Investigation of geochemical characteristics and hydrothermal alteration zone mapping supported by remote sensing of a porphyry-copper prospect, southeastern Iran: integrated applications to exploration

Abstract

This exploration methodology case study is situated along the Sistan Suture Zone where the granitoid suite is a mantle-derived multiphase intrusive complex. One of the characteristics of this region is the presence of large areas of sulfide-bearing, quartz-rich stockwork and pyritic veins. Geochemical findings show it is limited to the calc-alkaline to shoshonitic series intrusions and is associated with a volcanic arc (I-type) formed within an active continental margin subduction setting. The associated intrusive complex has characteristics consistent with Cu productive porphyries, supported by high K-adakitic Sr/Y, La/Yb, Y, and Al2O3/TiO2 geochemical signatures. The stockwork mineralization includes the hypogene (chalcopyrite and bornite), with locally superimposed supergene (covellite, malachite, goethite, and hematite) zones. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images (visible-near infrared (VNIR) and shortwave infrared (SWIR) bands) and Mixture Tuned Matched Filtering (MTMF) algorithm, enable identification of each hydrothermal alteration type, especially where pictures were innovatively classified by a concentration-number (C-N) fractal method. Four alteration types are evident, i.e. phyllic, argillic, and propylitic, as well as secondary (supergene) jarositethat are associated with gossans, which are an indicator of the hypogene pyritic shell. The propylitic alteration envelopes the phyllic and argillic varieties, forming a belt around the pyritic shell; alteration assemblages were confirmed by XRD analysis. Finally, all results show a mineralization-alteration pattern within this case study region that is similar to those of known porphyry copper and associated molybdenum- and gold-bearing systems in this region of Iran and worldwide.