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Aiyansh/Tseax is a volcano associated with a lava flow located in north-western British Columbia, Canada. It is the southernmost volcanic centre of the Northern Cordillera Volcanic Belt, currently lying dormant with its last eruption occurring in the 18th century. Structurally the volcano itself features a horseshoe shaped outer cone, with an inner tephra cone and a satellite cone located ~150-200 m to the north. The lava flow field covers ~36 km2, mostly following the Tseax River and Nass Valleys. The lava flow field can be split into four flow events belonging to a single eruption: the first two being phenocryst-poor pahoehoe and the latter two being phenocryst-rich ‘a‘ā. All eruptives are nepheline-normative basanite/tephrite to trachybasalt. Whole rock and mineral (olivine, plagioclase, oxides) geochemical data can be found in Sutherland-Brown (1969), Le Moigne (2020), Gallo (2018).
