Devonian lavas from Solund, West Norway - field relationships and geochemistry.
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Devonian volcanic rocks in the Hersvik area, Solund, West Norway are represented by two lava flows occuring close to the base of the Devonian conglomerate. They are composed largely of highly flow-banded and brecciared material. The lavas are of intermediate to acidic composition, the lower flow is trachytic (61-63% SiO2) and the upper one rhyolitic (67-70% SiO2). They were strongly altered by hydration and oxidation, probably mainly as a result of hydrothermal activity. Incompatible trace element abundances are very high, and of the same magnitude as in perkaline acidic rocks, suggesting a contonental rift environment for the Hersvik area.