Isotopic composition and distribution of lead, uranium, and thorium in a Precambrian granite

GSA Bulletin
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Abstract

The isotopic compositions and concentrations of lead and uranium have been determined in some separated minerals and the composite of a granite from Monmouth township, Haliburton County, Ontario. The chemical and mass spectrometric methods that were used are described. The age of the zircon from the granite is 1050 million years. Much of the lead, uranium, and thorium exists in chemically unstable and presumably interstitial phases of the granite. A comparison of the observed amounts of uranium, thorium, and lead in the various minerals with those amounts that should have been present, had these three elements existed within the minerals as closed systems, shows a non-balance of these elements in every case. It appears that the granite as a whole has closely approximated a closed system since it was formed with respect to uranium and its decay products, but has been an open system with respect to thorium and its decay products. Interpretations concerning the relationship of these data to lead ores are discussed.

Publication type Article
Publication Subtype Journal Article
Title Isotopic composition and distribution of lead, uranium, and thorium in a Precambrian granite
Series title GSA Bulletin
DOI 10.1130/0016-7606(1955)66[1131:ICADOL]2.0.CO;2
Volume 66
Issue 6
Year Published 1955
Language English
Publisher Geological Society of America
Description 18 p.
First page 1131
Last page 1148
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