Detection of gold-bearing quartz veins in the meta-sedimentary formation in the North-Eastern Guinea using remote sensing and geophysical exploration

Abstract

In the Siguiri volcano-sedimentary basin located in north-eastern Guinea, and particularly in the Alahina District, the lithological column consists of schistose argilitic to feldspathic sandstone rocks with micashists, limestone, and traversed by pyroclastites, monzogranites and Paleoproterozoic granodiorites of an age between 2040 and 2250 Ma. These formations are surrounded in places by Neoproterozoic sandstones and conglomerates. Some dolerite dykes and Mesozoic gabbros also affect these formations. The present study, using Landsat 8 satellite imagery data and a ground-based geophysical survey, by timedomain induced polarization, is designed to detect sulphide-associated gold veins within meta-sediments. The study includes fractures network mapping by remote sensing and discriminating zones susceptible to concentrate metal sulphides and silica. The fracture frequency map and geophysical anomalies (resistivity and chargeability) were validated from field observations which include structural measurements from outcrops, trenching and drilling. In resistive and chargeable zones, quartz veins sampled and processed by fire assay and optical emission spectrometry returned gold concentrations of up to 74 g/t. The N10° to N45° azimuths of these auriferous quartz veins coincide with the directions of the major lineaments highlighted by remote sensing. The chargeability and resistivity signatures of auriferous quartz veins concentration zones and their elongated sigmoidal shape suggest a context of mineralized shear-zone.