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Release of uranium from highly radiogenic zircon through metamictization: the source of orogenic uranium ores

Release of uranium from highly radiogenic zircon through metamictization: the source of orogenic uranium ores
Release of uranium from highly radiogenic zircon through metamictization: the source of orogenic uranium ores
Although circumstantial evidence from ore deposit mineralogy and geochemistry can imply potential sources for fluids and metals, rarely is direct evidence for metal leaching from source rocks seen in the vicinity of deposits. Here, we investigate the source of metals for a series of fault zone– and shear zone–hosted uranium occurrences in the Mount Isa inlier, Australia. As well as containing uranium, these deposits are enriched in Zr and rare earth elements (REEs), requiring that unusual fluids were responsible for addition of these typically immobile elements. During the Isan orogeny, highly saline metamorphic fluids infiltrated the sheared margin of a highly evolved granite intrusion, which contains elevated U, Th, F, Zr, and REEs. Synchrotron X-ray fluorescence spectroscopy and high-resolution electron microprobe mineral mapping show that this radioactive element–rich characteristic caused zircon crystals to become highly metamict, allowing the elements therein to become mobile. Thus, when orogenic fluids pervasively infiltrated along shear zones ?100 m.y. after granite intrusion, their unusually saline character allowed enhanced dissolution of regional carbonates and fluorite from the granite, providing the ligands needed for transport of uranium and the normally immobile elements from the metamict zircons.
0091-7613
15-18
McGloin, Matthew V.
58fac675-f0b4-4bf5-9646-970d3508cf2d
Tomkins, Andrew G.
e55fb466-2c71-4deb-81f2-6dca5d86788b
Webb, Gordon P.
381d6122-cf08-4297-884e-ae3cfab4189b
Spiers, Katherine
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MacRae, Colin M.
a36f1b44-ccf5-4f6a-b524-52273595f42c
Paterson, David
05aee07a-fe5b-4beb-99bb-5081e7a02b75
Ryan, Chris G.
365cbd33-ece5-477c-ab52-8ebdd3f7ba3b
McGloin, Matthew V.
58fac675-f0b4-4bf5-9646-970d3508cf2d
Tomkins, Andrew G.
e55fb466-2c71-4deb-81f2-6dca5d86788b
Webb, Gordon P.
381d6122-cf08-4297-884e-ae3cfab4189b
Spiers, Katherine
8c389da9-6b81-4d96-9938-a3fe5807e98a
MacRae, Colin M.
a36f1b44-ccf5-4f6a-b524-52273595f42c
Paterson, David
05aee07a-fe5b-4beb-99bb-5081e7a02b75
Ryan, Chris G.
365cbd33-ece5-477c-ab52-8ebdd3f7ba3b

McGloin, Matthew V., Tomkins, Andrew G., Webb, Gordon P., Spiers, Katherine, MacRae, Colin M., Paterson, David and Ryan, Chris G. (2015) Release of uranium from highly radiogenic zircon through metamictization: the source of orogenic uranium ores. Geology, 44 (1), 15-18. (doi:10.1130/G37238.1).

Record type: Article

Abstract

Although circumstantial evidence from ore deposit mineralogy and geochemistry can imply potential sources for fluids and metals, rarely is direct evidence for metal leaching from source rocks seen in the vicinity of deposits. Here, we investigate the source of metals for a series of fault zone– and shear zone–hosted uranium occurrences in the Mount Isa inlier, Australia. As well as containing uranium, these deposits are enriched in Zr and rare earth elements (REEs), requiring that unusual fluids were responsible for addition of these typically immobile elements. During the Isan orogeny, highly saline metamorphic fluids infiltrated the sheared margin of a highly evolved granite intrusion, which contains elevated U, Th, F, Zr, and REEs. Synchrotron X-ray fluorescence spectroscopy and high-resolution electron microprobe mineral mapping show that this radioactive element–rich characteristic caused zircon crystals to become highly metamict, allowing the elements therein to become mobile. Thus, when orogenic fluids pervasively infiltrated along shear zones ?100 m.y. after granite intrusion, their unusually saline character allowed enhanced dissolution of regional carbonates and fluorite from the granite, providing the ligands needed for transport of uranium and the normally immobile elements from the metamict zircons.

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More information

Published date: January 2015
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 387267
URI: http://eprints.soton.ac.uk/id/eprint/387267
ISSN: 0091-7613
PURE UUID: f02e2150-e129-4fd3-88e3-5ea29aa37f54

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Date deposited: 12 Feb 2016 09:55
Last modified: 14 Mar 2024 22:46

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Contributors

Author: Matthew V. McGloin
Author: Andrew G. Tomkins
Author: Gordon P. Webb
Author: Katherine Spiers
Author: Colin M. MacRae
Author: David Paterson
Author: Chris G. Ryan

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