The Delineation and Hydrothermal Alteration zones in Gitata Sheet, North Central Nigeria

Abstract

This research presents a summary of the research carried out within Talata_Mafara (31) and Kaura_Namoda (32) sheets in Zamfara State, and is bounded by the longitude 6°00´E and 7°00 E and latitude 12°30´N and 13°00´N using Aero-magnetic and Aero radiometric data. The structural deformation to the basement rocks interpreted as faults, fractures, dykes, joints and geological boundaries were delineated. From the radiometric data, regions that has suffered hydrothermal alterations due to potassium enrichment and Thorium depreciation were mapped and interpreted as regions of orogenic gold mineralization. Majority of the fault lines were identified and some subsistent fracture lines denoted as fs. A major fault line trending NE-SW, cut the study area into two runs diagonally for about 70 km. Regions of hydrothermal alteration were evaluated from K/Th ratio, K-deviation and F-parameter. Combination of these grid results obtained from the three methods stated above was used to build a ternary map, where K/Th is red, k-deviation is blue and F-Parameter as green. Analysis and interpretation of the ternary image indicate that regions where high K/Th values (0.19 – 0.25) %/ppm, high k-deviation values (0.63 – 1.20) and high F-Parameter values (0.43 – 0.67) appears as white on the colour aggregate, an indication of high hydrothermal altered zone. Area with grey colour indicating moderately altered zone. Regions that appears as dark colour indicate low values of K/Th, K-deviation and F-Parameter this occurs within the sedimentary formation of Bida Basin sand stone, located at the Northern end and South Eastern corner of the study area. A comprehensive analysis of these results delineated region of hydrothermal altered zones in white and grey colour that coincides with areas within the faulted and fractured basement. Delineated structures from the magnetic data that coincide with regions of potassium alterd hydrothermal zones are marked as regions of orogenic gold mineralisation haloes. Most of the features that are solid mineral hosts can be found within this vein and in the adjacent, highly deformed host rock located around Tagangani, Kwashebawa, Gyeranya, Yanbuki and Zurmi. The deformation appears to principally comprise of quartz schist, amphibolites schist, undifferentiated schist, mica schist, granite gneiss, porphyritic granite, migmatite, along medium grained granite.