Mineralogy and geochemical study of sulfide mineralization, in Kadikhel Valley, Western Kohistan Island Arc, North Pakistan

This study reports sulfide mineralization in Kadikhel Valley, Upper Dir region, for the first time, located in the western Kohistan Island Arc, north Pakistan. The area is poorly explored for exploration, mineral identification, ore characterization, and processes of ore genesis. This study aims to investigate the mineralogical and geochemical characteristics of sulfide mineralization and its origination within the quartz veins and associated host rocks (amphibolites), which is a new discovery in this region. Detailed field investigation, mineralogical, petrochemical, and O-S isotopic studies were conducted by analyzing the representative samples collected during the field using advanced instrumental techniques such as AAS, ICP-MS, XRD, and SEM-EDX. Results of the samples from the study area indicated three types of copper mineralization, including copper mineralization along Quartz veins, copper mineralization in amphibolites, and supergene enrichment of copper mineralization. The economically significant concentration of copper in the altered amphibolites ranges from 2.4 % to 5.78 %, while in mineralized quartz veins, it is from 5.2 % to 16.4 %. Trace elements (ppm) such as Pb (121-647), Zn (112-458), W (110-2069), Ni (15-491), Cr (115-538), Co (101-421), and Ag (5.1- 5.7) are found in relatively smaller amounts. The gain and loss analysis shows that the hydrothermal fluids were enriched in MnO, FeO, Cu, Pb, Zn, W, Ni, Cr, Co, Au, and Ag. The enriched elements formed an important part of the mineralizing hydrothermal fluids. The major ore minerals identified in the study area are chalcopyrite, bornite, chalcocite, pyrite, malachite, azurite, hematite, and magnetite, with minor concentrations of sphalerite and galena. The associated gangue minerals include quartz, biotite, muscovite, amphibole, plagioclase, epidote, and chlorite. Different ore phases and mineral textures were determined using ore microscopy, SEM-EDS, and XRD studies. Metallic mineralization is formed in two stages (i.e. hydrothermal and replacement stages). The average isotope values of sulfur (δ34S) 2.17 %, and oxygen (δ18O) 7.8 %, suggest that a magmatic-hydrothermal fluid derived from a magmatic source is responsible for the precipitation of sulfide mineralization in the mineralized quartz veins and adjacent mineralized/altered amphibolites. We suggest that the episodic intrusions of diorite/granodiorites of the Kohistan batholith are the main sources of metal-rich hydrothermal fluid responsible for the precipitation of the sulfide mineralization in the study area.