VIMP Report 24 - A geological interpretation of the geophysical data for the Horsham 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 As part of the Victorian Initiative for Minerals and Petroleum, in 1994 the north western part of the Horsham 1:250 000 map sheet area was flown with a high quality aeromagnetic survey. The survey complemented an earlier survey flown over the south eastern part of the area. This report gives the results of an interpretation of both data sets, in combination with gravity surveys and the geology from drill holes and extrapolated from elsewhere in the region. It contains the first comprehensive map of the Palaeozoic basement geology of the area. Another map shows the interpreted post-tectonic features. The magnetic basement of the Horsham 1:250 000 map sheet area has been subdivided into the Stawell Zone and the Glenelg Zone. To the east are the turbidites and oceanic basalts of the Stawell Zone. The rocks 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 north west. The boundary between the Stawell and Glenelg Zones is the northern extension of the Moyston Fault. A new geological and tectonic framework is proposed for the Glenelg Zone. It has been subdivided into the Dimboola, Miga and Ozenkadnook Subzones on the amounts and types of sedimentary and igneous rocks present, metamorphic grades and interpreted deformation histories. The Dimboola Subzone is mostly island arc rocks that have been weakly metamorphosed and simply deformed. The Miga Subzone includes both sediments and volcanics that have been variably metamorphosed and simply deformed. The Ozenkadnook Zone includes rocks that have been metamorphosed to amphibolite facies and show complex deformation. The rocks of the Glenelg Zone were deformed and intruded during the Late Cambrian to Early Ordovician Delamerian Orogeny. It is possible that the rocks of the Ozenkadnook Subzone were also deformed by an earlier orogenic event. The Stawell Zone was undeformed before the Late Silurian; at about this time the Grampians Group was deposited on the Glenelg Zone basement, in the Netherby Trough and further west. The Netherby Trough is a series of down thrown blocks which have largely moved on earlier basement faults in the Dimboola Subzone. Early Devonian granites intruded both the Grampians Group and the Stawell Zone, and may also have intruded other rocks further west than previously recognised. Middle Devonian granites may also be present. Many of the point magnetic sources have been attributed to ?Eocene basaltic plugs associated with the rifting of Antarctica. Almost the entire area is covered by a thin sheet of Murray Basin sediments. In the south eastern part of the Horsham 1:250 000 map sheet area depths range from 20 to 100 m, whilst in the north and west thicknesses of up to 300 m are present. The area contains several large heavy mineral sand deposits. No presently economic metalliferous mineral deposits are known, but exploration has been minimal. Gold could be targeted in the Stawell Zone, whilst the presence of arc volcanics of similar age to the Mt. Read Volcanics suggests potential for volcanic hosted massive sulfides. Other more speculative possibilities include diamonds and copper-gold deposits associated with A type granites. Bibliographic reference Moore, D.H., 1996. A geological interpretation of the geophysical data for the Horsham 1:250 000 map sheet area. Victorian Initiative for Minerals and Petroleum Report 24. Department of Agriculture, Energy and Minerals. Related products:
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