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TitleContrasting thermal and melting histories for segments of mantle lithosphere in the Nahlin ophiolite, British Columbia, Canada
AuthorMcGoldrick, S; Canil, D; Zagorevski, A
SourceContributions To Mineralogy and Petrology vol. 173, issue 3, 2018 p. 25-1 - 25-17,
Alt SeriesNatural Resources Canada, Contribution Series 20170345
Mediapaper; on-line; digital
File formatpdf; html; xlsx
ProvinceBritish Columbia; British Columbia
NTS104K/15; 104K/16; 104N/01; 104N/02
AreaMenatatuline Range
Lat/Long WENS-132.8333 -132.0000 59.0333 58.8333
Subjectstectonics; igneous and metamorphic petrology; geochemistry; mineralogy; crustal studies; crustal evolution; provenance; mantle; oceanic lithosphere; tectonic history; thermal history; island arcs; bedrock geology; lithology; sedimentary rocks; limestones; igneous rocks; volcanic rocks; intrusive rocks; ophiolites; thermal analyses; temperature; petrographic analyses; geochemical analyses; mass spectrometer analysis; electron probe analyses; peridotites; orthopyroxene; clinopyroxene; geothermometry; mineralogical analyses; metasomatism; mid-ocean ridges; Canadian Cordillera; Cache Creek Terrane; Nahlin Ophiolite; Nakina Formation; Kutcho Assemblage; Stikine Assemblage; Horsefeed Formation; French Range Formation; Teslin Formation; Menatatuline Massif; Hardluck Massif; melting history; rare earth elements; cooling rates; Phanerozoic; Mesozoic; Triassic; Paleozoic; Permian
Illustrationslocation maps; geoscientific sketch maps; cross-sections; photographs; photomicrographs; geochemical plots; tables; bar graphs; plots
ProgramWestern Cordillera, Cache Creek Terrane, GEM2: Geo-mapping for Energy and Minerals
Released2018 03 03
AbstractThe Permo-Triassic Nahlin ophiolite is the largest and best-preserved ophiolite in the Canadian Cordillera of British Columbia and Yukon, Canada. The ophiolite is well-exposed along its ~ 150 km length with mantle segments divisible into the Hardluck and Menatatuline massifs. Both massifs comprise mostly depleted spinel harzburgite (< 2 wt% Al2O3 and ~ 45 wt% MgO). Chondrite normalized REE abundances in clinopyroxene vary in (Gd/Yb)N from 0.2 to 1.1. Inversion modelling of clinopyroxene REE abundances requires 10-16% and 16-20% partial melting in the Hardluck and Menatatuline massifs, respectively. The two-pyroxene and Fe-Mg exchange temperatures in the mantle of the ophiolite also change systematically along strike with the degree of partial melt depletion. The temperatures recorded by REE and Ca-Mg exchange between coexisting pyroxenes require markedly higher peak temperatures and cooling rates for the Menatatuline massif (1250 °C, 0.1-0.01 °C/year) compared to the Hardluck massif (< 1100 °C, ~ 0.0001 °C/year). The differences between these two contiguous massifs can be reconciled by their evolution as two separate segments along a ridge system having varying melt depletion, with contrasting cooling rates controlled by presence or absence of a crustal section above the mantle lithosphere, or by rapid exhumation along a detachment.
Summary(Plain Language Summary, not published)
This report presents preliminary results and models developed through GEM2 program on the ancient oceanic crust in British Columbia and Yukon. It details the distribution and characteristics of the various rock packages on the basis of field and laboratory analyses. It compares these data to modern analogues. The results presented herein help progress GEM2 model to ultimately redefine the regional tectonic models of the Cordillera