Metal Earth Project: Isotopic Mapping
Isotopic mapping of the Superior Craton
Mineral Exploration Research Centre,
Past Lead: Dr. David Mole
Douglas Tinkham, Associate Professor of Metamorphic Petrology; Director of the Harquail School of Earth Sciences, Laurentian University
Kristine Nymoen, PhD student, Harquail School of Earth Sciences, Laurentian University
Jeffrey H. Marsh, Post-doctoral Fellow, Harquail School of Earth Sciences, Laurentian University
Phil Thurston, Professor, Harquail School of Earth Sciences, Laurentian University
John Ayer, MERC Associate Director, Harquail School of Earth Sciences, Laurentian University
Richard A. Stern – Faculty – University of Alberta
Scope of Project:
Lithospheric and crustal architecture – the framework of major tectonic blocks, terranes, their boundaries, and history – represents a fundamental first-order control on major geological systems, including ore deposits and the location of world-class mineral camps. Previous work, particularly by Begg et al. (2009) and Begg et al. (2010), used seismic tomography to demonstrate how gold and Ni-Cu-PGE camps are controlled by major inter-cratonic lithospheric discontinuities. In other studies, workers attempting to constrain time-resolved intra-cratonic lithospheric architecture turned to the mapping of isotopic systems from crustal rocks (mainly granitoids). Champion and Cassidy (2007) used regional Sm-Nd isotopic data to map the crustal architecture of the Yilgarn Craton (Figure 2), and Mole et al. (2013) demonstrated the association between that lithospheric architecture and BIF-hosted iron, orogenic gold, and komatiite-hosted Ni-Cu-PGE systems (Figure 3). Those results demonstrated the underlying control of lithospheric architecture and the potential for isotopic mapping as a greenfields area selection tool.
Further work by Mole et al. (2014), using Lu-Hf isotopes, demonstrated that the technique could account for rocks, events and mineral systems of different ages, showing how Ni-Cu-PGE mineralized komatiite systems of the Yilgarn Craton migrated with the changing lithospheric boundary (craton margin) from 2.9 to 2.7 Ga (Figure 1). Similar work has since been performed in West Africa (Parra-Avila et al., 2017), Tibet (Hou et al. 2015), and Canada (Lu et al. (2013); Bjorkman et al. 2015).
This project is using the Lu-Hf technique and applying it to the Superior Craton, in a bid to constrain large-scale intra-cratonic controls on magmatism, crustal evolution, and mineralization in the Earth’s largest Archean terrane.
The anticipated outcome of this work is a craton-scale Hf-isotope map of the Superior Craton, which will highlight the age, evolution and source of the crust in space and time. This in turn can be used to identify prospective regions in both space and time, allowing a more targeted and intelligent area selection program to be developed for exploration. Thus far, the work has shown that the Abitibi belt has variable mineral potential and in large part did not originate through subduction processes. Furthermore, this large new dataset will allow the investigation of craton evolution and Archean tectonics at a previously unseen scale and detail, and facilitate the coupled understanding of large-scale metallogenesis and crustal evolution; one of the primary aims of the Metal Earth project. An early publication on the Abitibi subprovince has been published (Mole et al., 2020) and a PhD project will provide more detail on the isotopic characteristics of the mineral-rich Abitibi subprovince. (Mole et al., 2021)
Transect Related Documents:
Research Update: Isotopic Mapping
Metal Earth Geohub - Isotopic Related Documents