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TitleGravity and magnetic models of the Iron Mask Batholith, south-central Canadian Cordillera, British Columbia
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorThomas, M D
SourceGeological Survey of Canada, Current Research (Online) 2019-1, 2019, 24 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Mediaon-line; digital
RelatedThis publication is related to Spatial relationship between porphyritic Cu-Au mineral occurrences and magnetic signatures within the Iron Mask Batholith, south-central Cordillera, British Columbia
File formatpdf (Adobe® Reader®)
ProvinceBritish Columbia
NTS92I/09; 92I/10
Lat/Long WENS-120.5667 -120.2667 50.6833 50.5333
Subjectseconomic geology; geophysics; Science and Technology; Nature and Environment; Lower Jurassic; Upper Triassic; crustal models; intrusions; batholiths; plutons; geophysical interpretations; modelling; gravity interpretations; gravity field; gravity anomalies; magnetic interpretations; magnetic field; magnetic anomalies; magnetic susceptibility; rock density analyses; bedrock geology; lithology; igneous rocks; intrusive rocks; diorites; gabbros; granitic rocks; granodiorites; mineral potential; porphyry deposits; copper; molybdenum; gold; mineralization; Iron Mask Batholith; Canadian Cordillera; Quesnel Terrane; Iron Mask Pluton; Cherry Creek Pluton; Nicola Group; Nicola Horst; New Afton Mine; Cherry Creek Tectonic Zone; Phanerozoic; Mesozoic; Jurassic; Triassic
Illustrationsgeoscientific sketch maps; gravity profiles; magnetic profiles; tables; schematic cross-sections; models
ProgramTargeted Geoscience Initiative (TGI-5) Intrusion/Porphyry ore systems
Released2019 08 01
AbstractCross-sectional crustal models of the Late Triassic to Early Jurassic dioritic Iron Mask and Cherry Creek plutons forming the Iron Mask batholith are derived from integrated modelling of correlative prominent gravity and magnetic anomalies. A model for the Iron Mask pluton, comprising two block-like density units (2880 kg/m3, 2955 kg/m3), indicates a pluton depth of about 5700 m, and lateral extensions northward and southward below adjacent Nicola Group volcanic cover. The densities are more typical of gabbros than diorites, suggesting compositional changes to gabbroic rocks at depth. Magnetic modelling indicates the density units include several steep and strongly magnetic sheet-like units.
The Cherry Creek pluton is associated with a prominent magnetic high, but lacks a gravity counterpart. A magnetic model, with a maximum depth of 5700 m, indicates marginal areas comprising vertical, relatively deep, and strongly magnetic sheets, with the pluton thinning centrally to less than 1000 m. A similar shallower (maximum depth of 2850 m) model can also reproduce the magnetic signature. In order not to produce a conspicuous gravity high, the density of the pluton must be less than about 2770 kg/m3, for either deep or shallow model.
North of the Iron Mask pluton, two large dioritic bodies buried mainly within units of Nicola Group rocks are modelled to explain conspicuous gravity highs. To the south, a large gravity low (-33 mGal amplitude) is modelled in terms of a large granitoid body descending to about 9700 m below surface, potentially representing an enlargement of a granodiorite body within the Nicola Horst.
Summary(Plain Language Summary, not published)
Shapes of the Late Jurassic-Early Triassic Iron Mask and Cherry Creek plutons hosting copper-gold porphyry-type deposits in the Cordillera are derived by quantitative modelling of associated gravity and magnetic anomalies. Results predict pluton depths as large as ~5700 m, though some evidence indicates the Cherry Creek pluton may be significantly thinner. A series of strongly magnetic, steep, generally relatively narrow units characterizes both plutons, suggesting steep faults played a critical role in influencing pathways for magma intrusion and mineralizing fluids. Modelling also indicates kilometre-scale extensions of the Iron Mask pluton laterally beneath adjacent Triassic volcanic cover, enlarging the area for potential exploration, though the cover is an obvious impediment. A large granitoid intrusion rivalling the neighbouring mineral-rich Guichon batholith in size, upper surface partially coincident with an area of granodioritic rocks, outlined on the south flank of the Iron Mask pluton may offer further potential for mineral exploration.

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