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Magmatic enrichment of uranium, thorium, and rare earth elements in late paleozoic rhyolites of southern New Brunswick, Canada: evidence from silicate melt inclusions

Citation

Gray, TR and Hanley, JJ and Dostal, J and Guillong, M, Magmatic enrichment of uranium, thorium, and rare earth elements in late paleozoic rhyolites of southern New Brunswick, Canada: evidence from silicate melt inclusions, Economic Geology and The Bulletin of The Society of Economic Geologists, 106, (1) pp. 127-143. ISSN 0361-0128 (2011) [Refereed Article]

Copyright Statement

Copyright 2011 Society of Economic Geologists, Inc.

DOI: doi:10.2113/econgeo.106.1.127

Abstract

The major and trace element geochemistry of silicate melt inclusions was investigated within late Paleozoic felsic rhyolites from the Piskahegan and Harvey Formations of southern New Brunswick, Canada, in order to provide further insight into the genetic history of the volcanic- and caldera-related U mineralization that occurs in the region. Glassy melt inclusions analyzed by laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) and electron microprobe show enrichment in most incompatible trace elements, but a marked depletion in Ba, Sr, and Eu compared to whole rock. At Harvey, melt trapped in early quartz phenocrysts ("preeruptive" inclusions) and in late quartz aggregates ("syneruptive" inclusions) within the groundmass of the rhyolites was significantly more fractionated than melt trapped in quartz phenocrysts at Piskahegan. Fractionation was associated with the crystallization of feldspar and resulted in progressive enrichment of the melt in U, Th, B, LILE, LREE, and other metals, as well as an increase in the U/Th ratio of the melt. A higher degree of melt fractionation, combined with postmagmatic leaching, may have been prerequisites for mineralization at Harvey. Because felsic volcanic rocks are highly susceptible to alteration, melt inclusion analysis may be the only method capable of providing constraints on melt chemistry and evolution in such ancient volcanic terrains. This may enable the evaluation of the economic potential of such terrains if the initial U and Th concentration, as well as the U/Th ratio of the volcanic products, affect the ultimate mineralizing potential of the system.

Item Details

Item Type:Refereed Article
Keywords:Magmatic enrichment, uranium, thorium, rare earth elements, paleozoic rhyolites, New Brunswick, Canada, silicate melt inclusions
Research Division:Earth Sciences
Research Group:Geochemistry
Research Field:Inorganic Geochemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Guillong, M (Dr Marcel Guillong)
ID Code:118262
Year Published:2011
Web of Science® Times Cited:7
Deposited By:CODES ARC
Deposited On:2017-07-07
Last Modified:2017-10-17
Downloads:0

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