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TitleMantle petrology, mineralogy and major elements geochemistry of the northern Cache Creek Terrane
AuthorCorriveau, A -S; Bédard, J H; Zagorevski, AORCID logo; Richer-Laflèche, M
SourceMargins through time: GAC-MAC 2016; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 39, 2016 p. 14 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 1.3 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20190390
PublisherGeological Association of Canada
MeetingGAC-MAC 2016; Whitehorse, YK; CA; June 1-3, 2016
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia; Yukon
Subjectsgeochemistry; igneous and metamorphic petrology; Science and Technology; Nature and Environment; Cache Creek Terrane
ProgramGEM2: Geo-mapping for Energy and Minerals Western Cordillera, Cache Creek Terrane
Released2016 06 01
AbstractThe northern Cache Creek terrane extends for more than 500 km in northern British Columbia and southern Yukon. This composite terrane comprises mafic and ultramafic complexes and carbonate and chert assemblages that have been interpreted by previous workers as components of accreted seamounts, spreading centers and rifted arc complexes. Our observations show that mantle facies are widespread and are generally structurally capped by brecciated hypabyssal and volcanic rocks, most with arc affinities. Mafic and ultramafic cumulates occurrences are rare.
Variably serpentinized mantle rocks were sampled in southern Yukon (Jakes Corner area), and northern B.C. (Atlin, Nahlin area and Dease Lake area). Ultramafic to gabbroic cumulates were found at King Mountain and in the Hardluck peak area. Foliated mantle harzburgite tectonite dominates, typically with 25-35% of porphyroclastic orthopyroxene and subordinate chromite. Orthopyroxenite to rare websterite layers are interpreted to be transposed dykes. Subordinate dunite dykes and pods are common. Where present, gabbroic dykes are consanguineous with overlying volcanics.
Chromite is unzoned, with high Cr# from 32 to 58 and low TiO2 and NiO contents. Olivine composition varies between Fo90 to Fo92 in the harzburgite and up to Fo94 in the dunite dykes. Enstatite and diopside respectively have Mg# of 91.3-91.6 and 92.9-94.2. They have low Al2O3 and Cr2O3 contents.
These results suggest a large range in degree of partial melting (18- 32%) for these peridotites. Such extensive melting is consistent with the scarcity of clinopyroxene and the low modal proportions of orthopyroxene. The involvement of an arc component during melting is suggested so as to explain the extensive melting. Resemblance between Cache Creek mantle rocks and arc-related mantle rocks supports this hypothesis; as does our data from Cache Creek cumulates, hypabyssal intrusions and volcanic rocks.

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