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TitleCross River sills, Rocky Mountains, southeastern British Columbia
AuthorMcMechan, M E; Anderson, R G; Richards, B C; Davis, W J
SourceGeological Survey of Canada, Scientific Presentation 59, 2017, 1 sheet,
PublisherNatural Resources Canada
Mediaon-line; digital
RelatedThis publication is related to McMechan, M; Anderson, B; Richards, B; Davis, B; (2017). Cross River Sills, Rocky Mountains, southeastern British Columbia; Cross River Sills, Rocky Mountains, southeastern British Columbia; Cross River Sills, Rocky Mountains, southeastern British Columbia; Cross River Sills, Rocky Mountains, southeastern British Columbia, 5th Annual Minerals South Conference & Trade Show 2009, abstracts
File formatpdf
ProvinceBritish Columbia
NTS82E; 82F; 82G; 82J; 82K; 82L; 82M; 82N; 82O
AreaCross River; Rocky Mountains; Mount Fowler; Nelson; Cranbrook; Calgary; Swanson Peak; Kananaskis; Front Ranges
Lat/Long WENS-120.0000 -114.0000 52.0000 49.0000
Subjectsgeochemistry; geochronology; geological history; thermal history; intrusions; sills; dykes; metamorphism; deformation; alteration; bedrock geology; lithology; igneous rocks; intrusive rocks; diorites; plagioclase; hornblende; mafic rocks; diatremes; breccias; volcanic rocks; ash; dacites; rhyolites; sedimentary rocks; limestones; argillites; structural features; folds; geochemical analyses; potassium; argon; fission-track dates; trace element geochemistry; major element geochemistry; minor element geochemistry; correlations; miogeoclines; Cross River Sills; Mount Docking Formation; Chancellor Group; Albert River Sills; Fenwick Creek Sills; McKay Group; Fowler Intrusive Suite; Milford Group; Clachnacudain Pluton; Omineca Belt; Exshaw Formation; Banff Formation; Fenwick Dyke; Laussedat Dyke; White River Trough; rare earth elements (REE); loss on ignition; trachyandesites; trachydacites; high field strength elements (HFSE); Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous; Paleozoic; Cambrian
Illustrationsgeological sketch maps; photographs; schematic cross-sections; tables; ternary diagrams; geochemical plots
ProgramDirector's Office, GSC Calgary Divsion
Released2017 05 03
AbstractDioritic sills up to 40 m thick were discovered by G.M. Dawson along the Cross River in the 1880's (Dawson, 1886). The Cross River Sills intrude Middle Cambrian limestone, argillaceous limestone, calcareous argillite and argillite of the Mount Docking Formation (middle Chancellor Group). The sills have metmorphosed the adjacent strata and are themselves regionally metamorphosed, folded, and crosscut by numerous nearly perpendicular quartz veins that locally contain minor chalcopyrite. Recent mapping in the Kananaskis area (McMechan, 2011; McMechan and Leech, 2011) discovered similar sills in the Mount Docking Formation along the Albert River and at Fenwick Creek. These locally contain abundant pyrrhotite and are cut by numerous barren quartz veins. They are considered to be part of the Cross River suite on the basis of geological setting, general lithology and geochemistry.
At Cross River a small zone of medium crystalline plagioclase-hornblende diorite was sampled for age dating. It contained no zircon. The hornblende had very low K content, excess Ar and produced highly disturbed spectra with non-interpretable results. Apatite fission track analysis indicates cooling in the early Tertiary and structural relationships require their intrusion by the Early Cretaceous.
High quality multi-element chemical analyses are used to characterize the compositions of the Cross, Fenwick, and Albert sills, and dykes in the McKay Group from the Kananaskis area, the Fowler sill, Milford Group and Clachnacudain pluton from the Omineca Belt and ash beds in the Exshaw and Banff formations exposed in the Front Ranges. These are compared with published results for intrusions associated with diatreme breccias in the Kananaskis area. Standard geochemical variation diagrams portray homogeneous and variable major and minor, trace and rare earth element (REE) compositions and help indicate geochemical similarities and differences amongst these suites.
Major element analyses indicate that many of the units are altered as indicated by their high loss on ignition values. Intrusive suites are mostly mafic with the exception of the dacite and rhyolite intrusive rocks in the Fowler suite and the trachyandesite and trachydacite of the Exshaw ash beds. The Albert sills are closest in major and minor element composition to the Cross and McKay intrusions. High field strength elements (HFSE) are less affected by alteration but similarly help group various suites and confirm the major element classifications. The Fowler and Cross suites have similar trace element compositions and compare closely with subalkaine, calc-alkaline, arc-type igneous rocks. The Fenwick, McKay, and Albert intrusions and alternatively Fowler and Cross sills overlap in compositional space on many of these plots but the Exshaw ash beds samples are distinct. All suites samples have continental affinities in K2O-TiO2-P2O5 space.
Multi-element plots and normalized to primitive mantle compositions help confirm some similarities amongst suites and show effects of alteration processes. The Cross, McKay, and Albert suites have the closest similarities in overall multi-element patterns and the Fenwick and Laussedat dyke are also closely similar.
Summary(Plain Language Summary, not published)
This poster presents unpublished trace and major element geochemistry data from sills and dykes in the Kananaskis area of southeastern British Columbia as well as Devono-Mississippian intrusions and tuffs. These show most of the sampled sills and dykes in the Kananaskis area have closely similar geochemistry.