VIMP Report 39 - Geological interpretation of the geophysical data of the Ouyen 1:250 000 map sheet area
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Product description:Download The downloadable version of this report is supplied in PDF format. Abstract In 1994, as part of the Victorian Initiative for Minerals and Petroleum, the Ouyen 1:250 000 map sheet area was flown with a high quality aeromagnetic and radiometric survey. This report presents a geological interpretation which combines the new information with older gravity data and the geology from drill holes, and is consistent with the regional geology. It contains the first comprehensive maps of the Palaeozoic basement geology of the area, the interpreted post-tectonic features, and depths to basement computed from the magnetic data. The magnetic basement of the Ouyen 1:250 000 map sheet area has been divided into the eastern Stawell Zone and the western Glenelg Zone. The geological and tectonic framework established for the Glenelg Zone on the Horsham 1:250 000 map sheet area has been continued northwards. The boundary between the Stawell and Glenelg Zones is the northern extension of the Moyston Fault. On the Ouyen 1:250 000 map sheet area, the Glenelg Zone has been subdivided into the Dimboola, Upson and Ozenkadnook Subzones based on the interpreted rock units, metamorphic grades and deformation histories. The Dimboola Subzone is mostly oceanic island arc and ocean floor rocks that have been weakly metamorphosed and simply deformed. There is little information on the Upson Subzone, but it includes low grade metasediments and mafic volcanic rocks that have previously been correlated with the Kanmantoo Group. The Ozenkadnook Zone includes rocks that have been metamorphosed to amphibolite facies and show complex deformation. Other lower metamorphic grade rocks have been fault emplaced over the amphibolite grade rocks. The Glenelg Zone was deformed and intruded during the Late Cambrian to Early Ordovician Delamerian Orogeny. The Ozenkadnook Subzone may also have been deformed by an earlier orogenic event. The turbidites and oceanic basalts of the Stawell Zone are typical of much of the Lachlan Fold Belt in western Victoria, although more metamorphosed. They are weakly magnetic, with most trends striking north to northwest. The Stawell Zone was undeformed before about 440 Ma. The Grampians Group was deposited mostly on the Dimboola Subzone basement, in the Netherby Trough, some time between the end of the Delamerian Orogeny and the intrusion of ?400 Ma granites. These Early Devonian granites intruded both the Grampians Group and the Stawell Zone. The Netherby Trough also contains significant amounts of the Carboniferous to Permian Urana Formation. Many of the point magnetic sources have been attributed to Upper Cretaceous to Eocene basaltic plugs. The area is generally covered by from 200 m to 500 m of Murray Basin sediments. The shallowest parts are in southwestern and southeastern Ouyen 1:250 000 map sheet area, and the deepest parts cover the Netherby Trough. The present interpretation of the radiometric, magnetic and digital elevation data in the eastern part of the area shows a significantly larger area of Loxton-Parilla Sands than on previous maps. Both the Loxton-Parilla Sands and a younger palaeolake system show indirect evidence of late Cainozoic faulting. Recently RGC have announced the discovery of two potentially economic heavy mineral sand deposits east of the town of Ouyen. The area contains several small occurrences hosted by the Parilla Sand. No presently economic metalliferous mineral deposits are known, but there has been no exploration, probably because of the Murray Basin cover and a lack of understanding of the basement geology. Gold could possibly be targeted in the Stawell Zone. Copper-gold deposits may be associated with the intrusions in the southwest corner of the area. Bibliographic reference Moore, D.H., 1997. A geological interpretation of the geophysical data for the Ouyen 1:250 000 map sheet area. Victorian Initiative for Minerals and Petroleum Report 39. Department of Natural Resources and Environment. Related products:
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