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Early, deep magnetite-fluorapatite mineralization at the Olympic Dam Cu-U-Au-Ag deposit, South Australia

Citation

Apukhtina, OB and Kamenetsky, VS and Ehrig, K and Kamenetsky, MB and Maas, R and Thompson, J and McPhie, J and Ciobanu, CL and Cook, NJ, Early, deep magnetite-fluorapatite mineralization at the Olympic Dam Cu-U-Au-Ag deposit, South Australia, Economic Geology and The Bulletin of The Society of Economic Geologists, 112, (6) pp. 1531-1542. ISSN 0361-0128 (2017) [Refereed Article]


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DOI: doi:10.5382/econgeo.2017.4520

Abstract

The Olympic Dam iron oxide copper-gold (IOCG)-uranium-silver deposit (South Australia) is hosted in the large Olympic Dam breccia complex within the ~1.59 Ga Roxby Downs Granite. This breccia complex formed through multiple stages of hydrothermal activity and texturally destructive brecciation that affected the granite. The deepest diamond drill hole to date (RD2773, end at ~2,329 m) intersected weakly altered, in situbrecciated granite (~370–2,329 m) and a quartz-phyric felsic unit (~2,010–2,265 m). These two rock units host coarse-grained hydrothermal minerals, from ~2,150 m to the end of the drill hole. The main minerals in this assemblage are magnetite (± hematite), pyrite, fluorapatite, and quartz, with minor disseminated chalcopyrite, sericite, chlorite, rare earth element (REE)-fluorcarbonates, monazite, uraninite, thorite, galena, sphalerite, anhydrite, schorl, rutile, and pyrrhotite. The assemblage is cut by abundant multiphase veinlets and calcite (± fluorite ± barite) veins.

A zircon U-Pb age for the felsic unit (1591 ± 11 Ma) implies that this unit is broadly coeval with the granite, whereas U-Pb ages for hydrothermal uraninite (1593.5 ± 5.1 Ma), fluorapatite (1583.3 ± 6.5 Ma), and hematite (1592 ± 15 Ma) indicate that deposition of the U-REE–rich hydrothermal magnetite-fluorapatite-pyrite-quartz assemblage and replacement of magnetite by hematite occurred soon after emplacement of the granitic host rocks. Sm-Nd dating of ubiquitous calcite veins suggests formation at ~1.54 Ga.

The deep ~1.59 Ga magnetite-fluorapatite-pyrite-quartz assemblage at Olympic Dam resembles those characteristic of iron oxide-apatite deposits and many other sensu stricto IOCG deposits. This study confirms that the ~1.59 Ga event involved significant and widespread IOCG mineralization in the Olympic Cu-Au province.

Item Details

Item Type:Refereed Article
Keywords:Olympic Dam, Iron oxide-apatite deposits, magnetite, geochronology, uraninite
Research Division:Earth Sciences
Research Group:Geology
Research Field:Ore Deposit Petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Apukhtina, OB (Miss Olga Apukhtina)
Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
Author:Kamenetsky, MB (Dr Maya Kamenetsky)
Author:Thompson, J (Mr Jay Thompson)
Author:McPhie, J (Professor Jocelyn McPhie)
ID Code:121449
Year Published:2017
Deposited By:CODES ARC
Deposited On:2017-09-29
Last Modified:2017-10-02
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