Geophysical Identification of Hydrothermally Altered Structures That Favour Gold Mineralisation.

J.O Ohioma,J.T Adegbite,J.I Ehilenboadiaye

doi:10.4314/jasem.v21i6.8

Abstract

This research study uses geophysical method (aeromagnetic) to identify hydrothermally altered structures which favour the inflow of hydrothermal fluid that usually brings about gold mineralisation in Egbe-Isanlu Schist Belt Area, North Central Nigeria. The application of data enhancement filtering algorithm such as reduction to the pole to the magnetic data aided in mapping of various hydrothermally altered structures that may favour gold mineralisation. The interpretation of the aero data set has enhanced a lot of hydrothermally altered structures that trend northeast-southwest(NE-SW). A number of hydrothermally altered structures are seen. Therefore the areas that are hydrothermally altered are potential sites for gold mineralisation, most importantly those areas that lie within or adjacent to major faults around Odogbe and Okolom in the North Central portion of the study area. Similarly, regions around Egbe in the western edge are suspected to be mineralized zones. The results obtained in this research study demonstrated that the geophysical tools adopted are powerful and effective means for gold mineral exploration. This method is unique because it is non-invasive which prevented any environmental degradation and it enhances the coverage of very large area. Keywords: Aeromagnetic Data; Isanlu; Structures; Gold Mineralisation; Hydrothermally Altered.

Highlights

The regional setting in Nigeria is very similar to the Ashanti and Sefwi systems in nearby Ghana, with gold being found in most parts of supracrustal (Schist) belts in the northwest and southwest
Though the precious metals are not essential for industrialisation, they are a high source of foreign exchange and their exploitation to a large scale promotes the establishment of ancillary industries. It was noticed by Woakes and Bafor (1984) that primary gold deposits are associated with some Schist belts of northwest and southwest Nigeria (e.g. Isanlu, Maru, Anka, Kushaka) but not with others (e.g. Wonaka, Karaukarau, Iseyin-Ogun River) and each covers several thousand square kilometres
The principle is similar to magnetic survey carried out with a hand-held magnetometer but enables larger areas of the Earth’s surface to be covered quickly for regional reconnaissance; this is needed because most of the Schist belts in which gold is found in Nigeria cover several thousand square kilometres

Summary

Introduction

The regional setting in Nigeria is very similar to the Ashanti and Sefwi systems in nearby Ghana, with gold being found in most parts of supracrustal (Schist) belts in the northwest and southwest. Though the precious metals are not essential for industrialisation, they are a high source of foreign exchange and their exploitation to a large scale promotes the establishment of ancillary industries It was noticed by Woakes and Bafor (1984) that primary gold deposits are associated with some Schist belts of northwest and southwest Nigeria (e.g. Isanlu, Maru, Anka, Kushaka) but not with others (e.g. Wonaka, Karaukarau, Iseyin-Ogun River) and each covers several thousand square kilometres. Other sources of heating that may be involved include energy released by radioactive decay or by faulting of the Earth’s crust These waters may deposit their dissolved minerals in openings in the rock, filling the cavities, or they may replace the rocks themselves to form so-called replacement deposits. Most gold deposits are sourced from metamorphic rocks because it is thought that the majority are formed by dehydration of basalt (mafic rock) during metamorphism

Objectives

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Results