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Geochemistry and age of magmatic rocks in the unexposed Narromine, Cowal and Fairholme Igneous Complexes in the Ordovician Macquarie Arc, New South Wales

Citation

Crawford, AJ and Cooke, DR and Fanning, CM, Geochemistry and age of magmatic rocks in the unexposed Narromine, Cowal and Fairholme Igneous Complexes in the Ordovician Macquarie Arc, New South Wales, Australian Journal of Earth Sciences, 54, (2/3) pp. 243-271. ISSN 0812-0099 (2007) [Refereed Article]

DOI: doi:10.1080/08120090701221714

Abstract

Much of the northern and southern sections of the Junee-Narromine Volcanic Belt of the Ordovician Macquarie Arc in central-western New South Wales are buried beneath the sediment cover of the Great Artesian Basin. Exploration drilling of these aeromagnetically defined blocks has provided important new material to assess the temporal and magmatic affinities of the rocks in the Narromine Igneous Complex (northern end) and the Cowal and Fairholme Igneous Complexes (southern end). Basement rocks are representative of Phase 1 magmatism in the Macquarie Arc, and consist of Lower Ordovician basalts and andesites and common volcaniclastic rocks, all with high-K calc-alkaline affinities. These are very similar compositionally to the Lower Ordovician Nelungaloo Volcanics that outcrop in the central part of the Junee-Narromine Volcanic Belt west of Parkes. Intruding the basement volcanic-volcaniclastic package are three distinct igneous suites. The oldest of these, dated at ca 466-460Ma (Middle Ordovician) and representative of Phase 2 magmatism in the Macquarie Arc, consists of stocks of monzogabbro, monzodiorite and monzonite with high-K calc-alkaline affinities, and is well represented in the Narromine and Cowal Igneous Complexes. Phase 2 suite rocks were, in turn, intruded in the Bolindian (445 ± 5 Ma) by kilometre-size stocks, narrow sheets and dykes made up of hornblende gabbro, diorite and granodiorite, and including quartz+plagioclase+hornblende-phyric dacitic porphyries in the Narromine Igneous Complex. These medium-K calc-alkaline rocks, assigned to the Phase 3 Copper Hill Suite that also occurs in the Molong and Rockley-Gulgong Volcanic Belts further east, crystallised from andesitic or more evolved magmas, probably derived via partial melting of low-K rocks in the arc basement, or amphibolites in the subducting slab. The youngest rocks in these igneous complexes are believed to be the high-level shoshonitic intrusives in the Cowal and Fairholme Igneous Complexes, which are correlated on petrographic and compositional grounds with the Macquarie Arc Phase 4 (Bolindian and Llandovery) magmatic products best represented by the Northparkes Igneous Complex in the central part of the Junee-Narromine Volcanic Belt.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Tectonics
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:Crawford, AJ (Professor Anthony Crawford)
Author:Cooke, DR (Professor David Cooke)
ID Code:51591
Year Published:2007
Web of Science® Times Cited:15
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2007-08-01
Last Modified:2009-05-07
Downloads:0

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