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Gadolinium-dominant monazite and xenotime; selective hydrothermal enrichment of middle REE during low-temperature alteration of uraninite, brannerite, and fluorapatite (Zimna Voda REE-U-Au quartz vein, Western Carpathians, Slovakia)

Martin Ondrejka, Pavel Uher, Stefan Ferenc, Stanislava Milovska, Tomas Mikus, Alexandra Molnarova, Radek Skoda, Richard Kopacik and Peter Bacik
Gadolinium-dominant monazite and xenotime; selective hydrothermal enrichment of middle REE during low-temperature alteration of uraninite, brannerite, and fluorapatite (Zimna Voda REE-U-Au quartz vein, Western Carpathians, Slovakia)
American Mineralogist (April 2023) 108 (4): 754-768

Abstract

A hydrothermal quartz vein with REE-U-Au mineralization in the Zimna Voda (Gemeric Unit, Western Carpathians, Slovakia) is associated with contact metamorphism between Permian granites and host phyllites and metaquartzites. It contains unique REE minerals of the monazite and xenotime groups. Monazite-(Ce), monazite-(Nd), monazite-(Sm), and Gd-dominant monazite ["monazite-(Gd)"], along with xenotime-(Y) to Gd-dominant xenotime ["xenotime-(Gd)"] and Gd-rich hingganite-(Y) show heterogeneous compositions and reflect a strong fractionation trend toward the enrichment of MREE (Sm to Dy), particularly Gd. Here, the gadolinium abundance reported in "monazite-(Gd)" (< or =23.4 wt% Gd (sub 2) O (sub 3) ) and Gd-rich xenotime-(Y) to "xenotime-(Gd)" (< or =28.7 wt% Gd (sub 2) O (sub 3) ) and accompanied by Gd-rich hingganite-(Y) (< or =15.8 wt% Gd (sub 2) O (sub 3) ), is among the highest Gd concentrations ever reported in natural minerals. The Gd-richest compositions show the following formulas: (Gd (sub 0.31) Sm (sub 0.24) Nd (sub 0.15) Ce (sub 0.10) La (sub 0.05) Dy (sub 0.03) Y (sub 0.03) ...) (sub 0.98) PO (sub 4) ["monazite-(Gd)"], (Gd (sub 0.36) Y (sub 0.32) Dy (sub 0.13) Sm (sub 0.08) Tb (sub 0.05) ...) (sub 0.98) (P (sub 0.96) As (sub 0.04) ) (sub 1.00 ) O (sub 4 ) ["xenotime-(Gd)"] and (Y (sub 0.71) Gd (sub 0.43) Dy (sub 0.23) Sm (sub 0.22) Tb (sub 0.06) Er (sub 0.04) Nd (sub 0.06) ...Ca (sub 0.06) ) (sub 1.9 6) ( (sub 0.87) Fe (sub 0.13) (super 2+) ) (sub 1.00) (Be (sub 1.82) B (sub 0.18) ) (sub 2.00) (Si (sub 1.90) As (sub 0.10) ) (sub 2 . 00) O (sub 8) (OH (sub 1.70) O (sub 0.30) ) (sub 2.00) [hingganite-(Y)]. The MREE-rich monazites, xenotimes, and hingganite-(Y) precipitated in response to the alteration of primary uraninite, brannerite, and fluorapatite by low-temperature hydrothermal fluids of heterogeneous compositions on a microscale. These are responsible for the strong enrichment of individual MREE, especially Gd in the secondary minerals. This is accompanied by the advancing development of the W-type tetrad effect on REE through monazite species. The substantial incorporation of Gd into both REE-selective monazite and xenotime structures that are accompanied by LREE vs. HREE segregation indicates the possibility of differently sized REE (super 3+) miscibility in REEPO (sub 4) solid solutions, as well as the stabilization of the Gd-rich orthophosphate structure by substitution of the remaining A-site cations with smaller HREE+Y in the xenotime-type, and/or larger LREE in the monazite-type structure.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 108
Serial Issue: 4
Title: Gadolinium-dominant monazite and xenotime; selective hydrothermal enrichment of middle REE during low-temperature alteration of uraninite, brannerite, and fluorapatite (Zimna Voda REE-U-Au quartz vein, Western Carpathians, Slovakia)
Affiliation: Comenius University, Department of Mineralogy, Petrology and Economic Geology, Bratislava, Slovakia
Pages: 754-768
Published: 202304
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 102
Accession Number: 2023-030284
Categories: Mineralogy of non-silicatesEconomic geology, general, deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 plates, geol. sketch map
N48°25'60" - N48°55'60", E19°06'00" - E21°19'60"
Secondary Affiliation: Matej Bel University, Department of Geography and Geology, SVK, SlovakiaMasaryk University, Department of Geological Sciences, CZE, Czech RepublicSlovak Academy of Sciences, Earth Science Institute, SVK, Slovakia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2023, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2023
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