An Appraisal of Airborne Geophysical Data from the Murrindal Survey, Victoria

VIMP Report 34

An appraisal of airborne geophysical data from the Murrindal survey, Victoria

R.J. Twyford

October 1996 Bibliographic reference: TWYFORD, R.J., 1996. An appraisal of airborne geophysical data from the Murrindal survey, Victoria. Victorian Initiative for Minerals and Petroleum Report 34. Department of Natural Resources and Environment.

ISSN 1323 4536 ISBN 0 7306 9404 6

Keywords: Geophysics, magnetics, radiometrics, digital terrain model, Murrindal, Bairnsdale, Yalmy Fault Zone, Reedy Creek area, Limestone Creek Graben, Silurian granites, Snowy River Volcanics, Buchan Group, Tertiary volcanics, mineral potential.

This report may be purchased from: Business Centre Department of Natural Resources and Environment Ground Floor, 115 Victoria Parade Fitzroy, Victoria 3065

For further technical information contact: Manager Geological Survey of Victoria Department of Natural Resources and Environment P O Box 2145 MDC Fitzroy, Victoria 3065 AIRBORNE SURVEY APPRAISAL - MURRINDAL 1

Contents Abstract 2 1 Introduction 3 2 Previous geophysics 6 3 Survey details 7 4 Data preparation 8 4.1 Data processing 8 4.2 Products 8 5 Geological appraisal 9 5.1 Structure 9 5.2 Ordovician 15 5.3 Yalmy Fault Zone 15 5.4 Reedy Creek area 16 5.5 Limestone Creek Graben 16 5.6 Silurian intrusions 16 5.7 Devonian 18 Snowy River Volcanics 18 Buchan Group 19 5.8 Dykes 19 5.9 Tertiary Volcanics 20 5.10 Mineral potential 20 6 Conclusions 21 7 Glossary 22 8 References 23 Appendix 1 24 Status of VIMP airborne surveys Appendix 2 25 Survey specifications and data processing Appendix 3 27 Products Victorian Initiative for Minerals and Petroleum report series 28 List of Figures 1 Location of VIMP airborne surveys 4 2 Location of the Murrindal airborne survey 5 3 Total magnetic intensity (HSI) image (back pocket) 4 Total count pseudocolour image (back pocket) 5 Potassium pseudocolour image (back pocket) 6 Thorium pseudocolour image (back pocket) 7 Uranium pseudocolour image (back pocket) 8 Radiometric RGB image (back pocket) 9 Digital terrain model image (back pocket) 10 Simplified geology map (back pocket) 11 Location of several mineral prospects and mines (back pocket) List of Tables 1 Airborne surveys conducted over the Murrindal region 6 2 Specifications of the Murrindal airborne geophysical survey 7 4 Summary of geophysical responses of lithological units 10 5 Status of VIMP airborne surveys 24 2 AIRBORNE SURVEY APPRAISAL - MURRINDAL

Abstract

This report provides a first look appraisal of new, detailed, airborne magnetic and radiometric data obtained over the Murrindal 1:100 000 mapsheet area. A brief discussion of the geological features highlighted by the new data is presented.

The geophysical data generally agrees well with the recently mapped geology. The magnetic data highlights moderately magnetic dykes, and subsurface extensions of magnetic granite bodies. Regional faults are clearly delineated in the magnetic data. Some mapped faults can be extended, and new faults are recognised.

The radiometric data defines the outcrop extent of different lithologies, and highlights compositional variations within the Silurian granite bodies. In particular, a new phase of the Nunniong Pluton has been recognised, based on its distinctive response. The Buchan Group sediments also have a distinctive radiometric response which can be used to map their extent.

The lava flows of the Older Volcanics have a strong, reversely magnetised signature, and a distinctive radiometric response.

The recognition of large subsurface extensions of the I-type, magnetic granites within the survey area may provide new areas for porphyry copper exploration. Dyke swarms within the Nunniong Pluton may indicate extensions of mineralisation in this area. AIRBORNE SURVEY APPRAISAL - MURRINDAL 3

1 Introduction

The data described within this report were obtained as part of the Victorian Initiative for Minerals and Petroleum (VIMP). They comprise detailed, helicopter mounted airborne magnetic and radiometric data, acquired by GeoInstruments in 1995/6, using 200 m line spacing.

The Murrindal 1:100 000 mapsheet (MURRINDAL) covers an area of 2460 km2, most of which is rugged mountainous terrain. Detailed geological mapping was undertaken in 1984 to 1989, prior to the acquisition of the detailed geophysical data (Orth et al., 1995). The MURRINDAL survey completes the coverage of the Eastern Highlands with quality detailed airborne magnetic and radiometric data. Data compilation and mineral resource assessment are also being undertaken as part of the VIMP Eastern Highlands Initiative.

These new data compliment the presently mapped geology, refining geological boundaries, and fault positions. The geophysical data will aid significantly in the geological understanding of the area, leading to a better understanding of the controls on mineralisation.

Images of the total magnetic intensity, total count, potassium, thorium, uranium, RGB radiometrics and digital terrain model are presented in Figures 3-9. A simplified geology map is presented as Figure 10. Figure 11 comprises a magnetic image with the location of several mineral prospects overlain.

6 AIRBORNE SURVEY APPRAISAL - MURRINDAL

2 Previous geophysics A detailed airborne magnetic and radiometric survey was flown over the southern part of MURRINDAL by BHP in 1989, and a number of There have been several airborne geophysical small airborne surveys have been carried out by surveys conducted throughout the other mineral exploration companies MURRINDAL region in previous years. A throughout MURRINDAL. Although these summary list of the airborne magnetic, detailed surveys are of limited use for regional radiometric, and EM surveys is presented in assessment, they may be used to enhance the Table 1. detail of the new regional data. The previous regional magnetic survey for Gravity coverage over the survey area is poor. MURRINDAL was flown by the Bureau of The BMR carried out road traverses with 2 to 8 Mineral Resources (BMR) in 1975. The survey kilometre station spacing during 1952, 1961, covered the Bairnsdale 1:250 000 mapsheet 1978. A helicopter transported gravity survey with E-W flight lines 1.5 kilometres apart, at a was undertaken in 1973, at approximately 11 constant altitude of 1680 m. The current VIMP kilometre station spacing (Withers et al., 1991). survey specifications means the new data The accuracy of the helicopter data is poor. supersede the previous regional magnetic and Improved gravity data, with better coverage radiometric surveys. would aid geophysical interpretation.

Table 1 Airborne surveys conducted over the Murrindal region

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

10 Eastern TMI BMR BMR 1956 1730 260 East-west Highlands 124 Bairnsdale TMI BMR BMR 1975 1500 1680 East-west 374 Buchan TMI/Rad BHP Austirex 1989 200 40/80 East-west 2665 Orbost TMI/Rad GSV Geo 1994 200 90 East-west/ Instruments North-south 3060 Murrindal TMI/Rad GSV Geo 1995/6 200 80 East-West Instruments AIRBORNE SURVEY APPRAISAL - MURRINDAL 7

3 Survey details

A summary of the specifications for the MURRINDAL airborne survey is provided in Table 2, with more detail given in Appendix 2. The geophysical data were obtained by Geo Instruments Pty Ltd, using a Bell JetRanger helicopter. The flight lines were east-west at 200 m spacing, with tie lines north-south at 2000 m spacing.

The magnetic data was acquired using a helium vapour magnetometer, towed with a mean terrain clearance of 80 m.

The radiometric data were acquired using a 256 channel spectrometer, and have been calibrated using the Bairnsdale Hover range in Eastern Victoria. The radiometric data has been corrected to an equivalent height of 80 m above ground level.

Table 2 Specifications of the Murrindal airborne survey

Location Murrindal, North East Victoria (Figs 1 & 2) Date of survey November 1995 - January 1996 Kilometres flown 14700 km Acquisition Geo Instruments Pty Ltd Flight line direction east - west Flight line spacing 200 m Tie line direction north - south Tie line spacing 2000 m Aircraft Bell JetRanger helicopter VH-RLV Navigation Novatel 951R GPS receiver Magnetics Magnetometer Geometrics G833 split beam helium vapour Mean sensor height 80 m above ground level Time sample interval 0.1 seconds Ground sample interval approx. 4 m Radiometrics Gamma spectrometer Exploranium GR820, 16.8l, 256 channel, calibrated radiometrics Mean sensor height 100 m above ground level Time sample interval 1.0 second Sample interval approx. 40 m Processing Kevron Geophysics Pty Ltd Client Geological Survey of Victoria, Department of Natural Resources & Environment, Victoria 8 AIRBORNE SURVEY APPRAISAL - MURRINDAL

4 Data preparation

4.1 Data processing

Processing of the data was undertaken by Kevron Geophysics Pty Ltd. Standard processing and corrections have been applied to the magnetic and radiometric datasets. The radiometric 256 channel data was processed using a spectral ratio method to remove the influence of radon. Further details of the processing methods are supplied in Appendix 2.

4.2 Products

The results of the MURRINDAL geophysical survey are available in both hardcopy and digital format. A complete list of products is provided in Appendix 3. Digital products include grids for the magnetics, radiometrics and DTM, located data, and a GIS data package. Map sets are available at 1:100 000 and 1:25 000 scale. The 1:100 000 scale map set includes colour and greyscale images, and black and white transparencies. The 1:25 000 scale map set includes flight lines, profiles, and contours as black and white transparencies. In addition to the map sets, various individual map items are available. AIRBORNE SURVEY APPRAISAL - MURRINDAL 9

5 Geological appraisal Faults are recognised in the magnetic image by truncation or change of magnetic signature. Some presently mapped faults can be extended, This appraisal provides a first look at the and some unmapped faults are evident (Fig. 3). geological features highlighted by the VIMP Murrindal survey. The total magnetic intensity The radiometric image shows the outcrop (Fig. 3), radiometric (Figs 4-8), and digital extent of different lithologies. Compositional terrain model (Fig. 9) images provide good variation within the granites and volcanics is definition of many geological units. highlighted. In areas of metamorphism, the response from the Ordovician and Silurian Detailed geological mapping was undertaken sediments is variable. prior to the availability of the new geophysical data, and the geology and mineral prospectivity The Tertiary Older Volcanics have a strong of the area is presented in Orth et al. (1995). reversely magnetised signature, and produce a The geological information summarised here is very low radiometric response. taken from this report. A simplified version of the presently understood geology is shown in Table 3 provides a summary of the geophysical Figure 10. responses for the geological units within the survey area. MURRINDAL lies within the complexly folded and faulted Lachlan Fold Belt. Mid Silurian deformation caused upwelling of granite 5.1 Structure magma, and formed the Limestone Creek Graben. Early Devonian rifting gave rise to the There are several major structural trends north-south trending Buchan Rift. Volcanism within MURRINDAL. Faults within the accompanied rifting, infilling the Buchan Rift Ordovician and Silurian sediments have a with Snowy River Volcanics (SRV). The dominantly east-west trend, and are associated Buchan Group carbonates were deposited with Mid-Silurian deformation. The faults have during a sea level rise in the Late Early to been mapped as a series of thrust faults (Orth Middle Devonian. The Middle Devonian et al., 1995). Tabberabberan deformation folded and faulted the contents of the Buchan Rift, creating the The later structures, associated with formation Murrindal Syclinorium. Old faults were of the Buchan Rift, have north-south and north reactivated, accompanied by the formation of westerly trends, and include both faults and new faults. dyke swarms.

The TMI image shows magnetic and non- The dominant structural feature on magnetic granites and volcanics, and non- MURRINDAL is the Buchan Rift. In the magnetic sediments and metamorphics. A northern section of the Buchan Rift, the broad north-south trending magnetic high Woongulmerang Caldera is preserved within dominates the image. This feature coincides SRV. The western margin of the caldera is the with the Buchan Rift. Most of the SRV within arcuate Wulgulmerang fault, which is clearly the rift are moderately to highly magnetic. defined in the magnetic data. The eastern margin of the caldera is the Little River Fault, On both sides of the rift, the image shows low which is also well defined. The magnetic data magnetic areas, which are due to non-magnetic suggests that the two bounding faults may be granite bodies and Ordovician and Silurian connected to the north. sediments. East of the rift is a north east trending magnetic high, which is attributed to The southern end of the Buchan Rift contains subsurface magnetic granites. North of this the Murrindal Synclinorium. The Buchan feature is the circular Mount Gelantipy Lobe, or Caves Limestone crops out in the core of the Gelantipy Plateau, which is well defined with a synclinorium. Its extent is clearly recognised in moderately high magnetic signature. There are the radiometric data (Fig. 8). many moderately magnetic linear features throughout MURRINDAL, the majority of The western margin of the Buchan Rift is which occur in granite bodies. They are formed by the Emu Egg Fault, which is a major interpreted as dykes, and the dominant trend of structure well defined in the magnetic data these features is to the north-west. Table 3 Summary of geophysical responses of lithological units

Age Unit Name Lithology Magnetic Radiometric response Comments response K Th U

Lower sandstone, siltstone, low high to high to moderately Decrease in radiometric response in Ordovician mudstone, chert moderate moderate high the K channel to the south. The OL channel response is higher in the Yalmy Fault Zone. Linear magnetic features parallel to thrust faults in Reedy Creek area.

Upper Bendoc Group sandstone, mudstone low moderate moderate moderately Increase in radiometric response in the Ordovician Ord high K and Th channels to the south.

Warbisco Shale siliceous shale low low low variable The outcrop in the NE corner has a Ouw high high radiometric response in all channels.

Silurian Enano Group Thorkidaan rhyolitic volcanics, low high to high to high Volcanics minor sediments moderate moderately Smv high

Yalmy Group sandstone, siltstone, low moderate high moderate Slight decrease in radiometric response Sy mudstone in K and Th channels to the south.

Towanga Sandstone Slw undifferentiated low high high moderately sandstone and high siltstone

Slw2 siltstone low moderate moderately moderate low

Slw3 siltstone low low to low to moderate Change in radiometric response across moderate moderately the Lyrebird Fault. The first response high is north of the fault.

Seldom Seen quartzite, low low low moderate Distinctive radiometric response. Formation conglomerate, Extent may be increased. Sls breccia Table 3 Summary of geophysical responses of lithological units (Cont'd)

Age Unit Name Lithology Magnetic Radiometric response Comments response K Th U

Silurian Intrusives Feltis Farm I-type granite, high low low moderately Has metamorphosed surrounding Tonalite G47 hornblende-biotite low sediments. Large subsurface extension tonalite indicated by magnetic data.

Postman Spur S-type granite, low moderate moderate high Th channel response is patchy. Granodiorite biotite granodiorite (variable) G59

Rodger River I-type granite, high low moderately moderately Large subsurface extension to the SW Granite G60 biotite-augite low low indicated by magnetic data. granodiorite

Bull Run Gap S-type granite biotite high moderate low to high moderately The core of the body has a higher Adamellite G62 adamellite to high low radiometric response than the rim.

Mount McLeod I-type granite, high moderately low moderately Magnetic data indicates subsurface Tonalite G65 hornblende-biotite low low extension beneath SRV to NW. tonalite

Campbells S-type granite, low high moderately moderate The SE half of the granite body has a Knob biotite granodiorite high to low low Th response. Granodiorite G66

Amboyne S-type granite, low high high variable, Granodiorite biotite granodiorite moderately G71 low

Suggan Buggan S-type granite, low high low moderate Granodiorite biotite-cordierite G74 granodiorite

Chilpin S-type granite, low high high high Granodiorite biotite granodiorite G76 Table 3 Summary of geophysical responses of lithological units (Cont'd)

Age Unit Name Lithology Magnetic Radiometric response Comments response K Th U

Silurian Barrabilly S-type granite, low moderate high to low low to high First response is for the rim, and the Adamellite G77 biotite-cordierite to high second for the core. adamellite

Nunniong S-type granite low moderately low to high moderately Th response is low in SW, and high in Pluton high high NE. G125-1

Nunniong S-type granite low moderately moderate moderate Pluton low G125-2

Nunniong low moderately high high New granite. Pluton high G125-3

Mellick Munjie S-type granodiorite low low moderately moderately Granodiorite low low G127

Forlorn Hope granite, adamellite low moderately low to moderate Th response is low in the core of the Granite G122 high moderate body, and moderately high on the rim.

Lower SNOWY RIVER Devonian VOLCANICS SRV

Timbarra ignimbrite, rhyolite, high moderately moderately moderate Magnetic signature decreases slightly Subgroup Dsb mudstone, sandstone high low to the south.

Windarra volcaniclastic breccia high moderately low moderately Magnetic signature decreases slightly Formation low low to the south. Dsbb Table 3 Summary of geophysical responses of lithological units (Cont'd)

Age Unit Name Lithology Magnetic Radiometric response Comments response K Th U

Lower Wombargo ignimbrite, ash, variable moderately moderate moderately Bands of high magnetic signature Devonian Subgroup Dsc sandstone, high low which follow the measured strike of conglomerates beds. Moderate background signature.

White Monkey ignimbrite, ashstone moderate- moderately low moderate Magnetic signal increases to the NE. Subgroup Dsd high low K is variable. The Mackiesons Spur Ashstone is a lot more potassic than the other members.

Lower Marroo Subgroup ignimbrite moderate moderate low moderate Response is variable Devonian Dse

Statham quartz-feldspar moderate- moderately low moderately Signatures based on large outcrop to Ignimbrite ignimbrite high low low the west of the rift. Elsewhere, outcrop Dsea mapped as Statham Ignimbrite has high radiometric response.

Black Satin quartz-feldspar moderate moderately low moderate Outcrop extent best defined in RGB Ignimbrite ignimbrite high image Dseb

Berrmarr ignimbrite and mega variable moderate moderately moderately Subgroup Dsf breccia moderate to high high low overall

Mount Dawson ignimbrite high moderately moderately moderately Magnetic signature sufficiently Subgroup Dsg high low low distinctive to map the boundary of outcrop.

Tulloch Ard quartz-felspar moderate- high moderately high Ignimbrite Dsha ignimbrite low high

Little River ignimbrite, ashstone, moderate- high moderately moderately Subgroup Dsk sandstone high low high Table 3 Summary of geophysical responses of lithological units (Cont'd)

Age Unit Name Lithology Magnetic Radiometric response Comments response K Th U

Lower Gelantipy Quartz-feldspar moderate- low moderate moderately Radiometrics suggest the outcrop Devonian Ignimbrite ignimbrite high high extent is much greater than presently Dskb mapped.

Detarka feldspar ignimbrite moderate low moderate to moderate to Much of outcrop underlain by Mount Ignimbrite low low McLeod Tonalite. Distinctive Dskg radiometric response. Southerly outcrop extent appears larger than presently mapped, on radiometric image.

Lower Wulgulmerang sandstone, ash, low low moderately moderately Low magnetic response can be used to Devonian Ashstone Dskl mudstone, breccia, high high define outcrop extent. May coincide conglomerate with caldera extent.

Frying Pan feldspar ignimbrite moderate- low moderately moderately Creek high low high Ignimbrite Dskr

Deddick Lava Dsla Rhyolite/ Rhyodacite moderate- high moderate to moderate to lava low high high

Undifferentiated volcanic lava, moderate- low moderately moderately Magnetic granite at depth beneath the Snowy River pyroclastics and high low high lava. K channel best shows outcrop Volcanics epiclastics extent. Ds

BUCHAN GROUP limestone, dolomite, low low high high Buchan Caves Limestone has slightly Dl sandstone more U, Taravale Marlstone is slightly more potassic, and the Murrindal Limestone response is variable.

Tertiary Older Volcanics basalt Reverse - low low low Basalts are reversely magnetised. high Radiometric data shows outcrop extent to be much less than is mapped. AIRBORNE SURVEY APPRAISAL - MURRINDAL 15

(Fig. 3). Interpretation of the magnetic data with the mapped Undifferentiated Ordovician indicates a different position for this fault (Figs sediments. 3 & 10). The extent of the fault can be traced throughout the entire length of the area. The Lower Ordovician sediments (OL) are mapped as extensive outcrops in the south To the west of the rift, the Buchan River Fault west, and south east corners, and on the appears as a splay from the Emu Egg Fault in western edge of the mapsheet. Elsewhere, the the magnetic image. The southern part of the sediments occur as slices within the Yalmy fault agrees with the presently mapped Fault Zone (Section 5.3), or faulted outcrop in position, while to the north the fault appears to the Reedy Creek area (Section 5.4). diverge from its mapped position and join up with the Emu Egg Fault. The inferred fault is Outside the Yalmy Fault Zone the Lower mapped as a geological boundary in this area, Ordovician sediments have a low magnetic but the magnetic image suggests the boundary response and moderate radiometric response could be fault controlled. The southern end of (Table 3). Subsurface magnetic features such the Buchan River Fault joins up with the as dykes or intrusions are easily recognised Carsons Creek Fault. within the Ordovician rocks, and are discussed in Section 5.8. The position of the Ensay Fault is not clearly defined on the magnetic image. The presence of 5.3 Yalmy Fault Zone non-magnetic sediments on both sides of the Ensay Fault makes recognising a break in the The Yalmy Fault Zone lies north east of the magnetic signal difficult. Interpreted splays off Lucas Point Fault, and east of the Buchan Rift. the Ensay Fault, which have a NNE trend and It contains complexly folded and faulted continue into SRV outcrop, are easier to Ordovician and Silurian sediments. delineate (Fig. 3). Within the zone, slices of non-magnetic Lower To the east of the Buchan Rift is the Yalmy Ordovician sediments, Upper Ordovician Fault Zone. The faults within the zone thrust Bendoc Group (Ord) sediments, and Silurian non-magnetic sediments against each other. Yalmy Group (Sy) sediments are thrust against The complexity of the faulting is not recognised one another. The complexity of faulting is not in the geophysical data. visible in the magnetic data, due to the uniform signature of the sediments. The Limestone Creek Graben, in the NW corner of the mapsheet, formed in the Middle Silurian North of the Rodger River lobe, and parallel to due to rifting. The shape and extent of the it, there is a high magnetic feature coinciding structure are clearly defined in the magnetic with outcrop of Yalmy Group sediments. The data. The southern bounding fault; the Reedy mapped geology shows pods of Rodger River Creek Fault, is recognised in the magnetic and Granite (G60) within the outcrop, which lie radiometric data. Its intersection with the Emu along the magnetic feature. This suggests that Egg Fault is not clear. the granite continues at depth beneath the Yalmy Group sediments, and is the source of 5.2 Ordovician the magnetic response.

The oldest rocks that crop out on MURRINDAL South of the Gelantipy Plateau, the Ordovician are Ordovician. They comprise the sediments sediments can be differentiated from the of the Broadbent River Sandstone, Pinnak Silurian sediments on the radiometric image. Sandstone, and the Upper Ordovician Bendoc The Ordovician sediments produce a lower Group. radiometric response in the Th and K channels, which creates a blue area on the RGB image Recent mapping by the GSV on the Benambra (Fig. 8). The Silurian sediments produce a 1:100 000 mapsheet no longer differentiates moderately high radiometric response in the Th between the Broadbent River Sandstone and channel. the Pinnak Sandstone formations (B Simons, pers. comm.). As it is not possible to North of the Gelantipy Plateau the sediments differentiate between the two formations in the are not as easy to differentiate. The Warbisco geophysical data, they have been treated as one Shale (Ouw) unit of the Bendoc Group still has Lower Ordovician unit in this report, together a distinctive U response in places, but the 16 AIRBORNE SURVEY APPRAISAL - MURRINDAL

overall response of the Silurian and Ordovician be differentiated from the adjacent siltstone sediments in this area is uniformly high. unit (Slw2). These rocks produce a moderate to moderately low radiometric response. All three 5.4 Reedy Creek area units parallel the strike of the Lyrebird Fault.

South of the Reedy Creek Fault there are The sandstone unit (Slw3) crops out both north several mapped thrust faults, which have and south of the Lyrebird Fault, and has a faulted Lower Ordovician sediments against different radiometric signature on either side. Silurian sediments of the Seldom Seen North of the fault the response is lower than on Formation (Sls) and the Towanga Sandstone the south side. This change in response makes (Slw). it possible to recognise the Lyrebird Fault in the geophysical data. The sediments of the Seldom Seen Formation have been previously mapped as a wedge The oldest formation within the graben is the shaped outcrop south of the Reedy Creek Fault. Blueys Creek Formation (Ouu). It crops out The extent of the outcrop can be easily defined north of, and parallel to, the Lyrebird Fault. from the low magnetic signal and distinctive The rocks are non-magnetic, and produce a moderately low radiometric response. A similar moderate Th channel response. The outcrop distinctive response is recognised within an appears as a green band on the RGB image area mapped as Lower Ordovician, about 2 (Fig. 8). kilometres north west of the wedge shaped outcrop. This may indicate that the Seldom Within the graben, the Enano Group is Seen Formation extends further than presently represented by the Thorkidaan Volcanics (Smv), mapped. which crop out adjacent to the Lyrebird and Carrabungla Faults. In both places the rocks Within the sediments of the Reedy Creek area have a low magnetic signature, and produce a there are several high frequency magnetic high Th channel response. linear features. These features trend approximately east-west and northwest, The Forlorn Hope Granite has intruded the parallel to the orientation of mapped thrust Towanga Sandstone between the Lyrebird and faults in this area. They are possible dykes, or Reedy Creek Faults. It has a low magnetic slices of volcanic rock brought up by the thrust signature which cannot be distinguished from faults. The Upper Buchan River pyrite that of the surrounding sediments. The granite prospect lies along one of the magnetic features appears to comprise two different phases on (Fig. 11). the radiometric image. The granite produces a distinctive high K, low Th radiometric response 5.5 Limestone Creek Graben in its northern part, with the rest of the body producing a high response in all channels. The Limestone Creek Graben formed in the Middle Silurian as a deep marine graben, due 5.6 Silurian intrusions to rifting. The graben extends from MURRINDAL onto the north east corner of Most of the plutons on MURRINDAL are S-type OMEO. Only the southern part of the graben, granites (Orth et al., 1995). Only the Mt between the Carrabungla and Reedy Creek McLeod, Rodger River and Feltis Farm granites Faults, is found on MURRINDAL. Outcrop are I-type. The plutons have intruded and within this section is dominated by the metamorphosed Ordovician and Early Silurian Towanga Sandstone (Slw) and the Forlorn Hope sediments, and are overlain unconformably by Granite (G122). the SRV. This constrains the time of the intrusions to between the (late?) Early Silurian, All units of the Towanga Sandstone are non- and the (middle?) Early Devonian (Orth et al., magnetic. 1995).

The Rough Creek Conglomerate Member and the sandstone and siltstone unit of the Towanga Sandstone occur as very thin slices (about 100 m wide) which are too thin to show up on Figure 10. Their radiometric response cannot AIRBORNE SURVEY APPRAISAL - MURRINDAL 17

Nunniong Pluton There appears to be several generations of dykes. These are discussed in Section 5.8. The Nunniong Pluton (G125) crops out west of the Buchan Rift, and extends onto OMEO. Amboyne Granodiorite Within MURRINDAL two intrusions have been mapped; the Nunniong Granodiorite and the The Amboyne Granodiorite (G71) extends from Mellick Munjie Granodiorite (G127). The beneath the SRV eastwards into BENDOC. radiometric data shows the area to be more The granite body has a low magnetic signature, complex than that which is presently mapped which is indistinguishable from the signal of (Fig. 4). Using the radiometrics, the Nunniong the host sediments. The dyke swarm in which Granodiorite is subdivided into three different the Deddick Ag-Pb field occurs is found within phases, which are named G125-1, G125-2, and the Amboyne Granodiorite (Fig. 11), and can be G125-3 in this report. seen on the magnetic image. The Amboyne Granodiorite produces a moderately high G125-1 crops out on the western edge of the radiometric response, and the outcrop extent of mapsheet. The granite has a low magnetic the body can be defined using the K or Th signature, and a moderately high radiometric channels alone (Figs 5 & 6). response. Campbell's Knob Granodiorite G125-2 has a low magnetic signature, and produces a weaker radiometric response than The Campbell's Knob Granodiorite (G66) has G125-1. Two areas of outcrop have been been intruded into sediments of the Yalmy and inferred from the radiometric data. The larger Bendoc Groups. The granite body produces a lies just south of the Reedy Creek Fault, while low to moderate magnetic signal, with the NW the smaller outcrop is further south and half of the pluton being more magnetic. There contacts with the G125-1 granite and the are many north west trending linear features Mellick Munjie Granodiorite. passing through the granite, some of which are mapped as Snowy River Volcanic dykes. The In the east of the Nunniong Pluton, G125-3 outcrop extent of the granite is clearly defined produces a distinctive high radiometric in the radiometric data (Fig. 8). In the Th response, which allows its extent to be well channel we can see that the pluton is composed constrained using the RGB image (Fig. 4). At of two compositional parts (Fig. 6). The the contact with the Lower Ordovician Campbell's Knob Cu-Pb-Zn field occurs within sediments there is a band of K enrichment, the Th rich, more magnetic, part of the granite which may be a result of metamorphism. The (Fig. 11). granite has a low magnetic signature. A magnetic rim is visible at the contact between Rodger River Granite G125-3 and the Mellick Munjie Granodiorite, which may also be a contact metamorphism The Rodger River Granite (G60) is probably an effect (Fig. 3). I-type granite, and has a slightly porphyritic texture. It crops out as three small pods north The Mellick Munjie Granodiorite has been of the Rodger River lobe, within mapped as part of the Nunniong Pluton. The metamorphosed Yalmy Group sediments. The granite has a low magnetic signature, and granite produces a moderately low radiometric produces a moderately low radiometric response, and has a high magnetic signature. response. The radiometric data indicates that The magnetic image (Fig. 3) shows that the the outcrop extent of the granite is larger than granite has a large subsurface extent, possibly is mapped. extending south west to the New Guinea Fault. Granite may also be the source of the distinct There are many linear magnetic features magnetic high feature in the core of the Rodger cutting through the granite, these are River lobe. This feature is very similar to the interpreted as dykes. The southern part of the response produced by the granite. The Eel and Nunniong Pluton shows many more dykes than Rodger River Au prospects, and the Rodger in the northern part. The Scorpion Creek, Red River Pb-Zn anomalies lie along this magnetic Steer and Tiger Creek copper prospects, and trend (Fig. 11). the Gil Groggin gold mine occur in this area (Fig. 11). Mount McLeod Tonalite 18 AIRBORNE SURVEY APPRAISAL - MURRINDAL

The Mount McLeod Tonalite (G65) is an I-type The Barrabilly Adamellite (G77) is a small granite which crops out in the southern end of granite body in the north eastern corner of the Buchan Rift. It produces a distinctive low MURRINDAL, surrounded by Warbisco Shale. radiometric response which can be used to The adamellite is highly magnetic. The define its outcrop extent. The tonalite has a response continues past the outcrop extent of high magnetic signature, which extends north the body, indicating the adamellite extends at east in a wide linear band, indicating that the depth beneath the Warbisco Shale. tonalite extends beneath the SRV. The tonalite appears to terminate to the south at the New 5.7 Devonian Guinea Fault. Snowy River Volcanics Feltis Farm Tonalite The Snowy River Volcanics form a broad north- The Feltis Farm Tonalite (G47) is an I-type south trending belt which extends throughout granite which occurs in the SE corner of the MURRINDAL. Within the Buchan Rift, the mapsheet. It produces an overall low rock relationships and outcrop patterns are radiometric response, and has a high magnetic complex. In general, the magnetic signature of signature. The high magnetic feature can be the SRV is complex and variable, with most seen to extend past the outcrop boundaries, units being moderately to highly magnetic. indicating the granite extends beneath Lower There is an overall increase in the magnetic Ordovician sediments (Fig. 3). The subsurface signal of the SRV to the south (Fig. 3). Many extent coincides well with the mapped contact subgroups of the SRV produce similar metamorphic aureole. geophysical responses, the details of which are outlined in Table 3. The Booth's Fancy copper mine, and the Pinnak prospect lie on the edge of the extended granite Within the Buchan Rift the SRV produce (Fig. 11). The Paradise Ridge Cu-Pb-Zn-Au several distinctive radiometric responses. A prospect lies close to the granite boundary. high K response is common to most of the units Bull Run Gap Adamellite of the SRV, and dominates within the rift. In the northern part of the rift a low potassium, In the east, the western edge of the Bull Run moderate Th response coincides with the Gap Adamellite (G62) extends into Wulgulmerang Ashstone (Dskl). This appears MURRINDAL. The adamellite has a as a green feature on the RGB radiometric moderately high magnetic signature. It image (Fig. 8). Outcrop of the Wulgulmerang appears to be compositionally zoned in the Ashstone is restricted to the Woongulmerang radiometric data (Fig. 8), with a Th depleted Caldera. The ashstone is truncated to the north rim, and a generally high response from the by the caldera bounding Wulgulmerang Fault. core. The southern boundary of this unit may define Suggan Buggan Pluton the southern extent of the Woongulmerang Caldera. On MURRINDAL the Suggan Buggan Pluton includes two different intrusions; the Suggan In the central part of the Buchan Rift a Buggan Granodiorite (G74) and the Chilpin distinctive blue/green feature is visible on the Granodiorite (G76). RGB image (Fig. 8). This low K, moderately low Th response coincides with the Gelantipy The Suggan Buggan Granodiorite has a and Detarka Ignimbrites. moderate to high magnetic signature, while the Chilpin Granodiorite has a low magnetic The Detarka Ignimbrite (Dskg) crops out in the signature. The Chilpin Granodiorite produces Butchers Creek Fault area. Its mapped extent an overall high radiometric response, while the can be increased slightly based on the response of the Suggan Buggan Granodiorite distinctive radiometric response. varies between channels ( Table 3). The Gelantipy Ignimbrite (Dskb) is found in Barrabilly Adamellite contact with the Tertiary Older Volcanics throughout the central part of the Buchan Rift. Much of this area has been inferred to be Older AIRBORNE SURVEY APPRAISAL - MURRINDAL 19

Volcanics. The radiometric signature over Carsons Creek Fault the boundaries between much of the mapped basalt is very similar to units of the Timbarra Subgroup (Dsb) are the response of the ignimbrite (Fig. 8). This visible (Fig. 3). suggests that the extent of the Gelantipy Ignimbrite is greater than presently mapped. Buchan Group

The similarity in radiometric responses of the The youngest Palaeozoic rocks on Gelantipy Ignimbrite, Detarka Ignimbrite, and MURRINDAL are the sediments of the Buchan Wulgulmerang Ashstone suggests a similar Group (DL). These non-magnetic sediments genetic origin for the three units. crop out mainly within the Murrindal Synclinorium. Outcrop elsewhere is much more East of the Buchan Rift there are two lobes of restricted. SRV. The White Monkey Subgroup (Dsd) forms the roughly circular Gelantipy Plateau. The Throughout MURRINDAL the Buchan Group subgroup is easily identified in the geophysical masks the magnetic response of the SRV, data (Figs 3 & 8), producing an overall producing a "fuzzy" signal in the magnetic moderately low radiometric response, and image. having a moderately high magnetic signature. The outer rim of the lobe comprises the The Buchan Group sediments are well defined Mackiesons Spur Ashstone, which produces a in the radiometric data. The signature is a much higher radiometric response in the K distinctive low K response, with a high response channel. This unit is also present in places in the Th and U channels. The Buchan Caves where gullies cut down through the upper unit. Limestone has a slightly higher U response, the Taravale Marlstone is slightly more potassic, The Rodger River Lobe, south of the Gelantipy while the Murrindal Limestone is variable. The Plateau, comprises Undifferentiated Snowy radiometric data can be used to map the River Volcanics (DS) which produce a low outcrop extent of the Buchan Group (Fig. 8). radiometric response. This feature appears as a north east trending blue band in the RGB 5.8 Dykes image (Fig. 8). It is truncated to the south west against the high K response of the SRV within There are many moderately magnetic, thin, the Buchan Rift. In the magnetic image linear features present throughout (Fig. 3), a north east trending magnetic high MURRINDAL, which are interpreted as dykes. coincides with the Rodger River Lobe. This West of the Buchan Rift they cross cut the feature continues past the boundary inferred Lower Ordovician sediments, and from the radiometric image, and the boundary approximately parallel the orientation of the is not seen in the magnetics. This apparent Ensay Fault. North of the Ensay Fault, dykes inconsistency between the magnetic and within the Nunniong Pluton, are quite long, radiometric data occurs because the magnetic continuous, more north-north-westerly trending data is reflecting the subsurface geology, while lineaments. Within this dyke swarm there are the radiometrics reflects the surface geology. In several known sites of mineralisation. places, the magnetic trends may be due to subsurface magnetic granites. There is an abrupt decrease in the number of dykes further north, which coincides with an The Eel and Rodger River gold prospects, and approximately north west trending feature that the Rodger River lead-zinc prospect lie along may be an extension of a small mapped fault the magnetic high (Fig. 11). splay off the Emu Egg Fault. The extent of the Mt Dawson Subgroup (Dsg) In the north west corner of MURRINDAL, there can be defined based on the distinctive high are several linear features which parallel the magnetic signature of the rocks (Fig. 3). This orientation of thrust faults in the area.A set of unit appears to be fault bound. In places this almost north-south trending dykes is present. may be a feature of a large change in magnetic These appear to truncate and cross cut the signature across a geological boundary. other dykes, and may be either dykes, or volcanic rock brought up by the thrusts. The magnetic data can also be used to define structures within subgroups, and boundaries between units. For example, west of the 20 AIRBORNE SURVEY APPRAISAL - MURRINDAL

To the east of the Buchan Rift, the dykes Several small stratabound, Irish style lead-zinc appear to have much shorter strike lengths. In deposits are hosted by basal dolomites of the the Lower Ordovician sediments in the south Buchan Caves Limestone. eastern corner of MURRINDAL the linear features have an approximately north west The Deddick silver-lead field and the Campbells trend near the contact with the Feltis Farm Knob copper-lead-zinc field (Fig. 11) both Tonalite, and a more west-north westerly trend comprise many small lodes associated with at the Lucas Point Fault. dyke swarms in granite bodies. West of the Buchan Rift the Tiger Creek and Red Steer Within the Campbells Knob Granodiorite the prospects are also associated with dyke swarms dykes which are recognised from the magnetic within a granite body (Fig. 11). South of these image have a NW trend, and are mapped as prospects, there is an apparently unexplored Snowy River Volcanic dykes. The strike length area within the Nunniong Pluton, which of many of these dykes can be extended using contains extensive NNW trending dykes. the magnetic data. Some of these dykes have been associated with the Campbells Knob Cu- Volcaniclastics within the Buchan Group, and Pb-Zn lodes. the Little River Subgroup frequently contain disseminated base metal sulphide grains. The North of the Gelantipy Plateau there are NW source of the disseminated sulphides has not trending and N-S trending dykes in the yet been located by exploration companies. Deddick area. This dyke swarm is the location Targets include massive sulphides or stock of the Deddick Pb-Ag field (Fig. 11), and has work mineralisation, which may be associated been mapped in detail (Ferguson, 1899; with volcanic centres, or small vent fumaroles Ringwood, 1955) (Orth et al., 1995).

Clearly there are several different generations Porphyry copper deposits related to granite of dykes, recognised by the different trends. bodies, such as the Dogwood prospect, are The most common dyke trend within associated with upper contacts of high level MURRINDAL is to the north west. intrusives, largely of granodiorite composition (Ramsay and Nott, 1988). The extension of 5.9 Tertiary Volcanics many of the I-type magnetic granites at depth may provide new exploration targets for this The Older Volcanics crop out in the central type of mineralisation. portion of the Buchan Rift, and as scattered remnants to the east and west. The rocks have a very distinctive low radiometric response, and a strong reversely magnetised signature. Within the Buchan Rift, the outcrop extent indicated by the radiometric signal is far less than the presently mapped extent.

5.10 Mineral potential

MURRINDAL has historically been regarded as a base metal province. Small amounts of copper and lead, zinc, silver ore have been produced from a variety of geological environments (Fig. 11). Over the past thirty years, additional base metal, and a few epithermal gold prospects have been discovered, although none have proven economically significant. Much of the mineralisation within MURRINDAL appears to be related to volcanic and subvolcanic activity associated with the SRV. AIRBORNE SURVEY APPRAISAL - MURRINDAL 21

6 Conclusions

These new detailed, quality datasets provide the opportunity for regional scale interpretation of MURRINDAL to be undertaken. A considerable amount of information can be extracted from the images, much more than could be presented here.

A number of features which are significant for the geological understanding and mineral prospectivity of the area have been identified in this brief appraisal. Structural controls on the Buchan Rift can be refined using the magnetic data. The presence of the Woongulmerang Caldera structure is confirmed.

Dyke swarms are clearly defined in the magnetic data, extending into unexplored areas. I-type magnetic granites are recognised at depth, providing new areas for mineral exploration. Many of the mineral occurrances on MURRINDAL appear to be associated with magnetic features. Extension of mineralisation around and on strike may also provide new areas for exploration.

The radiometric data has provided detail about compositional variation within granite plutons, and volcanic units. The southern extent of the Wulgulmerang Ashstone has been recognised, and may coincide with the southern margin of the Woongulmerang Caldera. 22 AIRBORNE SURVEY APPRAISAL - MURRINDAL

7 Glossary Pseudocolour. Colour spectrum used to display geophysical data where high values are red and low values are blue. DTM - Digital terrain model. This data is obtained by combining altimeter and GPS data. K-Ar dating. Geologic dating technique based It is calculated from the difference between the on the radioactive decay of potassium to argon. GPS elevation and altimeter height at the This dates the last major thermal event to aircraft. The result is a surface map of the affect the rock. terrain. The digital terrain model has not been warped to the Australian height datum and is Ma - Million years ago. Units of the unsuitable for navigation purposes. geological time scale. GPS - Global Positioning System. A eq % - equivalent percent. Units for display positioning system which provides location of potassium channel in radiometric data. determination by observation of satellites. The satellites broadcast their positions. An observer eq ppm - equivalent parts per million. receiving information from four or more Units for display of uranium and thorium satellites can calculate his/her three channels in radiometric data. dimensional location. cps - counts per second. Units for display of DGPS - Differential Global Positioning total count radiometric data. System. GPS using two receivers, one at a known location. By comparing the satellite AGL - above ground level. information recorded at the known and unknown locations a more accurate calculation ASL - above sea level. of the coordinates of the unknown location can be obtained.

Magnetic survey. Measurement of the magnetic field with the objective of locating concentrations of magnetic minerals or depth to basement. Differences from the normal field are attributed to the distribution of materials having different susceptibility.

Radiometric survey. A survey of the amount of electromagnetic radiation emitted from natural sources. Usually involves gamma ray spectrometry. A gamma ray spectrometer measures the abundance of gamma rays with different energy values.

TMI - Total magnetic intensity. All components of the magnetic field, ie. vertical and horizontal.

RGB - Red Green Blue composite image. Method of displaying three radiometric channels together, eg. red=potassium, green=thorium, blue=uranium.

HSI - Hue Saturation Intensity composite image. Method of displaying magnetic and DTM data with relief shading. AIRBORNE SURVEY APPRAISAL - MURRINDAL 23

8 References

FERGUSON,W.H., 1899. The geological survey of the Mount Deddick district. Geological Survey of Victoria Monthly Progress Report 4-5, pp. 19-20

GEO INSTRUMENTS PTY LTD, 1996. Operations report, helicopter geophysical survey, Dargo region, Victoria. Department of Natural Resources and Environment, Victoria (unpublished).

HAYDON, S.J., 1996. An appraisal of airborne geophysical data from the 1995 Omeo survey, Victoria. Victorian Initiative for Minerals and Petroleum Report 28. Department of Natural Resources and Environment.

ORTH, K., VANDENBERG, A.H.M., NOTT, R.J. & SIMONS, B.A., 1995. Murrindal 1:100 000 map geological report. Geological Survey of Victoria Report 100

RAMSAY, W.R.H., NOTT, R.J., 1988. Metallic Minerals in J.G. Douglas & J.A. Ferguson (eds.) Geology of Victoria. Geological Survey of Australia, Victorian Division, pp. 585-592

RINGWOOD, A.E., 1955. The geology of the Deddick-Wulgulmerang area, East Gippsland. Proceedings of the Royal Society of Victoria 67, pp. 19-66

SIMONS, B., 1995. An appraisal of new airborne geophysical data over the Tallangatta 1:250 000 map area, Victoria. Victorian Initiative for Minerals and Petroleum Report 12. Department of Agriculture, Energy & Minerals, Victoria.

WITHERS, J.A., MCDONALD, P., ROWBOTHAM, P. & HARMES, R., 1991. Victorian State (VIC) gravity database, progress report to February 1991. Geological Survey of Victoria Unpublished Report 1991/3 24 AIRBORNE SURVEY APPRAISAL - MURRINDAL

Appendix 1

Status of VIMP airborne surveys

Under the Victorian Initiative for Minerals and Petroleum (VIMP), airborne surveys (Fig. 1) have been conducted in the North West of Victoria, Eastern Highlands and the Otway Basin, and are currently being conducted in the central Victoria.

The surveys are outlined in the table below.

Table 4 Status of VIMP airborne surveys

Line Survey Contractor Kilometres spacing Status/Timing (metres)

Eastern Highlands (Mt Geo Instruments 7 369 200 Released Wellington) Eastern Highlands Geo Instruments 16 170 200 Released (Orbost) Bendigo NGMA AGSO/GSV 53 700 200/400 Released

North West Area Kevron Geophysics and 122 800 200/400 Released (Murray Basin) World Geoscience North West World Geoscience 23 595 200 Released (Glenelg) Eastern Highlands Geo Instruments 33 358 200 Released (Mallacoota) Eastern Highlands Geoterrex 52 397 200 Released (Tallangatta) Eastern Highlands Geo Instruments 13 780 200 Released (Omeo) Eastern Highlands Geoterrex 15 000 200 Available (Corryong) (approx) August 1996 Eastern Highlands Geo Instruments and 38 000 200 Available (Dargo, Murrindal) Kevron Geophysics (approx.) August 1996 Otway Basin (Offshore) Kevron Geophysics 44 379 500 Confidential (Available 1996)

TOTAL 418 000 (approx.) AIRBORNE SURVEY APPRAISAL - MURRINDAL 25

Appendix 2 - magnetometer in towed bird at 60 m - spectrometer in aircraft Survey specifications and data at 80 m processing Navigation - Novatel 951R receivers The following is a summary of survey and Omnistar wide area specifications and data processing for the differential GPS service Murrindal survey (Geo Instruments, 1996). Data acquisition - Geo Instruments G2000 Murrindal airborne geophysical survey digital acquisition Area - Murrindal region system Kevron job no. - 1363 Client - Department of Natural Ground base magnetometer Resources and Environment Geometrics, model G856A magnetometers (one Flown and compiled - November 1995 to as a backup), located at Swifts Creek, sampling January 1996 at 5 seconds, to record the diurnal variation. Survey company - Geo Instruments Pty Ltd Processing company - Kevron Geophysics Pty Magnetic data processing Ltd Diurnal magnetic variations have been Area falls within sheets: removed. System parallax of four fiducials has 1:100 000 - Murrindal 8523 been removed. The magnetic data has been corrected for regional gradient by subtraction of Area includes: IGRF model 1995 and secular variation model traverse lines 1 - 257 1995-2000. A constant value of 2000 nT was tie lines 1 - 47 then added to the total magnetic intensity data. Inclination and declination computed Murrindal survey is the polygon defined by: continuously over the whole area using IGRF 601000 5858000 to 587000 5858000 model 1995-2000 computed at year 1996.15. 587000 5858000 to 587000 5905000 Tie line levelling corrections have been 587000 5905000 to 635000 5905000 removed. Microlevelling has been applied. 635000 5905000 to 635000 5860000 635000 5860000 to 678000 5860000 IGRF inclination for area centre -68.15° 678000 5860000 to 678000 5855000 IGRF declination for area centre 12.77° 678000 5855000 to 601000 5855000 IGRF total field for area centre 59807.52 nT 601000 5855000 to 601000 5858000 Gamma spectrometer data processing Survey specifications Aircraft - VH-JWF Bell JetRanger The coefficients for the following corrections - VH-RLV Bell JetRanger have been derived from test flying at the Magnetometer - Geometrics G833 split Bairnsdale Hover Range. beam helium vapour Resolution - 0.001 nanoTesla Corrections have been applied for: Sensitivity - 0.01 nanoTesla - instrumental deadtime Cycle rate - 0.1 seconds - cosmic and aircraft background Sample interval - approximately 4 m - height correction to 80 m AGL Spectrometer - Exploranium GR820 - - temperature corrected 16.8 l of crystal volume - stripping to give c/s for K-40, Bi-214 and Cycle rate - 1.0 second Tl-208 Sample interval - approximately 40 m The influence of radon has been minimised by Traverse line spacing- 200 m the application of the spectral ratio method of direction - 090 - 270 degrees Minty (1992). Tie line spacing - 2000 m direction - 180 - 360 degrees Gridding Mean terrain clearance 26 AIRBORNE SURVEY APPRAISAL - MURRINDAL

Magnetic data was gridded using a 50 m square grid mesh. The gridding method is as described in Briggs (1974), utilising a four times line spacing search/scan radius. Filtering was not applied to the grid.

Radiometric data was gridded using the same procedure as the magnetic data, but initially using a 70 m square grid mesh, and then subsampled to a 50 m grid. Filtering was not applied to the grid.

Digital terrain model

A digital terrain model was generated from the GPS data and the radar altimeter data. The data was error corrected and micro-levelled. The grid was generated using a 50 m mesh and was not filtered. AIRBORNE SURVEY APPRAISAL - MURRINDAL 27

Appendix 3 Located data in ASCII format: Located total magnetic intensity; Located radiometrics. Products Grids in ERMapper format: Hardcopy Total magnetic intensity; First vertical derivative; The following hardcopy products are available. Total count; These may be purchased as map sets or as Potassium; individual items. Thorium; Uranium; 1:100 000 scale black and white products (paper Digital terrain model. or transparency): GIS dataset (for all of Bairnsdale 1:250 000): Flight path maps; Towns, roads, National Parks, map Total magnetic intensity profiles; boundaries; Total magnetic intensity contours (1 nT Current and expired Exploration Licences contour interval); and Mining Licences; Total magnetic intensity first vertical Geology, geochemistry, mineral occurrences; derivative contours (0.1 nT/km contour Magnetic, radiometric and digital terrain interval). model images. Digital terrain model contours.

Maps for individual 1:25 000 mapsheets are also available.

1:100 000 scale colour products (paper):

Total magnetic intensity contours (1 nT contour interval); Total count radiometrics contours (25 cps contour interval); Potassium contours (0.1% eK contour interval); Thorium contours (0.5 ppm eTh contour interval); Uranium contours (0.5 ppm eU contour interval).

1:100 000 scale colour products (pixel image):

Total magnetic intensity with relief shading; Total magnetic intensity greyscale; Total magnetic intensity first vertical gradient greyscale; Total count radiometrics; Radiometrics RGB (K, Th, U); Digital terrain model with relief shading.

Digital

The data is provided on five-gigabyte Exabyte tape or Compact Disc and contains the following information: 28 AIRBORNE SURVEY APPRAISAL - MURRINDAL

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, 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 24 MOORE, D.H., 1996. A geological 1:250 000 sheet. interpretation of the geophysical data of 11 CALUZZI, J., 1995. Mineral exploration the Horsham 1:250 000 map sheet area. history of the Tallangatta 1:250 000 25 VANDENBERG, A.H.M., HENDRICKX, sheet. M.A., WILLMAN, C.E., MAGART, 12 SIMONS, B.A., 1995. An appraisal of A.P.M., ROONEY, S. and ORANSKAIA, new airborne geophysical data over the A.N., 1996. The geology and Tallangatta 1:250 000 map area, prospectivity of the Orbost 1:100 000 Victoria. map area, eastern Victoria. AIRBORNE SURVEY APPRAISAL - MURRINDAL 29

26 HENDRICKX, M.A., WILLMAN, C.E., MAGART, A.P.M., ROONEY, S., VANDENBERG, A.H.M., ORANSKAIA, A. and WHITE, A.J.R. The geology and prospectivity of the Murrungowar 1:100 000 map area, eastern Victoria. 27 BOYLE, R. J., 1996. Mineral exploration history of the Omeo 1:100 000 map area. 28 HAYDON, S.J., 1996. An appraisal of airborne geophysical data from the 1995 Omeo survey, Victoria. 29 MAHER, S., 1996. Mineral resources of the Dunolly 1:100 000 map area. 30 CHIUPKA, J.W., 1996. Hydrocarbon Play Fairways of the Onshore Gippsland Basin, Victoria. 31 MEHIN, K., and LINK, A.G., 1996. Early Cretaceous source rock evaluation for oil and gas exploration, Victorian Otway Basin. 32 SLATER, K.R., 1996. An appraisal of new airborne geophysical data over the Dargo region, Victoria. 33 McDONALD, P.A., 1996. An appraisal of new airborne geophysical data over the Corryong region, northeastern Victoria. 34 TWYFORD, R., 1996. An appraisal of airborne geophysical data from the Murrindal survey, Victoria. 35 HUTCHINSON, D.F., 1996. Mineral exploration history of the Dunolly 1:100 000 map area. 36 BROOKES, D.G. and BOYLE, R.J., 1996. Mineral exploration history of the Bairnsdale 1:250 000 map area. 37 MAHER, S., HENDRICKX, M.A., BOYLE, R.J. and BROOKES, D.G., 1996. Geology and prospectivity of the Bairnsdale 1:250 000 map sheet area. 38 McDONALD, P.A. and WHITEHEAD M.L., 1996. Geological interpretation of geophysical data over the Ararat 1:100 000 map sheet. 39 MOORE D.H. 1996. A geological interpretation of the geophysical data of the Ouyen 1:250 000 map sheet area.