Paragenesis and composition of xenotime-(Y) and florencite-(Ce) from unconformity-related heavy rare earth element mineralization of northern Western Australia

Nazari-Dehkordi, Teimoor, and Spandler, Carl (2019) Paragenesis and composition of xenotime-(Y) and florencite-(Ce) from unconformity-related heavy rare earth element mineralization of northern Western Australia. Mineralogy and Petrology, 113 (5). pp. 563-581.

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Abstract

This study investigates the paragenesis and ore mineral composition of xenotime [(Y,HREE)PO4] and florencite [LREEAl3(PO4)(2)(OH)(6)] from heavy rare earth element (HREE) deposits/prospects of the Tanami and Hall Creek regions of Western Australia. Two stages of xenotime-(Y) formation are recognized: (1) early xenotime-(Y) in breccias (breccia-hosted) and in quartz-xenotime-(Y) veins (vein-type); and (2) late xenotime-(Y) that occurs largely as dipyramidal-shaped overgrowths on the pre-existing early xenotime-(Y). Similarly, florencite-(Ce) formed in two stages including: (1) early florencite-(Ce) that coexists with and is enclosed by early xenotime-(Y) within mineralized veins; and (2) late florencite-(Ce) that replaces early xenotime-(Y), or appears as narrow rims on early florencite-(Ce). All xenotime-(Y) types from a number of examined HREE deposits/prospects are characterized by elevated U contents and marked negative Eu anomalies that we interpret to be inherited from the metasedimentary rocks from which REE and P required for the phosphate ore mineralization, were sourced. Compared to the early xenotime-(Y), the late xenotime-(Y) is richer in HREE and depleted in P, owing to the formation of the coexisting late florencite-(Ce). Moreover, early florencite-(Ce) has a near end-member florencite (s.s.) composition similar to those associated with unconformity-related U deposits, whereas late florencite-(Ce) sits on the florencite-svanbergite compositional spectrum. The high U content of xenotime-(Y) and composition of early florencite-(Ce) potentially support a genetic association between the HREE mineralization and the coeval unconformity-related U deposits of northern Australia. Nevertheless, we also urge for caution in using xenotime-(Y) composition in isolation as an indicator of geological setting.

Item ID: 60556
Item Type: Article (Research - C1)
ISSN: 1438-1168
Keywords: Xenotime, Florencite, Aluminum-phosphate-sulfate minerals, Hydrothermal, Unconformity, Tanami region
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Copyright Information: © Springer-Verlag GmbH Austria, part of Springer Nature 2019
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A version of this publication was included as Chapter 5 of the following PhD thesis: Nazari Dehkordi, Teimoor (2018) The origin and evolution of heavy rare earth element mineralisation in the Browns Range area, Northern Australia. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Research Council (ARC), Northern Minerals Ltd
Projects and Grants: ARC Future Fellowship (FT 120100198)
Date Deposited: 09 Oct 2019 07:36
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040307 Ore Deposit Petrology @ 50%
04 EARTH SCIENCES > 0403 Geology > 040306 Mineralogy and Crystallography @ 50%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840107 Titanium Minerals, Zircon, and Rare Earth Metal Ore (e.g. Monazite) Exploration @ 100%
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