An Appraisal of New Airborne Geophysical Data Over the Glenelg Region, North West VIMP Area, Victoria

VIMP Report 14

An appraisal of new airborne geophysical data over the Glenelg region, North West VIMP area, Victoria

K.R. Slater

November 1995 Bibliographic reference: SLATER, K.R., 1995. An appraisal of new airborne geophysical data over the Glenelg region, North West VIMP area, Victoria. Victorian Initiative for Minerals and Petroleum Report 14. Department of Agriculture, Energy and Minerals

ISSN 1323 4536 ISBN 0 7306 7984 5

Keywords: Geophysics, magnetics, radiometrics, Hamilton SJ 54-7 mapsheet, Glenelg, Glenelg Zone, Glenelg River Group, Cambrian greenstones, Ordovician granites, Devonian granites.

This report may be purchased from: Business Centre, Department of Agriculture, Energy & Minerals, Ground Floor, 115 Victoria Parade, Fitzroy, Victoria 3065

For further technical information contact: General Manager, Geological Survey of Victoria, Department of Agriculture, Energy & Minerals, P O Box 2145, MDC Fitzroy, Victoria 3065

Acknowledgments: The author wishes to thank Alan Willocks, Bruce Simons, Paul McDonald and Marc Hendrickx for discussions and editing provided for this report. Thanks also to Gayle Ellis for the formatting of this report and Sally Heeps and David Bibby for the diagrams. AIRBORNE SURVEY APPRAISAL - GLENELG 1

Contents

Abstract 3 1 Introduction 4 2 Previous geophysics 6 3 Survey specifications 7 4 Data preparation 8 4.1 Data processing 8 4.2 Products 8 Hardcopy 8 Digital data 8 4.3 Future work 9 5 Geological appraisal 10 5.1 Summary of geophysical responses of main lithological units 10 5.2 Cambrian 11 Glenelg River Group 12 Volcanics 12 5.3 Ordovician 12 Plutonic rocks 12 5.4 Devonian 14 Plutonic rocks 14 Rocklands Rhyolite 14 5.5 Jurassic 14 Coleraine Trachyte 14 5.6 Cretaceous 14 Merino Group 14 Penola Trough 14 5.7 Tertiary 15 Older Volcanics 15 Heytesbury Group 15 Dorodong Sands 15 Laterite 16 5.8 Quaternary 16 Newer Volcanics 16 Paludal sediments 16 Malanganee Sands 16 Palaeo and present day channels 16 6 Structure 17 6.1 Structural features of greenstones and granites 17 6.2 Faults, fractures and dykes 17 6.3 Penola Trough and Kanawinka Fault 18 7 Mineral prospectivity 19 8 Conclusions 20 References 21 Appendix 22 Status of VIMP airborne surveys Victorian Initiative for Minerals and Petroleum (VIMP) report series 23 2 AIRBORNE SURVEY APPRAISAL - GLENELG

List of Figures

1 Airborne survey coverage and locality map 5 2 Total magnetic intensity image (HSI) (back pocket) 3 Occurrences of greenstones, intrusions, rhyolite and trachyte in the Glenelg region (back pocket) 4 RGB radiometric image (back pocket) 5 Total count pseudocolour image (back pocket) 6 Potassium pseudocolour image (back pocket) 7 Thorium pseudocolour image (back pocket) 8 Uranium pseudocolour image (back pocket) 9 Location of VIMP airborne surveys (back pocket) 10 Major geological units (back pocket)

List of Tables

1 Airborne surveys conducted over the Glenelg region 6 2 Specifications of the Glenelg and Glenelg extension airborne surveys 7 3 Summary of geophysical responses of lithological units 11 AIRBORNE SURVEY APPRAISAL - GLENELG 3

Abstract In the west, radiometric data have weak responses, compared to the south and east which is dominated by high potassium and Detailed geophysical airborne surveys were thorium responses. Drainage channels show flown in western Victoria during 1994 and 1995 high potassium, reflecting the wide distribution for the Geological Survey of Victoria, as part of of granitic intrusions in the region. Granitic the Victorian Initiative for Minerals and intrusives, volcanic extrusives, trachyte and Petroleum North West Initiative project. rhyolite vary in potassium response. High thorium responses reflects laterite that caps The magnetic data reflect a complex geological most of the land surface in the east. setting, comprising moderate to intense Quaternary Malanganee Sands show a distinct magnetic and non magnetic intrusives and low radiometric signature. extrusives, non magnetic sediments and magnetic drainage patterns and strand lines. The Glenelg region offers opportunities for the A number of these features are cut, or bound exploration of base metal, gold, diamond, by, linear magnetic, non magnetic or mineral sand and coal deposits. crosscutting trends related to the structural character of the area. The magnetic data show the dominant structural direction, in common with other parts of Victoria, to be northwest to north-northwest. Numerous lineaments and faults accompanied by dykes, reflect the strong deformation which has influenced the Glenelg region.

Metasediments and sediments are typically non magnetic, and units cannot be distinguished from one another.

In the southwest of the Glenelg region, multiple, moderate to intense, curvilinear, discontinuous magnetic features with a northwest trend are associated with thin belts of near surface greenstones.

Significant variations in magnetic properties of granitic intrusions are apparent, and may aid in mapping and classifying these bodies. Major discrepancies between the mapped geology of the Harrow, Chetwynd River and Dergholm granites are indicated from interpreted boundaries from the magnetic data.

Many intrusions display northwest, north- northwest, north-northeast, northeast and east- northeast lineations represented typically by magnetic lows. These lineations maybe be due to faults, joints or quartz veining within the intrusions.

The Rocklands Rhyolite has a variable magnetic response. The magnetic data can be related to different flows.

Small high frequency magnetic responses scattered throughout the Glenelg region, interpreted to be Tertiary basalts, are represented by plugs and lava flows. 4 AIRBORNE SURVEY APPRAISAL - GLENELG

1 Introduction

This report presents an appraisal of new detailed airborne magnetic and radiometric data obtained over the Glenelg region (Fig. 1). It outlines the survey operations, presents preliminary results from the surveys, and provides a brief discussion of regional features identified in the new data.

The Glenelg and Glenelg extension surveys (GLENELG) were flown in the Glenelg region of western Victoria during 1994 and 1995 for the Geological Survey of Victoria (GSV). These surveys were conducted as part of the Victorian Initiative for Minerals and Petroleum (VIMP). GLENELG cover parts of the Edenhope, Balmoral, Casterton and Coleraine 1:100 000 mapsheets. The surveys were flown east-west, and acquired total magnetic intensity and radiometric data.

Images of the total magnetic intensity (TMI) and radiometric (RGB), total count, potassium, uranium and thorium are presented in Figures 2, 4-8. The TMI image comprises data from Glenelg and Glenelg Extension, Cavendish, Horsham and Otway Basin surveys as a composite image. Figure 3 is an interpretation of occurrences of greenstones, intrusions, rhyolite and trachyte in the Glenelg region. Potassium, thorium and uranium data are presented as K %, eTh ppm and eU ppm respectively.

As a result of VIMP, the whole of the North West Initiative area has now been covered by detailed, high quality airborne surveys (Fig. 9). Geological mapping, data compilation and mineral resource assessment are also being undertaken as part of VIMP. The objective of the work in the Glenelg region is to promote mineral exploration in the region. The data from these surveys will allow for a detailed geological interpretation and assessment of the prospectivity of the area. Geophysical surveys being undertaken as part of VIMP are outlined in the Appendix.

6 AIRBORNE SURVEY APPRAISAL - GLENELG

2 Previous geophysics Two geophysical airborne surveys, flown in the 1980's by CRA Exploration (CRAE), covered parts of the Glenelg region. These surveys, Airborne surveys conducted over the Glenelg Cavendish and Horsham, collected total region are presented in Table 1. magnetic intensity and radiometric data, and were flown east-west. A 1974 regional airborne survey was flown by the Bureau of Mineral Resources (BMR, now Gravity coverage of the Glenelg region is poor, the Australian Geological Survey Organisation with 1018 gravity stations collected between - AGSO) with a line spacing of 10 kilometres 1949-1980 by the BMR. Regional gravity and an altitude of 460 m. During 1989, a surveys by the GSV collected an additional 2000 regional airborne survey was flown for the GSV gravity stations over the Edenhope and in conjunction with the BMR. This survey was Balmoral 1:100 000 mapsheets during 1995. flown east-west with a line spacing of 1500 m These data will be released in November 1995. and an altitude of 100 m. The new survey data presented here, supersede the 1974 and 1989 data in the Glenelg region.

Table 1 Airborne surveys conducted over the Glenelg region

GSV Survey Survey Operator Contractor Year Line Altitude Direction survey name type spacing (AGL) number

118 Horsham- TMI BMR BMR 1974 10 000 m 460 m East-west Hamilton 193 Horsham TMI/Rad CRAE Geosearch 1980/81 250 m 80 m East-west 238 Casterton TMI/Rad CRAE Austirex 1983 250 m 80 m East-west 362 Otway Basin TMI/Rad GSV/BMR Kevron 1989 1500 m 100 m East-west 363 Cavendish TMI/Rad CRAE Austirex 1989 250 m 70 m East-west 3053 Glenelg TMI/Rad GSV World 1994/95 200 m 80 m East-west Geoscience 3055 Glenelg TMI/Rad GSV World 1995 200 m 80 m East-west extension Geoscience AIRBORNE SURVEY APPRAISAL - GLENELG 7

3 Survey specifications Flight path navigation data was acquired using GPS satellite positioning. Detailed magnetic and radiometric data was The magnetic data were acquired using a split acquired for the GSV in the Glenelg region by beam Caesium Scintrex V201. The radiometric World Geoscience Corporation Ltd, using data were collected with a 33.56 litre, 256 Cessna Stationair U206G fixed wing aircraft channel spectrometer. (VH-AZG and VH-UPK). The Glenelg survey was flown during October-November 1994, and The Glenelg extension survey contains a small Glenelg extension flown in April 1995. Some hole in the data due to aviation regulations additional flying to complete the contract for prohibiting flying over the town of Coleraine. the Glenelg survey, was undertaken in July The VIMP Glenelg surveys were flown adjacent 1995. The specifications of the Glenelg and to and overlapping the CRAE Horsham and Glenelg extension surveys are shown in Cavendish surveys. Table 2. GLENELG was flown at a line spacing of 200 m and an altitude of 80 m.

Table 2 Specifications of the Glenelg and Glenelg extension airborne surveys

Glenelg Glenelg extension

Location North west Victoria (Fig. 1) North west Victoria (Fig. 1) Client Geological Survey of Victoria, Department of Geological Survey of Victoria, Department of Agriculture, Energy & Minerals, Victoria Agriculture, Energy & Minerals, Victoria Contractor World Geoscience Corporation Ltd World Geoscience Corporation Ltd GSV number 3053 3055 Survey area 1:100 000 mapsheets 7123, 7223 (Edenhope, 1:100 000 mapsheets 7122, 7222 (Casterton Balmoral) and Coleraine) Date of survey October-November 1994, July 1995 April 1995 Kilometres flown 15 752 km 5 875 km Total area covered 3 210 km2 1 053 km2 Flight line direction East-west East-west Flight line spacing 200 m 200 m Tie line direction North-south North-south Tie line spacing 2000 m 2000 m Flying height 80 m above ground level 80 m above ground level Navigation GPS satellite positioning GPS satellite positioning Ground base station based at 142° 2' 58.74"E Ground base station based at 142° 2' 58.74"E 37° 44' 41.8"S 37° 44' 41.8"S Aircraft Cessna Stationair U206G fixed wing aircraft Cessna Stationair U206G fixed wing aircraft (VH-AZG and VH-UPK) (VH-UPK) Data acquisition 11 channel RMS GR33A 11 channel RMS GR33A chart recorder chart recorder Picodas PDAS 1000 digital acquisition system Picodas PDAS 1000 digital acquisition system Magnetometer Split Beam Caesium Scintrex V201 Split Beam Caesium Scintrex V201 (± 0.001 nT resolution) (± 0.001 nT resolution) Time sample interval 0.1 second 0.1 second Sample interval 7 m 7 m Gamma spectrometer 33.56 litre, 256 channel ENMOS 1000 33.56 litre, 256 channel ENMOS 1000 Time sample interval 1.0 second 1.0 second Sample interval 70 m 70 m 8 AIRBORNE SURVEY APPRAISAL - GLENELG

4 Data preparation 1:250 000 scale products: Flight path maps; 4.1 Data processing Total magnetic intensity profiles; Total magnetic intensity contours (20 nT The data processing was undertaken by World contour interval); Geoscience Corporation Ltd. Total count radiometric contours (100 cps contour interval); The magnetic data has been corrected for Potassium contours (0.02 K % contour regional gradient by subtraction of IGRF model interval); 1990 and secular variation model 1990-1995. Thorium contours (1.0 eTh ppm contour Diurnal magnetic variations and system interval); parallax have been removed, and microlevelling Uranium contours (0.5 eU ppm contour has been applied. Two Geometrics, model interval). G856A magnetometers were located at Hamilton airport, sampling at 5 seconds, to 1:100 000 scale black and white products: record the diurnal variation. Inclination and declination were computed continuously over Flight path maps; the whole area using IGRF model 1990 Total magnetic intensity profiles; computed separately for each survey (World Total magnetic intensity contours (5 nT Geoscience Corporation Ltd, 1994). contour interval).

The gamma spectrometric data processing has 1:100 000 scale colour products: involved correcting for instrument deadtime, cosmic and aircraft background, Compton Total magnetic intensity contours (1 nT scattering, height corrected to an altitude of contour interval); 80 m, and stripping to give counts per second Total count radiometric contours (25 cps for potassium, bismuth and thallium (K-40, contour interval); Bi-214, and Tl-208 respectively). These data Potassium contours (0.02 K % contour were converted to K %, eTh ppm and eU ppm interval); using calibration data from the calibration Thorium contours (0.5 eTh ppm contour range at Burkitt Hill, South Australia. interval); Uranium contours (0.5 eU ppm contour 4.2 Products interval); Total magnetic intensity with relief shading Hardcopy image (pseudocolour and greyscale); Total magnetic intensity with AGC enhancement image (greyscale); The following maps, profiles and images are First vertical derivative of total magnetic available for the Glenelg and Glenelg extension intensity image (pseudocolour and surveys from the GSV. The hardcopy products greyscale); conform to the standard 1:250 000, 1:100 000 Total count radiometric image; and 1:25 000 mapsheets. Black and white Radiometric ternary RGB image. products are available as paper or transparent copies, and colour products on paper. 1:25 000 scale black and white products: RGB (red, green, and blue) ternary images of Flight path maps; the radiometric data represent the potassium, Total magnetic intensity profiles; thorium and uranium radiometric channels Total magnetic intensity contours (1 nT respectively in a composite image. contour interval). In addition to individual items, various sets of the data are available, including complete Digital data datasets for individual 1:100 000 and 1:25 000 mapsheets. The processed located data, TMI, first vertical derivative, digital terrain model, total count, potassium, thorium and uranium grids, are available in digital format. Digital regional AIRBORNE SURVEY APPRAISAL - GLENELG 9

geological data and current exploration licence boundaries are also available.

The located line data were gridded with a 50 m piecewise bicubic spline mesh, supplied as ERMapper grids to the GSV by World Geoscience.

The data is provided on a 5 gigabyte Exabyte tape containing the following information:

Located TMI and radiometric data: ASCII format;

TMI, first vertical derivative, digital terrain model and four radiometric grids (50 x 50 m): ERMapper format.

In addition, a composite MAP INFO dataset is available comprising magnetic and radiometric grid data, geology, exploration licence boundaries, mineral title history, mineral occurrences, geochemical surveys, boreholes, roads, drainage, towns, 1:100 000 mapsheet boundaries, and National Parks.

4.3 Future work

A detailed geological interpretation of the geophysical datasets will be undertaken by the GSV during 1996.

It is anticipated that geological mapping will be undertaken on the Hamilton 1:250 000 mapsheet by the GSV during 1997. 10 AIRBORNE SURVEY APPRAISAL - GLENELG

5 Geological appraisal Tertiary and Quaternary (Older and Newer Volcanics respectively). This geological appraisal has been prepared to accompany the data release for the VIMP 5.1 Summary of geophysical Glenelg and Glenelg extension airborne surveys responses of main as a first look at the newly acquired data. The lithological units quality and detail present in the data indicate that more information than that presented The detail in the TMI (Fig. 2) and the here, can be extracted. radiometric data (Figs 4-8) highlights a number The geological history outlined in this report is of areas where the geological map needs summarised from Bush et al., 1995, and revising. Limited bedrock exposure makes provides a geological perspective for the surface mapping difficult. The data provide a geophysical appraisal. better understanding of the relationship between the various units. The magnetic image The Glenelg region covers part of the reflects a complex geological setting, and westernmost Palaeozoic zone of Victoria, the consists of northwest trending highly magnetic, Glenelg Zone (Gray, 1988). This zone probably thin, curvilinear features; large zones of represents an equivalent of the Kanmantoo magnetic highs and lows; and regions of high Group of South Australia. Recent work frequency, high relief magnetic responses (Figs suggests the easternmost boundary of the 2 & 3). A number of these features are Kanmantoo Fold Belt lies east of the terminated, or bound by, linear magnetic, non Grampians Ranges, ie. east of the Glenelg magnetic or crosscutting trends relating to the region (R. Cayley, Geological Survey of Victoria, structural character of the survey area. A pers. comm. September, 1995). summary of the magnetic responses of interpreted lithological units is presented in The Glenelg region is a geologically complex Table 3. area, with a history commencing in the Early Cambrian, or possibly Late Proterozoic with a Palaeozoic metasediments and Mesozoic period of volcanism followed by the deposition sediments in the Glenelg region have a low of deep marine sediments on oceanic crust. magnetic response. Numerous Cambrian The sediments were deformed and greenstone belts are apparent in the magnetic metamorphosed to lower greenschist facies and data as intense, thin curvilinear features. The intruded by granites during the Late Cambrian magnetic data is dominated by high and low - Early Ordovician Delamerian deformation. amplitude, long wavelength signatures from Subsequent compression during the Ordovician and Devonian granitic intrusives. Delamerian deformation produced northwest Devonian and Jurassic extrusive volcanics have directed thrusts. Intrusion of Devonian a high frequency and variable amplitude granitoids was followed by volcanism magnetic responses. Normal and reversely represented by the Rocklands Rhyolite. Glacial magnetised volcanics suggest at least two sediments deposited during the Permian were episodes of volcanic activity. followed in the Jurassic by volcanism represented by the Coleraine Trachyte. The radiometric data (Fig. 4) is characterised by high thorium values in the east, dominated by Parts of the southern margin of the Murray potassium in the south, and low values in the Basin, and the northern margin of the Otway west, except along the Glenelg River where Basin are within the Glenelg region. Cainozoic there are high potassium responses. sediments of the Murray Basin and Otway Basin overlie Palaeozoic sediments and A detailed interpretation of lithological units is volcanics of the Kanmantoo Fold Belt. The described in sections 5.2 to 5.8. Penola Trough, on the northern margin of the Otway Basin was formed during the initial rifting phase of the Otway Basin. Extensive laterisation of the land surface occurred during the Tertiary. Since the Early Mesozoic the area has been uplifted and eroded, with occasional outpourings of alkali basalt lavas during the AIRBORNE SURVEY APPRAISAL - GLENELG 11

Table 3 Summary of geophysical responses of lithological units

Age Unit Magnetic response Radiometric response

Cambrian Glenelg River Group Low, not distinguished due to Indistinct absence of contrast with other sediments Volcanics High - intense, thin units, Low curvilinear in a northwest trend

Ordovician Padthaway Batholith Moderate - high, and non Subsurface magnetic Dergholm Granite Non magnetic, moderate - High K, low - moderate high, multiple intrusions Th and U Ferres Creek Granite Low - high High K, moderate Th and U Wando River Granite Moderate - high High Wando Vale Granodiorite Moderate High K, low Th and U Harrow Granite Moderate - high, jointing and High faulting shown by lows Chetwynd River Granite Moderate - high, joints and High faults shown by lows

Devonian Konong Wootong Granite Moderate - high High Hassalls Creek Granite Moderate - high High Rocklands Rhyolite Low - high Indistinct

Jurassic Coleraine Trachyte Low - high High

Cretaceous Merino Group Low High K, low Th and moderate U

Tertiary Older Volcanics Normal and reversely Indistinct magnetised dykes; typically circular or dendritic in pattern Dorodong Sands Low, except strand lines of Low moderate response Heytesbury Group Low Low - moderate Laterite Low Low - moderate K, high Th, moderate - high U

Quaternary Newer Volcanics Moderate Low Alluvial terraces and Low Low lagoon and swamp deposits and dune sand Palaeo and present day Low - moderate Low channels 12 AIRBORNE SURVEY APPRAISAL - GLENELG

5.2 Cambrian typically moderately magnetic (Figs 2 & 3). The granite numbers (GN) refer to a numbering Glenelg River Group system used in Geology of Victoria (White & Chappell, 1988). Within the Glenelg Zone, Cambrian marine Variable magnetic responses shown by sandstone and siltstone have been intrusions are consistent with zoning, and metamorphosed to biotite and staurolite schist different phases of magma generation. Low (Fig. 10). Areas of low, uniform magnetic magnetic signatures associated with the response (Fig. 2) correspond to metamorphic intrusives are interpreted to be non magnetic rocks and sediments. The similar magnetic and phases within the plutons. In addition, thin, radiometric response of the Glenelg River linear magnetic lows are present, interpreted to Group and other sediments makes them be alteration along joints and faults, or quartz difficult to distinguish. veining.

Volcanics Short wavelength, high frequency magnetic signatures often superimposed on magnetic A series of moderate to intense curvilinear, signatures of intrusions, are interpreted to be discontinuous magnetic features dominate the overlying Tertiary volcanic rocks. The southwest of the region. They form a northwest boundaries of granites are often difficult to trending zone approximately 15 kilometres delineate due to these volcanic rocks. Magnetic wide and 70 kilometres long (Fig. 2). The thin, drainage patterns, strand lines and magnetic curvilinear, highly magnetic character of these units produce signatures that mask subtle units, suggests they are caused by bands of features in granitic intrusions. near surface greenstones. One of these magnetic highs coincides with the Hummocks Padthaway Batholith Serpentinite (Figs 3 & 10), a greenstone mapped west of Wando Vale. Outcrops of A suite of Early Ordovician post-tectonic greenstones are limited in extent. The intrusives are exposed along the Padthaway greenstones that crop out in the Glenelg region Ridge from Kanmantoo in South Australia, to comprise albitised basic lavas, serpentinite, Dergholm in western Victoria. peridotite, metabasalts, amphibolites, chert and The Padthaway Batholith is a large magnetic shale (Geological Survey of Victoria, 1994). The intrusion in the northwest (Figs 2 & 3). It magnetic data (Fig. 2) show a much greater consists of at least three intrusions and covers a distribution of subsurface greenstones, large portion of the Edenhope 1:100 000 compared with geological mapping (Fig. 10) and mapsheet and extends into South Australia do not have a characteristic signature in the (Fig. 10). To the south the batholith has been radiometric data. intruded by a non magnetic pluton. The variable magnetic character of the batholith Numerous northeast trending cross-cutting may represent numerous intrusions or zoning faults disrupt these magnetic units. These within the batholith. The batholith is fault magnetic features are similar to the magnetic bound to the east. In the south this granite has character seen over greenstones elsewhere in been mapped as the Dergholm Granite. Victoria such as Heathcote and Mt Stavely (Simons et al., 1992). Dergholm Granite (GN424)

5.3 Ordovician The boundaries of the Dergholm Granite as depicted on the Hamilton 1:250 000 map Plutonic rocks (Geological Survey of Victoria, 1994) and Figure 10, do not coincide with those derived from the Granite bodies of Early Ordovician age intrude magnetic data (Figs 2 & 3). The magnetic data the Glenelg River Beds within the Glenelg indicates that the mapped Dergholm Granite region. Intrusions comprise granites, corresponds with multiple intrusions of granodiorites, tonalites, monzonites and different magnetic character, and as such, gabbros (Anderson and Gray, 1994, Ferguson, indicates separate granites. 1993, Kemp, 1995). They exhibit a variety of magnetic characteristics ranging from non In the northwest where the mapped Dergholm magnetic to intensely magnetic, but are Granite crops out, the magnetic data indicates AIRBORNE SURVEY APPRAISAL - GLENELG 13

that it should be considered part of the Outcrops of the Wando River Granite (Fig. 10) Padthaway Batholith. coincide with these northern and southern magnetic features. The Dergholm Granite as mapped coincides with a roughly circular non magnetic feature. Wando Vale Granodiorite (GN422) Other outcrops of the Dergholm Granite correspond with a roughly circular, moderately West of the Wando Vale River intrusions, three magnetic signature. This indicates that the small, circular to elongate features of variable Dergholm Granite is at least two separate magnetic response, trend northwest (Figs 2 & intrusions. The Dergholm Granite does not 3). Outcrops of the Wando Vale Granodiorite display the fracturing observed in the coincide with the southern magnetic response. Padthaway Batholith. Magnetic data show this pluton to be fault bound to the northwest and southeast. The Future mapping of the granite can be greatly granite is non magnetic with a magnetic rim. improved from the magnetic data. The central feature is non magnetic with a Ferres Creek Granite (GN423) magnetic rim. Magnetic data show the pluton to be fault bound to the northwest and Adjacent to the eastern margin of the southeast. Padthaway Batholith, is a "D" shaped magnetic feature (Figs 2 & 3). This feature coincides The pluton in the north has variable magnetic with the Ferres Creek Granite (Geological character. It displays a magnetic core, a non Survey of Victoria, 1994 and Fig. 10). Outcrops magnetic outer core, and a magnetic rim. It is are limited to parts of the Glenelg River, Ferres interpreted as representing multiple intrusions Creek and tributaries south of Ferres Creek. or a zoned granite. Magnetic responses on the Monzonite, quartz diorite, and gabbro have rim may represent a magnetic contact been noted by Ferguson (1993). metamorphic aureole. The pluton is elliptical in From the magnetic data and geological a northwest direction possibly associated with mapping, the inner core, of low magnetic the regional northwest grain. response is interpreted to be quartz diorite, and the outer high magnetic responses interpreted Harrow Granite (GN407) and the Chetwynd to be gabbro. Magnetic data show the pluton is River Granite (GN408) fault bound to the north, south and west. The mapped boundaries of the Harrow and Wando River Granite (GN421) Chetwynd River granites are shown in Figure 10. The Harrow and Chetwynd River granites Two magnetic features are seen in the Wando have been mapped as two large bodies that crop Vale area in the south of GLENELG, that have out in creeks and tributaries. The magnetic similar magnetic characteristics (Figs 2 & 3), data (Fig. 2) indicate major discrepancies and show potassium highs in creeks and between the mapped geology and interpreted tributaries (Figs 4 & 6). boundaries from the magnetic data. The magnetic data indicate a very different The northern magnetic feature is oval shaped, distribution of granites compared to what has trending east-west and comprises two been mapped (Geological Survey of Victoria, intrusions. The western pluton which has a 1994). Magnetic data indicates that there are lower magnetic response than the eastern more than two intrusions characterised by pluton is a roughly circular moderate magnetic different magnetic responses. high. Faulting along the western side of the body has produced a 'lobe' effect. The eastern A variety of magnetic intrusives, trending pluton is a roughly circular magnetic high that north-northwest to northwest occur in the cross-cuts the eastern edge of the western central part of GLENELG (Fig. 2). Some of pluton and therefore intruded at a later stage. these intrusives show numerous magnetic lows with a linear pattern. Trending northwest, The southern feature is a roughly circular north-northwest, north-northeast, northeast magnetic high. A rapid change in magnetic and east-northeast, they represent faulting and gradient shows the pluton to be fault bound to jointing, or quartz veining. the west. 14 AIRBORNE SURVEY APPRAISAL - GLENELG

To the east, is a large magnetic high trending margins of the zone show higher magnetic north-northwest to north-south (Fig. 2). The responses, which are thin and sometimes north-south Yarramyljup Fault cuts this curvilinear. Linear features do not crosscut the feature (Fig. 3). zone implying that the Rocklands Rhyolite postdates these structures. Possible Ordovician plutons The Rocklands Rhyolite is a densely welded A non magnetic granite occurs east of the rhyolitic ignimbrite often displaying flow bands Padthaway Batholith, and has magnetic highs (Geological Survey of Victoria, 1994). on it's margin (Figs 2 & 3). Geological mapping has identified a variety of lavas, including ignimbrites and volcaniclastics, In the east of GLENELG, an oval shaped latites and quartz-feldspar lavas (C. Simpson, magnetic low is interpreted to be a non Melbourne University, pers. comm. September magnetic granite (Figs 2 & 3). 1995).

Arcuate magnetic high signatures surrounding The rhyolite has high magnetic and non these non magnetic granites may represent magnetic responses indicating different units or magnetic contact metamorphic aureoles (Fig. 3). flow regimes present within the formation. The Often the aureoles are discontinuous, possibly magnetic highs on the margins of the body may due to radial fractures and the destruction of due to a magnetic basal unit of the rhyolite magnetite along shear zones. Metamorphic possibly comprising andesites and latites. aureoles have not been identified by field mapping. 5.5 Jurassic

5.4 Devonian Coleraine Trachyte

Plutonic rocks In the south of GLENELG, the magnetic image shows an area of magnetic highs (Fig. 2) some Several granite bodies of Devonian age intrude of which coincide with mapped Coleraine the Glenelg River Group within the Glenelg Trachyte (Fig. 10), an extrusive sanidine - region (Fig. 10). bearing trachyte lava (Geological Survey of Victoria, 1994). Similar magnetic signatures In the south of the Glenelg region, outcrops of extending south of the Sawpit Gully Granite in the Konong Wootong Granite (GN420) and the east, to the northern part of the Konong Hassalls Creek Granite (GN409) (Geological Wootong Granite, are interpreted as trachyte. Survey of Victoria, 1994), coincide with high magnetic responses trending north-northwest 5.6 Cretaceous (Fig. 2). The body is obscured by the magnetic response of the Jurassic Coleraine Trachyte Merino Group (Fig. 3). The magnetic data indicate a different distribution to that of the mapped granites. Moderate to high total count responses west of the Wando Vale area, coincide with the mapped The Hassalls Creek Granite has a low thorium Merino Group. In other areas where this group response (Fig. 7), and this can be used to map has been mapped, the potassium channel the surficial granite outcrop. dominates the radiometric image. The potassium high is most likely to be the response Rocklands Rhyolite from potassic clays of the Merino Group (Fig. 4).

In the east of the Glenelg region is a zone that Penola Trough shows a variety of magnetic responses corresponding with the mapped Rocklands The Otway Basin is an Early Cretaceous to Rhyolite (Figs 2, 3 & 10). The zone trends Tertiary rift basin, consisting of fluvial to north-northwest to north-south. In the north of marine mudstone, sandstone, siltstone and coal this zone, magnetic responses are typically and Tertiary basalts (Wopfner et al., 1971). The smooth and broad. The responses in the Penola Trough is the northern part of the southeast of this zone, are more complex, Otway Basin, and forms the southwest corner of having high frequencies and amplitudes. The the Glenelg region. The Penola Trough is an AIRBORNE SURVEY APPRAISAL - GLENELG 15

Early Cretaceous elongate structure extending trend northwest, northeast and north- from western Victoria into South Australia. northeast. They are typically 200-400 m wide, with strike extents of 2-5 kilometres. The basal part of the Penola Trough generally comprises an alternating sequence of basalts, Dendritic patterns in the magnetic data tuffs and weathered or altered volcanics with represent basalt flows that have infilled valleys. intervals of mudstone, sandstone, siltstone, Other responses in the central part of shale and coal (Casterton Formation). The GLENELG are circular in shape and represent periodic influx of locally derived volcanic debris volcanic plugs and dykes. Thick accumulations is associated with the first stages of rifting. The of the Older Volcanics northwest of Dergholm varieties of magnetic sources present are are interpreted to be due to the extrusion of derived from Cainozoic volcanics, fault-related basalts into the Murray Basin. sources (such as basic dykes), and Jurassic volcanics. Pre-Mesozoic basement lithologies Numerous bulls-eye high magnetic signatures are also evident in the magnetic images. are visible in the data along the southern margin of the Murray Basin, showing through In the magnetic data, the Penola Trough is thin Tertiary fluvial and marine cover shown to be bound to the northeast by a series sequences. Some of these responses have been of faults (Fig. 3). The magnetic data show a drilled by CRAE and have been identified as largely non magnetic basement comprising mostly alkali-rich basic intrusives and volcanic metasedimentary phyllitic rocks. Major faults breccia pipes of nephelinite-basalt-basinite - or basement highs characterised by magnetic fiodite series, and their igneous equivalents highs define the northern extent of the Penola such as diorite and gabbro (Bush et al., 1995). Trough. Faults or zones of weakness trend in a north-northwest direction, and may represent Heytesbury Group intra-sedimentary horizons within the Penola Trough. Major fault orientations are northwest In the southwest of the Glenelg region, a thin, with several east-west trends also apparent. northwest trending feature is seen in the radiometric data (Figs 4-8). Adjacent to a 5.7 Tertiary northwest trending fault, this feature has low to moderate total count, potassium and thorium Older Volcanics responses, and a moderate to high uranium response. Geological mapping of the High frequency, high amplitude, bulls-eye Heytesbury Group coincides with these magnetic signatures are widely distributed responses. across GLENELG (Fig. 2). These signatures are interpreted to be Older Volcanics The Heytesbury Group is of Miocene-Oligocene comprising tholeiitic and minor alkaline age, comprising polyzoal marl and marly basaltic lavas and plugs (Geological Survey of limestone (Geological Survey of Victoria, 1994). Victoria, 1994). Isolated mapped outcrops along It has a non magnetic response and cannot be sections of the Glenelg River, Chetwynd River identified in the magnetic data. and Steep Bank Rivulet, coincide with magnetic highs. The magnetic data suggest that the Dorodong Sands volcanics are more extensive than presently shown by the geological map. Mapped Dorodong Sands show radiometric responses of moderate total count and Different flows of basalt are evident with potassium, and low uranium (Figs 5-8). The normally polarised and reversely polarised Dorodong Sands are Pliocene in age, and magnetic signatures apparent. consist of ferruginous sandstones, sand, grit, fine conglomerates, clays and ironstone Linear magnetic trends most likely reflect (Geological Survey of Victoria, 1994). The significant dyke emplacement over the Glenelg sands can be distinguished from the region. Within GLENELG dykes sometimes Malanganee Sands by their higher radiometric overprint some of the broad magnetic features. response. The dykes are generally narrow, continuous, straight, and consistent in magnitude and Curvilinear magnetic signatures are shape throughout their length. Dykes typically interpreted to be strandlines, representing palaeo-beach deposits. Trending north-south to 16 AIRBORNE SURVEY APPRAISAL - GLENELG

south-southwest, their strike extents are northwest, which show a higher potassium discontinuous. The strand lines overprint the response. In the southwest of the region magnetic responses and are suspected to be mapped paludal sediments cannot be Late Miocene to Early Pliocene in age that distinguished from the radiometric data. corresponding to the receding sea of the Murray Basin to the northwest (Lanzer, 1991). Malanganee Sands

Laterite Areas of low radiometric responses in the west of the Glenelg region coincide with mapped Radiometric images (Figs 4-7) show a marked Quaternary Malanganee Sands. These sands change in response trending north-northeast in consist of aeolian sediments of coastal and the Glenelg region. The east is dominated by inland dunes. Similar radiometric responses in moderate to intense responses reflecting the northwest of the region are interpreted to laterite cover, granite either cropping out, or represent a similar lithology, which have not subcropping. High thorium responses trend been mapped. The Malanganee Sands are non northeast and correspond with laterite. In the magnetic. west, except for the rivers and creeks, the radiometric data shows low to moderate Palaeo and present day channels responses of the sediment cover. Numerous moderate magnetic highs coincide Laterite is of Pliocene-Pleistocene age and with current drainage in GLENELG. Dendritic exhibits a non magnetic response and cannot be drainage patterns are present in the magnetic distinguished from non magnetic sediments and data in the northeast and south of GLENELG. metasediments. Prominent signatures, superimposed on intrusives, strike north-south, whereas others 5.8 Quaternary are smaller in length and more sinuous. The source of these is currently unknown, but Newer Volcanics probably result from magnetic detritus, possibly maghemite related to local pisolitic laterite High frequency magnetic responses, with a development. wide range of amplitudes, occur in the southeast corner of the Glenelg region (Fig. 2). The radiometric signature of the present day The features display characteristic high channels usually reflect the radiometric frequency and high amplitude signatures. signature of the weathered rocks or clays which are being transported. Many of the drainage The Newer Volcanics which crop out are the systems in GLENELG show up as potassium source of these magnetic signatures. They highs in the radiometrics where they occur in comprise valley filling tholeiitic to alkaline areas of high potassium granites where they basalts, scoria and ash (Geological Survey of either crop out or occur near surface. Victoria, 1994). They are less magnetic than the Older Volcanics.

Sinuous magnetic responses south of Coleraine coincide with volcanic flows occurring close to the present day Wannon River. The flows when extruded probably followed a prior river course.

The Newer Volcanics have a low radiometric response (Fig. 4).

Paludal sediments

Areas of moderate total count responses and moderate to high potassium responses in the northwest of the region coincide with mapped Quaternary paludal sediments. They can be distinguished from the Dorodong Sands in the AIRBORNE SURVEY APPRAISAL - GLENELG 17

6 Structure 6.2 Faults, fractures and dykes

The Glenelg region has a complex structural Cross-cutting linear magnetic discontinuities history which is reflected in the geophysical displaying northwest, north-northwest and data. The earliest known event was a period of northeast orientations are widespread. These compressional deformation during the trends are associated with faulting, fracturing, Delamerian deformation which resulted in jointing, or quartz veining. The intensity of metamorphism and the emplacement of faulting and fracturing in the Glenelg region greenstones. Thrusting of the Grampians east increases from southwest to northeast, of the Glenelg region occurred possibly during coinciding with increasing grade of the Late Silurian to Early Devonian (Bush et metamorphism. In the magnetic data, faults al., 1995). The correlation of the various faults show up as offsets of other magnetic features seen in the geophysical data with the various and as abrupt, near linear, changes in magnetic deformational events which have influenced the response and texture. Fracture systems often Glenelg region will form part of a more detailed appear as bands of low magnetic responses. interpretation. Numerous linear magnetic trends coincide with dykes which have intruded along lines of 6.1 Structural features of weakness, often parallel to the regional structural trend. greenstones and granites Faults identified in the magnetic data often The major structural trend in the Glenelg have a topographic expression. It is suggested region is a northwest-southeast direction, which that a system of northeast and northwest is exhibited in the various magnetic signatures trending faults controls the course of many of of greenstones, the Padthaway Ridge, many of the drainage systems. For example the the intrusive complexes, faults, fractures and magnetic data suggests faulting causes the joint sets. The greenstones were emplaced by abrupt change in direction of Red Cap Creek thrusting during the Delamerian deformation. west of Wando Vale. As previously discussed these appear on the TMI data as curvilinear high magnetic Many of the faults interpreted from the signatures, which suggests the presence of magnetic data, coincide with changes in the arcuate northwest trending thrust-planes radiometric character. This radiometric which extend beneath the western Murray character probably reflects the influence of the Basin to the west as far as Dergholm. These faulting on the topography. A package of high belts are often offset by northeast trending thorium signatures in the east of GLENELG breaks in the magnetic data, probably appear to be linearly banded with low representing minor strike-slip faults. radiometric responses. This area has been mapped as extensive laterite and Ordovician The Ordovician and Devonian granitic granites where creeks have been incised intrusives often show magnetic trends (Geological Survey of Victoria, 1994). This may consistent with fracturing and jointing. From represent reactivation of faults or movement the magnetic data, pluton emplacement within along joint planes at a later stage. the Glenelg region has often been accommodated by brittle faulting and jointing The magnetic data shows jointing and with some of these fractures extending into the fracturing to be generally broad lows due to country rocks. Sharp contacts often occur in lower magnetic responses than the surrounding the magnetic data between plutons and the rocks. This lower magnetic response is country rock. Bounding the eastern margin of probably due to demagnetisation within the the Padthaway Batholith is a major north-south fractures. The linear features associated with trend, interpreted as a fault extending south to joints have low magnetisation, limited length, the greenstones. The Penola Trough in the do not displace lithological layering, and southwest does not appear to be affected by this generally form sets of subparallel low magnetic structure and therefore the fault is interpreted signatures. These can generally be mapped to be pre- Jurassic in age. In the Harrow only in areas of high magnetic responses. Granite there are northeast, northwest and north-northeast magnetic trends associated with jointing. 18 AIRBORNE SURVEY APPRAISAL - GLENELG

6.3 Penola Trough and Kanawinka Fault

A period of extension occurred during the Late Jurassic - Early Cretaceous as a result of separation of the Australian and Antarctic continents. This formed the Penola Trough in the southwest of the Glenelg region, as a fault bound half-graben. In the Glenelg region the northern margin of the Penola Trough is bound by the south dipping, normal Kanawinka Fault (Perincek et al., 1994). The magnetic data shows the Kanawinka Fault (Figs 2 & 3) defined by thickening of sediments to the south resulting in a reduction in magnetic frequency and associated magnetic character. The radiometric data also shows a northwest trending feature further north, parallel to these magnetic features (Figs 2 & 3). This feature represents a fault within Palaeozoic geology and parallel to the regional structural grain. The Kanawinka Fault has been mapped as a curvilinear, typically northwest trending structure (Geological Survey of Victoria, 1994). The position of this fault has been revised based on seismic data (Perincek et al., 1994) which has the fault corresponding with the magnetic data.

Major faults (such as the Kanawinka Fault and the Kanawinka South Fault Zone) are interpreted to have been initiated during the Late Jurassic - Early Cretaceous rifting and reactivated during the Miocene. In the magnetic data, the Kanawinka South Fault Zone is a series of parallel northwest trending discontinuous magnetic highs.

Other northwest trending faults interpreted from seismic data also correspond with magnetic lineaments and interpreted as Miocene - Recent in age. During the Miocene - Recent, compressional stresses in a northwest - southeast direction resulted in strike slip faults oriented northwest - southeast, and normal faults oriented northeast - southwest (Perincek et al., 1994). A number of these northwest - southeast and northeast - southwest trends are apparent in the magnetic data. AIRBORNE SURVEY APPRAISAL - GLENELG 19

7 Mineral prospectivity

The mineralisation and exploration history of the Glenelg region is covered in detail by Bush et al., 1995.

The new geophysical data presented here will substantially aid mineral exploration in the Glenelg region. In addition to increasing the understanding of the geological history and mapping of the area, the geophysical data will allow for further refining of mineralisation models, identification of similar potentially mineralised areas and correlation between structures, intrusives and mineralisation.

Mineralisation within the Glenelg region is associated with Cambrian metasediments and greenstones, Ordovician granites, and dykes of various ages. The geophysical data allows for more accurate mapping of these various lithologies and should contribute to identifying further potential mineral bearing areas.

Metasediments, greenstones, granites, glacial deposits, rhyolite, mafic dykes and laterite, are considered prospective for gold mineralisation. The ability to locate valley volcanic flows should assist in the exploration of deep leads for gold.

Bulls-eye anomalies in the north of the Glenelg region may represent kimberlites which may be prospective for diamonds.

Strand lines have potential for mineral sands. To the northeast of the Glenelg region large deposits of mineral sands have been located near Horsham. Geophysics may aid in delineating mineral sands, provided they are subcropping or moderately magnetic. In the absence of clay layers overlying the mineral sands, radiometrics can be a useful tool to effectively outline surface deposits.

The Penola Trough is prospective for hydrocarbons and coal. Detailed drilling over the 'basement highs' in the southeast of the region may identify thick coal seams at shallow depths. 20 AIRBORNE SURVEY APPRAISAL - GLENELG

8 Conclusions land surface in the east. The radiometric data has major applications to assist with and improve the geological mapping of the Glenelg The extent, quality and detail available in the region. new datasets indicate that a considerable amount of information can be extracted from the results. The brief appraisal presented here has identified a number of features in the geophysical data that are significant for the geological understanding and mineral and petroleum prospectivity of the Glenelg region. The quality of the data will enable a detailed interpretation of the Glenelg region to be conducted. The combination of magnetic and radiometric data will assist future exploration in the area.

The Glenelg region offers opportunities for the exploration of base metal, gold, diamond, mineral sand and coal deposits.

The magnetic data has the ability to 'see through' the laterite and sedimentary cover sequences that severely hinders surface geological mapping.

In the southwest of the Glenelg region, greenstones have been mapped by the magnetic data and show a large subsurface extent. The magnetic data defines discrete granitic bodies and their subsurface extent. The outline of the granites as defined from the magnetic data bears little resemblance to their mapped distribution. The magnetic data will substantially aid the remapping of the granites. A number of these intrusives are cut, or bound by, linear magnetic, non magnetic or crosscutting trends related to the structural character of the area. These lineations display northwest, north-northwest, north-northeast, northeast and east-northeast and possibly represent faults, joints or quartz veining within the intrusions.

The magnetic data shows the dominant structural direction to be northwest to north- northwest. Numerous lineaments and faults accompanied by dykes, reflect the strong deformation which has influenced the region.

In the west, radiometric data have weak responses, compared to the south and east which is dominated by high potassium and high thorium responses. Drainage channels show high potassium responses, reflecting the wide distribution of high potassium granitic intrusions in the region. High thorium responses reflects laterite that caps most of the AIRBORNE SURVEY APPRAISAL - GLENELG 21

References WOPFNER, H., KENLEY, P.R. & THORNTON, R.C.N., 1971. Hydrocarbon occurrences and potential of the Otway Basin in Otway Basin of ANDERSON, J.A.C. & GRAY, C.M., 1994. southeastern Australia (Eds. H. Wopfner and Geological affinities of the Glenelg River J.D. Douglas). Special Bulletin of Geology Complex, western Victoria, Australian Journal Surveys, South Australia and Victoria. pp. 385- of Earth Sciences, 41, pp. 141-155. 435.

BUSH, M.D., CAYLEY, R.A. & ROONEY, S., 1995. WORLD GEOSCIENCE CORPORATION LTD, 1994. Geology and prospectivity of the Glenelg region, VIMP airborne geophysical survey. Glenelg North West VIMP area. Victorian Initiative for and Glenelg extension areas of Victoria. Minerals and Petroleum Report 13. Logistics report. Department of Agriculture, Energy and Minerals.

FERGUSON, D.J., 1993. The geology of the Glenelg River Complex in the Dergholm District of Western Victoria. BSc. (Hons) La Trobe University (unpublished).

GEOLOGICAL SURVEY OF VICTORIA, 1994. Hamilton 1:250 000 SJ 54-7 Geological map. Mapping by Douglas, J.D. and Spencer-Jones, D., 1970, with recent additions compiled by A.H.M. VandenBerg.

GRAY, D.R., 1988. Structure and tectonics. In J.G. Douglas and J.A. Ferguson (eds). Geology of Victoria. Geological Society of Australia, Victorian Division, Melbourne, pp. 1-36.

KEMP, T.I.S, 1995. Geology of the Glenelg River Complex in the Harrow district of western Victoria. BSc. (Hons) La Trobe University (unpublished).

LANZER, L.A., 1991. Victoria's industrial minerals. Heavy mineral sands. Geological Survey of Victoria Unpublished Report 1991/55.

PERINCEK, D., SIMONS, B. & PETTIFER, G.R., 1994. The tectonic framework and associated play types of the western Otway Basin, Victoria, Australia, 460-478. Australian Petroleum Exploration Association Journal 1994 Volume 34 Part 1, pp. 1-920.

SIMONS, B.A., MCDONALD, P.A. & WITHERS, J.A., 1992. New magnetic and gravity images of Victoria, Australia. Geological Survey of Victoria.

WHITE, A.J.R. & CHAPPELL, B.W., 1988. Petrology of igneous rocks: Granites In J.G. Douglas and J.A. Ferguson (eds). Geology of Victoria. Geological Society of Australia, Victorian Division, Melbourne, pp. 427-439. 22 AIRBORNE SURVEY APPRAISAL - GLENELG

Appendix

Status of VIMP airborne surveys

Under the Victorian Initiative for Minerals and Petroleum (VIMP), airborne surveys (Fig. 9) are being conducted in the North West of Victoria, the Eastern Highlands and the Otway Basin.

The surveys are outlined below.

Survey Contractor Kilometres Line Status/Timing spacing (metres)

Eastern Highlands Geo Instruments 7 369 200 Released August (Mt Wellington) 1993 Eastern Highlands Geo Instruments 16 170 200 Released (Orbost) August 1994 Bendigo NGMA AGSO/GSV 53 700 200/400 Released February 1995 North West Area Kevron Geophysics and 122 800 200/400 Released (Murray Basin) World Geoscience May 1995 North West World Geoscience 23 500 200 Available (Glenelg) November 1995 Eastern Highlands GeoInstruments 33 000 200 Released (Mallacoota) Eastern Highlands Geoterrex 52 397 200 Available (Tallangatta) November 1995 Eastern Highlands GeoInstruments 12 900 200 Available (Omeo) February 1996 Eastern Highlands Current Tender 50 000 200 Available (Corryong, Dargo, (approx.) August 1996 Murrindal) Otway Basin Kevron Geophysics 44 379 500 Confidential (Offshore) (Available 1996)

TOTAL 417 000 (approx.) AIRBORNE SURVEY APPRAISAL - GLENELG 23

Victorian Initiative for 13 BUSH, M.D., CAYLEY, R.A. and ROONEY, S., 1995. The geology and Minerals and Petroleum prospectivity of the Glenelg region, (VIMP) report series North West VIMP area 14 SLATER, K.R., 1995. An appraisal of 1 BUCKLEY, R.W., BUSH, M.D., new airborne geophysical data over the O'SHEA, P.J., WHITEHEAD, M. and Glenelg region, North West VIMP area, VANDENBERG, A.H.M. 1994. The Victoria. geology and prospectivity of the Orbost 15 RYAN S.M., KNIGHT, L.A. and Survey area. PARKER, G.J., 1995. The stratigraphy 2 VANDENBERG, A.H.M., WILLMAN, and structure of the Tyrendarra C., HENDRICKX, M., BUSH, M.D. and Embayment, Otway Basin, Victoria. SANDS, B.C. 1995. The geology and 16 KNIGHT, L.A., McDONALD, P.A., prospectivity of the 1993 Mount FRANKEL, E. and MOORE, D.H., 1995. Wellington Airborne survey area. A preliminary appraisal of the pre- 3 HOLDGATE, G., 1995. The exploration Tertiary infrabasins beneath the potential of the Permian Numurkah Murray Basin, Northwestern Victoria. Trough and Ovens Graben, Victoria. 17 PERINCEK, D., SIMONS, B.A., 4 BUSH, M.D., CAYLEY, R.A., ROONEY, PETTIFER, G.R. and GUNATILLAKE, R., SLATER, K. and WHITEHEAD K., 1995. Seismic interpretation of the M.L., 1995. The geology and onshore Western Otway Basin, Victoria. prospectivity of the southern margin of 18 LAVIN, C.J. and NAIM, H.M., 1995. the Murray Basin. The structure, stratigraphy and 5 ROONEY, R., 1995. Mineral petroleum potential of the Portland exploration history of the North West Trough, Otway Basin, Victoria. VIMP area. 19 SIMPSON, C.J., SIMS, J.P. and 6 WILLOCKS, A.J., 1995. An appraisal of ORANSKAIA, A., 1995. The geology the new airborne surveys over the and prospectivity of the Mt Elizabeth North West VIMP area. area, Eastern Highlands VIMP area. 7 WHITEHEAD, M.L., 1995. Geological 20 ORANSKAIA, A., 1995. A geological interpretation of geophysical data over interpretation of geophysical data over the Dunolly 1:100 000 sheet. the Mallacoota 1:250 000 sheet, Eastern Highlands VIMP area. 8 VANDENBERG, A.H.M., CALUZZI, J., WILLOCKS, A.J. and O'SHEA, P.J., 21 SARMA, S., 1995 Seismic 1995. The geology and prospectivity of interpretation of the offshore Otway the Mallacoota 1:250 000 sheet, Eastern Basin, Victoria. Highlands VIMP area. 22 MEHIN, K., and LINK, A.G., 1995. 9 SANDS, B.C., 1995. A geological Early Cretaceous source rocks of the interpretation of the geophysical data Victorian onshore Otway Basin. from the Orbost 1994 airborne survey. 23 PARKER, G.J., 1995. Early Cretaceous 10 OPPY I.D., CAYLEY, R.A. and stratigraphy along the northern margin CALUZZI, J., 1995 The geology and of the Otway Basin, Victoria. prospectivity of the Tallangatta 1:250 000 sheet. 11 CALUZZI, J., 1995 Mineral exploration history of the Tallangatta 1:250 000 sheet. 12 SIMONS, B.A., 1995 An appraisal of new airborne geophysical data over the Tallangatta 1:250 000 map area, Victoria.