Application of geophysical and geochemical techniques for prospection of sulfide ore minerals in Drosh-Kaldam Gol area, Chitral, Northern Pakistan

Abstract

Abstract Ground magnetic and electrical self potential methods of geophysical exploration have been employed for sulfide minerals prospects at Drosh-Kaldam Gol area of district Chitral, northern Pakistan. The core objectives of the study were to map subsurface sulfide mineralization, analyze structural lineaments and their influence on mineralization, ascertain the depth of causative source bodies, pinpoint economically viable drilling prospects in the area and validate integrated geophysical interpretations by cross-referencing them with the geochemical findings and information obtained from the shallow boreholes. The self-potential tool served to qualitatively delineate lateral variances in the dispersal of shallow sulfide minerals, notably pyrite and chalcopyrite, by analyzing the differences in natural surface potential while magnetic tool was employed to map the lateral heterogeneities in the Earth's magnetic field, aiming to delineate the distribution of magnetically susceptible mineralization, including magnetite associated with sulfide mineralization, as well as to qualitatively map geologic structures like faults or fractures that influence the distribution of mineralization. The acquired geophysical data reveals a shallow and sporadic network of circular to semicircular magnetic discontinuities which is one of the characteristic of porphyry deposits which is further supported in places by low SP signatures that might represent a stock work of fractures/veins in the subsurface that could potentially be the target zones for sulfide mineral prospection in the area. Structural delineation using horizontal gradient map of magnetic method shows that the area is characterized by NE-SW trending structural lineaments i.e faults or fractures. Based on the analysis of self-potential and magnetic profiles, the average depth to the top of the anomaly sources in the study area ranging from near surface to 22.37 meters. To validate the results, two shallow boreholes were drilled in the study area which intersects disseminated and fracture filled sulfide mineralization within the uppermost 6 feet of the surface, with the potential for continued mineralization at deeper depths. Based on the insights derived from integrated analysis of geophysical responses, core drilling data and geochemical outcomes it can be inferred that sulfide mineralization in Drosh-Kaldam Gol region is governed by northeast-southwest trending fault or fracture systems and is intricately linked with dioritic-granodioritic intrusion, exhibiting characteristics akin to porphyry systems.