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K—Ar isotopic age determinations from some Lake District mineral localities

Published online by Cambridge University Press:  01 May 2009

P. R. Ineson
Affiliation:
Department of Geology, University of Sheffield, Mappin Street, Sheffield S1 3JD, U.K.
J. G. Mitchell
Affiliation:
Department of Geophysics and Planetary Physics, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RV, U.K.

Summary

Forty-seven new K—Ar analyses are reported from 15 mines in the Lake District. Analyses of clay mineral concentrates from vein gouges and altered wallrock support a hypothesis of at least 3 distinct isotopic events. Caledonian ages (388 Ma) are reported from the Coniston Copper deposits, while the extensive mineralization in and around the Vale of Newlands indicates a metasomatic event occurring at around 360 Ma. The ages of the sporadic mineral localities to the E of the area (i.e. Greenside, Threlkeld, etc.) are grouped around 325 Ma while those of the Caldbeck Fell deposits are close to 230 Ma. An epidosic model may be advanced for the Carrock Fell Tungsten deposits with a range from 197 to 282 Ma. The geochronological significance of these and other previously published results is considered.

Type
Articles
Copyright
Copyright © Cambridge University Press 1974

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