The mantle source for olivine nephelinite; basanite, and alkaline olivine basalt at Fort Selkirk, Yukon, Canada

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Authors:Francis, Don; Ludden, John N.
Author Affiliations:Primary:
McGill Univ., Dep. Geol Sci., Montreal, QC, Canada
Other:
Univ. Montreal, Canada
Volume Title:Journal of Petrology
Source:Journal of Petrology, 31(2), p.371-400. Publisher: Clarendon Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:1990
Note:In English. 78 refs.; illus. incl. 8 tables, geol. sketch map
Summary:These lavas of the Quaternary Fort Selkirk volcanic complex in the central Yukon, represent three distinct alkaline magma series which have evolved along different paths; they cannot be related by low-P crystal-liquid fractionation, and systematic differences make it difficult to derive them by variable degrees of melting of a common mantle source. Field evidence indicates however, that these three magma series are intimately related in time and space and share a number of anomalous chemical characteristics including low Ca/Na ratios with respect to the majority of terrestrial equivalents. When the effects of differential olivine fractionation are ignored, the compositional spectrum of these lavas approximates a binary mixing line between transitional alkaline basalt and olivine nephelinite. A population gap along this mixing line, between the nephelinite and basanite composition, coincides with the compositions of amphibole and/or amphibole-garnet-clinopyroxene assemblages seen in mantle xenoliths. This compositional gap may represent a thermal divide separating two minimum-melt compositions in a mantle source consisting of a lherzolite host cut by amphibole-garnet clinopyroxenite veins. The olivine nephelinite end-member may have been derived by early melting in these veins, whereas the transitional alkaline basalt would represent more extensive melting of the host lherzolite. [R.A.H.]
Subjects:Alkalic composition; Basalts; Basanite; Cenozoic; Composition; Differentiation; Genesis; Igneous rocks; Lava; Magmas; Melting; Mineral composition; Nephelinite; Olivine basalt; Parent materials; Petrology; Processes; Quaternary; Volcanic rocks; Volcanism; Volcanoes; Volcanology; Canada; Western Canada; Yukon Territory; Fort Selkirk
Abstract Numbers:90M/4719
Record ID:1990035905
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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