Abstract
LONDON. Geological Society, June 25.—J. E. Richey: Tertiary igneous complex of Ardnamurchan. The district is chiefly noteworthy on account of its intrusive rocks, and only small outliers of the widespread Tertiary plateau basalt-lavas are preserved. The types of intrusion include volcanic vents piercing the basalt-lavas, and largely filled with % acid and trachytic fragmental materials; minor intrusions, including cone-sheets, chiefly quartz-dolerite, and dykes; and plutonic masses, nearly all gabbro or dolerite, occurring mainly as ring-dykes. The above, excepting the dykes, are arranged in concentric series around three different centres, marking three foci of igneous activity which functioned successively. Itr is suggested that the three complexes are successively more deep-seated, due, presumably, to the growth of an overlying volcanic pile. The regular ring-patterns marked by the intrusions are of more especial interest and contitute evidence of the formation of annular or arcuate fissures that are considered here, as in Mull, to have resulted from localised stresses set up in the roof of an underlying magma-reservoir.
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Societies and Academies. Nature 126, 262–264 (1930). https://doi.org/10.1038/126262b0
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DOI: https://doi.org/10.1038/126262b0