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Pb-isotope evidence on the origin of the West Shropsh orefield, England

Published online by Cambridge University Press:  01 May 2009

R. Haggerty
Affiliation:
Ancient Metallurgy Research Group, Department of Archaeological Sciences, University of Bradford, Bradford BD7 1DP, UK
B. M. Rohl
Affiliation:
Isotrace Laboratory, Nuclear Physics Building, 1 Keble Road, University of Oxford, Oxford 0X1 3RH, UK
P. D. Budd
Affiliation:
Ancient Metallurgy Research Group, Department of Archaeological Sciences, University of Bradford, Bradford BD7 1DP, UK
N. H. Gale
Affiliation:
Isotrace Laboratory, Nuclear Physics Building, 1 Keble Road, University of Oxford, Oxford 0X1 3RH, UK

Abstract

Pb-isotope data on ore galenas from the West Shropshire orefield show a significant spread of 20pb/204pb values, with minor variation in 207Pb/204Pb and 208Pb/204Pb ratios. These indicate that lead was derived from multiple sources, some of them uranium-enriched and incompletely mixed prior to ore deposition. Four possible mineralizing agents are considered: circulating sea-water, metamorphic waters, basinal brines and convecting formation waters. Pb-isotope data exclude a circulating sea-water origin for the mineralization, and best support a convecting formation water mineralizing agent. A model involving a single fluid tapping multiple lead sources is proposed to explain the observed Pb-isotope variation.

Type
Articles
Copyright
Copyright © Cambridge University Press 1996

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