This project seeks to utilize the Re-Os isochron method on sulphides to determine precise ages for two classes of metal deposits in WA: . VHMS Zn-Pb-Cu deposits and orogenic gold deposits. Selected VHMS deposits from the Murchison (Golden Grove, Scuddles), eastern Yilgarn (Jaguar, Nimbus) and Pilbara (Sulphur Springs) will be studied as part of this project. The ages of mineralization for only two orogenic gold deposits in WA have been determined using the Re-Os isochron method on sulphides: at Sunrise Dam and Tropicana. The former example states an age uncertainty of +/-6 Ma and provides encouragement that ages, with precision similar to that gleaned from the U-Pb and Ar-Ar methods, are achievable. This project will seek Re-Os isochron ages on sulphides for undated deposits in the western Yilgarn (. Boddington, Murchison), to build a comparative database to the eastern Yilgarn: . ∼20 dated deposits using mainly ore-associated phosphates. The Re-Os ages will be complemented by U-Pb and Ar-Ar data to establish a 4D framework, where appropriate.
As part of the development of the Re-Os method in the John de Laeter Centre, we have recently determined a Re-Os age for molybdenite from the Central Bore gold prospect within the Yamarna terrain, in the eastern Yilgarn craton (Fuller et al., AESC proceedings, Newcastle, 2014). Here, gold is closely associated with molybdenite and is found in veins and inclusions in molybdenite. The Re-Os molybdenite age was 2620±10 Ma, which is compatible with U-Pb hydrothermal titanite ages from the same samples and slightly younger than zircon ages of hosting felsic volcanics (2677±7 Ma) and a minimum age for sandstone (2682±5 Ma) from the Yamarna terrain. It is also close to the timing of the gold deposition event (2640-2630 Ma) recorded at Kalgoorlie (Vielreicher et al., 2010), which is the youngest known mineralization event in the EGP (Vielreicher et al., in prep.). This pilot study suggests confirmation of the robust nature of Re-Os geochronometer in molybdenite and its potential application in WA, where molybdenite occurs.
Moreover, we recently performed a collaborative project with Russian Academy of Sciences in order to date the Olimpiada gold deposit using arsenopyrites. The reasonable isochron model age of 689±28 Ma was obtained (Borisenko et al., Acta Geol Sin, 2014), which is compatible with host rocks geochronology. PPrevious work of Dr Tessalina included determining isochron model ages on pyrite separates for several Urals VHMS deposits (., Gannoun et al., 2003 Chem Geol; Tessalina et al, 2008 OGR). In addition, JdLC Director Professor Brent McInnes was previously a Project Leader on AMIRA P563 Re-Os Geochronology of Ore Systems (1999-2002: $320,000), an industry-ARC sponsored project that investigated the application of Re-Os isotope systematics in major ore deposits around the globe (McInnes et al., 1999, 2004 and 2008). This project generated research results for the Mount Morgan Cu-Au deposit in Queensland (Unpublished AMIRA P563 Final Report 2003).
Barzun’s critique of the cult of evolutionary theory and the canonisation of Darwin himself is impressive but it is difficult to identify where Barzun stands on the scientific status of evolutionary theory and this is the least convincing part of his work. He appears to be dissatisfied with materialism and determinism without explaining whether he adhered to vitalism, or some form of mysticism or religion. This underlines the problem of pursuing such a wide-ranging research project without the assistance of co-workers, so his reach may have exceeded his grasp at some points. This is especially apparent when he attempted to locate his work in the context of twentieth century physics and biology, where he was operating too far from his base in history and cultural studies.
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