Document Type : Research Paper
Authors
Department of mining engineering, faculty of engineering, Urmia University, Urmia, Iran
Abstract
The Janja Porphyry Copper Deposit, situated in the Zabol–Zahedan–Saravan structural zone of eastern Iran, is obscured by alluvial cover, posing significant exploration challenges. This study investigates the geochemical distribution of elements in surface cover to delineate anomaly patterns associated with concealed mineralization. A total of 153 stream sediment samples and 16,300 drill core samples from 74 boreholes (38 in overburden, 36 in exposed bedrock) were analyzed using ICP-MS and Fire Assay techniques. To mitigate the closure effect in compositional data, Centered Log-Ratio (CLR) transformation was applied, followed by Sequential Factor Analysis (SFA) to identify multi-element associations. The Geochemical Mineralization Prediction Index (GMPI) was utilized to map spatial anomalies accurately. Drilling results reveal elevated concentrations of Ag, As, Cd, Mo, Pb, S, Sb, and Zn in the semi-transitional overburden (enrichment indices up to five times Clarke values), while Cu and Au are enriched in exposed porphyritic diorite zones, with average copper concentrations of 1,211.53 ppm in overburden and 2,561.4 ppm in the hypogene zone. SFA on stream sediment data identified three elemental groups: lithogenic (Al, Fe, Mn), mineralization-related (Cu, Pb, Zn, Ag), and broadly dispersed (Mo, As, S). Anomalous Ag, Mo, Cd, and S concentrations in overburden serve as key indicators for concealed deposits. This study offers an innovative multivariate geochemical approach to optimize exploration in covered terrains within global porphyry belts.
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