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TitleIngress of magmatic Ni-Cu sulphide liquid into surrounding brittle rocks: Physical & structural controls
AuthorSaumur, B -M; Cruden, A R
SourceOre Geology Reviews vol. 90, 2017 p. 439-445,
Alt SeriesEarth Sciences Sector, Contribution Series 20160372
Mediapaper; on-line; digital
File formatpdf
ProvinceNewfoundland and Labrador
AreaVoisey's Bay
Lat/Long WENS -62.0000 -61.5000 56.5000 56.2500
Subjectsigneous and metamorphic petrology; magmatic rocks; sulphides; sulphide deposits; mineral deposits; host rocks; intrusions; deformation; ore systems; critical accumulation height; Dense Non Aqueous Phase Liquids; DNAPL
Illustrationsphotographs; schematic diagrams; graphs
ProgramBaffin Bedrock Mapping, GEM2: Geo-mapping for Energy and Minerals
AbstractField 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. In this work, using analogies with other systems, we evaluate the structural and physical controls on the behaviour of sulphide liquid for ingress 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 fluids in groundwater systems, i.e. 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 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 to well-established petro-geochemical concepts in order to better understand the genesis of magmatic Ni-Cu-PGE sulphide deposits.
Summary(Plain Language Summary, not published)
Sulphur rich magmas, which often host nickel (Ni) and copper (Cu) deposits, are very dense and have a very low viscosity (they are runny like water); this means that they can easily flow downwards outside of magma intrusions and into the surrounding crust. However, the physics of such processes are poorly understood. We propose different models that help explain some of the features of sulfide injection and infiltration observed at many Ni-Cu mineral deposits.