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TitleMusings on intrusion geometry, chonoliths and mineral deposits
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AuthorSaumur, B -M
SourceGeological Survey of Canada, Scientific Presentation 71, 2017, 41 pages, https://doi.org/10.4095/305828
Year2017
PublisherNatural Resources Canada
Documentserial
Lang.English
Mediaon-line; digital
File formatpptx
ProvinceNunavut; Newfoundland and Labrador
NTS13M; 13N; 13O; 14C; 14D; 14E; 14F; 14L; 24I; 49F/12; 49F/13; 49G; 59E; 59F/01; 59F/07; 59F/08; 59F/09; 59F/10; 59F/14; 59F/15; 59F/16; 59G; 59H; 340B/03; 340B/04; 340B/05; 340B/06; 340B/11; 340B/12; 340B/13; 340B/14; 340C/03; 340C/04; 340C/05; 340C/06; 560A; 560D/01; 560D/02; 560D/03; 560D/04; 560D/05; 560D/06; 560D/07; 560D/08
AreaCanadian Arctic Archipelago; Ellesmere Island; Wootton Peninsula; Axel Heiberg Island; Middle Fiord; Labrador; Voisey's Bay
Lat/Long WENS -96.0000 -84.0000 81.5000 78.0000
Lat/Long WENS -64.5000 -58.0000 59.0000 55.0000
Subjectseconomic geology; structural geology; igneous and metamorphic petrology; mineral deposits; ore mineral genesis; ore controls; structural controls; mineralization; intrusions; chonoliths; dykes; sills; laccoliths; emplacement; geometric analyses; porphyry deposits; porphyry copper; sulphide deposits; nickel; copper; volcanism; magmatism; magmas; flow structures; flow systems; fluid flow; bedrock geology; lithology; mafic rocks; intrusive rocks; structural features; shear zones; modelling; High Arctic Large Igneous Province (HALIP); Voisey's Bay Intrusion; Nain Batholith; Wootton Intrusive Complex; platinum group elements (PGE); post-emplacement structure; magma conduits; 3D modelling; Phanerozoic; Tertiary; Mesozoic; Cretaceous; Paleozoic; Carboniferous; Precambrian; Proterozoic
Illustrationsphotographs; schematic representations; graphs; geological sketch maps; 3-D images; geophysical images; stereonet projections; 3-D models; profiles; photomicrographs; diagrams
ProgramWestern Arctic, High Arctic LIP, GEM2: Geo-mapping for Energy and Minerals
Released2017 09 22
AbstractSeveral types of intrusion-hosted ore-deposits are formed within geometrically complex bodies, and the so-called "space problem" associated with the emplacement of these bodies within the crust is generally poorly understood. Felsic to intermediate porphyry-Cu systems are often hosted within vertical pipes or stocks that are circular to elongate in plan view. Ni-Cu magmatic sulfide deposits are hosted within structurally complex feeder systems. These often have irregular to tube-shaped geometries unlike typical dykes, sills or laccoliths, which has led to the resuscitation, by exploration and economic geologists alike, of the once-obsolete term "chonolith" to characterise such irregular intrusions. Both porphyry-Cu and magmatic Ni-Cu sulfide systems share other first-order similarities, such as late-stage volatile-rich magmas and emplacement within environments of active deformation, indicating that despite their differences emplacement dynamics may be analogous.
In many cases irregular intrusion geometries can be explained internal and external structural processes. At Voisey's Bay (Labrador, Canada) for instance, magmatic Ni-Cu sulfides are located within dikes and at the base of a geometrically complex magma chamber. The chamber could, a priori, be termed a chonolith; however, detailed 3D structural analysis of the chamber indicates that it consists of an amalgamation of sill-like magma bodies affected by intermittent local activity of faults. Dike-hosted mineralization is located within thickened portions of feeder dikes, which locally resemble some mafic chonoliths in cross-section. The geometry of these dikes is strongly controlled by the interaction of pre-emplacement wall rock structure with intruding magmas, and dike widening by thermo-mechanical erosion of the surrounding wall rocks.
Chonoliths are ideal sites of Ni-Cu-PGE mineralization because they promote high magma fluxes and protracted magma flow-through, thereby favouring the interaction between metal-bearing mafic magmas and sulfide liquids that are progressively enriched in metals. Such processes occur at the relatively local scales of 1-10 km magmatic complexes, and successful exploration must consider small-scale targeting within larger, regional scale igneous provinces. As an example, several magmatic complexes of the High Arctic Large Igneous Province (Nunavut) show first-order architecture that would favour Ni-Cu-PGE potential.
Summary(Plain Language Summary, not published)
This science presentation reviews the structural controls on the emplacement of hot magmatic intrusions in the crust, and highlights how oddly shaped (tube-shaped) intrusions often host mineral deposits. Case studies are shown from the Voisey's Bay Ni-Cu deposit (Labrador) and magmatic complexes of the High Arctic Large Igneous Province (Nunavut).
GEOSCAN ID305828