Ingress of magmatic Ni-Cu sulphide liquid into surrounding brittle rocks: Physical & structural controls |
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| Institution: | 1. Geological Survey of Canada, Ottawa, ON K1A OE8, Canada;2. School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC 3800, Australia;1. Queen’s University, Department of Geological Sci. and Geological Engineering, Kingston, Ontario K7L 3N6, Canada;2. North American Palladium Ltd, 10th Avenue, Thunder Bay, Ontario P7B 2R2, Canada;3. Department of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812, United States;1. School of Environmental and Life Sciences, University of Newcastle, University Drive, Callaghan 2308, NSW, Australia;2. School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC 3800, Australia;3. Geological Survey of Canada, 601 Booth St., Ottawa, ON K1A 0E8, Canada;1. Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK;2. Carrog Consulting, 21 Rue Jean de la Bruyère, 78000 Versailles, France;3. Carl Zeiss Microscopy Ltd, 509 Coldhams Lane, Cambridge CB1 3JS, UK;4. Pacific Centre for Isotopic and Geochemical Research, Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Colombia V6T 1Z4, Canada;1. Sciences de la Terre, Université du Québec à Chicoutimi, QC G7H 2B1, Canada;2. Department of Earth and Planetary Sciences, McGill University, QC H3A OE8, Canada;3. United States Geological Survey, Spokane Office, WA 99201, USA |
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| Abstract: | Field observations and theoretical considerations suggest that dense magmatic sulphide liquids are injected into and/or passively infiltrate surrounding wall rocks late in the emplacement history of intrusion-hosted magmatic ore systems. Using analogies with other engineering and mineral systems, we evaluate the structural and physical controls on the ingress of sulphide liquid into brittle host rocks. Gravity-driven infiltration of sulphide liquid out of the host igneous intrusion into country rock may be analogous to the behaviour of dense immiscible fluids in groundwater systems (Dense Non Aqueous Phase Liquids; DNAPL), which is controlled by the body force of the liquid itself. Downward penetration of sulphide liquid into micro-fractures may occur once a sufficient thickness of sulphide, known as the critical accumulation height, is reached in the overlying intrusion. Upward and lateral injection of sulphide liquid is a similar process to the behaviour of crustal hydrothermal fluids, where active deformation, fluid pressure and host-rock anisotropy play critical roles. Such physical controls must be considered and integrated with well-established petro-geochemical concepts in order to better understand the genesis of magmatic Ni-Cu-PGE sulphide deposits. |
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