Alkaline Rocks and Carbonatites of the World

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Atlin

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Occurrence number: 
031-00-012
Country: 
Canada
Region: 
British Columbia
Location: 
Longitude: -132.75, Latitude: 59.5

Approximately 50 km east of Atlin and 2 km north of the Mount Llangorse quartz diorite intrusion five small intrusions of nephelinite cut thermally altered Permian-Pennsylvanian cherts. Three of the intrusions are carbonate-rich nephelinites (Higgins and Allen, 1982), but two are fresh olivine nephelinites with olivine and clinopyroxene phenocrysts, some of the latter altered to amphibole, in a groundmass of clinopyroxene (40%), nepheline (40%), a little (?)analcime and zeolite. One of the olivine nephelinite intrusions contains locally abundant xenoliths which are principally spinel lherzolites and harzburgites with a few of websterite, spinel peridotite and orthopyroxenite; megacrysts include kaersutite and biotite. Chemical data for xenolith-free rock are available (Higgins and Allen, 1985, Table 1).

Age: 
Late Pleistocene.
References: 
HIGGINS, M.D. and ALLEN, J.M. 1982. Carbonate-rich basalt, andesite and dacite associated with nephelinites from NW British Columbia, Canada. Abstracts with Programs, Geological Society of America, 14: 514. HIGGINS, M.D. and ALLEN, J.M. 1985. A new locality for primary xenolith-bearing nephelinites in northwestern British Columbia. Canadian Journal of Earth Sciences, 22: 1556-9
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith