Geology and Ore 13, 2024

Iron oxide copper-gold (IOCG) mineralising systems in Greenland

In the wake of the discovery of the giant Olympic Dam Cu-U-Au-Ag-REE deposit in South Australia in 1975, a conception developed of an important class of ore deposits not previously recognised as such. Subsequent realisation of its signifcance by the discovery of new deposits of this type attracted keen interest both from academic institutions and exploration companies worldwide. 

Due to its economic importance, over the last two decades, the so-called iron oxide copper-gold (IOCG or FeOx-Cu-Au) class of deposits has become a prime target for exploration. Since the frst defnition and description of the IOCG deposit, new discoveries, re-classifcation and increasing worldwide research have shown that IOCG deposits encompass a wide spectrum of hydrothermal ore deposits.

Introduction

It is understood now that the IOCG class represents a family of related mineral deposits that share a number of distinguishing features:

  •  low-Ti magnetite and/or hematite (< 2.0 wt % TiO2)
  • extensive Na-K (-Ca) alteration
  • REE, Co, Ag ± U, P
  •  generally coeval magmatism

The current inadequate state of knowledge about this deposit class is refected in the lack of comprehensive genetic models. Consequently, a genetic classifcation appears to be an unnecessary limitation when identifying new deposits. Therefore, the classifcation for the World Minerals Geoscience’s Database Project (Geological Survey of Canada), defning six types of IOCG deposits, is used in the fact box. The characteristics of these IOCG deposit types can be directly compared to geological features recognised in Greenland.

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