Wouter Bleeker and Ian Honsberger, Research Scientists, Geological Survey of Canada
Wouter Bleeker is a Research Scientist with the Geological Survey of Canada (GSC). A graduate from the Free University (Amsterdam) and the University of New Brunswick (Fredericton), he has worked in industry in both Europe and Canada, prior to joining the GSC in 1994. Since then his research has taken him across Canada working on regional geological syntheses, typically with a focus on the setting of large mineral deposits. While living and working in Timmins, he studied key aspects of gold mineralization in the southern Abitibi greenstone belt, most recently summarized in his 2015 paper “Synorogenic gold mineralization in granite-greenstone terranes: The deep connection between extension, major faults, synorogenic clastic basins, magmatism, thrust inversion, and long-term preservation”. This will be the subject of today’s presentation, in particular a scale and process comparison with younger orogenic gold belts such as central Newfoundland.
Ian Honsberger, a University of New Hampshire graduate, recently joined the GSC as a Research Scientist and has been leading the research on the setting of gold mineralization in central Newfoundland. For the past 10 years, Honsberger’s research has focused on understanding structural, petrological, and tectonic processes involved in mountain building, particularly in the northern Appalachian orogen. At the GSC, Honsberger has been researching the setting, age, and tectonic drivers of orogenic gold mineralization in central Newfoundland, which bears remarkable similarity to the prolific
Abitibi greenstone belt. Honsberger’s work demonstrates that late Silurian (ca. 422 Ma), extension-related syntectonic magmatism and sedimentation in central Newfoundland immediately preceded Early Devonian (ca. 410 Ma) orogenic gold mineralization associated with collision of Avalonia with composite Laurentia. The most recent results of this research are summarized in his 2020 paper “The emerging Paleozoic gold district of central Newfoundland: New insights on structural controls and tectonic drivers of gold mineralization and preservation”. Both papers mentioned here are available through GSC’s Geoscan download portal.
The Abitibi greenstone belt is one of Canada’s principal gold belts, with on the order of 200 Moz of gold produced over the last century. Although a variety of gold deposits has been documented, there is a distinct concentration of deposits along and proximal to major, crustal-scale fault zones, the so-called “breaks” of the southern Abitibi greenstone belt. The spatial correlation of gold deposits with these first-order faults, and most commonly with the footwall side, indicates a deep fluid source, most likely a devolatilizing lower crust with or without magmatic input. The key faults were not initiated during early thrust imbrication, but rather later during a phase of synorogenic extension and magmatism, before being re-imbricated as thick-skinned thrusts and reverse faults under a regime of fluid pressure cycling that formed the vein systems. The thick-skinned thrust re-imbrication buried wedges of synorogenic conglomerates, exhumed gold deposits on the hanging-wall side, and preferentially preserved them on the footwall side, before being overprinted by later strike slip.
This template of tectonic processes is common to orogenic gold belts around the world and across geological time. A transient phase of synorogenic extension is a key driver of mantle-derived magmatism, initiates key faults and triggers a thermal pulse, and limits post-orogenic uplift, thereby playing a role in long-term preservation. Overall gold endowment may scale with the volume and intensity of synorogenic magmatism. In this presentation we take this template to Paleozoic central Newfoundland, where the ~5 Moz Valentine Lake deposit is set to enter production in the near future, and highlight the remarkable similarities with the Archean settings.
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