isotope results constrained the mineralizing fluid within the range of metamorphic fluids with possible involvement of meteoric fluid. The amethyst mineralization in Dutsen Bakura is thus considered as precipitated from silica-rich fluids produced by deformation during cataclastic metamorphism.
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THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES
AHMADU BELLO UNIVERSITY, ZARIA;
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE AWARD OF MASTERS
OF SCIENCE DEGREE IN GEOLOGY
Keywords
GEOLOGY,, GEOCHEMISTRY,, GENESIS,, METHYST,, MINERALIZATION,, ASSOCIATED,, ROCKS,, DUTSEN BAKURA HILL,, NORTHCENTRAL, NIGERIA.