GeoFile 2013-01: Geochemistry of Metabasalts from the Knob Hill complex and Anarchist Group in the Paleozoic basement to southern Quesnellia
GeoFile 2013-1 supplements the geological synthesis in Massey and Dostal (2013), by providing spreadsheets containing a complete geochemical dataset from the Knob Hill complex and Anarchist Group and additional geochemical plots.
The Knob Hill complex and Anarchist Group constitute part of the Paleozoic basement to southern Quesnellia. These units occupy adjacent northward-dipping, south-vergent thrust sheets extending along the Canada-Washington State border. Metabasalts in both units are tholeiitic to transitional or alkalic, comprising three magma types. The ophiolitic Knob Hill complex contains rocks of predominantly island arc affinity (IAT), with local MORB and E-MORB varieties. They probably formed by subduction-related rifting processes, but the precise setting remains unclear. The Anarchist Group metabasalts display predominantly within-plate E-MORB geochemical traits; local IAT and MORB signatures are indistinguishable from those in the Knob Hill Complex. The basalt geochemistry suggests that that the two units share a magmatic history and may have once been contiguous, with the Anarchist Group having formed off axis relative to spreading represented by the Knob Hill complex.
Text document (Word, 90 KB)
Figures (ZIP, 2.7 KB)
Geochemical data Knob Hill complex (Excel, 102 KB)
Geochemical data Anarchist Group (Excel, 70 KB)
Massey, N.W.D. and Dostal, J., 2013. Geochemistry of metabasalts from the Knob Hill complex and Anarchist Group in the Paleozoic basement to southern Quesnellia. In: Geological Fieldwork 2012, British Columbia Ministry of Energy, Mines and Natural Gas, British Columbia Geological Survey Paper 2013-1, pp. 45-52. (PDF, 1.3 MB).
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