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Natural Resources Research

, Volume 28, Issue 4, pp 1353–1370 | Cite as

Supergene Mass-Balance Study Assuming Zero Lateral Copper Flux Using Geostatistics to Recognize Metal Source Zones in Exotic Copper Deposits

  • Alireza Arabpour
  • Omid AsghariEmail author
  • Hassan Mirnejad
Original Paper
  • 71 Downloads

Abstract

Recognition of effective factors that influence the spatial extension of supergene weathering zones is important both for the identification of high potential areas of exotic deposits and for the cost-effective planning of mining. In particular, recognition of exotic mineralization around porphyry copper deposits early in mine development prevents them from being buried beneath mine infrastructures such as waste dump and tailing structures. Mass-balance modeling, a practical method for determining high potential areas of undiscovered exotic mineralization, investigates important factors in forming exotic deposits. Mass-balance modeling is a two-phase methodology that becomes progressively more detailed. An initial result, presented here as phase 1, is based solely on Cu assays. Phase 2 incorporates relict sulfide mineral studies to improve phase 1 modeling results and computes actual fluxes of copper that escaped vertically downward from the leached cap to form the enrichment blanket and then flowed laterally away to form exotic mineralization. In addition, geostatistical approaches, especially sequential Gaussian simulation, are useful tools for investigating the spatial relationships and modeling of mass-balance results in phase 1 studies. This paper introduces a method for interpolation and downscaling of the preliminary mass-balance analysis (phase 1) to highlight the role of geological features in the evolution of the supergene process. Using only copper assays without any need for relict sulfide mineralogy, this approach can be used to approximately identify the geographic direction of metal movement in exotic copper deposits, and thus serve as an initial exploration guide in prospecting for exotic deposits. For this, a vertical columnar block model was constructed for each of the supergene weathering zones and preliminary analysis of mass balance was conducted to reconstruct the apparent total leached zone column height assuming zero lateral flux. This analysis was applied to each of the vertical block model columns. The results of mass balance were interpolated in a 5 × 5 m grid by sequential Gaussian simulation method, and the simulated surface of the total leached zone was conflated with geological features. The roles of topography, argillic alteration and linear structures were identified in the transport of supergene solutions in the Miduk porphyry copper deposit of Iran. In the northern section of the deposit, which is in accordance with the topography gradient and the presence of advanced argillic alteration zone, the computed top total of leaching is below the actual surface topography, whereas the hypogene isograd curves confirm the expansion of primary copper in these areas. The northern section of the deposit was introduced as a susceptible area for the removal of copper-bearing solutions from the supergene enrichment system.

Keywords

Mass-balance modeling Supergene process Exotic copper Porphyry copper deposit Geostatistics Sequential Gaussian simulation 

Notes

Acknowledgments

The authors would like to thank the R&D Unit of National Iranian Copper Industries Company (nicico) for collaborating in accessing and collecting the data and providing permissions. Special thanks to Professor George H. Brimhall for sharing his experiences and his guidance for interpretations of mass-balance analysis in this study. Also, we should thank the Simulation and Data Processing Laboratory of Mining Department of University of Tehran, Iran, for providing software and hardware facilities. We would like to thank Professor Carranza for editorial handling of the manuscript and two anonymous reviewers for their valuable comments.

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Copyright information

© International Association for Mathematical Geosciences 2019

Authors and Affiliations

  1. 1.School of Geology, College of ScienceUniversity of TehranTehranIran
  2. 2.Simulation and Data Processing Laboratory, University College of Engineering, School of Mining EngineeringUniversity of TehranTehranIran
  3. 3.Department of Geology and Environmental Earth SciencesMiami UniversityOxfordUSA

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