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Postmagmatic magnetite - apatite assemblage in mafic intrusions: a case study of dolerite at Olympic Dam, South Australia

Citation

Apukhtina, OB and Kamenetsky, VS and Ehrig, K and Kamenetsky, MB and McPhie, J and Maas, R and Meffre, S and Goemann, K and Rodemann, T and Cook, NJ and Ciobanu, CL, Postmagmatic magnetite - apatite assemblage in mafic intrusions: a case study of dolerite at Olympic Dam, South Australia, Contributions to Mineralogy and Petrology, 171, (1) Article 2. ISSN 0010-7999 (2016) [Refereed Article]

Copyright Statement

© Springer-Verlag Berlin Heidelberg 2015

DOI: doi:10.1007/s00410-015-1215-7

Abstract

An assemblage of magnetite and apatite is common worldwide in different ore deposit types, including disparate members of the iron-oxide copper–gold (IOCG) clan. The Kiruna-type iron oxide-apatite deposits, a subtype of the IOCG family, are recognized as economic targets as well. A wide range of competing genetic models exists for magnetite–apatite deposits, including magmatic, magmatic-hydrothermal, hydrothermal(-metasomatic), and sedimentary(-exhalative). The sources and mechanisms of transport and deposition of Fe and P remain highly debatable. This study reports petrographic and geochemical features of the magnetite–apatite-rich vein assemblages in the dolerite dykes of the Gairdner Dyke Swarm (~0.82 Ga) that intruded the Roxby Downs Granite (~0.59 Ga), the host of the supergiant Olympic Dam IOCG deposit. These symmetrical, only few mm narrow veins are prevalent in such dykes and comprise besides usually colloform magnetite and prismatic apatite also further minerals (e.g., calcite, quartz). The genetic relationships between the veins and host dolerite are implied based on alteration in the immediate vicinity (~4 mm) of the veins. In particular, Ti-magnetite–ilmenite is partially to completely transformed to titanite and magmatic apatite disappears. We conclude that the mafic dykes were a local source of Fe and P re-concentrated in the magnetite–apatite veins. Uranium-Pb ages for vein apatite and titanite associated with the vein in this case study suggest that alteration of the dolerite and healing of the fractures occurred shortly after dyke emplacement. We propose that in this particular case the origin of the magnetite–apatite assemblage is clearly related to hydrothermal alteration of the host mafic magmatic rocks.

Item Details

Item Type:Refereed Article
Keywords:IOCG deposits, Olympic Dam, mafic magmatism, colloform magnetite, hydrothermal alteration, radiogenic isotopes
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Other Mineral Resources (excl. Energy Resources)
Objective Field:Mineral Resources (excl. Energy Resources) not elsewhere classified
Author:Apukhtina, OB (Miss Olga Apukhtina)
Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
Author:Kamenetsky, MB (Dr Maya Kamenetsky)
Author:McPhie, J (Professor Jocelyn McPhie)
Author:Meffre, S (Dr Sebastien Meffre)
Author:Goemann, K (Dr Karsten Goemann)
Author:Rodemann, T (Dr Thomas Rodemann)
ID Code:107930
Year Published:2016
Web of Science® Times Cited:2
Deposited By:Earth Sciences
Deposited On:2016-03-31
Last Modified:2017-10-24
Downloads:0

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