Archean quartz-pebble conglomerates are one of the most extensively studied stratigraphic horizons and are globally well known for their gold and uranium prospects of economic grades. Similar quartz-pebble conglomerate horizons have been delineated within the Neoarchean-Paleoproterozoic Gorumahisani-Badampahar schist belt and Dhanjori volcano-sedimentary basin lying along the northeastern fringe of the Singhbhum-Orissa craton in eastern India. Gold and uranium occurrences have been reported previously from the quartz-pebble conglomerates of the Singhbhum craton; however, no detailed report on gold occurrences and genesis is available. This work focuses on the nature and genesis of gold mineralization hosted by radioactive quartz-pebble conglomerates from the eastern Iron Ore Group and the Dhanjori basin within the Singhbhum-Orissa craton. The quartz-pebble conglomerates reported in this work are predominantly matrix supported and oligo-mictic in nature. Petrography, microprobe data, and scanning electron microscopy studies reveal the presence of chromite, zircon, rutile, magnetite, monazite, pyrite, chalcopyrite, pyrrhotite, stibnite, and brannerite. Laser ablation-inductively coupled plasma-mass spectrometry analyses on various generations of arsenian pyrites reveal significant concentrations of Au in solid solution. The gold was initially incorporated in its detrital form onto growing pyrite surfaces, possibly due to microbial mediation. The trace element data coupled with back-scattered electron images and X-ray compositional maps suggest remobilization of detrital Au and associated trace elements from the diagenetic pyrites and their precipitation onto the younger hydrothermal pyrites. The sulfide-hosted gold mineralization, trace element signatures, and zoning patterns studied in this work mimic the mineralization style reported from sediment-hosted gold deposits such as Spanish Mountain and Carlin. However, in broad terms, the origin of Au within these quartz-pebble conglomerates resembles the modified placer model of gold deposition within the Witwatersrand conglomerates. This is the first report of refractory gold mineralization within arsenian pyrites from the radioactive quartz-pebble conglomerates of eastern India and has important implications for gold exploration in this region and analogous areas.

Numerous iron ore deposits are hosted within the Meso to Neo-Archean banded iron formations (BIFs) extending across the Singhbhum-Orissa Craton, eastern India. Despite the widespread distribution of BIFs, which forms part of the iron ore group (IOG), heterogeneity in their grade and mineral composition is occasionally observed even within a single ore deposit. Kiriburu-Meghahatuburu iron ore deposit (KMIOD), west Singhbhum district, Jharkhand, eastern India is characterized by a dominant hematite (often martitized) occurrence with a total resource of >150 million tonnes (MT) at 62.85 wt % Fe. Very high-grade blue dust ore (friable and powdery hematitewith~67% Fe), high-grade massive, hard laminated hematitic ores (~66% Fe) and medium to low grade goethitic/lateritic ores (50%–60% Fe) are the common iron-ore lithologies in KMIOD. These ores can be distinguished in the field from their physical appearance, meso-scale texture and spatial occurrences with the host rocks along with the variation in chemical composition. The high-grade ores are characterized by high Fe (>62 wt %), low Al₂O₃ (1.5–2.5 wt %), low SiO₂ (2.0–4.5 wt %) and low P (<0.06 wt %). Detailed field studies and laboratory investigations on the ore mineral assemblages suggest that the mineralization of high-grade iron ores at KMIOD is controlled by three major parameters, i.e., lithological, paleoclimatic and structural controls. High-grade iron ores such as blue dust seem to be formed during leaching processes through inter-bedded ferruginous shale and banded hematite jasper (BHJ) occurring within BIFs. Structural elements such as folds, joint network, fracture arrays, local faults and steeply dipping bedding planes are surmised as strong controls for the evolution of different iron ore types from the BHJ. Most of the high-grade ores are concentrated at the hinge portions of second generation folds (F₂) owing to the easy access for circulation of meteoric solution along the fractures developed due to release of stresses at the hinge portions aided by supergene ore enrichment processes. The BHJ and interbedded ferruginous shale seem to have been given a significant contribution for the formation of different grades of iron ores over the area. Lithologically, the BIFs are governed by rheological features providing channel ways in the ore enrichment process. The variation in the iron ore mineralogy is caused by the variation in depositional and paleoclimatic environment, structural setting and lithological attributes. Hence, these parameters could be used for future exploration and grade recovery of iron ore resources in the region and in the adjoining areas.

The North Singhbhum Mobile Belt (NSMB) in the eastern Indian shield is an excellent example of a diverse lithological domain with multiphase shear/fracture zones. It is a well-acknowledged prospective region known for various mineralizations, e.g., Cu, Au, U, and Fe. The present study was conducted in the Babaikundi–Birgaon Axis (a shear and fracture zone within NSMB) within Babaikundi village. The study suggests that anomalous zones are possibly related to gold-associated sulfide mineralization using photomicrography and geophysical methods such as magnetic, self-potential (SP), and very low-frequency (VLF) electromagnetic (EM) methods. Photomicrography on quartz samples and Scanning Electron Microscope (SEM) Backscattered-Electron (BSE) images show that gold particles are present in the quartz reef vein in Babaikundi. Magnetic data are presented in the total magnetic intensity (TMI), upward continuation, and analytical signal maps. VLF-EM data were analyzed using different processing techniques to delineate anomalous auriferous zones. Furthermore, the SP data were inverted using the Particle Swarm Optimization (PSO), Very Fast Simulated Annealing (VFSA), and Genetic Algorithm (GA) approaches for comparative study of the resultant model parameters and their suitability considering a 2D inverted resistivity section derived using VLF-EM. The photomicrography study indicates the existence of gold/ pyrite/pyrrhotite within the Babaikundi–Birgaon axis, which corresponds to a low magnetic anomaly based on a magnetic study; a high current density, a high Fraser value, and a low resistivity based on the VLF-EM study; and a negative SP value was found based on the SP study. The combined study generally supports mapping auriferous zones and demarcates the Babaikundi–Birgaon axis within the Babaikundi–Birgaon area.