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Source ages of zircons in an Archaean quartzite, Rona, Inner Hebrides, Scotland

Published online by Cambridge University Press:  01 May 2009

D. R. Bowes ,
A. M Hopgood  and
R. T. Pidgeon
D. R. Bowes
Affiliation:
Department of Geology, University of Glasgow, Glasgow, G12 8QQ Scotland
A. M Hopgood
Affiliation:
Department of Geology, University of St. AndrewsSt. Andrews, KY16 9ST, Scotland
R. T. Pidgeon
Affiliation:
School of Earth Sciences, Australian National University, Canberra 2601, Australia
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Summary

The internal variations in the discordance of an inhomogenous zircon population from a bedded quartzite within a c. 2700 Ma old gneiss have been studied. Varying degrees of response to events in a common multi-episodic, post-depositional history are reflected in the uranium and lead isotopic systems of size and magnetic fractions.

A minimum 207Pb/206Pb age for non-magnetic zircons is 2840 Ma with 206Pb/238U and 207Pb/235U data for the three size fractions raising the possibility of an age of at least 3250 Ma. This is interpreted as a minimum age for crustal material that was in existence in the region before the formation of the Lewisian complex. Some of the slightly magnetic zircons also have a pre-2700 Ma radiogenic lead component.

Type
Articles
Information
Geological Magazine , Volume 113 , Issue 6 , November 1976 , pp. 545 - 552
Copyright
Copyright © Cambridge University Press 1976

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