Nature and genesis of a carbonatite-associated fluorite deposit at Speewah, East Kimberley region, Western Australia

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Abstract

The Speewah fluorite deposit (>2.28 Mt at 25.5% CaF2) is sited adjacent to the crustal-scale Greenvale Fault on the western side of the Halls Creek Orogen, in the East Kimberley region of Western Australia. Host rocks are Palaeoproterozoic sedimentary rocks, dolerite and granophyre, Early Cambrian basalt, and the Yungul carbonatite. The deposit comprises mainly fluorite-quartz veins associated with lesser barite, sulfides and calcite, controlled by NNE-SSW and N-S brittle faults and fractures. Cross-cutting field relationships indicate that the fluorite veins were deposited post Early Cambrian.Fluorite-quartz vein textures, including colloform banding and comb texture, combined with microthermometric data from primary fluid inclusions, indicate that fluorite was deposited by the incremental infill of open-space structures in an epizonal, and probably epithermal, environment (<160&DEG;C) from complex, Li-Ca-Mg-rich, highly saline ore-fluids.The Yungul carbonatite and intimately-associated replacement-type fluorite have similar levels of REE enrichment and identical chondrite-normalised HREE patterns. Samarium and neodymium isotopic analyses of the fluorite indicate extreme differentiation of the Sm-147/Nd-144 ratio, from 0.0709 to 0.6918. These Sm-Nd isotopic data correspond to a mineral isochron with an age of 122&PLUSMN;24 Ma, interpreted to represent the age of fluorite deposition.Based on the potentially magmatic fluid composition, the replacement-type fluorite within the carbonatite, the similar HREE patterns of fluorite and carbonatite, and direct, if imprecise, isotopic dating of the fluorite, which confirms that fluorite mineralization is younger than the Early Cambrian basalts, the Speewah fluorite deposit is interpreted to be genetically related to the Yungul carbonatite. The large fluorite resource cannot have been derived from the exposed, low-volume carbonatite dyke. Rather. it must have been sourced from a larger carbonatite body at depth, whose presence is implied from basement-derived xenocrystic zircons in the Yungul carbonatite.
Original languageEnglish
Pages (from-to)127-153
JournalMineralogy and Petrology
Volume80
Issue number3-4
DOIs
Publication statusPublished - 2004

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Fluorspar
carbonatite
fluorite
Deposits
deposits
veins
Quartz
quartz vein
basalt
Fluids
fluids
textures
quartz
Textures
replacement
texture
minerals
Samarium
samarium
Barium Sulfate

Cite this

@article{7b1c31f86d614ebf8943c6b77c9ace9d,
title = "Nature and genesis of a carbonatite-associated fluorite deposit at Speewah, East Kimberley region, Western Australia",
abstract = "The Speewah fluorite deposit (>2.28 Mt at 25.5{\%} CaF2) is sited adjacent to the crustal-scale Greenvale Fault on the western side of the Halls Creek Orogen, in the East Kimberley region of Western Australia. Host rocks are Palaeoproterozoic sedimentary rocks, dolerite and granophyre, Early Cambrian basalt, and the Yungul carbonatite. The deposit comprises mainly fluorite-quartz veins associated with lesser barite, sulfides and calcite, controlled by NNE-SSW and N-S brittle faults and fractures. Cross-cutting field relationships indicate that the fluorite veins were deposited post Early Cambrian.Fluorite-quartz vein textures, including colloform banding and comb texture, combined with microthermometric data from primary fluid inclusions, indicate that fluorite was deposited by the incremental infill of open-space structures in an epizonal, and probably epithermal, environment (<160&DEG;C) from complex, Li-Ca-Mg-rich, highly saline ore-fluids.The Yungul carbonatite and intimately-associated replacement-type fluorite have similar levels of REE enrichment and identical chondrite-normalised HREE patterns. Samarium and neodymium isotopic analyses of the fluorite indicate extreme differentiation of the Sm-147/Nd-144 ratio, from 0.0709 to 0.6918. These Sm-Nd isotopic data correspond to a mineral isochron with an age of 122&PLUSMN;24 Ma, interpreted to represent the age of fluorite deposition.Based on the potentially magmatic fluid composition, the replacement-type fluorite within the carbonatite, the similar HREE patterns of fluorite and carbonatite, and direct, if imprecise, isotopic dating of the fluorite, which confirms that fluorite mineralization is younger than the Early Cambrian basalts, the Speewah fluorite deposit is interpreted to be genetically related to the Yungul carbonatite. The large fluorite resource cannot have been derived from the exposed, low-volume carbonatite dyke. Rather. it must have been sourced from a larger carbonatite body at depth, whose presence is implied from basement-derived xenocrystic zircons in the Yungul carbonatite.",
author = "M.P. Alvin and Jan Dunphy and David Groves",
year = "2004",
doi = "10.1007/s00710-003-0015-3",
language = "English",
volume = "80",
pages = "127--153",
journal = "Mineralogy and Petrology",
issn = "0930-0708",
publisher = "Springer",
number = "3-4",

}

TY - JOUR

T1 - Nature and genesis of a carbonatite-associated fluorite deposit at Speewah, East Kimberley region, Western Australia

AU - Alvin, M.P.

AU - Dunphy, Jan

AU - Groves, David

PY - 2004

Y1 - 2004

N2 - The Speewah fluorite deposit (>2.28 Mt at 25.5% CaF2) is sited adjacent to the crustal-scale Greenvale Fault on the western side of the Halls Creek Orogen, in the East Kimberley region of Western Australia. Host rocks are Palaeoproterozoic sedimentary rocks, dolerite and granophyre, Early Cambrian basalt, and the Yungul carbonatite. The deposit comprises mainly fluorite-quartz veins associated with lesser barite, sulfides and calcite, controlled by NNE-SSW and N-S brittle faults and fractures. Cross-cutting field relationships indicate that the fluorite veins were deposited post Early Cambrian.Fluorite-quartz vein textures, including colloform banding and comb texture, combined with microthermometric data from primary fluid inclusions, indicate that fluorite was deposited by the incremental infill of open-space structures in an epizonal, and probably epithermal, environment (<160&DEG;C) from complex, Li-Ca-Mg-rich, highly saline ore-fluids.The Yungul carbonatite and intimately-associated replacement-type fluorite have similar levels of REE enrichment and identical chondrite-normalised HREE patterns. Samarium and neodymium isotopic analyses of the fluorite indicate extreme differentiation of the Sm-147/Nd-144 ratio, from 0.0709 to 0.6918. These Sm-Nd isotopic data correspond to a mineral isochron with an age of 122&PLUSMN;24 Ma, interpreted to represent the age of fluorite deposition.Based on the potentially magmatic fluid composition, the replacement-type fluorite within the carbonatite, the similar HREE patterns of fluorite and carbonatite, and direct, if imprecise, isotopic dating of the fluorite, which confirms that fluorite mineralization is younger than the Early Cambrian basalts, the Speewah fluorite deposit is interpreted to be genetically related to the Yungul carbonatite. The large fluorite resource cannot have been derived from the exposed, low-volume carbonatite dyke. Rather. it must have been sourced from a larger carbonatite body at depth, whose presence is implied from basement-derived xenocrystic zircons in the Yungul carbonatite.

AB - The Speewah fluorite deposit (>2.28 Mt at 25.5% CaF2) is sited adjacent to the crustal-scale Greenvale Fault on the western side of the Halls Creek Orogen, in the East Kimberley region of Western Australia. Host rocks are Palaeoproterozoic sedimentary rocks, dolerite and granophyre, Early Cambrian basalt, and the Yungul carbonatite. The deposit comprises mainly fluorite-quartz veins associated with lesser barite, sulfides and calcite, controlled by NNE-SSW and N-S brittle faults and fractures. Cross-cutting field relationships indicate that the fluorite veins were deposited post Early Cambrian.Fluorite-quartz vein textures, including colloform banding and comb texture, combined with microthermometric data from primary fluid inclusions, indicate that fluorite was deposited by the incremental infill of open-space structures in an epizonal, and probably epithermal, environment (<160&DEG;C) from complex, Li-Ca-Mg-rich, highly saline ore-fluids.The Yungul carbonatite and intimately-associated replacement-type fluorite have similar levels of REE enrichment and identical chondrite-normalised HREE patterns. Samarium and neodymium isotopic analyses of the fluorite indicate extreme differentiation of the Sm-147/Nd-144 ratio, from 0.0709 to 0.6918. These Sm-Nd isotopic data correspond to a mineral isochron with an age of 122&PLUSMN;24 Ma, interpreted to represent the age of fluorite deposition.Based on the potentially magmatic fluid composition, the replacement-type fluorite within the carbonatite, the similar HREE patterns of fluorite and carbonatite, and direct, if imprecise, isotopic dating of the fluorite, which confirms that fluorite mineralization is younger than the Early Cambrian basalts, the Speewah fluorite deposit is interpreted to be genetically related to the Yungul carbonatite. The large fluorite resource cannot have been derived from the exposed, low-volume carbonatite dyke. Rather. it must have been sourced from a larger carbonatite body at depth, whose presence is implied from basement-derived xenocrystic zircons in the Yungul carbonatite.

U2 - 10.1007/s00710-003-0015-3

DO - 10.1007/s00710-003-0015-3

M3 - Article

VL - 80

SP - 127

EP - 153

JO - Mineralogy and Petrology

JF - Mineralogy and Petrology

SN - 0930-0708

IS - 3-4

ER -