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
Copyright Information: © Springer-Verlag GmbH Austria, part of Springer Nature 2019
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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