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TitleGeochemistry of volcanic and plutonic rocks from the Nahlin ophiolite with implications for a Permo-Triassic arc in the Cache Creek terrane, northwestern British Columbia
AuthorMcGoldrick, S; Zagorevski, AORCID logo; Canil, D
SourceCanadian Journal of Earth Sciences vol. 54, issue 12, 2017 p. 1214-1227, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20170126
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS104J; 104K; 104N; 104O
AreaMenatatuline Range; Hall Lake; Mount Nimbus
Lat/Long WENS-133.5000 -132.0000 59.2500 58.7500
Subjectsstructural geology; tectonics; ophiolites; terranes; spinel; harzburgites; lherzolites; dykes; dykes, mafic; lithogeochemistry; magmatic arcs; tholeiites; oceanic tholeiites; Kutcho assemblage; French Range; Moho Saddle; Nakina transect; Cache Creek; Permian; Triassic
Illustrationslocation maps; tables; geological sketch maps; photographs; graphs; diagrams
ProgramGEM2: Geo-mapping for Energy and Minerals Western Cordillera, Cache Creek Terrane
Released2017 08 24
AbstractIn northwestern British Columbia, the Permian Nahlin ophiolite in the northern Cache Creek terrane comprises spinel harzburgite tectonite with minor lherzolite, lower crustal mafic and ultramafic cumulates, gabbroic rocks including dikes intruding mantle harzburgite, and basaltic volcanic and volcaniclastic rocks. New lithogeochemical data from the Menatatuline Range area confirm that plutonic and volcanic rocks of the ophiolite are tholeiitic and arc-related, while only a minor component of volcanic rocks are alkaline intraplate basalts. Tholeiitic basalts of the Nahlin ophiolite represent the products of 2 - 20% fractional melting, and their complementary residue may be peridotite from the ophiolite mantle section. Correlative tholeiitic volcanic sections can be found elsewhere in the northern Cache Creek terrane, and may be linked to a regionally extensive (~200 km) intraoceanic arc. The arc tholeiite geochemistry of the lower and supracrustal rocks, and the highly depleted nature of the mantle residues imply that the Nahlin ophiolite formed in a supra-subduction zone (SSZ) environment. The Nahlin ophiolite therefore occupied the upper plate during intraoceanic collision prior to emplacement of the Cache Creek terrane. The volumetrically minor OIB-type volcanic rocks in the northern Cache Creek terrane are associated with carbonate successions bearing Tethyan fauna. These sequences are likely fragments of oceanic plateaux and their carbonate atolls sliced off of the subducting plate, and are unrelated to the Nahlin ophiolite - arc system.
Summary(Plain Language Summary, not published)
This report presents results and models developed through GEM2 program on volcanic and plutonic rocks in British Columbia. It details the age and characteristics of magmatic rocks and associated mineralization on the basis of field and laboratory analyses. The results presented herein help progress GEM2 model to ultimately redefine the regional tectonic models of the Cordillera.

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