EES Departmental Seminar: Lord of the Rings: a new interpretation for the origin of ring schlieren in the South Mountain Batholith

Thu, 17 Sep 2026 14:30:00 GMT

Dr. D. Barrie Clarke
Adjunct Professor
Earth and Environmental Sciences, ��⴫ý

Title: Lord of the Rings: a new interpretation for the origin of ring schlieren in the South Mountain Batholith

Abstract: Ring schlieren are enigmatic, metre-scale, alternating melanocratic gradational to leucocratic bands, forming open to closed, nested, circular to elliptical, concentric to eccentric structures, with centres aligned along the major axis or minor axis of the outer ellipse, with a cylindrical form in three dimensions, and in which cross-cutting relations show a younging direction towards the interior of the nested rings. Except for their interiors, the rings are normally devoid of coarse constituents, suggesting that segregation based on grain size has occurred during their formation. Previous interpretations for the origin of ring schlieren include Bagnold dispersive grain pressure, intra-plutonic diapirs, flow in magma tubes, shear flow around rising gas bubbles in a magma mush, and liquid immiscibility. A new interpretation relates ring schlieren to partially melted xenoliths, ascent resulting from Rayleigh-Taylor instabilities, segregation by a combination of Bagnold dispersive grain pressure and particle collisions, evisceration of the core, and reinjection.

Speaker: Dr. D. Barrie Clarke was professor of igneous petrology at ��⴫ý from 1970-2007. His principal areas of research were on the Paleocene volcanic rocks of Davis Strait and on the Devonian peraluminous granites of Nova Scotia. His one venture into forensic petrology determined the source of the Titanic headstones in Halifax to be an abandoned quarry in SW New Brunswick.

Barrie will not be able to meet with the audience for coffee before his lecture

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EES Departmental Seminar: Lord of the Rings: a new interpretation for the origin of ring schlieren in the South Mountain Batholith