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Constraints on the age and genesis of the Llanrwst and Llanfair–Talhaiarn orefields, North Wales from K–Ar and Rb–Sr studies

Published online by Cambridge University Press:  01 May 2009

R. Haggerty ,
S. H. Bottrell ,
R. A. Cliff  and
D. C. Rex
R. Haggerty
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
S. H. Bottrell
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
R. A. Cliff
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
D. C. Rex
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
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Abstract

The Llanrwst Pb–Zn and Llanfair–Talhaiarn Cu–Pb–Zn orefields contain vein mineralization similar to Lower Palaeozoic-hosted base metal deposits elsewhere in the British Isles, which are believed to have formed in the late Palaeozoic. K–Ar and Rb–Sr data on intensely sericitized wallrock material indicate that the main phase of mineralization at both orefields occurred between the mid-Devonian and theTournasian (386–350 Ma). The latest veins at Llanrwst formed in Visean–Westphalian times. Gangue mineral Sr isotope compositions indicate a mixture of radiogenic wallrock-derived Sr with less radiogenic Sr, with a poorly-defined trend to more radiogenic compositions with time.

The age of the main mineralization precludes dewatering of Carboniferous basins as a source of ore fluid. More generally Sr isotopes rule out unmodified basinal brines or metamorphic fluids as mineralizing agents, since their Sr content would be too radiogenic. Local sources of unradiogenic Sr are available at Llanrwst in metadolerites and calcareous sandstones and at Llanfair–Talhaiarn in thin Ludlow Limestone beds.

Type
Articles
Information
Geological Magazine , Volume 132 , Issue 4 , July 1995 , pp. 387 - 398
Copyright
Copyright © Cambridge University Press 1995

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