From Core to Ore: emplacement dynamics of deep-seated nickel sulphide systems

This project investigates the genesis of ore deposits containing nickel, copper and the immensely valuable platinum group elements. These systems provide insights into fundamental questions regarding the evolution and dynamics of the Earth System, because these ore deposits are windows into the deep mantle of our planet. the aim in this program will be to develop an integrated model of these deposits that will underpin a new generation of exploration strategies. In addition to this immediate economic imperative, deep-seated nickel sulphide systems are windows into the mantle of our planet and provide crucial insights into fundamental questions regarding the evolution and dynamics of the Earth System.

Unlike many metal resources that are concentrated in the continental and oceanic crust and can be recycled and redistributed through typical crustal processes, nickel (Ni), copper (Cu) and the platinum group elements (PGE) are heavily partitioned into the core and mantle of our planet, residing primarily in reservoirs that are inaccessible to direct observation and sampling (> 300 km deep). A number of times over the last ca. 3.5 billion years, however, large cataclysmic magmatic events have disturbed this segregated system, remobilising a portion of the metal content of the mantle and depositing large quantities of these elements in the crust in the form of Ni-Cu-PGE sulphides. Such deep-seated magmatic systems can be thought of as nature’s blast furnaces – giant reactors where hot, mobile bodies of liquid iron sulphides scavenge nickel, copper and the immensely valuable platinum group elements from large volumes of molten rock and concentrate them into ore bodies worth, in some cases, many billions of dollars. Although formed dominantly in the deep crust, post-mineralisation exhumation has in some cases brought such magmatic Ni-Cu-PGE sulphide bodies into the accessible near-surface environment – and we exploit these deposits today for their base and noble metal content.

Industrial extraction and use of this metal is rapidly exhausting known examples of such ore bodies, while our success at locating them is not keeping pace. Academic research on these types of ore systems over the past 20 years has focused on their geochemical evolution. While successful in explaining
the metal content of different types of intrusions, however, this approach has made only incremental progress in the theoretical understanding of these systems, but failed to generate fundamental advances that could drive new exploration models for nickel sulphide deposits and resolve the looming resource
limitation issue.

The key elements missing from the understanding of these systems revolve around the poorly constrained fluid dynamics by which magmatic sulphide deposits are emplaced and evolve – how are immiscible sulphide liquids transported and deposited within magmatic systems? This study has put these questions at the heart of an integrated research strategy, applying structural, geochemical and isotopic investigations to resolve the emplacement and temporal evolution of Ni-Cu-PGE sulphide systems. The aim in this program is to gain crucial insights into the evolution and dynamics of the Earth System and to develop an integrated model of deep-seated nickel sulphide systems that will underpin a new generation of exploration strategies.

Collaborator/s

  • Associate Professor Boswell Wing, McGill University
  • Associate Professor Giorgio Garuti and Dr Federica Zaccarini, Leoben University
  • Dr Marilena Moroni, University of Milano
  • Professor David Baratoux, University Paul Sabatier