Authors / CoAuthors
Blewett, R.S. | Goleby, B.R. | Heinson, G. | Henson, P.A. | Champion, D.C. | Roy, I.
Abstract
Our knowledge of the crustal architecture of the Yilgarn Craton has increased greatly over the last decade through the increased collection of a wide range of geophysical and geochemical/isotopic data sets. This range in data varies from: - lithospheric-scale studies using distant earthquakes as sources to obtain information on the entire craton down to depths in excess of 350 km, through; - regional-scale studies providing information at the province scale and down to depths of 30-40km, to; - mine- and camp-scale studies - providing information on the local-scale down to the top few kilometres of the crust. Receiver Function and broad-band teleseismic results map significant variations in crustal and upper mantle velocities across the Yilgarn Craton. The results are also providing information on potential velocity differences between the mineralized Kalgoorlie Terrane and the less mineralized Youanmi Terrane. An anomalous high velocity body (>4.8 km/s shear wave) occurs at around 100-120 km depth, and has steps and edges that correspond with mantle-derived magmas and the main gold camps. The fast velocity layer may represent mantle alteration (mapping a gradient), delaminated eclogite layer, or fossil oceanic slab? Maps of crustal age across the craton have been derived from ~250 analyses of granites of all ages. The Nd model age maps show that the granites were separated from the mantle at a range of ages from 3.6-2.7 Ga. Most ages are significantly older than the crystallisation age (200-300 My) so the crust was extensively recycled. The major changes in crustal age map the different terranes of the Yilgarn Craton and are leading to first order prospectivity for gold, nickel and base metals. Deep crustal seismic reflection studies have provided excellent 2D crustal architecture information in the eastern part of the craton, which in turn, have provided information on the region's mineral systems. These seismic data have imaged the numerous shear zones and are critical in defining the gross 3D architecture (maps) of the crust. Magneto-tellurics map the main boundaries of the Kalgoorlie Terrane. These data reveal that the prospective Kalgoorlie Terrane is special (in MT space), and is characterised by a highly conductive (graphite-bearing?) upper crust (along strike from the Super Pit) and a dome or 'upwelling' of conductive mantle beneath. Together these data provide first-order insights into the physical and chemical properties of the Yilgarn Craton. These insights provide geodynamic clues and constraints on why the Yilgarn is so well endowed.
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nonGeographicDataset
eCat Id
65330
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- GA PublicationRecord
- ( Theme )
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- geophysics
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- seismics
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- geomagnetism
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- geochemistry
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2007-07-16T00:00:00
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