The Geology and Prospectivity of the Wangaratta 1:250 000 Map Sheet Area

VIMP Report 46

The geology and prospectivity of the Wangaratta 1:250 000 map sheet area

S. Maher, A.H.M. VandenBerg, P.A. McDonald and P. Sapurmas

November, 1997 Bibliographic Reference: MAHER, S., VANDENBERG, A.H.M., MCDONALD P.A. AND SAPURMAS P., 1997. The geology and prospectivity of the Wangaratta 1:250 000 map sheet area. Victorian Initiative for Minerals and Petroleum Report 46. Department of Natural Resources and Environment.

ISSN 1323 4536 ISBN 0 7306 9425 9

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

For further technical information, contact: General Manager, Geological Survey of Victoria, P O Box 500, East Melbourne, Victoria 3002

Authorship and acknowledgements: Major contributors: Economic Geology—S. Maher and P. Sapurmas, Geology—A. VandenBerg, Geophysics—P. McDonald, Prospectivity—S. Maher and P. McDonald.

Osprey Gold NL and Warren Jay Holdings P/L generously gave permission to publish information from confidential Exploration Licence reports.

Digital terrain model data from GSV and GEODATA DEM-9S.

Figures were produced by D. Jansen. Editing was by A.H.M. VandenBerg, R. Buckley, A. Willocks and P.J. O'Shea. Formatting was by G. Ellis.

4 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Contents

Abstract 7 1 Introduction 8 2 Geophysics 10 2.1 Summary 10 2.2 Previous geophysics 10 2.3 VIMP/NGMA survey details 10 VIMP specifications 10 NGMA specifications 13 2.4 Products 13 3 Structural framework 15 4 Geological history 16 4.1 Summary 16 4.2 Lachlan Fold Belt 16 4.3 Late Palaeozoic and Mesozoic epi-cratonic sedimentation 17 4.4 Late Cretaceous break-up of Gondwana (ca 95–65 Ma) 17 5 Sedimentary and volcanic rock units 19 5.1 Cambrian 19 5.2 Ordovician (–Silurian?) 20 Hotham beds 20 5.3 Silurian—Omeo Metamorphic Complex 21 5.4 Silurian–Lower Devonian—Melbourne "Trough" 21 5.5 Devonian volcanics and sediments 22 Violet Town Caldera 22 Wabonga Caldera: Tolmie Igneous Complex 22 5.6 Upper Devonian–Carboniferous(?) Mansfield Group 23 5.7 Carboniferous–Permian 24 Boorhaman Conglomerate 24 Urana Formation 25 5.8 Tertiary 25 "Tp"—White Hills Gravel? 25 Renmark Group 25 Older Volcanics 25 Calivil Formation 26 Newer Volcanics 26 Shepparton Formation 26 5.9 Quaternary sediments 27 Alluvium (Qra) 27 Colluvium, gully alluvium (Qrc) 27 Swamp deposits (Qrm) 27 Dune deposits (Qo) 27 6 Intrusive rocks 29 6.1 Granites 29 Yackandandah Batholith 31 Pilot Range Batholith 32 Warby Range Batholith 33 Subsurface granites 34 Granite ages 35 6.2 Dykes 35 7 Economic geology 36 7.1 History of mining 36 7.2 Mineral production 39 7.3 Gold deposits 41 GEOLOGY AND PROSPECTIVITY - WANGARATTA 5

Placer gold deposits 42 Orogenic gold deposits 46 7.4 Antimony-?gold deposits in the Tolmie Igneous Complex 52 7.5 VHMS and epigenetic gold deposits in Cambrian greenstones 52 7.6 Granite-hosted tin deposits 52 7.8 Porphyry molybdenite deposits 53 7.9 Porphyry gold-copper deposits 54 7.10 Copper deposits in the Mansfield Group 54 7.11 Placer diamond occurrences 55 7.12 Coal 56 7.13 Non-metallics 57 Construction materials 57 Feldspar 57 Gemstones 58 Fluorite 58 Calcite 58 Wollastonite 58 Quartz crystals 59 Talc 59 Phosphate 59 Dimension stone 59 8 Soil and stream sediment geochemistry 61 9 Mineral resource potential and prospectivity 66 Orogenic gold 66 Placer gold 66 Thermal aureole gold 67 VHMS and epigenetic gold deposits in Cambrian greenstones 67 Antimony-?gold deposits in the Tolmie Igneous Complex 67 Porphyry gold-copper-molybdenite deposits 67 Copper deposits in the Mansfield Group 67 Diamond deposits 67 Coal 68 Industrial minerals 68 References 69 Appendix 1 77 Status of VIMP airborne surveys 77 Appendix 2 77 VIMP Survey specifications and data processing 78 NGMA Survey specifications and data processing 79 Appendix 3 81 VIMP Products 81 NGMA Products 81 Victorian Initiative for Minerals and Petroleum (VIMP) report series 83

List of figures 1 Airborne surveys and detailed geological mapping, Wangaratta 1:250 000 map area 10 2 Total magnetic intensity image 1:500 000 (Back pocket) 3 Radiometric RGB image 1:500 000 (Back pocket) 4 Digital terrain model image 1:500 000 (Back pocket) 5 1:500 000 simplified geology, Wangaratta 1:250 000 map area. (Back pocket) 6 Geology, mineral resources and tenements, Wangaratta 1:250 000 map area (Back pocket) 7 Mineral resources within the Wangaratta 1:250 000 map area 38 8 Primary, alluvial and total goldfield production. 41 9 Annual goldfield production. 42 6 GEOLOGY AND PROSPECTIVITY - WANGARATTA

10 Gold-quartz vein orientations, Wangaratta 1:250 000 map area 48 11 Distribution of stream sediment samples analysed for gold (excluding samples analysed with the bulk cyanide leach method) 63 12 Distribution of stream sediment samples analysed for gold by bulk cyanide leaching (BCL) 63 13 Distribution of stream sediment samples not analysed for gold 64 14 Distribution of diamond indicator stream sediment samples 64 15 Distribution of soil samples analysed for gold (excluding samples analysed with the bulk cyanide leach method) 65 16 Distribution of soil samples analysed for gold by bulk cyanide leaching (BCL) 65 17 Distribution of soil samples not analysed for gold 66 18 1:500 000 TMI image showing mineral resources (Back pocket)

List of tables 1 Summary of geophysical responses of non-intrusive rock units 12 2 Airborne surveys on WANGARATTA 14 3 Specifications of the WANGARATTA airborne survey 15 4 Summary of granite plutons 31 5 Production for goldfields between 1864 and 1996 42 6 Gold production from principal mines operations in the Chiltern-Rutherglen goldfield 44 7 Principal gold mining operations in the Beechworth and Eldorado goldfields 45 8 Principal dredging and sluicing operations in the southern goldfields 46 9 Major primary gold producers from each goldfield of the Dargo-Harrietville gold province 48 10 Gemstone occurrences 59 11 Status of VIMP airborne surveys 78 GEOLOGY AND PROSPECTIVITY - WANGARATTA 7

Abstract

This report summarises the geology and prospectivity of the WANGARATTA 1:250 000 map area in northeastern Victoria.

New airborne geophysics conducted over WANGARATTA as part of the Victorian Initiative for Minerals and Petroleum (VIMP) and National Geoscience Mapping Accord (NGMA) programs has enabled a reappraisal of the regional geology and prospectivity of the area. This has been complemented by compilations of mineral resources, mineral exploration and exploration geochemistry.

Broad areas with potential to host a variety of styles of mineralisation have been outlined as a result of this reappraisal. These include:

· Cainozoic placer and supergene gold deposits; · extensions to and repetitions of historic primary gold deposits; · thermal aureole gold deposits related to the Strathbogie Granite; · unrecognised sediment-hosted disseminated gold deposits; · volcanic-hosted massive sulphide and epithermal gold deposits associated with Cambrian greenstones; · stratiform base metal-uranium deposits in Upper Devonian–Lower Carboniferous basins and Ordovician Hotham Group; · tin, molybdenum and gold deposits hosted by granites; · Cainozoic placer tin deposits; · diamond deposits; · Permian coal deposits; · antimony-gold deposits associated with Upper Devonian calderas; · porphyry gold-copper-molybdenite deposits associated with high-level intrusions; and · a variety of industrial minerals. 8 GEOLOGY AND PROSPECTIVITY - WANGARATTA

1 Introduction

This report summarises the geology and mineral resources of the Wangaratta 1:250 000 map area (WANGARATTA) in northeastern Victoria (Fig. 1), and includes an appraisal of new airborne geophysical data. This information is designed to aid mineral exploration and mineral resource development. It complements new airborne magnetic and radiometric data and stream sediment and soil geochemical data compiled from expired Exploration Licences covering WANGARATTA collected as part of the Victorian Initiative for Minerals and Petroleum (VIMP) program, and detailed geological maps which cover most of the northern half of WANGARATTA (Fig. 1). Mineral exploration in WANGARATTA, including details on anomalies in geochemical surveys and significant drill intersections, is summarised in Wilkie and Brookes (1997).

Detailed information on the location, production and geology of mines and prospects within WANGARATTA accompanies this report in the WANGARATTA Mine Database. The database, explanatory notes and references are supplied on a 3.5 inch DOS disk in the following formats:

WANGARATTA Mine Database Wangmine.mdb Microsoft Access 2.0 format Wangmine.ldb Microsoft Access 2.0 format *.txt Tab delimited ASCII text files derived from the Access Database

Explanatory Notes Readme.doc Microsoft Word 6.0 format Readme.txt ASCII text file format

References Referenc.doc Microsoft Word 6.0 format Referenc.txt ASCII text file format

The mine database is only one layer in the GIS data set covering WANGARATTA. Other layers include geology, geochemistry (also available in ASCII text and relational database formats), magnetic and radiometric images, current and expired Exploration Licences (ELs), national parks and roads. This data set is available from the Geological Survey of Victoria. GEOLOGY AND PROSPECTIVITY - WANGARATTA 9

Figure 1 Airborne surveys and detailed geological mapping, Wangaratta 1:250 000 map area. 10 GEOLOGY AND PROSPECTIVITY - WANGARATTA

2 Geophysics assessment, they may be used to complement the detail of the new data.

2.1 Summary WANGARATTA is covered by approximately 900 gravity stations, mostly AGSO stations Detailed airborne magnetic and radiometric spaced at 11 km. Detailed gravity surveys are data were obtained over WANGARATTA as concentrated in northwestern WANGARATTA part of the Victorian Initiative for Minerals and over the Dookie greenstones. Petroleum (VIMP, Appendix 1) and the National Geoscience Mapping Accord (NGMA). 2.3 VIMP/NGMA survey details The surveys (Fig. 1) cover an area of WANGARATTA is a joint ASGO/GSV project, approximately 14 850 km2. The VIMP survey and a summary of the specifications for the was flown using a helicopter over steep terrain VIMP and NGMA surveys are provided in while the NGMA survey was flown using a Table 3, with more details given in Appendix 2. fixed wing aircraft over gently undulating terrain. AGSO collects NGMA survey data at 400 m line spacing, but, the GSV paid AGSO to upgrade The details in the total magnetic intensity the flight line spacing to the VIMP survey (Fig. 2), radiometric RGB (K, Th, U) (Fig. 3) and specification of 200 m. digital terrain model (Fig. 4) images provide good definition of many geological units (Fig. 5) The ground conditions, for both surveys, were and structural controls in WANGARATTA. predominantly dry. Occasional frontal systems, with associated high winds and rain, crossed The geophysical characteristics and subsurface the area. extent of the geological units are included with the descriptions of the units. The geophysical responses of the non-intrusive rock units are VIMP specifications presented in Table 1, responses of the granite plutons are summarised in Table 4 (see The geophysical data were collected by Chapter 6). GeoInstruments P/L, using a Bell 'Jet Ranger' helicopter. The flight lines were flown east– west at 200 m spacing, with tie lines north– 2.2 Previous geophysics south at 2000 m spacing. Navigation data were provided by satellite Global Positioning System A number of airborne geophysical surveys have (GPS). been conducted within WANGARATTA (Table 2). The magnetic data were acquired using a forward boom-mounted caesium vapour The regional geophysical survey flown by the magnetometer with a mean terrain clearance of Australian Geological Survey Organisation 80 m. (AGSO formerly Bureau of Mineral Resources, (BMR) in 1972 covered the Bendigo, The radiometric data were acquired using a 256 Wangaratta and Tallangatta 1:250 000 channel spectrometer, and have been calibrated mapsheets with east–west flight lines spacing using AGSO's calibration pads in Canberra, and of 1500 m, at a constant altitude of 150 m the calibration range in Bairnsdale. (1800 m east of 146 degrees 30 minutes). Data processing was undertaken by Des The current VIMP and NGMA survey Fitzgerald and Associates P/L. Standard specifications and quality of the new data processing and corrections have been applied to supersede the previous surveys. These surveys the magnetic and radiometric datasets. The abut the VIMP Tallangatta survey (Appendix 1) survey data are provided with co-ordinates to the east and the Bendigo NGMA survey to referenced to the AGD66 and WGS84 datums. the west. Digital terrain model data have been corrected to the AHD datum. Further details of the Several small exploration company airborne processing methods are supplied in Appendix 2. magnetic and radiometric surveys have been carried out in WANGARATTA. Although these detailed surveys are of limited use for regional Table 1 Summary of geophysical responses of non-intrusive rock units

Age Unit/ Lithology Magnetic Radiometric response Comments Province response K Th U

Cambrian metabasalt, high low low low A N–S 'belt' of metabasalts extends from Tatong gabbro, sediment to Major Plains. The magnetic data indicate a similar 'belt' between Greta South and Youarang.

Ordovician Hotham beds sandstone, low low– low– low– Northwest-trending dykes in possible fault zone, mudstone moderate moderate moderate within Hotham beds, west of Mount Angus Granite.

Silurian Omeo schist, gneiss low low–high moderate– low–high NW-trending dykes in Kancoona fault zone, Metamorphic high within OMC metasediments, NE of Morilla Complex Granite. Possible bedding seen in magnetic (OMC) data.

Silurian– Melbourne sandstone, low low–high low–high low–high High radiometric response matches bedrock Lower "Trough" siltstone, ridges north of Strathbogie Granite. Sediments Devonian mudstone, may be more extensive than mapped. conglomerate

Devonian Violet Town quartz ignimbrite low low–high low–high low– Two flows seen in radiometric data. Caldera moderate

Wabonga conglomerate, low low–high low–high moderate– Possible compositional variations within the Caldera ignimbrite, high ignimbrites seen in the radiometrics. rhyolite

U. Devon.– Mansfield conglomerate, red low low low low Weak magnetic marker horizons are interpreted Carb. Group mudstone as bedding. Tertiary volcanic plugs present.

Carb.– Boorhaman tillite weak low low low Some mapped Permian boundaries correlate well Permian Conglom. with the radiometrics. Table 1 Summary of geophysical responses of non-intrusive rock units

Age Unit/ Lithology Magnetic Radiometric response Comments Province response K Th U

Tertiary White Hills conglomerate, weak low moderate low Thorium response possibly due to laterisation. Gravel (?) gravel, sand Older basalt high low low low Negatively and positively magnetised basalt Volcanics flows apparent. Newer basanite, leucitite high low low low Subsurface basalt flows identified from Volcanics magnetics.

Shepparton silty clay, weak low–high low–high low–high Magnetic, present-day/fossil drainage patterns Formation interbedded sand prominent. High radiometric responses from outwash fans.

Quaternary colluvium composition high low–high low–high low–high Maghemite within drainage. Radiometric reflecting source responses reflect sediment source.

swamp black clay weak low–high low–high low–high Radiometric response indicate extent of water- deposits logging.

dune deposits sand, silt, clay weak moderate low low Potassium responses possibly reflect clay content. GEOLOGY AND PROSPECTIVITY - WANGARATTA 13

Table 2 Airborne surveys on WANGARATTA

Survey name Survey type Operator Contractor Year Flight line Altitude spacing (m) (m AGL)

Wangaratta TMI/Rad BMR BMR 1972 1500 150/1800 Peechelba TMI/Rad Geometrics Pennzoil 1979 250 80 Murray Basin TMI/Rad Geosearch CRAE 1980 250 80 Murmungee Basin TMI/Rad GeoX BHP 1981 250 80 Dookie TMI Scintrex Freeport 1981 330 90 Wooragee TMI Geoterrex Triad 1990 100 65 Rochester TMI/Rad Austirex CRAE 1991 250 60 & 800 Flowerdale TMI/Rad GeoInstruments Range River Gold 1996 200 50 Tolmie TMI/Rad GeoInstruments Range River Gold 1996 100 50 Wangaratta TMI/Rad GeoInstruments GSV 1997 200 80 Wangaratta TMI/Rad AGSO AGSO/GSV 1997 200 80

NGMA specifications and greyscale images, black and white transparent contour, and flight line and profile The geophysical data were collected by AGSO, plots. using an Aero Commander plane. The flight lines were flown east–west at 200 m spacing, with tie lines north–south at 2000 m spacing. Navigation data were provided by satellite (GPS).

The radiometric data were acquired using a 256 channel spectrometer, and have been calibrated using AGSO's calibration pads in Canberra.

Data processing was undertaken by AGSO. Standard processing and corrections have been applied to the magnetic and radiometric datasets. Survey co-ordinates are referenced to the WGS84 datum. Digital terrain model data have been corrected to the AHD datum. Further details of the processing methods are supplied in Appendix 2.

2.4 Products

The results of the surveys are available in hard copy and digital format. A list of products is provided in Appendix 3.

Digital products include grids for the magnetic (total field, 1VD and AGC), radiometric (total count, potassium, thorium and uranium) and DTM data. Located data and a GIS data package are also available.

Map sets are available at 1:250 000, 1:100 000, 1:50 000 (NGMA survey only) and 1:25 000 (VIMP survey only) scale. Maps include, colour 14 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Table 3 Specifications of the WANGARATTA airborne survey

VIMP survey NGMA survey

Location WANGARATTA (Fig. 1) WANGARATTA (Fig. 1) Date of survey November 1996–March 1997 March–May 1997 Traverse line kilometres 40 238 41 106 Tie line kilometres 6 716 4 353 Total line kilometres 46 954 45 459 Acquisition GeoInstruments P/L AGSO Processing Des Fitzgerald & Associates P/L AGSO 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 Aircraft Bell Helicopter 206B VH-JWF Aero Commander VH-BGE Navigation Novatel 951R GPS receiver Ashtec Ranger GPS receiver

Magnetics Magnetometer Geometrics G-822A Caesium Vapour Geometrics G-822A Caesium Vapour Mean sensor height 80 m 80 m Time sample interval 0.1 s 0.1 s Ground sample interval approx. 4 m approx. 7 m

Radiometrics Gamma spectrometer Exploranium GR-820, 256 channel Exploranium GR-820, 256 channel (calibrated) (calibrated) Mean sensor height 80 m 80 m Time sample interval 1.0 s 1.0 s Sample interval approx. 40 m approx. 70 m Client GSV GSV/AGSO GEOLOGY AND PROSPECTIVITY - WANGARATTA 15

3 Structural framework

WANGARATTA lies at the northern end of three structural zones, the Tabberabbera Zone, which covers most of the region, flanked in the west by the Melbourne Zone and in the northeast by the Omeo Zone (Fig. 5). The zone boundaries are major fault zones: the Mount Wellington Fault Zone in the west marks the eastern limit of the thick Silurian–Devonian marine Melbourne "Trough" sequence and has discontinuous exposure of the underlying Cambrian greenstones, and in the east the Kancoona Fault, with a wide mylonite belt, marks the western limit of the Omeo Metamorphic Complex.

The Upper Devonian cover rocks in central WANGARATTA include two calderas (Fig. 5) which, together with granite plutons, form the Central Victorian Magmatic Province and are overlain by sediments which are part of the Howitt Province, a broad northwest-trending graben that continues almost to the coast at Bairnsdale.

Late Carboniferous and Permian rocks are mainly confined to the Ovens Graben in central WANGARATTA, with less extensive deposits in the Numurkah Trough in the west (Fig. 5). In the northwest, the Palaeozoic rocks are covered by Tertiary sediments which were deposited in the shallow Murray Basin. 16 GEOLOGY AND PROSPECTIVITY - WANGARATTA

4 Geological history turbidity currents into the deep marine environment along the eastern margin of the Australian Craton. Turbidity currents were 4.1 Summary less common in some areas which accumulated occasional thin cherts. The detritus that makes WANGARATTA during the Palaeozoic lay in up the turbidites was mainly derived from a the Lachlan Fold Belt, a region with a complex continental source to the west which was history of marine and subaerial sedimentation composed of sediments, granites, and some and volcanism interrupted by several major metamorphic rocks. contractional deformations and periods of granite intrusion. The final Lachlan event was In the Late Ordovician, WANGARATTA mild folding of molasse-type redbeds in the continued to be in a deep marine environment, Carboniferous, after which there was prolonged but for some reason turbidite input was largely erosion. In the Late Carboniferous and blocked, so that the main depositional process Permian, extensive glaciation was followed by was quiet accumulation of silt and mud on a deposition of quite thick marine mudstones, deep anoxic seafloor. which are only preserved in several basins in the north and west of WANGARATTA. Further The Bendoc Group, east of the Mount erosion after the Permian resulted in a Wellington Fault Zone, consists mainly of the landscape of low relief by late Mesozoic times. black siliceous Warbisco Shale, with silica The breakup of Gondwana in the Cretaceous probably largely derived from radiolarians. It caused uplift of several thousand metres to contains abundant graptolites and records a form the Eastern Highlands, which extend into long time span, 20–25 million years, of very the southern part of WANGARATTA. At the quiet pelagic and hemipelagic sedimentation. same time, subsidence in the north created the In the Melbourne Zone, very similar black shale Murray Basin. Since then, the history has been forms the Mount Easton Shale with a similar mainly one of erosion in the highlands and age span. It has not yet been recorded from deposition of fluvial and minor marine within WANGARATTA but occurs just to the sediments in the Murray Basin and Riverine south at Bonnie Doon. Plain, with several episodes of basalt eruption during the Early Tertiary. Early Silurian Benambran Deformation (430-425 Ma) 4.2 Lachlan Fold Belt The Benambran Deformation appears to have Cambrian volcanism and sedimentation been the main episode of cratonization in much (530-490 Ma) of eastern Victoria, including the Tabberabbera and Omeo zones, but left the Melbourne Zone The rock record in Central Victoria began in the rocks unaffected. Cambrian with eruption of basalts and andesites on the sea floor, alternating with During this event, the Ordovician rocks were episodes of quiet accumulation of pelagic shale, tightly folded along northwesterly trending chert and deposition of volcanogenic sediments. folds. High heat flow and upwelling of granite At Dookie, these basalts and sediments were magma altered the deeply buried sediments in intruded by a thick gabbroic sill. the east in a regime of low pressure metamorphism (Omeo Metamorphic Complex). Ordovician deep marine sedimentation Metamorphic minerals such as cordierite, (490-430 Ma): Adaminaby and Bendoc Groups biotite, sillimanite and K-feldspar grew as the rocks were folded, and a strong schistosity was At about the Cambro-Ordovician boundary, a imprinted in many of the metamorphic rocks. large submarine fan systems encroached into Granite magma slowly moved towards the the region from the west, extending across most surface and began to metamorphose local of Victoria and southeastern New South Wales. country rock. In some places, the heat was In the WANGARATTA region, these rocks are sufficient to begin melting the sedimentary represented by the "Hotham beds" which rocks, forming migmatites. includes both Lower Ordovician Pinnak Sandstone and Upper Ordovician Bendoc Early Silurian to Early Devonian marine Group. The Pinnak Sandstone consists of sedimentation (430–385 Ma): Melbourne sandstones and mudstones deposited by "Trough" GEOLOGY AND PROSPECTIVITY - WANGARATTA 17

Deep marine sedimentation continued from the and fluvial sedimentation occurred prior to the Late Ordovician through the Silurian into the eruption of the Molyullah Ignimbrite, the late Early Devonian without interruption in the youngest preserved unit. Further block Melbourne "Trough" west of the Mount faulting and erosion took place prior to the Wellington Fault Zone. The Silurian and lower main phase of Late Devonian fluvial part of the Lower Devonian sequence consists of sedimentation of the Mansfield Group. slowly deposited mudstone and fine-grained quartzose sandstone, known as the Jordan Late Devonian "redbed" style sedimentation River Group. This is overlain by the thick and (370–355 Ma): Mansfield Group rapidly deposited Walhalla Group, consisting of thick- to thin-bedded sandstone turbidites and In the Late Devonian, a large river system mudstone, and minor conglomerate. deposited flood-plain sediments across much of the region. The sequence is broadly upward Middle Devonian Tabberabberan Deformation fining from conglomerate and sandstone in the (385–380 Ma) basal Mount Timbertop Conglomerate, to predominantly red overbank mudstones of the In the Middle Devonian, the second major Devils Plain Formation. compressional deformation to affect WANGARATTA folded and faulted the rocks of Early Carboniferous Kanimblan Deformation the Melbourne Zone, and produced overprinting (350 Ma?) fabrics in the older rocks. South of the Strathbogie Granodiorite the folds trend NNW The Mansfield Group are largely undeformed but farther north they follow a broad arc within the Mansfield structural basin except around the Violet Town Caldera. The Mount along the margins. The Rose River Fault along Wellington Fault Zone was formed at this time. the northeastern margin of the basin is marked The chronology of large-scale faulting in by a shear zone along which the Mansfield eastern WANGARATTA is generally difficult to Group sediments have been upturned and in pinpoint but some faulting certainly took place places overturned. The Barjarg Fault along the in the Early Devonian. The Glen Creek Fault western margin of the Mansfield Basin is near Yackandandah is stitched by the Bruarong largely obscured by Cainozoic sediments but Granite which has a late Early Devonian appears to be a normal fault, along which the cooling age. The Kancoona Fault Zone is Timbertop Conglomerate and lower Devils ductile (mylonitic) where it crosses the Plain Formation are missing, as well as an Bruarong Granite, but forms a brittle fault zone unknown thickness of Delatite Group along the eastern margin of the Late Devonian sediments. Pilot Range Batholith, suggesting several episodes of displacement. 4.3 Late Palaeozoic and Middle to Late Devonian caldera volcanism Mesozoic epi-cratonic (375–365 Ma): Violet Town and Wabonga sedimentation calderas Late Carboniferous to Early Permian The evolution of the Violet Town caldera was (300-285? Ma): Boorhaman Conglomerate and simple, with eruption of rhyolite lavas in what Urana Formation. appear to be small domes followed by caldera collapse and explosive eruption of the thick At this time Australia lay near the South Pole rhyolitic Violet Town Ignimbrite. The Wabonga and had a glacial climate. The Boorhaman Caldera is much more complex and began with Conglomerate consists of tillite, slump deposits deposition, in the late Middle Devonian, of the and sandstone and siltstone deposited by fluvial and colluvial Lewis Farm Conglomerate glaciers and periglacial and sub-glacial streams, followed by the first collapse phase, with probably in a glaciomarine environment. The explosive eruption of the Hollands Creek Urana Formation is entirely marine but was Ignimbrite. This first phase was followed by deposited in quiet, anoxic water. block faulting and erosion prior to the second 4.4 Late Cretaceous break-up of eruptive phase, in which three thick ignimbrites were deposited, the Mine Creek, Gondwana (ca 95–65 Ma) Ryans Creek and Toombullup ignimbrites. These show a trend of decreasing silica content. The history during the last 100 million years Yet another episode of block faulting, erosion was controlled by the break-up of the 18 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Gondwana supercontinent, especially the separation of Australia from Antarctica and New Zealand. This began in the mid- Cretaceous about 95 million years ago, when the Tasman Sea began to open, and major subsidence occurred in the Gippsland and Otway Basins. This was combined with major uplift of a broad belt to the north of the coastal plain, forming the Great Dividing Range, whereas the area farther north remained subdued and became the Murray Basin.

Late Cretaceous to Recent stream incision, basaltic volcanism, block faulting, fluvial sedimentation (80? Ma–Recent)

The Late Cretaceous uplift began a cycle of incision and lateral erosion that continues at the present day. There were localised interruptions to this erosion cycle by eruption of basalts, and by block faulting in the Ovens Graben.

The earliest post-breakup landscape is recorded by the White Hills Gravel, and these show that a mountainous landscape existed by Late Cretaceous or Palaeocene times in the area fringing the Murray Basin. In the late Eocene and Oligocene, basalts of the Older Volcanics were erupted onto an elevated plateau in the Tolmie area from which they flowed down valleys to the north. Block faulting in Miocene times created the Ovens Graben into which the fluvial Calivil Formation was deposited.

Fluvial sedimentation in the Murray Basin began in the Eocene within WANGARATTA and has continued to the present day, with the only change during this time being the gradual increase in the area covered by the Riverine Plain. GEOLOGY AND PROSPECTIVITY - WANGARATTA 19

5 Sedimentary and volcanic 300 m (McGoldrick, 1976). Brown (1961) found small inarticulate brachiopods in the rock units northernmost chert outcrop. By themselves these are of little use in age determination, but 5.1 Cambrian the gross similarity of the sequence with that of Lancefield suggests correlation with the Middle Cambrian Monegeetta Shale and Late Cambrian rocks outcrop in three main locations Cambrian Goldie Chert (VandenBerg, 1992 in WANGARATTA: a large area around Mount Kilmore). Major and a smaller area south of Katandra, in the west; several outcrop areas on the eastern Cambrian rocks have recently been discovered and northern flanks of Mount Samaria in the in the headwaters of Glen Creek, south of south, and a recently discovered small belt near Mount Strathbogie, by Sandl (1989). The Tallangalook. None of the Cambrian rocks sequence consists of a lower unit of volcanics have been given formal rock unit names. and an upper unit of chert and mudstone, but is more similar to those of Jamieson River and The best documented Cambrian rocks are Licola farther south in that the volcanics are around Mount Major near Dookie, which calc-alkaline andesites. Sandl described the have been subdivided into a number of different volcanics as extrusive porphyritic andesitic lava rock types, but of which the stratigraphic 100–300 m thick, in part vesicular and with succession and rock relationships are still not good flow texture. Overlying this is a polymict well understood. In particular, the role of breccia consisting of shale and siltstone bedding parallel thrusts has probably been fragments, basaltic andesite, impure quartzite overlooked by previous mappers. There are and possibly felsic volcanic clasts. Curiously, three main rock types: metabasalt, gabbro and Sandl noted clasts "of granitic origin" as well as sediments. of ultramafic material. These are the first granitic clasts known from Cambrian rocks in The basalts are all tholeiitic types consisting of Victoria. Interbedded with the breccia are lithic plagioclase and augite with various alteration quartz sandstone and carbonaceous mudstone products (Christie, 1978; Tickell, 1989). The and siltstone. The total thickness of this basalt appears to lie between two successions of sedimentary unit is 200 m at the most. similar sedimentary rocks. These sediments comprise mainly chert which includes beds Geophysical characteristics consisting of quartz and albite, probably volcanic ash (Christie, 1978) and also includes Magnetic: north–south to northwest trending rare detrital quartz grains and sponge spicules. highly magnetic elongate units are interpreted Also present are black shale and siltstone, and to be Cambrian metabasalts. The metabasalts sandstone and conglomerate with grains and form a north–south semi-continuous 'belt' from clasts of basalt and gabbro. south of Tatong to Major Plains, from where they trend westwards. The Cambrian rocks In the "lower", southern belt of sediments on were thrust up along the Governor Fault which Mount Major is a thick sill of gabbro which separates the Melbourne Zone from the Christie (1978; see also Tickell, 1989) has Tabberabbera Zone (Fig. 5). subdivided into pyroxene-rich, plagioclase-rich and normal types. Cumulate layering is quite A similar subsurface 'belt' of magnetic common in these rocks. metabasalts, approximately 10 to 15 km east of the Governor Fault, are interpreted to mirror The outcrops at Tatong north and east of the rocks along the Governor Fault. These Mount Samaria have been described by metabasalts also form a semi-continuous 'belt' McGoldrick (1976) who mapped a lower unit of which trends northwest from Greta South to metavolcanics overlain by (Ordovician?) chert. Yourang. Immediately north of the Youarang The metavolcanics comprise tholeiitic dolerites Granite, the metabasalts trend westwards. and basalts with interbedded volcanogenic, Similar subsurface northwest-trending partly pyroclastic chert and graded sandstone. responses are seen to the north of the Almonds The volcanics show alteration assemblages Granite. These rocks may also be subsurface indicative of zeolite to lower greenschist facies. metabasalts. Overlying the metabasalts is a unit of finely laminated chert with a total thickness of about 20 GEOLOGY AND PROSPECTIVITY - WANGARATTA

The responses of the Mount Major rocks are complex and variable. Northwest-trending The Lower Ordovician sediments consist of greenstones (basalt?) occur in the subsurface massive micaceous sandstone and shaley near Major Plains. The greenstones are highly mudstone at Tatong (McGoldrick, 1976). Rare magnetic and diverge to the southeast from a chert beds are interbedded north of Tatong single unit, approximately 300 m wide, into two (O'Shea, 1977). The only recorded graptolites separate units approximately 200 m wide. from these rocks are Castlemainian and East–west trending greenstone units occur to Darriwilian (at Dookie; Thomas & Singleton, the west of Mount Major. They are highly 1959; Tickell, 1989) and Darriwilian northeast magnetic subsurface basalts and vary in width of Tatong ("Middle Ordovician"; Brown, 1961). from ~ 600 m to 2000 m. The geometry of these The lithological descriptions and graptolite basalts suggests that they are complexly faulted faunas suggest these rock belong to the Pinnak and possibly folded. Sandstone of Eastern Victoria (VandenBerg et al., 1992, 1996; Orth et al., 1995). South of Tatong, the metabasalts are thin (~ 200 m) highly magnetic units trending The Upper Ordovician sediments include black approximately north–south. These units have shale, silicified shale, mudstone and fine- strike lengths of up to 6 km and appear to be grained sandstone, usually well bedded and internally faulted. Highly magnetic north-east with graptolites present in many places trending basalts crop out at Tatong, and are (O'Shea, 1977; Tickell, 1977, 1989). Previous interpreted to continue under cover for descriptions make reference to substantial approximately 4 km. These basalts are wider thicknesses of sandstone in the Upper (~ 300 m) than the units to the south and Ordovician but this mapping preceded the appear to converge into a single north–south discovery, in East Gippsland, of faulted trending unit approximately 300 m wide. relationships between Upper Ordovician black shale (Bendoc Group) and Lower Ordovician The rocks at the head of Glen Creek, have a sandstone (Pinnak Sandstone; VandenBerg moderate but variable response. In the south, et al., 1992; Glen & VandenBerg, 1987; Glen this varies from low to moderate. Northwest- et al., 1990). In the light of this work, it is trending dykes or faults cut the volcanics. suggested that more detailed mapping is necessary to resolve the structural and Moderate to high responses within the stratigraphic relationships of the various Wabonga Caldera northeast of Mt Samaria are Ordovician rocks in WANGARATTA. interpreted to reflect subsurface magnetic volcanics, possibly greenstones. Geophysical characteristics

Radiometric: the radiometric response of the Magnetic: the Hotham beds have a low Cambrian rocks is distinctively low. The response. In the southeast, the sediments are geological boundaries are well defined in the cut by numerous north-northwest trending thin radiometric data. linear magnetic responses, interpreted to be dykes, indicating a possible fault zone west of 5.2 Ordovician (–Silurian?) the Mount Angus Granite. West of the Peechelba pluton, subtle northwest trending weak responses may be from bedding. Hotham beds Moderate magnetic responses with a dendritic pattern, reflect magnetic material within palaeo Most of the area between the Mount Wellington and present day streams. and Kancoona faults consists of undifferentiated Ordovician sediments, In the south the Hotham beds are bounded by formerly referred to Hotham beds. There has the Rose River Fault. This fault is marked by a been no attempt to carry out lithological contrast in the magnetic character between the mapping in this area, and the scanty fossil Hotham beds and Mansfield Group. In the information that is available indicates that both north, the Rose River Fault separates the Lower and Upper Ordovician rocks are present. Hotham beds from the Ryans Creek Rhyolite In view of the recent discovery of Silurian and is visible as a magnetic low, probably due sediments (Cobbannah Group; Fergusson, in to destruction of magnetite. press) in the upper Howqua River to the south, it is possible that such sediments also occur in the Hotham beds within WANGARATTA. GEOLOGY AND PROSPECTIVITY - WANGARATTA 21

Radiometric: the responses of the Hotham beds East of the Yackandandah Granite and vary widely (low to high) across southwest of the Kergunyah Adamellite, a WANGARATTA. Northwest-trending low moderately magnetic 'unit' within the mapped responses, southwest of Mount Buffalo, coincide Omeo Metamorphic Complex is fault bounded with bedding trends and possibly reflect thick by northwest-trending faults to the northeast sandstone units. A moderate potassium and southwest. The unit is also fault bounded response within the Hotham beds to the by a north-northeast trending fault on its southwest of the Mount Emu Granite is northwestern margin. possibly due to unmapped outcrops of this granite. Radiometric: the radiometric response of the metamorphics is moderate to high. Northeast The detailed data indicate that the Hotham of the Morilla Granite, northwest-trending high beds can be subdivided. An example can be potassium responses are seen within the seen north of the Mount Stanley Adamellite, metamorphics, and may be from slivers of where a 'unit' with low potassium, moderate granite within the Kancoona fault zone. thorium, low uranium responses occurs. This 'unit' lies within the moderate to high response 5.4 Silurian–Lower Devonian— from the surrounding Hotham bed sediments and is bounded by the Kancoona and Melbourne "Trough" Beechworth Faults. The rocks on the western and southern side of the Mount Wellington Fault Zone are 5.3 Silurian—Omeo undifferentiated Silurian and Early Devonian Metamorphic Complex sediments belonging to the Jordan River and Walhalla Groups. Some mapping has been done High-grade metamorphic rocks are confined to in the area south of the Strathbogie pluton the area east of the Kancoona-Kiewa fault (Phillips & Wall, 1980; Sandl, 1989), which system. The rocks are all derived from the forms the northern extremity of the Mount Pinnak Sandstone and range from biotite and Easton Fault Zone, and unpublished mapping spotted to knotted cordierite schist to migmatite by the author in this area has shown that most and gneiss. The highest grade rocks in of the formations of the Jordan River Group headwaters of Commissioner's Creek are fine- (Bullung Siltstone, Sinclair Valley Sandstone, grained banded gneiss with "pegmatitic" Whitelaw Siltstone and Eildon Sandstone) (presumably K-feldspar and quartz) continue from the south well into porphyroblasts and locally containing WANGARATTA. However, further detailed sillimanite (Leggo, 1964; Leggo & Beavis, 1967). mapping is necessary to resolve the structural and stratigraphic relationships here. The rocks Geophysical characteristics here consist of laminated siltstone and generally fine-grained quartz-rich sandstone, in Magnetic: these sediments have a very low places with abundant small scale cross bedding. response within which there are northwest- In the Walhalla Group east of Tallangalook trending low responses, interpreted to be Creek, Sandl (1989) has mapped several units possibly due to bedding. The metamorphic of sandstone, lithic sandstone and mudstone rocks are bounded in the west by the Kancoona with conglomerate beds occurring in the Fault. sandstone and mudstone units. The conglomerates consist mostly of quartzite and The Kancoona Fault is readily identified in the minor sandstone, but the lithic sandstone data and can be extended beyond its mapped contains feldspar and occasional grains of mafic northern limit. The Kancoona Fault defines the or intermediate volcanics (Sandl, 1989), as well western edge of the High Plains Subzone within as grains of mudstone and quartz sandstone. the Omeo Zone. It is ~ 6 km wide at the The mudstone formations are generally thin- Beechworth Fault and narrows to the bedded with thin beds of fine-grained quartz northwest. Moderate northwest-trending sandstone. responses northeast of the Morilla Granite are interpreted to be dykes within the Kancoona In the Tatong area, undifferentiated Silurian– fault zone. Unmapped faults that trend Devonian sediments occur northwest of Mount northwesterly to westerly and northeasterly cut Samaria. McGoldrick (1976) found these to these dykes and surrounding metamorphics. consist of massive quartz sandstone 22 GEOLOGY AND PROSPECTIVITY - WANGARATTA

interbedded with grey mudstone, and mudstone Violet Town Caldera with interbedded thin sandstone. This contains a single mapped pyroclastic unit, To the north of the Violet Town caldera, the Violet Town Ignimbrite, consisting of quartz undifferentiated Silurian–Devonian sediments ignimbrite of rhyodacitic composition, with crop out in a broad arc of low hills. The only biotite, estimated to be 450 m thick. White mapping in this area was done south of Dookie (1954) called it a quartz-biotite-hypersthene by Tickell (1989) who shows folds that trend dacite but Lim (1984) did not mention the parallel to the arc-like outcrop pattern. He presence of hypersthene; he noted the presence described the rocks as thin-bedded, mostly fine- of cordierite and garnet. The ignimbrite is grained sandstone interbedded with mudstone mostly recrystallized and without lithic and rare pebble conglomerate. fragments except at the margins, where the base is exposed. There are also small outcrops Geophysical characteristics of rhyolite lava which underlie the ignimbrite. White (1954) stated that the rock has the same Magnetic: the magnetic response of the composition and dark grey appearance as the sediments is low. A high response in the main collapse-phase ignimbrites of the Mount southwest is due to the magnetic Terip Terip Dandenong, Acheron and Cerberean calderas. pluton beneath the Strathbogie Granite and The caldera has a broad basin-like structure sediments. South of the Strathbogie Granite, with a mostly subhorizontal base but with the numerous small high-frequency moderate ignimbrite steeply upturned around the responses are from man-made constructions. marginal ring fault. In the south and west, this North of this granite, abundant dendritic ring fault juxtaposes ignimbrite against the magnetic highs are interpreted to be from Strathbogie Granodiorite except in two places, magnetic material within present-day and fossil where plug-like bodies of hornfels are the drainage. remnants of a bedrock screen. Lim (1984) mapped several flows rich in hornfels lithic Radiometric: the radiometric responses vary fragments at the southern boundary, some of from moderate to high. High responses coincide which may be debris flow deposits. The with bedrock ridges north of the Strathbogie ignimbrite post-dates the Strathbogie Granite, Granite. A moderate thorium response is shown by the presence of both hornfels and coincident with the mapped Melbourne Zone granite fragments in the volcanics. sediments. This response continues to the southeast, between Violet Town and Benalla, Geophysical characteristics where Shepparton Formation is mapped. The radiometric data suggest that the Melbourne Magnetic: the volcanics have a low magnetic Zone sediments may be more extensive than response. A high response in the southwest is mapped. due to the magnetic Terip Terip pluton beneath the Strathbogie Granite and sediments. 5.5 Devonian volcanics and Numerous small high-frequency responses sediments within the volcanics are interpreted to be from man-made constructions. Upper Devonian volcanics and sediments are Radiometric: the volcanics have low to high confined to the southwestern and southern part radiometric responses. The variations in the of WANGARATTA, but a small area of Lower data possibly represent different flows, of which Devonian volcanics occurs at Albury. at least two can be identified. The mapped boundary between the volcanics and the The Upper Devonian volcanics occur in two Strathbogie Granite to the south is well defined medium-sized calderas, the Violet Town caldera in the data. around Violet Town, and the Wabonga Caldera in the Tolmie Highland. Both contain S-type volcanics, indicated by the presence of garnet Wabonga Caldera: Tolmie Igneous and rare cordierite. Complex

This is a complex caldera which extends from Molyullah and Tatong in the northwest, to the foot of Mount Stirling in the southeast. The southern half is largely obscured by overlying GEOLOGY AND PROSPECTIVITY - WANGARATTA 23

Mansfield Group sediments. The northwestern granodiorite, suggesting that its vent lay near part of the caldera was first mapped by Brown the southern margin of the caldera where it (1961) and subsequently the entire caldera by abuts the Mirimbah Granodiorite. Gaul (1982, 1995). The structure and eruption history of the caldera are more complex than of Considerable block faulting and erosion any other Devonian caldera in Victoria, and occurred within the caldera prior to the were controlled by a series of northwest- and eruption of the youngest pyroclastic unit, the north-trending faults that follow the underlying Molyullah Ignimbrite, preserved only in the bedrock trend. The largest of these is the northern part of the caldera where it lies Stockyard Creek Fault, in the middle of the unconformably on both the Ryans Creek and northwestern part of the caldera, which has Toombullup ignimbrites, in places separated by brought underlying Ordovician bedrock to the quartzose sandstone and conglomerate which surface. lack volcanic material. Although only small remnants of the Molyullah Ignimbrite are Collapse began in a relatively small area near preserved, it is densely welded in part and the northwestern end of the caldera, with 200 m thick one outcrop, suggesting that it was deposition of the strongly lenticular Lewis once a much more extensive and thick unit. Farm Conglomerate. This consists of quartzose conglomerate and interbedded Small stocks of granodiorite porphyry occur sandstone overlying Cambrian volcanics and along the marginal faults around the caldera Ordovician sediments, and contains Givetian and on one of the internal faults. They intrude (late Middle Devonian) fish fossils (Long, 1982). the Ryans Creek and Toombullup ignimbrites The conglomerate is overlain by the Hollands were erupted and represent the final phase of Creek Ignimbrite, a thick rhyolitic to igneous activity in the caldera. rhyodacitic ignimbrite of relatively small extent. Judging from Gaul (1982) the rock is Geophysical characteristics moderately to densely welded, and at least 300 m thick, although Gaul cites a maximum Magnetic: these volcanics have a low to thickness of about 200 m. Its eruption marks moderate magnetic response. Northeast of the close of the first phase in the Wabonga Mt Samaria, moderate to high responses are Caldera, and was followed by a period of tilting interpreted to be subsurface magnetic volcanics, and erosion. This episode is represented by a possibly greenstones. High-frequency, high- few outcrops of conglomerate (Brown, 1961). amplitude responses are due to magnetic material within present-day and fossil The second eruptive phase began with eruption drainage, and unmapped Older Volcanics. of the Mine Creek Rhyolite, which is only exposed along the upturned southern and Radiometrics: these volcanics have moderate to southeastern margins of the caldera. It consists high radiometric responses and their mapped of rhyolitic lava, in part autobrecciated and boundary matches the edge of these responses. containing garnet phenocrysts, which overlies The volcanics can be divided into at least three the Mirimbah Granodiorite. Most of this separate flows from their radiometric formation lies to the south of WANGARATTA. responses. They are (1) a high potassium, The rhyolite is overlain by the very thick thorium and uranium flow, (2) a high Ryans Creek Ignimbrite, the first of the two potassium, low thorium, moderate uranium collapse-phase ignimbrites of the Wabonga flow, and (3) a low potassium, high thorium, Caldera. It is at least 450 m thick (Gaul, 1995 moderate uranium flow. The radiometric data cites a maximum thickness of 400 m but this is could be used to supplement detailed mapping clearly an underestimate, judging from his in order to determine the relationships between map) and is a pale-coloured rhyolitic quartz the flows, and the mapped Ryans Creek, ignimbrite with cordierite and garnet Toombullup and Molyullah Ignimbrites. phenocrysts. The rock is densely welded to recrystallized over most of its outcrop area (Birch, 1978a). The overlying Toombullup Ignimbrite is the final collapse-phase ignimbrite and consists of more than 700 m of recrystallized rhyolitic to rhyodacitic ignimbrite with biotite and garnet and, in places, hypersthene. This ignimbrite also is the only one that contains lithic fragments of hornblende 24 GEOLOGY AND PROSPECTIVITY - WANGARATTA

5.6 Upper Devonian– seen within the Mansfield Group east of the Carboniferous(?) Mansfield King River. Group Radiometric: this unit has a distinctively low response, south of the Wabonga Caldera, in The Mansfield Group outcrops extensively at contrast to the surrounding high-response the surface in the Mansfield Basin between the sediments, granites and volcanics. East of the Broken River and Rose River, and occurs in the Barjarg Granite, material with a high response subsurface in the Ovens Graben. The group lies is being shed from an unknown source and conformably on all older sediments, including transported downstream along the present-day the various volcanics of the Wabonga Graben, drainage. A distinctive low potassium, which had been planated prior to the deposition moderate thorium and low uranium response of the Mansfield Group. It also post-dates the around Hansonville may be from unmapped Strathbogie and Barjarg granites, although Mansfield Group. contacts between them are generally faulted. The Mansfield Group is a very simple sequence, 5.7 Carboniferous–Permian consisting of a thin basal conglomerate, the Timbertop Conglomerate, overlain by the very Small scattered remnants of the Late thick Devils Plain Formation. In a few places, Carboniferous Boorhaman Conglomerate occur for instance near Whitfield, the conglomerate is at the surface along the southern and eastern underlain by red claystone and arkosic margins of the Ovens Graben, and at Wooragee sandstone that may be the only representatives northeast of Beechworth. There are much more of the Delatite Group within WANGARATTA. extensive deposits, however, of Boorhaman Conglomerate and the overlying Permian According to Marsden (1976, p. 170; 1988, Urana Formation below Murray Basin p. 179) the Timbertop Conglomerate is sediments in the Numurkah Trough northwest continuous across the Mansfield Basin and it is of Dookie, and in the Ovens Graben which is shown accordingly on all maps. Gaul (1995), the southern extension of the Oaklands Graben. however, stated that it is absent from the northern part of the basin. It is 100–350 m Boorhaman Conglomerate thick, consisting of massive conglomerate, generally well sorted with rounded pebbles of The outcrops in the Ovens Graben and at quartzite, vein quartz, chert and jasper, and Wooragee consist of grey diamictite ("tillite") occasional volcanics, and has interbedded with minor intercalations of mudstone. The coarse to fine sandstone, pebbly sandstone and best drill intersection in Laceby 2 bore, minor mudstone. This is overlain by several southeast of Laceby, showed 176 m of diamictite hundred metres of quartzose white sandstone, interbedded with sandstone and mudstone lithic micaceous sandstone and mudstone. overlying red and green mudstone of the Devils Plain Formation. The diamictite consists of The Devils Plain Formation is a thick rounded clasts, up to boulder size, of various sequence (1200 m or more) of red mudstone Lower Palaeozoic rock types, loosely scattered with minor white and red medium to fine- in a very poorly sorted sand-silt-mud matrix grained sandstone, often occurring in discrete (Tickell, 1977). Older maps show these rocks as packages and with a variety of bedding and "Permian" but spore-pollen analysis has shown cross bedding styles indicative of channel that they belong to Stage 1, assigned to the deposits. Late Carboniferous (see Holdgate, 1995). The formation is also present in the Numurkah Geophysical characteristics Trough.

Magnetic: the magnetic response is low. A Geophysical characteristics moderate response over the sediments is possibly due to basal volcanics, while a high Magnetic: the magnetic response of this unit is response is due to a subsurface magnetic very low. granite south of Tolmie. Numerous small circular moderately magnetic highs are Radiometric: the radiometric responses are low, interpreted to be Tertiary volcanic plugs. similar to those of the Mansfield Group. Subtle northwest- to north-trending weakly Correlations between the radiometrics and the magnetic responses, which may be bedding, are mapped boundaries vary. Mapped patches of GEOLOGY AND PROSPECTIVITY - WANGARATTA 25

Boorhaman Conglomerate south of Wangaratta White Hills Gravel which is extensive in correlate well with the radiometrics. A southern tributary valleys of the Murray Basin distinctive low potassium, moderate thorium in central and western Victoria. and low uranium response is evident around Hansonville. This response may be from Geophysical characteristics unmapped Boorhaman Conglomerate , but is more likely to be from unmapped Mansfield Magnetic: the magnetic response of the gravels Group. is very low.

Urana Formation Radiometric: moderate thorium responses are associated with these sediments, possibly This formation only occurs in the subsurface in reflecting laterisation. In central Victoria, the the Ovens Graben and Numurkah Trough. White Hills Gravel has a low radiometric Holdgate (1995) described them as dark grey to response, and a moderate thorium response black organic-rich mudstone and siltstone with where it is laterised (Cayley & McDonald, marine microfossils which indicate Early 1995). Permian age. They are relatively thin in the southern part of the Ovens Graben but thicken Renmark Group rapidly north of Boorhaman, reach a maximum of 900 m farther north in the Jerilderie area Sediments of the Renmark Group only occur in (Holdgate, 1995). The formation is also present the deeper parts of the Numurkah Trough in in the Numurkah Trough. the westenmost part of WANGARATTA, where it is shown in a cross-section in Holdgate (1995). 5.8 Tertiary No lithological details are provided, but Holdgate stated that the group includes the Olney Formation of Eocene to Miocene age, Tertiary sediments are extensive in the comprising mainly sands, clays and minor subsurface, underlying the surficial Quaternary brown coal. The sediments fill valleys cut into sediments of the Murray Basin. They are very the underlying Permo-Carbonifous sediments. thin in the Ovens Graben but up to 100 m thick in the Numurkah Trough near the western border of WANGARATTA. Outcropping Older Volcanics Tertiary rocks include Older Volcanics in the Tolmie Highlands and Miocene or Pliocene Basalts of the Older Volcanics occur as widely basalts south of Euroa and at Cosgrove. High- scattered hilltop and plateau remnants in the level gravels occur in several of the tributary Tolmie Highlands, with two long narrow valleys of the Murray flood plain, and along the tongues extending north on either side of Boggy Murray River itself at Albury. Although Creek towards Moyhu. Basalt has also been previously mapped as Pliocene, these are intersected in a drillhole (Boorhaman 1) in the probably much older, correlating with the Ovens Graben, 20 km north of Wangaratta, Palaeocene? White Hills Gravel. overlying the Permian Boorhaman Conglomerate. The rocks are mostly tholeiitic "Tp"—White Hills Gravel? basalts but include basanite and alkali olivine basalt (Price et al., 1988). Small patches of high-level gravel have been A very small outcrop of basalt occurs at mapped along the Ovens River at Myrtleford, at Glenrowan where the Hume Highway crosses Reedy Creek north of Beechworth, along the Warby Range (Eaton, 1984). Yackandandah Creek and at Bonegilla south of Albury. They are given a Pliocene age on Wellman (1974) has obtained K/Ar ages of previous maps (King, 1979, 1983; O'Shea, between 43 and 36 Ma (late Eocene to early 1979a, b) but their topographic relationship Oligocene) from the basalts in the Toombullup with the Calivil Formation indicates that they region. are older. They are described as conglomerate, gravel, sand, and at Bonegilla overlie laminated silts and sand with bands of ferruginization (King, 1979) or as cemented sand and gravel. Most descriptions indicate either a red colour or ferruginous cement, and most are auriferous. This suggests correlation with the Palaeocene? 26 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Geophysical characteristics its physiographic setting suggests a relatively young age, probably Pliocene (Hills, 1939). Magnetic: the Older Volcanics have a high- amplitude magnetic response, with both Geophysical characteristics negatively and positively magnetised basalt flows apparent. The magnetic data show Magnetic: these basalts have high-amplitude, inaccuracies in the mapped basalt boundaries high-frequency magnetic responses. The data and shows unmapped basalts west of Myrrhee. suggest that the flows within the Seven Creeks valley are much more extensive than mapped. Radiometric: the Older Volcanics have low Basalts are also interpreted to occur north of radiometric responses. The majority of mapped Euroa and southwest of Violet Town. basalt boundaries correlate well with the radiometric data. The unmapped basalts west Radiometric: the radiometric data support the of Myrrhee seen in the magnetics are also magnetic interpretation that the basalts south evident in the radiometric data. of Euroa are more extensive than mapped. The basalts identified from the magnetic data, north Calivil Formation of Euroa and southwest of Violet Town, have no radiometric responses, suggesting that they are This formation is very widely distributed in the in the subsurface. Murray Basin, having been found as far inland as the Kiewa Valley near Kergunyah and in the Cosgrove Leucitite Ovens Graben at Wangaratta. In most places it is the oldest post-Palaeozoic unit. It consists of Leucite-bearing lava outcrops on a small hill light grey quartz gravel and sand and is an near Cosgrove, 7 km WSW of Dookie (Birch, important aquifer. It is generally quite thin, 1976, 1978b). The rock is a dark grey olivine between 10 and 20 m, rarely more than 25 m. leucitite with olivine and less commonly clinopyroxene phenocrysts in a groundmass of Newer Volcanics clinopyroxene, leucite, Fe-Ti oxides, interstitial nepheline and a brown mica rich in barium and Two small areas of Newer Volcanics occur in titanium. Birch (1978b) also observed the WANGARATTA. One is a basanite in the presence of veins of a coarse-grained pegmatoid valley of Seven Creeks, the other a leucitite at differentiate. Cosgrove west of Dookie. They have both Geophysical characteristics returned late Miocene K/Ar ages: 5.8 Ma for the Cosgrove rock, and 6.8+ Ma for the Seven Creeks Basalt (Wellman, 1974). These are very Magnetic: the magnetic response of this rock is similar to the ages of the alkali-rich basalts of masked by highly magnetic subsurface the Woodend region northwest of Melbourne, greenstones. which are considered to be the oldest lavas of the Newer Volcanics. Radiometric: this lava has a low radiometric response which matches its mapped boundary. Seven Creeks Basalt Shepparton Formation A flow of basanite ("limburgite") occupies the valley of Seven Creeks, south of Euroa, This is the thickest and most extensive of the outcropping as a narrow strip just above the Tertiary formations in the Murray Basin within valley floor (White, 1954). It extends in the WANGARATTA. It consists mainly of silty subsurface to Euroa and there is an isolated clay, but with variable amounts of interbedded patch about 7 km northwest of Euroa. Hills sand. It reaches a maximum thickness of about (1939) described it as a "limburgitic basalt" 120 m in the Numurkah Trough and about containing numerous phenocrysts of olivine set 100 m in the Ovens Graben. The formation has in a groundmass of augite, glass and a few been subdivided into a number of members, plagioclase laths, with plentiful "black iron separated by soil horizons. The channel sands ores" (presumably magnetite, judging from its are commonly clayey, micaceous and magnetic character). Dunn (1914) also feldspathic, reflecting their granitic source. mentioned the presence of scoria and ash beds. They are usually internally stratified and show No age determination has been carried out, but either planar bedding or trough-type cross- bedding when exposed at the surface. Beds commonly fine upwards. Clay layers are GEOLOGY AND PROSPECTIVITY - WANGARATTA 27 generally internally stratified (beds between Colluvium, gully alluvium (Qrc) 0.2–10 m), contain fossil soil horizons, and can often be traced for several kilometres (Tickell, These deposits are generally confined to the 1977). The formation ranges from Pliocene to smaller streams and gullies in the dissected Pleistocene. mountain tract. They consist of poorly rounded and poorly sorted material, grading from cobble Geophysical characteristics to clay size, whose composition closely reflects its source. Magnetic: these sediments are very weakly magnetic. Subtle north-trending and Geophysical characteristics northwest-trending low responses are evident south of Wangaratta and southwest of Magnetic: the responses from the colluvium are Yarrawonga. The low response trends are the result of either magnetic sources from possibly magnetic marker horizons within the underlying rocks or of surface maghemite found underlying Mansfield Group rather than within stream sediments. In many places, the magnetic beds within the Shepparton magnetic signature consists of closely spaced Formation. Abundant dendritic magnetic highs parallel responses indicating that it comes from within the sediments are interpreted to be from the terraces, not from the alluvial flats. East of magnetic material within the present-day and the Mount Bruno Granite (and nearby granites) fossil drainage. a north–south magnetic response is evident within the mapped colluvium. This trend is Radiometric: the radiometric responses vary interpreted to be the Warby Springs Fault. from low to high. Distinctive responses from outwash fans are prominent across Radiometric: the radiometric response from the WANGARATTA, including those from the colluvium is often a reflection of the source rock Broken River, King River and Reedy Creek. from which it was derived. The exception is in They reflect their source rock (i.e. high- areas south and north of the Yackandandah potassium responses from sediments derived Granite where high thorium responses possibly from granites). For example, the Strathbogie reflect laterisation. Granite is the source of potassium-rich sediments in the Broken River. North of Swamp deposits (Qrm) Benalla, the river flows to the west, but the radiometric data indicate that it once flowed Small swamps occur on the Riverine Plain in northwards producing an outwash fan with a the north of WANGARATTA and in the area high radiometric response. north of Violet Town. They contain black clay.

A low response is evident northwest of Mount Geophysical characteristics Major and extends to Nine Mile Creek. This is interpreted to be from water-logged sediments, Magnetic: the responses from these deposits are as the area is heavily irrigated. due to magnetic sources within the underlying rocks or maghemite within present-day or older 5.9 Quaternary sediments stream sediments.

Quaternary sediments occur throughout the Radiometric: the responses vary from low to map area but are generally confined to river moderate. Dowdle Swamp north of valleys, lower slopes and around existing Boomahnoomoonah has a distinctly low swamps. They include alluvium (Qra), response, indicating that it was filled with colluvium, hillwash and scree deposits (Qrc), water at the time of the survey. swamp deposits (Qrm) and source-bordering dune deposits (Qo, Qu). Dune deposits (Qo)

Alluvium (Qra) Dune deposits only occur on the Riverine Plain in the north of WANGARATTA. They are This consists of unconsolidated sand and gravel, described in the map legend as consisting of grading downstream into sand, silt and clay. sand, silt and clay. Recent alluvium in the Murray Basin has often been referred to the Coonambidgal Formation. Geophysical characteristics 28 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Magnetic: the dune deposits have no magnetic response. Responses evident in these areas are the result of magnetic sources within the underlying rocks or maghemite within present- day or older stream sediments.

Radiometric: the deposits south of Cobram have a distinctive high-potassium response, possibly reflecting clays within these deposits. The response correlates well with the mapped boundaries. Unmapped, high-potassium, deposits occur along the Murray River. GEOLOGY AND PROSPECTIVITY - WANGARATTA 29

6 Intrusive rocks Magnetic: the granite is possibly multi-phased with a non-magnetic southern portion and a Granites occur across the whole of moderately magnetic portion in the north. WANGARATTA. Most of them have been Moderately magnetic sediments around the studied in some detail, so that their granite possibly are a contact aureole; an petrographic character and mineral composition alternative interpretation is that a highly are known. Several have had their age magnetic pluton is present at depth beneath determined by radiometric means. Table 4 lists Mount Buffalo. Two highly magnetic plugs the rock and geochemical classification and occur near the centre of the granite. measured/estimated age of all the plutons, and their characteristic magnetic and radiometric Radiometric: the granite has high potassium, response. low thorium and moderate uranium responses which are coincident with its mapped boundary. 6.1 Granites G162 Mount Emu Granite The geophysical responses of the various Batholiths, and subsurface granites identified It is a grey, strongly porphyritic rock with from the magnetic data, are described under phenocrysts of all three felsic minerals. Modal their respective headings. composition: 32% quartz, 30% K-feldspar, 24% plagioclase, 10% biotite, 2% hornblende, and G158 Mt Selwyn Granite accessory magnetite and muscovite.

This is located in the southeast Geophysical characteristics WANGARATTA. Within WANGARATTA it is a buried, highly magnetic pluton but it crops out Magnetic: this granite is non-magnetic; farther south as granite. There is no other however, a highly magnetic pluton is evident information available for this intrusion. approximately 3 km to the southwest (see Cropper pluton description). G160 Mount Angus Granite Radiometric: the granite has moderate This small pluton consists of grey evenly fine to potassium, low thorium and uranium medium-grained hornblende granodiorite. responses. The extent of the radiometric Modal composition: 30% quartz, 18% K- responses is much larger than the mapped feldspar, 37% plagioclase, 11% biotite, 2% granite boundary, suggesting that the boundary hornblende, accessory sphene, magnetite. needs remapping.

Geophysical characteristics G176 Baranduda Granite

Magnetic: the granite is interpreted to consist of This small pluton consists of evenly medium- three plutons, two non-magnetic and one highly grained grey two-mica adamellite. Modal magnetic pluton. On its western edge, the composition: 32% quartz, 27% K-feldspar, 20% granite is moderately magnetic and trends plagioclase, 10% biotite, 10% muscovite. north–south and is interpreted to be buried. The northeastern portion of the granite is Geophysical characteristics interpreted to dip to the northeast under cover. Magnetic: this granite is non-magnetic and has Radiometric: the highly magnetic portion of the a similar response to the northern part of the granite has moderate potassium and uranium Yackandandah Granite (see also G178 note). responses and a low thorium response. Radiometric: the radiometric responses vary G161 Mount Buffalo Granite from low to high within its mapped boundary.

The granite forms a high plateau. The rock is very coarse-grained and leucocratic, with a modal composition of 36% quartz, 36% K-feldspar, 24% plagioclase, 3% biotite, and accessory muscovite. Geophysical characteristics 30 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Table 4 Summary of granite plutons

G Name Rock type Type1 Age Authors2 Mag3 Rad4 No. K Th U

158 Mount Selwyn ? Devonian? H 160 Mount Angus granodiorite I F u Devonian Eaton 1986 M–H L L L 161 Mount Buffalo granite I F f E Devon Eaton 1986 W–M H L V 162 Mount Emu adamellite Devonian Eaton 1986 W M L L 176 Baranduda adamellite Devonian Eaton 1986 W M L V 177 Yackandandah adamellite I M u E Devon Lightbody 1984 M–H H L V 178 House Creek "paragneiss" S M u Silurian? Leggo 1964 179 Mudgeegonga adamellite I M u E Devon? Lightbody 1984 180 Kergunyah adamellite Devonian Eaton 1986 W M L V 181 Bruarong adamellite I M u E Devon? Lightbody 1984 182 Barnawartha granodiorite S F u Silurian? Leggo 1964 N H V H (Lady Franklin) 183 Mount Stanley adamellite Devonian Eaton 1986 W–M V L L 193 Woolshed Valley granite I F f Lt Devon? Young 1983 W H M H 194 Morrilla adamellite I Lt Devon? Young 1983 W V V V 195 Beechworth granite I F f Lt Devon Young 1983 W H V H 196 Golden Ball adamellite I F u Lt Devon? Young 1983 W H L V 197 Byawatha aplite I F u Lt Devon? O'Shea 1981 W H L V 198 Everton granodiorite I F u Lt Devon? Waldon 1977 H H L L 199 Murmungee granodiorite I M u Devonian Eaton 1986, I H M L McDonald 1988 200 Lurg granite Devonian Eaton 1986 W H V V 201 Kelly Gap granite Lt Devon? Eaton 1984 W H H V 202 Glenrowan granite Lt Devon Eaton 1984 W H H H 203 Warby Springs granite Lt Devon? Eaton 1984 N H M H 204 Taminick Gap granite Lt Devon? Eaton 1984 W H V V 205 Mount Bruno granite I Lt Devon? Eaton 1984 N H V H 206 Killawarra granite Lt Devon? Eaton 1984 N H L V 207 Almonds granite I Lt Devon? Eaton 1986 N V L V 208 Youarang granite Lt Devon? Eaton 1986 N H M V 209 Katandra granite Lt Devon? Eaton 1986 N H L L 210 Bungeet granite Lt Devon? Eaton 1986 W H V H 211 Chesney Vale granite Lt Devon? Eaton 1984 W H H H 214 Baddaginnie ? S M u Lt Devon? 215 Swanpool ? Lt Devon? W V M V 216 Barjarg granite, S F f Lt Devon Nisbet 1978 W V V V granodiorite 217 Strathbogie granite S F f Lt Devon Lim 1984 N V V V Kelfeera granite Devonian Eaton 1986 158 Mt Selwyn5 H GEOLOGY AND PROSPECTIVITY - WANGARATTA 31

Table 4 Summary of granite plutons (Cont'd)

G Name Rock type Type1 Age Authors2 Mag3 Rad4 No. K Th U

711 Peechelba5 H 712 Terip Terip5 H 713 Brimin5 H 714 Berachah5 H 715 Cropper5 H 716 Bandiana5 H 717 Thurgoona5 H 718 Tangambalanga5 H 719 Lake Mokoan W

1 I = I-type, S = S-type, F = felsic, M = mafic, u = unfractionated, f = fractionated; taken from Chappell et al., 1991. 2 Author(s) of most recent information. 3 Magnetic response; N = non magnetic, W = weakly magnetic, M = moderately magnetic, H = highly magnetic, I = intensely magnetic.. 4 Radiometric response; L = low response, M = moderate response, H= high response, V = variable response (L–H), and K = potassium, Th = thorium, U = uranium. 5 Subsurface pluton identified from magnetic data.

G178 House Creek to be carried out in this area to resolve the differences between the mapping and This is an area shown as gneiss (Osn) on geophysics. current maps, lying east of the Kiewa Fault and northwest of the Yackandandah Granite. Leggo Yackandandah Batholith (1964) described the rock as fine-grained paragneiss (implying it is a metamorphosed King (1979, 1983) mapped two granites in this sedimentary rock) but noted that it is relatively batholith, the Mudgeegonga Granite in the homogeneous and without relict bedding. It is upper reaches of Barwidgee Creek, and the fine-grained, rich in biotite, with feldspar, Yackandandah Granite which lies mainly quartz and rarely sillimanite porphyroblasts northeast of the Glen Creek Fault but also (phenocrysts?). The mineral composition is surrounds the Mudgeegonga Granite. biotite, quartz and feldspar with lesser Lightbody (1984) separated part of the body muscovite, cordierite, sillimanite and minor lying between the Kancoona and Glen Creek schorlite. faults off as the Bruarong Adamellite.

Geophysical characteristics Geophysical characteristics

Magnetic: this granite is non-magnetic and has Magnetic: the magnetic data support the three- a similar response to the northern part of the fold subdivision of Lightbody (1984) but Yackandandah Granite. Numerous moderately indicates that the granite south of the magnetic dykes are interpreted within a fault Kancoona Fault is a single multi-phased zone (see Dykes) on the southwestern margin of intrusion which shows pronounced concentric the granite. magnetic banding. The Yackandandah Granite northeast of the Glen Creek Fault is non- Radiometric: this granite has a moderate magnetic and is obviously a different intrusion. potassium and uranium, and a high thorium The Mudgeegonga Granite is interpreted to response. The radiometric responses are stitch, and hence post-date, the Glen Creek similar to the Omeo Metamorphic Complex Fault. (OMC) metasediments to the southeast. Radiometric: the batholith is characterised by a The magnetic and radiometric responses high potassium response. conflict with the mapped granite and OMC G177 Yackandandah Granite: this narrow, metasediment boundaries. Further work needs northeast-trending pluton is porphyritic with 32 GEOLOGY AND PROSPECTIVITY - WANGARATTA

large (to 100 mm) K-feldspar phenocrysts, Geophysical characteristics many of which show plagioclase overgrowths. Biotite forms mafic aggregates. Modal Magnetic: the granites of the batholith are non- composition: 25% quartz, 26% K-feldspar, 35% magnetic except for the Murmungee Granite plagioclase, 11% biotite, accessory allanite, and the subsurface Berachah pluton. The sphene, ilmenite, hornblende. Murmungee Granite contains 2% magnetite which is responsible for its intensely high G179 Mudgeegonga Granite: oval intrusion magnetic response. The highly magnetic lying southwest of the Kancoona Fault, showing subsurface Berachah pluton is a deep intrusion strong onion-shell magnetic banding whose core north of the Murmungee Granite. lies very close to the fault. Outcrops as large tors of medium-grained equigranular felsic Radiometric: the batholith is characterised by a granite. high potassium response. The Morilla and Lurg granites have high radiometric responses. The Modal composition: 46% quartz, 37% outcrop of the Murmungee Granodiorite is too K-feldspar, 6% plagioclase, 8% biotite, 1% small to determine its radiometric responses. tourmaline G193 Woolshed Valley Granite: porphyritic G180 Kergunyah Granite: medium-grained, in all felsic minerals; K-feldspar shows slightly porphyritic with K-feldspar to 25 mm plagioclase overgrowths, and granophyric showing plagioclase overgrowths. Modal texture with quartz. Modal composition: 33% composition: 35% quartz, 31% K-feldspar, 30% quartz, 40% K-feldspar, 22% plagioclase, 4% plagioclase, 3% biotite, accessory magnetite. biotite, accessory muscovite.

G181 Bruarong Granite: this small, kidney- G194 Morilla Granite: coarse-grained, shaped intrusion occupies most of the area slightly porphyritic in all felsic minerals, pink- between the Kancoona and Glen Creek faults. red K-feldspar phenocrysts to 20 mm. Modal Appearance is variable, mostly felsic coarse- composition: 37% quartz, 36% K-feldspar, 21% grained porphyritic with large K-feldspar plagioclase, 5% biotite also muscovite, allanite, phenocrysts (to 60 mm long). Modal topaz, ilmenite, magnetite, sphene, monazite. composition: 35% quartz, 30% K-feldspar, 31% plagioclase, 3% biotite, accessory sphene. G195 Beechworth Granite: even-grained, medium-grained, leucocratic. K-feldspar G182 Barnawartha (Lady Franklin) typically with overgrowths of plagioclase. Granite: medium-grained, foliated, mafic Modal composition: 33% quartz, 40% granodiorite intruded in lit-par-lit fashion into K-feldspar, 22% plagioclase, 4% biotite, schist; also contains abundant pegmatite and accessory muscovite. foliated pegmatite bodies. G196 Golden Ball Granite: evenly medium- G183 Mount Stanley Granite: medium- grained, leucocratic, with silicified zone in the grained, equigranular, felsic rocks with pinkish northwest. Mineral composition: quartz, colour. Modal composition: 27% quartz, 35% K-feldspar, plagioclase, biotite, accessory K-feldspar, 30% plagioclase, 6% biotite, 1% muscovite, fluorite, topaz, ilmenite, zircon. muscovite. G197 Byawatha Granite: aplitic phase along Pilot Range Batholith the northwestern margin of the batholith.

This consists of I-type granites which have been G198 Everton Granodiorite: leucocratic, subdivided into four main separate rock types. pink, porphyritic with K-feldspar phenocrysts Outcrop is generally poor. Hydrothermal to 10 mm. Small mafic enclaves are common. alteration is common and consist of sericite Mineral composition: quartz, plagioclase, alteration and production of tourmaline, and K-feldspar, hornblende, biotite, also magnetite, drusy topaz veins. allanite, sphene, apatite, zircon, fluorite. GEOLOGY AND PROSPECTIVITY - WANGARATTA 33

G199 Murmungee Granite G202 Glenrowan Granite: small pluton, This small oval pluton has only a single shows extensive hydrothermal alteration with outcrop, at the northeastern margin of the veins containing pyrite, chalcopyrite, pluton—the remainder is covered by arsenopyrite, tourmaline, fluorite. Modal Quaternary sediments. Core samples show that composition: 46% quartz, 37% K-feldspar, 6% the granite is homogeneous. It is an evenly plagioclase, 8% biotite, 1% tourmaline. medium-grained grey hornblende granodiorite with 29% quartz, 16% K-feldspar, 33% G203 Warby Springs Granite: medium- plagioclase, 9% hornblende, 7% biotite, 3% grained grey, porphyritic (K-feldspar to 30 mm magnetite and accessory sphene, muscovite and long). Modal composition: 38% quartz, 42% allanite (Young 1983); 26% quartz, 14% K-feldspar, 7% plagioclase, 8% biotite, 4% K-feldspar, 49% plagioclase, 3% biotite, 3% cordierite. Cordierite is fresh; also contains hornblende, 2% magnetite, accessory sphene, garnet. pyroxene (McDonald 1988). G204 Taminick Gap Granite: coarse-grained G200 Lurg Granite (K-feldspar up to 30 mm, plagioclase to 25 mm); modal composition 38% quartz, 41% K-feldspar, Eaton (1986) observed that this consists of two 10% plagioclase, 7% biotite; accessory muscovite bodies separated by Ordovician rocks. This and fluorite. granite is porphyritic in both feldspars (to 8 mm) with an extremely fine-grained G205 Mount Bruno Granite: generally highly groundmass. The granite contains spherical weathered; leucocratic (K-feldspar up to and elongate quartz bodies interpreted as 25 mm); modal composition 43% quartz, 46% granite-filled miarolitic cavities. Modal K-feldspar, 5% plagioclase, 3% muscovite, 2% composition: 42% quartz, 31% K-feldspar, 14% biotite; accessory garnet. plagioclase, 12% biotite, and also contains vermiculite. G206 Killawarra Granite: pavement-type outcrops; medium to coarse, grey. Modal Warby Range Batholith composition: 44% quartz, 36% K-feldspar, 10% plagioclase, 9% biotite; accessory muscovite. This name was originally applied to the intrusions that form the Warby Ranges (Tickell, Hunken Granite: small stock, mafic medium- 1987; Eaton, 1984) but is here extended to grained with a few K-feldspar phenocrysts. include the intrusions farther west and Modal composition: 40% quartz, 42% northwest, extending to Katandra and Yourang. K-feldspar, 7% plagioclase, 3% biotite, 5% The batholith thus includes the granites of the cordierite; accessory muscovite, garnet; small Warby Ranges (G201–G206), and the Almonds, tourmaline nodules indicate of hydrothermal Youarang, Katandra, Bungeet and Chesney alteration. Vale granites, and the Lake Mokoan pluton underlying Lake Mokoan which is entirely G207 Almonds Granite: this large pluton is buried. largely covered by Murray Basin sediments and by thin colluvium. It is coarse-grained, Geophysical characteristics porphyritic with K-feldspar phenocrysts to 15 mm long. K-feldspar in the groundmass Magnetic: the granites have non-magnetic to shows granophyric intergrowth with quartz. weakly magnetic responses and can be Modal composition: 33% quartz, 35% identified by the absence of magnetic character, K-feldspar, 19% plagioclase, 5% biotite, 6% in contrast to the magnetic characteristics of muscovite, accessory fluorite. much of the surrounding rocks. G208 Youarang Granite: the only outcrops, Radiometric: the granites have either high on Pendle Hill, lie at the northwestern end of a potassium or high total count responses. moderate-sized buried pluton. It is coarse- grained, porphyritic in both feldspars G201 Kelly Gap Granite: fine to medium- (K-feldspar to 40 mm, plagioclase to 30 mm), grained grey, porphyritic (plagioclase up to with miarolitic cavities and abundant 10 mm long). Modal composition: 43% quartz, tourmaline nodules. Modal composition: 27% 43% K-feldspar, 8% plagioclase, 5% biotite. quartz, 42% K-feldspar, 18% plagioclase, 9% Contains miarolitic cavities, trace magnetite. biotite, 2% cordierite; accessory muscovite. 34 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Geophysical characteristics G209 Katandra Granite: a very small outcrop just south of Katandra is the only surface Magnetic: the granite has a low magnetic exposure of a fairly sizeable intrusion. The response. Subtle, northwest-trending weakly outcrop is at the margin of the pluton, intrusive magnetic trends within the granite are possibly into Cambrian chert and varies from evenly faults. In addition the data suggest the medium-grained to coarse-grained, weakly presence of a northwest trending, negatively porphyritic in both feldspar types. magnetised dyke. Hydrothermal alteration is shown by the presence of tourmaline, both disseminated and Radiometric: the granite has a high potassium, in nodules. Modal composition: 36% quartz, low thorium and a moderate uranium response 40% K-feldspar, 15% plagioclase, 4% biotite, 3% coincident with its mapped boundary. muscovite, accessory tourmaline. G217 Strathbogie Granodiorite G210 Bungeet Granite: this is an evenly medium-grained, pinkish rock with vermiculite, The main part of the intrusion consists of indicating some hydrothermal alteration. The coarse-grained porphyritic cordierite granite modal composition is very similar to the with quartz phenocrysts to 10 mm across, and Almonds Granite: 33% quartz, 41% K-feldspar, garnets up to 20 mm across. Near the contact 21% plagioclase, 4% biotite, with accessory with the Violet Town Ignimbrite the rock is muscovite, fluorite. more felsic and finer grained, with aplitic and pegmatitic dykes. The average modal G211 Chesney Vale Granite: small intrusions composition of the coarse-grained phase is 30% of fine to medium-grained pinkish granophyre, quartz, 18% K-feldspar, 38% plagioclase, 5% contains tourmaline nodules. Consists of biotite, 4% garnet and minor cordierite and quartz, plagioclase, K-feldspar, biotite, zircon, accessory muscovite. tourmaline, opaques. Geophysical characteristics G214 Baddaginnie Granite: no information Magnetic: the Strathbogie Granodiorite is non- G215 Swanpool Granite: no information magnetic. The underlying, highly magnetic, Terip Terip pluton dominates the magnetic Geophysical characteristics response of the region.

Magnetic: this granite is non-magnetic and has Radiometric: the radiometric responses vary a similar response to the Strathbogie Granite. from low to high. Distinct responses are evident within the granite, suggesting that it Radiometric: the granite has a high potassium, may be further subdivided. moderate thorium and a low uranium response. The area of the responses is smaller than the Kelfeera Granite: this is a tiny intrusion mapped boundary, suggesting that the granite 11.5 km SE of Benalla. It consists of medium- is only partially exposed. grained, slightly porphyritic biotite granite. Modal composition: 29% quartz, 44% G216 Barjarg Granodiorite: this small K-feldspar, 19% plagioclase, 7% biotite. pluton consists of dark orange biotite-cordierite granite with minor muscovite (Brown, 1961). Geophysical characteristics Grain size varies from fine to coarse, and from even-grained to porphyritic—the latter contains Magnetic: the granite is non-magnetic. large garnet phenocrysts in addition to plagioclase phenocrysts. Tourmaline is an Radiometric: the radiometric responses are accessory mineral. masked by transported sediments from Ryans Creek.

Subsurface granites

G711 Peechelba pluton: a deep, highly magnetic pluton, located north of Wangaratta. It is situated in the middle of the Ovens Graben, where bores have encountered GEOLOGY AND PROSPECTIVITY - WANGARATTA 35

Permian Boorhaman Formation beneath the extending from the late Early Devonian to early Murray Basin sediments. Middle Devonian.

G712 Terip Terip pluton a deep, highly Late Devonian granites with measured ages are magnetic pluton. This pluton is approximately "Glenrowan" (probably G202, 368 ± 15 Ma); 40 km in diameter and is situated beneath the Beechworth (369 ± 15 Ma); Strathbogie (362 ± Strathbogie Batholith. 4 Ma by K/Ar and 365 Ma by Rb/Sr) and Barjarg (360 ± 21 Ma; Richards & Singleton, G713 Brimin pluton a near-surface, highly 1981). The entire Warby Range batholith is magnetic pluton, located west-southwest of probably Late Devonian. Undated granites in Corowa (New South Wales). east of WANGARATTA that are either Early or Late Devonian are Murmungee, Mount Angus, G714 Berachah pluton a deep, highly Mount Emu, Mount Stanley, Baranduda and magnetic pluton, located north of Murmungee. Kergunyah.

G715 Cropper pluton a deep, highly magnetic 6.2 Dykes circular pluton, located west of the Mount Emu Adamellite. Northwest-trending magnetic Low to moderately magnetic northwest dykes are interpreted to cross-cut this pluton. trending responses seen throughout WANGARATTA are interpreted to be dykes. G716 Bandiana pluton located south of Albury and is a highly magnetic, near-surface A suite of dykes with strike lengths of up to pluton. 7 km occur in a possible fault zone west of the Mount Angus Granite. The dykes intrude the G717 Thurgoona pluton a near-surface, Hotham beds and Cropper pluton. north-northwest trending elongate pluton located east of Albury. It is highly magnetic Northeast of the Morilla Granite dykes are with a non-magnetic core. interpreted within the Kancoona fault zone. Unmapped northwest-west and northeast faults G718 Tangambalanga pluton: only part of cut these dykes and surrounding metamorphics. this lies within WANGARATTA, south of the Thurgoona pluton. It is interpreted to be a Low magnetic response dykes are interpreted near-surface highly magnetic pluton. within the Pilot Range Batholith and the response indicates that they are associated with G719 Lake Mokoan pluton interpreted to lie the deep Berachah pluton. beneath Lake Mokoan. Dykes are interpreted to overprint this weakly magnetic pluton. Moderately magnetic dykes intrude the Taminick Gap Granite. Granite ages Low magnetic response dykes intrude the Lake Age determinations and stratigraphic Mokoan pluton. relationships show at least three groups of granite ages: Silurian, Early Devonian and Late Devonian. The ages of the gneissic House Creek pluton and Barnawartha Granite have not been determined radiometrically but are regarded as Early Silurian by analogy to the numerous S-type granites of the Omeo Metamorphic Complex.

Early Devonian granites with measured ages are Yackandandah ("Osborns Flat"; 380 ± 15 Ma; Bruarong ("Kingchington Ck"; 389 ± 15 Ma) and Mount Buffalo (394 ± 4 Ma; Richards & Singleton, 1981). The entire Yackandandah Batholith is probably of the same age. These ages span an interval 36 GEOLOGY AND PROSPECTIVITY - WANGARATTA

7 Economic geology 7.1 History of mining

Mines within WANGARATTA have produced in At the end of July 1997, 24 Mining Licences and excess of 85 t of gold, 9000 t of tin concentrate, 65 extractive industry Work Authorities were about 17 000 t of molybdenite and unknown held on WANGARATTA, which in 1994/95 had quantities of other metals. In addition, the an approximate production value of $20.7M. value of sales of non-metallic minerals produced Most of this value was from construction within WANGARATTA exceeds $20M per materials. Historically, however, gold has been annum. WANGARATTA has several strategic the most valuable commodity. mineral resources, including large placer gold deposits, Victoria’s largest tin and molybdenite The history of mining within WANGARATTA deposits, and its most significant diamond dates back to the discovery of gold near occurrences. Mines and exploration prospects Beechworth in 1852. The following history is where significant mineralisation has been mostly taken from O’Shea et al. (1994). proved are shown in Figures 6 and 7. Gold was discovered at Spring Creek near The following styles of mineralisation are Beechworth in 1852, and was followed by recognised within WANGARATTA: widespread small-scale mining of shallow leads. As these were depleted, miners moved · Cainozoic placer gold and tin deposits; downstream where deposits were deeper. Mining was first carried out by prospectors and · orogenic gold deposits; small syndicates, but as working conditions · volcanic-hosted massive sulphide deposits became more difficult, public companies associated with Cambrian greenstones; subscribed the necessary capital to open larger mines. These were commonly deeper mines · antimony-?gold deposits associated with the accessed by shafts. Large volumes of water and Upper Devonian Tolmie Igneous Complex; other difficulties following covered leads were · tin deposits hosted by granites; an impediment to this type of underground mining, and by 1925 underground mining of · porphyry gold-copper and molybdenum deep deposits had largely ceased. Some deposits associated with high-level magnetic shallower deposits were reworked by sluicing intrusions; and bucket-dredging in the period 1890–1950. · copper deposits in Late Devonian redbed sequences; Quartz mining commonly followed alluvial mining as detrital gold was traced back to its · Cainozoic placer diamond occurrences; source. · Cainozoic and Permian coal deposits; While gold was the primary aim of alluvial · a variety of industrial minerals. mining, in some areas cassiterite was recovered as a valuable by-product. Cassiterite was Gold deposits are grouped into the Harrietville- common in deposits along Reedy Creek in the Dargo, Melbourne and Benambra gold Beechworth and Eldorado goldfields, and in provinces. These provinces, defined by Ramsay some leads within the Chiltern-Rutherglen and Willman (1988), are shown in Figure 7, and goldfields. have been subdivided into goldfields to aid description of local characteristics of Chiltern-Rutherglen goldfield mineralisation. The location of goldfields has been modified after Weston and Nott (1990) to Lloyd (1985) described the history of the take account of more detailed information. Chiltern-Rutherglen goldfield.

Modern mineral exploration for Despite the discovery of gold near Black Dog WANGARATTA is summarised in Wilkie and Creek around 1853, it was not until gold was Brookes (1997). found west of Albury at Indigo Creek in 1858 that significant gold mining was undertaken in the Chiltern-Rutherglen goldfield. Most gold produced was taken from alluvial deposits, with GEOLOGY AND PROSPECTIVITY - WANGARATTA 37

Figure 7 Mineral resources within the Wangaratta 1:250 000 map area. 38 GEOLOGY AND PROSPECTIVITY - WANGARATTA

only relatively minor production from quartz Sheppard (1982) described the history of the veins. Eldorado goldfield.

About 24 deep leads were discovered around From late 1880, companies were able to acquire Chiltern and Rutherglen between 1858 and large leases and rework ground by hydraulic 1861. Gold production from these peaked sluicing and bucket dredging (O'Shea, 1981). between 1886 and 1890, during a major period Large areas of worked ground were reworked of mine development. Many mines continued to by large-scale operations to depths of about work until the 1920s. Underground mining 30 m up to the mid-1950s. The use of amalgam reached depths greater than 120 m, and allowed gold to be easily separated from followed channels for up to 4 km (Viet, 1968). cassiterite, and recovered as a valuable by- product of some deposits. Gold-bearing quartz veins were discovered northwest of Rutherglen in 1865. Quartz Myrtleford and Yackandandah goldfields mining on a large scale had mostly ceased by 1904 (Thompson, 1962). Viet (1968) attributed Following the discovery of gold on a tributary of the failure of many quartz mines to diminishing upper Yackandandah Creek in 1853, the free gold at depth, and complicated faulting in population of Yackandandah grew from 150 to host rocks which commonly displaced about 3000 by 1862. Sluicing won high-grade mineralised veins. gold from the Upper Yackandandah Creek until 1888, when hydraulic dredging was introduced. Beechworth and Eldorado goldfields These dredges were replaced by bucket dredges in 1910 (Ivett & Oldfield, 1988). On the Gold was discovered at Shepards Hut near Barwidgee Creek, dredges operated until the Beechworth in February 1852, and rushes to early 1900s (Foster & Roberts, 1988). Spring Creek, Pennyweight Flat and Reedy Intermittent small-scale dredging and sluicing Creek followed shortly after. The Woolshed continued until the 1950s (Cuffley, 1985). Valley on Reedy Creek was first worked in 1853, and by 1855 was the main goldfield of the Twists Creek was first worked at the beginning area. New diggings downstream from of 1854. Gold in quartz veins was discovered Woolshed Valley at the Devils Elbow, there, and at the junction of the Buffalo and Sebastopol, Napoleon Flat and Eldorado were Ovens Rivers near Myrtleford in about 1860. also being worked at this time. In 1853, the Alluvial deposits near Myrtleford commonly Victorian Gold Escort transported 5972 kg of were low grade and unpopular with miners. gold from the workings (Viet, 1968). Mining at Wooragee on Magpie Creek followed in 1856. Rileys reef (later known as the Reform mine), located at the junction of the Ovens River and In 1854, timbered shafts and steam driven Myrtle Creek, was first worked in 1854. pumps for dewatering were being used to mine Unusually, an alluvial rush in January 1856 by gold from deeper alluvium in the Woolshed two thousand people to nearby Happy Valley Valley (O'Shea, 1981), and by 1857, most of the followed first quartz mining. Barwidgee Creek richer and easily won gold had been mined was rushed in August of the same year. along Reedy Creek and its tributaries. Gold was first discovered at Bowmans Forest Deeply buried gold, groundwater and swelling near Buckland Gap in 1855, and the nearby ground hindered early attempts to mine gold at Perseverance lead was opened in 1860. Many Eldorado (Swift, 1938), and it was not until other leads were also worked, as well as quartz 1859, when these obstacles were countered by veins in the catchments of leads. The discovery timbered shafts and pumps, that the deposits of the White lead at Stony Creek was followed were worked successfully. The most productive by a brief rush, and in 1875 the area was companies were the Kneebones Company (also reworked following the discovery of the Fire called the Hindmarsh Co) which operated lead. Quartz mining continued until the turn of between 1858 and 1872, the McEvoy Gold the century. A minor revival coincided with the Mining Company (taken over by the United depression in the 1930s (Meltech, 1985). Eldorado Co) which operated intermittently between 1859 and 1901, and the Wellington Company which operated between 1859 and 1878. GEOLOGY AND PROSPECTIVITY - WANGARATTA 39

Buckland goldfield 7.2 Mineral production

Pardew and party discovered rich deposits of Whilst accurate production records are gold in alluvium on the Buckland River in July available for some metallic minerals, until 1853 (Easton, 1912). A rush followed, and by recently other production has not been late 1853 the mining population had grown to systematically recorded. about eight thousand. Shortly after, sickness drove most miners from the area, and the Current production mining population fell below 300. This increased in the summer of 1857, when large Modern mining has been dominated by numbers of Chinese miners arrived (Swift, development of industrial mineral resources. 1942). One of the earliest anti-Chinese riots Construction materials worth approximately occurred on the 4th of July, 1857 at Buckland $20.5M were extracted in 1994/95 under the River (Laing, 1974). Extractive Industries Act 1966 (Department of Natural Resources & Environment records). The richest deposits were on Fairleys Creek, a Three mines have produced significant tributary of the Buckland River. Terrace quantities of gold in the period July 1993 to gravels on Clear Creek, East Branch and West June 1996. This production has an Branch, and other tributaries of the Buckland approximate value of $0.7M, and represents River were worked downstream to Buffalo Flat. 0.3% of Victoria's gold production for this Dredging commenced around the turn of the period. century, and the last bucket dredge ceased operating in 1920 (Swift, 1942). Coonambidgal Formation clay and sand is extracted from the Murray River, Broken River, Gold in quartz veins was discovered in 1858. King River and Ovens River Valleys close to Despite common quartz mining after 1859, Albury, Benalla, Everton and Wangaratta. production was low compared to alluvial gold This is used for aggregate, concrete and fine production (Cogar Mining, 1986). Most quartz sand, fill and road base. Small quantities of mining was centred around the junction of the clay were extracted for brick manufacture. East and West branches of the Buckland River. Hotham beds sandstone is extracted close to Glenrowan, Chiltern, Youarang and Benalla Bright-Wandiligong goldfield and is used for aggregate, road base, armour and fill. Hornfels adjacent to granites is Alluvial gold mining in the upper Ovens Valley commonly used as aggregate. Newer Volcanics commenced in 1853 (Roberts, 1988a). By 1856, basalt is extracted from Cosgrove. This is used mining had spread to Morses Creek at Bright for aggregate, road base and fill. Silurian and Growlers Creek at Wandiligong (Flett, sandstone is extracted close to Cosgrove South, 1979). In 1857, the population of the Bright Euroa and Karn, south of Benalla. This is used district (including around Buckland River) had for aggregate, fill and road base. Upper grown to 1469. Mining of deep leads using Devonian ignimbrite is extracted close to Violet timbered shafts followed in about 1861, and had Town. This is used for road base, aggregate mostly ceased by 1868 (Lloyd & Nunn, 1987). and armour. Large quantities of Glenrowan Dredging was introduced at the turn of the Granite from a quarry at Glenrowan is used for century. aggregate, road base, armour and fill. Cambrian metasediment is extracted at C. & E. Cotsworth discovered the Pioneer reef Cusgrove South and Kilandra for road base and directly to the south of the current township of fill. Taminick Gap Granite is extracted for road Bright in 1858 (Lloyd & Nunn, 1987). The base, aggregate and fill at Chesney Vale, west Oriental reef was also discovered in 1858 and of Glenrowan. Small quantities of Youarang was the largest primary gold mine within Granite are extracted at Youarang for fill. WANGARATTA (Flett, 1979). Up to three hundred gold-bearing quartz veins were mined Small quantities of Beechworth granite at in the ranges between the Ovens River and Sheep Station Creek have been extracted by Wandiligong. Quartz mining declined in the ACI Resources Ltd (ML 1657) for pilot plant 1890s, but intermittent mining has continued to tests to demonstrate that the granitic feldspar the present day (e.g. the Williams United is suitable for glass manufacture. mine—MIN 4004, near Bright). 40 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Three mines have produced significant quantities of gold in the period July 1993 to June 1996. J.F. Wilcox (MIN 4688) produced 1926 g at Stringers Ridge southeast of Beechworth between July 1993 and June 1994. Williams Mines P/L (MIN 4004) produced 22 342 g from the Williams United mine at Wandiligong between July 1993 and June 1995. Ranger Gold P/L (MIN 4807, TTL 528 & TRL 5461) recovered 14 836 g between July 1994 and June 1995 re-treating alluvial tailings of the Great Southern Consols mine which operated between 1895 and 1920 near Rutherglen. Large quantities of very fine- grained gold were unable to be recovered prior to the introduction of cyanide treatment.

Historic production

Records of the Department show that mines in WANGARATTA have historically produced large quantities of gold, and small amounts of tin, molybdenite, and other minerals. Approximate quantities of these three metals are:

· in excess of 85 t of gold; · about 9000 t of tin concentrate (Cochrane & Bowen, 1971); and · about 17 000 t of molybdenite.

Detailed production information for all mines is included in the WANGARATTA Mine Database, which accompanies this report.

Gold production for WANGARATTA for the period 1864 to 1996 captured from Mines Department reports is listed in Table 5, and shown in Figures 8 and 9. These figures show that about of 70 t of gold was produced during this period. Checks against more detailed records of alluvial production in Canavan (1988) show alluvial production has been understated by at least 12 t for the Chiltern- Figure 8 Rutherglen goldfield, and 3 t for Buckland and Primary, alluvial and total goldfield production. Only Bright-Wandiligong goldfields. production between 1864–1996 from Mines Department Reports is shown. Alluvial production values are low in the Gold was discovered in WANGARATTA in Chiltern-Rutherglen, Bright-Wandiligong and Buckland River 1852. Significant production, mostly alluvial, goldfields. TM = Tallangalook and Merton goldfields, occurred prior to 1864, and is not included in CR = Chiltern-Rutherglen goldfield, BMYE = Beechworth, Table 5. Viet (1968) reported that 5972 kg of Myrtleford, Yackandandah and Eldorado goldfields, gold was transported from the workings at BBW = Buckland River and Bright-Wandiligong goldfields. Beechworth by the Victorian Gold Escort in 1853. If this was typical for WANGARATTA between 1852–1863, an additional 6 t of gold may have been produced. GEOLOGY AND PROSPECTIVITY - WANGARATTA 41

Figure 9 Annual goldfield production. Only production between 1864–1996 from Mines Department Reports is shown. Alluvial production values are low in the Chiltern-Rutherglen, Bright-Wandiligong and Buckland River goldfields.

Table 5 Production for goldfields between 1864 and 1996

Goldfield Alluvial Primary Residual Total production production production Production (kg) (kg) (kg)

Chiltern-Rutherglen 31 115 2893 23 34 031 Beechworth, Myrtleford, 11 906 3806 52 15 765 Yackandandah and Eldorado Buckland and Bright- 4384 10 797 179 15 360 Wandiligong1 Tallangalook and Merton2 4356 354 - 4710 Total 51761 17850 254 69866

Source: Mines Department Annual, Quarterly and Monthly reports, 1864–1996. 1 Total value for the Buckland Division; includes production outside WANGARATTA. 2 Source: Griffiths (1981).

Since 1859, records of gold production have 7.3 Gold deposits been published in Mines Department monthly, quarterly, and annual reports. Systematic Gold deposits can be broadly subdivided into reporting commenced in 1864. Official primary and placer deposits. Within statistics are considered to be more reliable for WANGARATTA, most production is from placer later years when large-scale mining dominated deposits. Supergene processes may be the industry. Large amounts of alluvial important in both primary and placer deposits. production were not reported in early years, and these figures will have been significantly Most primary mineralisation can be described understated. as orogenic-style gold. Some of these deposits have characteristics in common with thermal aureole and sediment-hosted disseminated (Carlin type) gold deposits. Rare reports of gold in granite are also discussed below. Lower Devonian caldera-related antimony-gold deposits, and epigenetic and VHMS deposits in 42 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Cambrian greenstones are discussed separately be an artefact of the low gradient (Canavan, in later sections. 1988). There was continuous mining over 48 km along the main palaeovalley (Hunter, Placer gold deposits 1903; Canavan, 1988).

Gold production from placer deposits within The source rocks of most of the gold are WANGARATTA is at least 66.8 t, or about auriferous quartz veins in Ordovician Hotham three-quarters of the total recorded beds. Less than 10% of Chiltern-Rutherglen WANGARATTA gold production. First reports gold came from these primary deposits, which of alluvial mining were from near Beechworth has led many authors to speculate about in 1852. Given that systematic recording of additional alternative sources of gold. These production from large alluvial mining include disseminated and vein gold in nearby operations commenced in 1864, reported granite, and detrital and hydrothermal production is probably significantly disseminated gold in Hotham beds. understated. Baragwanath (1946) noted the crystallinity of very fine "flour" gold from some deposits. This Production is from placer deposits in Cainozoic may indicate a supergene provenance, or in situ alluvium. In most instances, the primary supergene aggregation, and is discussed in source of this gold has been shown to be more detail under Orogenic gold below. orogenic gold-quartz veins within alluvium Another possible source of gold is quartz veins catchments, although gold in granite and in Hotham beds underlying the leads. sandstone have been suggested as the source of rich deposits in the Chiltern-Rutherglen, Cassiterite was mined as a minor by-product in Beechworth and Eldorado goldfields. some mines, and is sourced from nearby granite (Canavan, 1988). Cochrane and Bowen (1971) Alluvial gold occurs in (Oppy et al., 1995): reported a total production of 108.2 t of cassiterite concentrate from Chiltern- · shallow alluvial/colluvial scree deposits; Rutherglen mines.

· Recent to Pleistocene low- and high-level The Prentice, Indigo and Chiltern Valley leads terrace deposits. Terraces represent are the principal leads within the goldfield. successive stages in valley erosion; and Named sections and tributaries of these leads · Pliocene deep leads. are listed in Canavan (1988). The depth to most wash precluded dredging and sluicing, Chiltern-Rutherglen goldfield and production was mostly from shafts. Production from the principal mines operating Alluvial placer deposits or "leads" within the on these leads is given in Table 6. Chiltern-Rutherglen goldfield form the most important gold deposits in WANGARATTA, Tributaries of the Chiltern Valley lead drained contributing about half of all gold produced. the Skeleton and Kincardinshire ranges, east Most production was from deep leads. These and north of Chiltern, and the hills further are described in Hunter (1903, 1909), Hunter northwest towards Rutherglen. and Mulvaney (1937), Canavan (1988) and Rooney (1994). The largest producer on the Chiltern Valley lead was the Chiltern Valley Gold Mining Co Leads mostly occur in early Pliocene to Recent which operated between 1877 and 1920, and fluvial deposits. A synthesis of the worked a 6.5 km section of the lead. The palaeogeography of the area is given in company resulted from amalgamation of the Canavan (1988). Unlike modern drainages Sons of Freedom Co, Extended Sons of Freedom which trend west (e.g. the Black Dog and Co and Doma Mungi Gold Mining Co which Diddak creeks), leads trend to the north and operated from 1870. The average width of the have very low gradients. Productive channels wash along this section was 170 m, with a were very wide and consisted of one or more maximum of 300 m. The average grade worked auriferous "wash" layers, which were commonly was about 8 g/m2. The depth of wash in the about 1 m thick (Minax Gisselle, 1987). The mine was between 83 and 97 m, and thickness leads had very sinuous geometries which may from 60 to 90 cm (Canavan, 1988). GEOLOGY AND PROSPECTIVITY - WANGARATTA 43

Table 6 Gold production from principal mines operations in the Chiltern-Rutherglen goldfield

Company Lead Operated Produced (kg)

Chiltern Valley Barambogie Gold Mining Co Barambogie 1894–1902 1228 Chiltern Valley Extended G.M. Co1 Chiltern Valley 1902–08 462 Chiltern Valley G.M. Co2 Chiltern Valley 1870–1920 94573 Prentice Great Southern & Chiltern Valley United G.M. Co Prentice 1899–1903 250 Great Northern Extended Consols G.M. Co Prentice 1893–1910 8890 Great Northern Extended G.M. Co Prentice 1888–98 3335 Great Southern Consols G.M. Co Prentice 1895–1916 7215 Great Southern G.M. Co Prentice 1889–1914 4314 Great Southern No 1 G.M. Co Prentice 1897–1905 1989 Prentice & Southern Deep Lead G.M. Co Prentice 1893–1910 3531 Prentice Freehold Gold Mining Co Prentice 1893–98 2053 Prentice United Gold Mining Co Prentice ? 326

Source: Canavan (1988). 1 Former Chiltern Valley Consols G.M. Co. 2 From 1870–1876 worked as the Doma Mungi G.M. Co, Sons of Freedom and Sons of Freedom Extended G.M. Cos. 3 Hunter and Mulvaney (1937) quote 10 018 kg of gold.

The Prentice Valley lead embraces all workings by cyaniding and other processes. Canavan downstream from and including the workings of (1988) noted that the lead probably drains west the Great Southern and Chiltern Valley United and joins up with the Prentice lead. Gold Mining companies. Whether it is a continuation of the Chiltern Valley lead is Cochrane and Bowen (1971) noted that uncertain. cassiterite was mined from the bottom wash of the Chiltern Valley Lead, and two levels of The largest producer on the Prentice lead was wash in some headwater leads, notably the the Great Northern Extended Consols G.M. Co Lancashire and Deep Creek Valley leads. which commenced operating in about 1888. Headwater lead deposits close to outcrops of The company worked wash which had an granite were probably richest. average width of 150 m, and thickness between 75 and 90 cm. This graded about 6 g/m2. The Cochrane's (1971) review of Mines Department depth to wash was about 110 m. In addition to Annual Reports showed principal mines on the gold, some cassiterite was also produced Prentice lead were the Great Southern Co, (Canavan, 1988). Great Southern Consols Co and Great Northern Extended Consols Co which reported tin Hunter (1909) reported the Indigo lead “was concentrate totalling 27.3 t in 1906–12 and discovered in 1858... Being the first lead 1917. worked in the district, a large number of miners were attracted, and they found profitable Beechworth and Eldorado goldfields employment for almost twelve months, but then the field was almost deserted”. Detailed Dunn (1913) described Reedy Creek as a “giant information on the lead is rare. Canavan (1988) sluice box”, where falls and rapids acted as reported some coarse gold, including nuggets up riffles, and alluvial flats as boxes. These flats to 342 g. Hunter and Mulvaney (1937) reported contain rich deposits of gold and tin which have large quantities of very fine-grained gold not been worked over 35 km spanning the recovered by early methods, and later recovered Beechworth and Eldorado goldfields. Apart 44 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Table 7 Principal gold mining operations in the Beechworth and Eldorado goldfields

Company Lead Operated Gold kg

Cocks Eldorado Gold Dredging Co Eldorado 1936–55 2198 Cocks Pioneer Gold and Tin Mines NL Eldorado 1901–41 3650 D.A. Fletcher Wooragee 1907–17 341 Kneebones Company Eldorado 1858–72 180 McEvoy Gold Mining Co Eldorado 1867–1901 630 Punds Gold Mining Co Baarmutha 1904–46 668 Rocky Mountain Extended Co Rocky Mountain 1904–21 1096 Rocky Mountain Gold Sluicing Co Rocky Mountain 1877–90 308 Wellington Gold Mining Co Eldorado 1860–78 337 Woolshed Hydraulic Sluicing Co Woolshed Valley 1905–11 375

Source: Canavan (1988).

from the open mature valleys in the headwaters average depths were about 3.5 and 9 m of its tributaries, Reedy Creek is deeply incised respectively (Canavan, 1988). into granite of the Pilot Range. It emerges at Eldorado. Reedy Creek has two main tributaries, Wooragee Creek and Spring Creek. Most Deposits are usually less than 15 m deep and mining was in the Magpie and Stony Creek comprise Recent sediments along the present areas where alluvium is probably more than streams and White Hills Gravel(?) which forms 50 m thick. This overlies granite and Permian terraces above the stream level. Some changes tillite basement (Canavan, 1988). in drainage patterns have been attributed to tectonic movement (Canavan, 1988). On the upper Eldorado flat, the depth of alluvium is between 12 and 20 m. Boring and It is difficult to estimate the grade and quantity mine records show deeply buried leads west of of gold in leads of the goldfields. There is no Eldorado (Canavan, 1988). record of gold mined by thousands of miners who had claims in the field, and records of Little is known of the depth of alluvium in the companies operating before the turn of the Wooragee Valley, and the course of the main century are incomplete. However, it appears lead in Tertiary high-level gravels has not been that grades were highest around the traced. Dunn (1887) mentioned two deep leads, Beechworth township, and lower downstream Chinamans lead which is exposed at Wooragee (Canavan, 1988). Dunn (1871) reported that Creek, and Wallaces lead. the original average grade of wash at Reid’s Flat was 450 g/m2, and 50 g/m2 at Woolshed, The highest producers within the goldfields while Canavan (1988) reported the grade at were the Cocks Pioneer Gold and Tin Mines NL Eldorado to have been from 9 to 18 g/m2. and Cocks Eldorado Gold Dredging Co. Both O'Shea (1981) noted a corresponding decrease companies operated at Eldorado. in the grainsize of gold downstream toward Eldorado. Estimates of gold production from The McEvoy Gold Mining Co commenced large-scale operations are listed in Table 7. operating before 1871, working deep deposits Canavan (1988) reported that most near Eldorado. Shafts were used to access underground mining companies closed before wash which was around 75 m deep. Gold was their leases were worked out due to poor also recovered from wash above a cemented equipment and bad management. “false bottom” at 27 m depth. The mine ceased operating in 1878, but was reopened by another The maximum depth of alluvium near company in 1890. This company worked wash Beechworth is 12 m at Pennyweight Flat and at a depth of 60 m for a short time, then; Woolshed. At Reid’s Flat and Sebastopol the GEOLOGY AND PROSPECTIVITY - WANGARATTA 45

Table 8 Principal dredging and sluicing operations in the southern goldfields

Company Goldfield Period Volume Gold Avge Avge treated kg grade depth x1000 m3 g/m3 m

Altona Buckland 1915–17 1 890 276 0.15 4.2 Buckland River Buckland 1902–20 3 340 670 0.20 5.2 Buckland River South Buckland 1903–14 1 370 301 0.22 5.8 Buckland Star Buckland 1909–16 2 600 225 0.08 5.1 Confidence uncertain 1907–14 1,900 266 0.14 4.4 Enterprise Bright-Wandiligong 1905–14 2,960 470 0.16 4.5 Excelsior uncertain? 1906–14 1,430 265 0.19 4.7 Junction No. 1 Bright-Wandiligong 1906–15 2,200 332 0.15 3.8 Junction No. 2 Bright-Wandiligong 1906–21 >2,450 536 0.16 4 Kia Ora No. 1 Buckland 1906–13 1,970 271 0.14 4 Kia Ora No. 2 Buckland 1906–16 2,190 351 0.16 7.4 Morses Creek Bright-Wandiligong 1905–07 1,650 443 0.27 3.8 Myrtleford Myrtleford 1907–20 377 Ovens Valley Bright-Wandiligong 1903–06 >2,790 568 0.17 4.3 Perseverance Bright-Wandiligong 1902–11 603 Phoenix Buckland 1903–19 2 740 655 0.21 5.3 Porepunkal Bright-Wandiligong 1908–20 >2,560 412 0.09 5.6 Racecourse uncertain? 1909–16 1,400 215 0.14 5 Reform uncertain? 1916 26 Smoko Bright-Wandiligong 1906–16 475

Sources: BHP Minerals (1981), O’Shea (1988) and Canavan (1988). resumed working the shallow wash. The (1977) reported a small tin mine operating in average grade was of this wash was 9.5 g/m2 the late 1970s along Clear Creek, north of and was 4 g/m2 when the mine closed in 1901 Reedy Creek. (Canavan, 1988). Bright-Wandiligong, Buckland, Myrtleford and Cocks Pioneer Gold and Tin Mines NL sluiced Yackandandah goldfields ground previously worked by the McEvoy Gold Mining Co. In addition to a large quantity of In the south, the principal leads are tributaries gold, the company produced 1673 t of cassiterite of the Ovens River, notably the Buckland River concentrate. and Morses Creek. There are deep auriferous leads in the Upper Ovens and Morses Creek, Cocks Eldorado Gold Dredging Co bucket- and shallow deposits in the Buckland River. dredged previously worked ground near Eldorado. It treated about 27 million m3, which Murray (1898) described many of the older contained 0.081 g/m3 gold, and also yielded workings in this area. He wrote “From the 1356 t of cassiterite concentrate. head branches of the Ovens down to Cassiterite was produced as a by-product of Porepunkah ..., the old alluvial workings can be gold mining in many operations along Reedy seen, as also from the upper waters of the Creek. It is sourced from nearby granite Buckland to within about 8 km of its junction (Canavan, 1988), and deposits were generally with the Ovens. Workings also occur at richest in northern tributaries of Reedy Creek. intervals along the Ovens, from Porepunkah to Cochrane and Bowen (1971) reported a total of below Myrtleford. ... The workings have mostly 9144 t of cassiterite concentrate was produced been confined to easily accessible deposits at from Beechworth and Eldorado mines. Tickell shallow depths, either on bedrock or on false 46 GEOLOGY AND PROSPECTIVITY - WANGARATTA

bottoms...”. Murray foresaw the possibility of working deeper ground by large-scale In the Melbourne gold province, Sandl (1989) operations, which began with the introduction demonstrated gold emplacement during contact of hydraulic sluicing in the following century. metamorphism of Silurian and Devonian rocks by the Strathbogie Granodiorite. The timing of Details of alluvial gold mining are given in other mineralisation within the province is O’Shea et al. (1994) and Canavan (1988). unclear but must be contemporaneous with or Table 8 lists large-scale operations which post-date folding, which is Middle Devonian in operated in the southern goldfields. most of the province.

Orogenic gold deposits Southeast of WANGARATTA, auriferous and argentiferous veins within the Benambra gold Orogenic deposits occur within three gold province largely trend north-south. This is the provinces defined by Ramsay and Willman same trend as the Tabberabberan folds, and (1988): Harrietville-Dargo, Melbourne and suggests a Middle Devonian mineralising event. Benambra. Mineralisation is distinctive in Alternatively, this trend may be related to these provinces, and to a lesser extent between dilatant riedel shears developed in response to goldfields within these provinces. dextral strike-slip movement on the Kancoona fault during the Late Silurian Bindian Deposits are characterised by auriferous quartz Deformation. Both of these models are veins which occupy reverse faults, bedding consistent with mineralised quartz veins planes and tension gashes (O’Shea et al., 1994). truncating granites and Early Silurian These are commonly controlled by regional metamorphic isograds in Ordovician turbidites. structures, while ore shoots are commonly controlled by the intersection of veins with The source of gold is uncertain. carbonaceous beds and deviations in bedding or cleavage orientation related to refolding. Wall- Harrietville-Dargo gold province rock alteration and gangue mineralogy of most deposits consists of white micas, chlorite, This gold province coincides with the carbonates and sulphides (Hughes et al., 1997). Tabberabbera Zone, which is a structurally Within the Harrietville-Dargo and Melbourne defined corridor extending from the Mount gold provinces, gold occurs with low sulphide Wellington Fault Zone (now Governor Fault) in (average less than 2%) quartz veins, and a the west, to the Kancoona Fault in the east dominant pyrite-arsenopyrite association. (Gray, 1988). The province roughly corresponds Some Melbourne gold province deposits also with the Howqua granite province ("basement have significant stibnite. Detailed study of terrane") of White and Chappell (1988). fluid inclusions of similar mineralisation at Wattle Gully in central Victoria by Cox et al. Primary mines within the province have (1995) indicates ore deposition at around 300°C, produced about 17.5 t of gold since 1864. Major at depths around 7–10 km, from near-neutral producers are listed in Table 9. About two- thirds of this gold is from the Bright- pH, low salinity H2O-CO2-CH4 fluids. In contrast, deposits within the Benambra gold Wandiligong goldfield. The province is province typically include significant silver and characterised by northwest-trending fissure- base metal, and have high sulphide contents. and fault-controlled low-sulphide auriferous Hughes et al. (1997) suggested fluids with quartz veins in Ordovician sedimentary rocks different compositions, possibly more saline, (Ramsay & Willman, 1988). Gold is largely were responsible for these deposits. non-refractory, and is occasionally associated with minor pyrite, arsenopyrite and galena. Within the Dargo-Harrietville gold province, most veins lie within a 15 km zone west of the Most veins lie within a 15 km zone west of the Kancoona Fault, and occupy northwest- Kancoona Fault, which suggests some trending fissures and faults cross-cutting relationship between mineralisation and this Ordovician Hotham beds (Fig. 10). This trend fault. Veins are commonly truncated by low is parallel to the Benambran folds, and suggests and high angle faulting, indicating deformation a late Early Silurian mineralising event. following mineralisation. Auriferous veins in the Devonian Pilot Range Batholith and Mount Stanley pluton indicate a later episode of gold deposition. GEOLOGY AND PROSPECTIVITY - WANGARATTA 47

Figure 10 Gold-quartz vein orientations, Wangaratta 1:250 000 map area.

Table 9 Major primary gold producers from each goldfield of the Dargo- Harrietville gold province

Mine Goldfield Production Average grade g/t (kg)

Oriental Bright-Wandiligong 1829 14.4 London & Myrtle Bright-Wandiligong 673 36.7 and 18.1 Williams United Bright-Wandiligong 284 ? Happy Valley Myrtleford 1003 29.2 Homeward Bound Myrtleford 913 16.7 Magenta Chiltern-Rutherglen 307 14.0 Golden Bar Chiltern-Rutherglen 387 16.4 Red Jacket Buckland 245 40.7 Alta Buckland 102 38.3

Source: O’Shea et al. (1994). 48 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Brief descriptions of individual goldfields and Studies of gold purity by Bartlett (1995) are major producers follow. These have mostly consistent with this. Gold probed in two been taken from O’Shea et al. (1994). sandstone cobbles (47.3 & 109.9 g/t Au) from mullock dumps adjacent the Indigo and Chiltern-Rutherglen goldfield Caledonian leads had very high purity (no detectable silver). This is akin to the gold in Primary gold occurs chiefly in quartz veins supergene deposits in Western Australia (Butt, which occupy northwest-trending reverse(?) 1988). Apart from being oxidised, these faults in Ordovician Hotham beds (Minax samples were nearly identical to fresh Giselle, 1987). These veins dip steeply, and are Ordovician Hotham beds drilled nearby. typically about 1 m thick, though veins up to 6 m thick are known. Veins also occupy minor Hunter (1903) described many of the deposits conjugate(?) faults which trend northeasterly. within the Chiltern-Rutherglen goldfield. The Less common quartz stockworks also carry gold. two largest were the Magenta reef and Golden Hunter (1903) noted sinistral cross-faults which Bar reef. The Magenta reef was worked truncate and displace some mineralised veins. without interruption between 1858 and 1901. Underground workings reached a maximum Gold occurs with minor pyrite and arsenopyrite, depth of 100 m and followed two quartz veins. and rare silver, chalcopyrite and scheelite. These trend north-northwest and dip to the Carbonate alteration accompanies some quartz east. Stockwork related to these veins near the veins (Ivett, 1982). Ore shoots are typically surface was worked by an open cut. 0.2–1 m wide, and pitch north. Some shoots are Baragwanath (1925) noted that large quantities very rich (e.g. Eastern mine which produced of host rock to the veins was also crushed. The 279.9 kg of gold from 3048 t of ore), though Golden Bar Reef was worked at surface for many pinch out close to the water table about 300 m along strike. The mine consisted (Thompson, 1962). Minax Giselle (1987) of six levels and reached a depth of 222 m. Gold attributed some shallow high-grade zones to occurred in two quartz veins with pyrite and supergene enrichment. arsenopyrite.

Many workers, including Hunter (1903), Myrtleford and Beechworth goldfields Wilkinson (1907) and Baragwanath (1946), noted very fine-grained crystalline gold in Gold occurs in quartz veins and quartz sandstone and shale pebbles in leads and stockworks which occupy faults and fissures in outcrop. This was mostly too fine to recover, Ordovician Hotham beds and younger dykes though in some instances profitably worked (Hochwimmer, 1988). These are commonly (e.g. Devonshire, Bradys, and the Twelve associated with fold hinges. Stockworks are Apostles reefs; Hunter, 1903). Donnelly (1993) common, and historically many of these were noted that this gold was associated with mined by wide stopes and open cuts muscovite, sericite, and iron oxide in the (Hochwimmer, 1988). Gold-bearing veins sandstone matrix, was mostly less than 20 mm, generally follow the strike of Ordovician and was preferentially orientated. Hotham beds host rock, though mostly dip to the west, cross-cutting the dip of strata (Easton, This gold has been called detrital and 1912a; Meltech, 1985). Veins in the Mount hydrothermal (Henley, 1974; Canavan, 1988). Stanley Granite and Pilot Range Batholith were Superficially similar sediment-hosted also worked for gold (Dunn, 1906). disseminated gold deposits are mined at Carlin in Nevada. This style of mineralisation is Gold occurs with small amounts of pyrite and characterised by extremely fine-grained arsenopyrite, and lesser galena and sphalerite refractory (arsenopyrite) disseminated gold (Foster & Roberts, 1988). Malachite has also (Arehart, 1996). Host rocks are mostly silty been reported from the Washington reef. carbonates, and show argillic alteration, Chlorite and carbonate alteration accompany silicification and carbonate depletion close to mineralisation. deposits. Fluid inclusion work by Arehart (1996) point to ore genesis pressures Ore shoots are typically short, and generally corresponding to 2–4 km, temperatures near pitch steeply south. Shoots are commonly 1 m 225°C, and near-neutral hydrothermal fluids. wide, but locally up to 4 m. Mining of these shoots was commonly hampered by their Dunn (1903) attributed gold in sedimentary unpredictable geometries, and complex cross- rocks at Chiltern to supergene processes. and low-angle faulting. Cuffley (1988) noted GEOLOGY AND PROSPECTIVITY - WANGARATTA 49

that reefs were typically rich close to the Gold production from the Wallaby reef between surface, and poorer below the weathered zone. 1870 and 1904 was 176.2 kg at 12.7 g/t. The nearby Rechabite reef produced 41.1 kg at Easton (1912a) described mining of quartz veins 3.6 g/t between 1871 and 1891 (Dunn, 1908). under the headings: Myrtleford belt, Stanley belt and Twists Creek belt. The general trends The Homeward Bound reef was the highest of these belts are northwest. Easton (1912b) producer within the Twists Creek belt, and is described mines at Happy Valley and Buffalo located 9.6 km east of Stanley. The Homeward Creek separately, but these are merely Bound was discovered in 1865 and was worked extensions of the Twists Creek and Myrtleford continuously until 1880. The reef dips steeply belts. Major producers from these belts are toward 105°. It was between 1 and 7 m wide, described below. and was worked to a depth of about 130 m (440 ft). The vein is truncated by a fault north The Tubal Cain reef is the highest producer in of the main shaft and has at least two branches the Myrtleford belt, and is located in the (Kenny, 1921). At the surface, the ore shoot headwaters of Basin Creek. The reef was was 67 m long, and is now marked by a 17 m worked to a depth of 53.6 m, and stoped to the deep open cut. Additional shoots were worked surface. The gold shoot was approximately 9 m at depth. Between 1865 and 1893, 821.3 kg of long at the surface, and increased to about gold was produced at 17.9 g/t (Dunn, 1906). 115 m at the 46 m (150 ft) level where grades The mine was reopened between 1913 and decreased. The reef was between 0.3 and 2.4 m 1918, and an additional 91.5 kg of gold was wide, averaging about 0.9 m (Meltech, 1985). produced at 10.4 g/t (Kenny, 1921). Between 1867 and 1883, the mine produced 43.3 kg of gold at 21.9 g/t. Many mines around Happy Valley lie just outside the contact-metamorphic aureole of the Most quartz mining in the Buffalo River area Yackandandah Granite. Gold occurs in steep was centred around Buffalo Creek, south of south-pitching quartz veins which rarely exceed Myrtleford. The Valentine reef is the highest 1.5 m in width (Woods, 1988). producer in the area, and is located west of Buffalo Creek. It is at the southern end of a The Happy Valley line was the highest 240 m line of working which includes the producer at Happy Valley. The line was first Mountain View mine. The northern portion of worked in 1866 following the discovery of the the line was discovered in 1867 by Kitts, whose Old Happy Valley reef. The line was later prospecting of the 0.4 m wide vein yielded about worked by the Wallace Company, which ceased 3 kg of gold grading 91.8 g/t. The Mountain production in 1883. Gold production for this View reef was worked to a depth of 33 m period was 1002.5 kg at 29.2 g/t. A south- (100 ft) between 1867 and 1905, yielding pitching shoot was worked to 150 m (495 ft; 10.9 kg of gold at a grade of 30.4 g/t. The reef seven levels) by adits and a shaft. The shoot dips very steeply toward 233°. At Valentine was about 50 m long and between 1.2 and 4.5 m reef, five shoots were worked from a 55 m wide. Veins were displaced by common (180 ft) deep shaft. The shoots have a vertical subvertical and horizontal faults and were lost spacing of between 3 and 13 m, and pitch 18° to to faulting at depth. the south. The longest shoot was 53 m. Between 1882 and 1908 the Valentine reef Easton (1912a) reported NNW-trending produced 24.9 kg of gold at a grade of 31.2 g/t. auriferous quartz veins which are parallel to bedding in the Dingle Range. These dip steeply The Wallaby reef was the highest producer in to the west and shoots pitch to the south. the Stanley belt, and is located in the upper Production from mines in the Dingle Range was reaches of Nine Mile Creek. The mine consists small and grades were commonly between 15 of extensive surface and underground workings, and 90 g/t. and is one of a group of mines within a corridor of strong shearing and common veining. This Some gold-bearing quartz veins can be traced corridor is about 900 m long and 100 m wide. along strike into the Pilot Range Batholith Ivett and Oldfield (1988) recognised two (374 ± 4 Ma; McKenzie et al., 1984) and generations of veining: (1) an unmineralised, therefore must be younger than Early Devonian northwest-trending set parallel to bedding, and (O'Shea, 1981). Kenny (1920) reported that the (2) a gold-bearing north-northwest trending Indigo Pioneer mine north of Wooragee vein and stockwork set controlled by shears. produced gold and silver from quartz veins in granite. Similar deposits have also been also 50 GEOLOGY AND PROSPECTIVITY - WANGARATTA

reported at Skeleton Hill and Mt Stanley long shoot to a depth of 230 m. The shoot (Dunn, 1906). pitched south at 55° and was between 0.3 and 2.6 m thick. The mine consisted of three adits Bright-Wandiligong goldfield intersecting the vein at depths of 45 m (140 ft), 100 m (330 ft) and 163 m (536 ft). Between Cuffley (1985) noted that most gold-bearing 1873 and 1903, it produced 409.7 kg of gold at quartz veins occupy faults in Ordovician 36.7 g/t. Hotham beds. These typically dip moderately to steeply to the east, through west-dipping The Myrtle mine, which worked a 50 m long strata (Roberts, 1988b). This trends is parallel shoot pitching 45° to the south, produced to the axis of folds. Fault-controlled veins often 263.41 kg of gold at 18.05 g/t (Spaargaren, branch into hanging walls, and footwalls 1968). The mine consisted of a 235 m adit that commonly contain spurry veins (Cuffley, 1985). cut the vein at a depth of 165 m, and drives Some veins occur in dykes (Kenny, 1925). which followed the vein over 565 m. Workings Veins are commonly truncated by faults which reached a depth of 280 m. trend northeast (Cuffley, 1985). The Williams United mine was discovered in Kenny (1925) noted that shoots often occur at 1926 and is located south of the junction of the intersection of veins and indicator beds. Morses and Growlers Creeks. This mine is These generally pitch steeply south (Cuffley, currently operated by Williams Mines P/L 1985). Gold occurs with minor arsenopyrite and under MIN 4004. Between 1926 and 1929, pyrite, and trace galena and sphalerite. 20.1 kg of gold was mined from an underlay Alteration about veins consists of quartz, shaft (Lloyd & Nunn, 1987). Later mining, sericite, chlorite, carbonate and albite (Cuffley, from 1934 to 1951 and 1957 to 1958 yielded 1985; MacKay, 1984) 142.8 kg at 39.8 g/t and 0.4 kg respectively. The mine was reopened in 1983 and has Many veins lie within a 20 km by 4 km zone produced 121.2 kg of gold to June 1996. Gold which trends north-northwest, parallel to the occurs with minor pyrite and arsenopyrite, and Kancoona Fault. Swensson and Patterson trace chalcopyrite, sphalerite and galena. (1989) observed shear zones characterised by MacKay (1984) recognised a northwest-trending brecciation and quartz stockwork veining fault system which dips steeply to the northeast within this zone. Large quantities of gold were and has controlled mineralisation. produced at the Oriental reef, London and Myrtle reefs and Williams United mine which Buckland goldfield still operates. Thin gold-bearing quartz veins occupy fractures The Oriental reef was the highest gold producer and form spurry formations in host Ordovician within WANGARATTA and was one of the first Hotham beds, and less commonly in dykes. veins discovered at Wandiligong. The vein Veins commonly trend northwesterly, parallel cropped out east of Wandiligong and was 15 m to the strike of the Hotham beds. Most gold wide and showed free gold when discovered. occurs in shoots between 10 and 50 m long The vein trends northwest and was worked at which rarely extend below 100 m depth (Cogar the surface along this trend over 365 m. In the Mining, 1985). Gold occurs with minor pyrite north, it splits into up to five veins between 0.6 and arsenopyrite. Most quartz mining took and 2 m thick. Most quartz was mined by place around the junction of the east and west stoping from adits to 60 m (200 ft) depth. branches of the Buckland River (O'Shea, 1989). Between 1860 and 1884, 1829.4 kg of gold was mined grading 14.4 g/t. Production from quartz veins is relatively small compared to alluvial production, which The size and richness prompted companies to contrasts with neighbouring goldfields. Quartz prospect deeper levels of the vein. Several mining in the Buckland goldfield was described small, low-grade shoots were found by this by Easton (1912b). work, but nothing to warrant development (Reilly 1968). The two largest deposits were the Alta and the Red Jacket reefs. The Alta reef is located on The London and Myrtle mines worked adjacent Nelson Creek. It consists of a small south- shoots on the same “line of reef”, which trends pitching shoot which was mined to a depth of northwesterly and dips moderately to the east. 65 m (220 ft) below the level of Nelson Creek. In the north, the London mine worked a 3 m This shoot cuts across bedding (Cogar Mining, GEOLOGY AND PROSPECTIVITY - WANGARATTA 51

1985). The workings consist of two adits and a shaft (Robinson, 1988). At the surface, the reef Major production came from the Golden had a grade of 398 g/t, but this decreased to Mountain mines at Tallangalook—about 268 kg 38 g/t at depth. From commencement of mining at 3.0 g/t (Griffiths, 1981). Production was from in about 1861, 102 kg of gold was mined before three open cuts and an unspecified number of the underground workings were flooded underground workings (Dunn, 1917). Gold is sometime after 1878. disseminated around two generations of fracture systems in high-grade pelitic hornfels. The Red Jacket reef is located close to the head Sandl (1989) and Wall and Taylor (1991) of Red Jacket Gully, near Clear Creek. It was demonstrated that gold had been emplaced discovered in the 1860s and little is known with biotite and pyrite during contact- about its early history. The mine contains metamorphism, followed by emplacement of several decomposed dykes, which are unrelated gold and arsenopyrite during retrograde to mineralisation. Multiple veins trend north metamorphism. This is one of the type and dip moderately to the west. These are localities of Wall and Taylor's (1991) thermal displaced by numerous faults. A 15 m long aureole gold model. Sandl (1989) observed that shoot, worked at the surface, pitches to the steeply dipping east-west–striking north. Three adits were developed on the vein carbonaceous beds and major steeply dipping set. The “main reef” is between 0.5 and 1.0 m north-south–trending faults were favourable wide and graded 30.6 g/t. The mine reached a sites for gold deposition. maximum depth of about 105 m (350 ft). Between 1868 and 1904, 249.5 kg of gold was Dunn (1917) recorded similar deposits nearby produced at a grade of 40.7 g/t. at Woolfs Mine and an open cut worked by Falks. The Bonnie Doon mine on Glen Creek Melbourne gold province was one of several mines which worked quartz veins in hornfels. First crushings yielded about Within WANGARATTA, the Melbourne gold 4 kg at almost 200 g/t. Like many others, the province roughly coincides with the Melbourne reef was worked to 25 m and abandoned at the Zone of Gray (1988) and the Central Victorian water table (Dunn, 1917). Magmatic Province of Ramsay and VandenBerg (1986; = Melbourne "Basement Terrane" of At least two veins also contained significant White & Chappell, 1988). The province stibnite. East of Merton, the Heyfield vein contains rocks ranging from Cambrian to yielded up to 248 g/t gold, with relatively low Devonian. Some orogenic gold deposits are yields in some parcels attributed to high close to and probably related to the Strathbogie antimony content (Whitelaw, 1899). The vein is Granodiorite. Outside WANGARATTA, dyke- about 0.5 m thick and was worked over a strike affiliated and sediment-hosted deposits are also of 275 m to a maximum depth of 70 m. About important mineralisation styles (e.g. the 150 kg of stibnite was mined, of which one-third Nagambie deposit and deposits in the Woods was burnt in attempts to recover refractory gold Point dyke swarm). (Whitelaw, 1899). Egans reef near Merton also contains abundant stibnite. It was worked by The province within WANGARATTA includes pits and shafts over a distance of 3 km the Merton, Hells Hole (Tallangalook) and (Whitelaw, 1899). Benalla goldfields defined by Weston (1992). The Merton and Tallangalook deposits have Gold is recorded in quartz veins in Siluro- essentially the same setting, hosted by variably Devonian rocks at Honeysuckle Creek, contact metamorphosed Silurian and Devonian Tamleugh and Benalla. Only minor production siltstone and sandstone close to the Strathbogie has been reported from deposits within these Granodiorite. Ramsay and Willman (1988) areas. Dunn (1914) reported "only a few described many open cuts and pits located ounces" from the Tamleugh quartz reef, despite within cordierite hornfels within these several shafts up to about 20 m deep. These goldfields. Recently recognised Cambrian were worked intermittently from 1851 until at greenstone adjacent to the Tallangalook least 1909. goldfield may be important to the genesis of these deposits. The Cambrian inlier does not Benambra gold province have a prominent response in aeromagnetic data—in this respect it resembles the The Benambra gold province coincides with the greenstones of the Jamieson inlier farther Omeo Zone east of the Kancoona Fault southeast (VandenBerg et al., 1995). (Ferguson, 1988), and the Wagga granite 52 GEOLOGY AND PROSPECTIVITY - WANGARATTA

province ("Basement Terrane") of White and greenstone are present under shallow cover Chappell (1988) within WANGARATTA.. The within WANGARATTA. province includes only the minor House Creek goldfield. This lies 20 km west of a NNE- South of WANGARATTA, company exploration trending zone containing significant deposits of has recognised VHMS-style Au-Cu and Au-Ag- the Benambra gold province (Ramsay & Ba mineralisation in the calc-alkaline Jamieson Willman, 1988; Oppy et al., 1995). Descriptions Volcanics at Hill 800 and Rhyolite Creek near of mining within this goldfield are sketchy. Jamieson. The small Rippins Reef, Howqua Auriferous quartz veins and alluvium yielding United and Great Rand gold mines occur in "a grain and a half to the dish" were reported by MORB-type Cambrian greenstones; the Great Kennan (1861) from Rats Castle, along House Rand contain 215 000 t @ 6 g/t gold (Ramsay & Creek. The quartz veins occur in gneiss of the Willman, 1988). Omeo Metamorphic Complex. Company exploration has indicated uneconomic 7.4 Antimony-?gold deposits in VHMS-style mineralisation at Wrightley in WANGARATTA. Banded pyrrhotite-rhodonite- the Tolmie Igneous Complex chert was intersected in two holes drilled by CVT P/L (EL 1019) and CRA Exploration Pty. Small lodes of stibnite occur in quartz veins at Limited (ELs 3218 and 3224) on the Northwest Hollands Creek near Toombullup. Veins are up Samaria Creek Grid and Spring Gully Prospect. to 1.5 m thick, dip at 60° to the south east and These rocks have characteristics of VHMS-style have been traced over 15 m. The Tatong deposits. Despite elevated Au, Cu, Zn, As and Antimony Mine operated for three periods Ba in soils and rocks, intersections lack between about 1895 and 1925, and produced elevated base and precious metal values (Wilkie about 37 t of first class and fairly clean stibnite & Brookes, 1997). Weathering of these units (Grieve, 1925). has produced a belt of iron and manganese oxides (Laing et al., 1977). Veins occur in rhyolite and rhyodacite ignimbrite of the Upper Devonian Tolmie Significant but unsuccessful exploration Igneous Complex, although this was described programs have been undertaken at Dookie by as "metamorphic rock" by Grieve. Geary and Minocor Exploration under EL 1921 and Colliver (1994) noted similar deposits with Freeport of Australia under EL 991 (Wilkie & minor gold associated with caldera ring dykes of Brookes, 1997). the Cerberean caldera, south of WANGARATTA. Nearby alluvial gold deposits of the Toombullup goldfield may be sourced 7.6 Granite-hosted tin deposits from similar veins and Late Devonian felsic dykes within the complex. Tin occurs mostly in alluvial deposits, but small low-grade cassiterite lodes in granite are The Toombullup goldfield consists of alluvial recognised in the Pilot Range near Beechworth. deposits of gold and minor cassiterite close to These deposits are part of a 500 x 130 km "the tree riddled with the bullets fired at NNW-trending belt called the Tallebung- Sergeant Kennedy by the Kellys" near Stingy- Albury-Mt Wills Tin Province (Cochrane & bark Creek (Stirling, 1898). About 230 miners Bowen, 1971). Primary deposits within this were working these deposits when Stirling province are characterised by cassiterite as visited in 1898. Stirling noted deposits disseminations in veins with and without bottomed on "granite" and had no known quartz, and associated with greisen and primary source. pegmatite veins within and adjacent to granites. Oppy et al. (1995) noted that mineralisation in nearby TALLANGATTA was 7.5 VHMS and epigenetic gold related to hydrothermal alteration near deposits in Cambrian Silurian S-type and Early Devonian I-type greenstones granitoids. Dunn (1913) identified four settings of primary Cambrian greenstones crop out along the cassiterite within WANGARATTA: Mount Wellington Fault Zone at Dookie and Wrightley, and were recently recognised north · within thin quartz veins in granite; of Maindample at Glen Creek. Aeromagnetic data suggests that large areas of unrecognised · disseminated in thick lodes of greisen; GEOLOGY AND PROSPECTIVITY - WANGARATTA 53

· associated with chalcopyrite-garnet- tourmaline within thin 'fissures' in granite; 7.8 Porphyry molybdenite and deposits · disseminated in granite. Low-grade, quartz vein–related and Young (1983) argued that the latter setting is disseminated molybdenite occurs within the genetically improbable and was probably an Everton Granodiorite and related dykes and attempt to explain the source of nearby large contact-metamorphosed Ordovician Hotham placer deposits. Young also observed abundant beds in the Everton area. These have been sericite and arsenopyrite in cassiterite-bearing intermittently mined since about 1917. quartz veins. The Everton Molybdenite Mine was the largest The Pilot Range consists of five intrusions, producer of the Everton molybdenite field and some of which have porphyritic phases. White operated in the periods 1917–26, 1937–40 and and Chappell (1988) described these rocks as 1942–44. The mine worked two porphyritic strongly fractionated and "reduced I-types". granodiorite pipes to depths of 45 m. Airborne magnetic data indicates only two large Molybdenite occurs within and adjacent to circular intrusives, which do not correspond to quartz veins, in joints and as disseminations. It mapped subdivisions. is often associated with pyrite and less frequently pyrrhotite, chalcopyrite and The Woolshed Valley Granite southeast of the arsenopyrite (Waldon, 1977). Azurite and Pilot Range contains cassiterite lodes worked by malachite were reported in the north of the the Lone Hand and Hidden Friend shafts. field (Kenny, 1921). Total molybdenite These are the most significant primary production from the No 1 ore body was 12 591 workings in WANGARATTA. Kenny (1937) tonnes @ 1.54% between 1917–1940 (including reported low grades from assays of two parallel 700 tonnes from No 2 ore body) and 4377 tonnes lodes worked by the Hidden Friend mine. Since @ 0.41% between 1940–44 (Kenny, 1948). the Pilot Range has already been extensively prospected, the probability of finding large Aeromagnetic data suggests that the Everton primary tin deposits is low. Granodiorite (384 ± 6 Ma; McKenzie et al., 1984) is a late phase of the recessively It is difficult to reconcile the large quantity of weathered Murmungee Granite (376 ± 4 Ma; cassiterite in placer deposits with the small and McDonald, 1988) to the south. It forms a highly low-grade primary sources. Cochrane and magnetic, 3.5 km long discontinuous belt Bowen (1971) speculated that richer primary adjacent to or truncating the magnetic sources either remain undiscovered, or have Murmungee Granite. In the north of the field, been eroded away. The latter is probably true, where molybdenite veining is common, the since greisens and stockworks are usually Everton Granodiorite is porphyritic, suggesting concentrated at the upper contact of granite intrusion at shallow levels (O'Shea, 1979a). intrusions, and granites near the Pilot Range Close to the Murmungee Granite, the appear to have been eroded to intermediate granodiorite is nearly equigranular and levels (Young, 1983). Intermediate pluton surrounded by resistant hornfels suggesting a levels are suggested by aeromagnetic data and deeper level of intrusion. the absence of roof pendants. Minor amounts of molybdenite also occur in The source of a small quantity of alluvial placer quartz veins at Kitchington Creek in the Mount cassiterite reported by Howitt (1908) north of Stanley Granite, which is a fine-grained Maindample is probably the S-type Strathbogie leucocratic adamellite (Laing et al., 1977). Granodiorite. Bismuth and bismuthinite have been reported Cochrane and Bowen (1971) noted minor gold from placer deposits at Pennyweight Flat by in some tin-bearing granites in the Pilot Range Dunn (1913). Young (1983) suggests these were area. In addition, small wolframite-quartz derived from the Everton molybdenite field or veins in gneiss of the Omeo Metamorphic Mt Stanley where small quantities of these Complex were worked by the Archers Mine at minerals occur with molybdenite. Indigo Creek. Small quantities of scheelite were mined at the Lady Rose Mine from veins in Ordovician Hotham beds (Laing et al., 1977). 54 GEOLOGY AND PROSPECTIVITY - WANGARATTA

7.9 Porphyry gold-copper 7.10 Copper deposits in the deposits Mansfield Group

Porphyry copper deposits are characterised by Although sedimentary copper mineralisation disseminated and stockwork copper was first reported from the Mansfield Basin in mineralisation associated with high-level the 1860s, detailed investigation for copper, plutons (Evans, 1987). Potential for gold-copper uranium and vanadium deposits were not porphyry-style deposits within WANGARATTA undertaken until the early 1970s. These is suggested by the recent development of programs, principally by Jennings Mining porphyry gold-copper deposits in the Lachlan under ELs 409 and 466, and Northern Mining Fold Belt in NSW. under EL 412 (Wilkie & Brookes, 1997), identified many minor copper occurrences at South of WANGARATTA, porphyry-style two stratigraphic levels of the Devils Plain copper mineralisation is associated with high- Formation of the Late Devonian Mansfield level oxidised Siluro-Devonian granititc Group, but failed to delineate mineralisation of intrusives. Whilst similar mineralisation has economic significance. not been recognised within WANGARATTA, oxidised Devonian granites are fairly common Ordovician black shales within WANGARATTA in the map area. The Murmungee Granite may also be prospective for base metal deposits, (376 ± 4 Ma; McDonald, 1988) is particularly although reconnaissance exploration by CRA interesting because it is recessively weathered, Exploration P/L (ELs 330 & 610) failed to possibly reflecting hydrothermal alteration. identify significant prospects (Wilkie & Also, the nearby Everton molybdenite field Brookes, 1997). covers bulk, low-grade molybdenite mineralisation related to the Everton Copper has been found at two stratigraphic Granodiorite. Aeromagnetic data suggest that levels of the Devils Plain Formation in the the Everton Granodiorite (384 ± 6 Ma; western part of the Mansfield Basin: in a 185 McKenzie et al., 1984) is a late phase of the m thick section of "lower sandstone", and in the Murmungee Granite (376 ± 4 Ma; McDonald, overlying 150 m thick "upper cupriferous shale" 1988). Test drilling of the Murmungee Granite (informal names). Both of these units have by Dampier Mining Company Ltd (EL 708 and elevated K and Th radiometric responses in EL 729) intersected patchy gold mineralisation, airborne radiometric data. Cochrane (1982) including 3 m @ 2.0 g/t from 54.0 m (Wilkie & summarised this stratigraphy which was Brookes, 1997). defined by Meyer (1973). Copper occurs in locally reduced grey and green zones within these units.

Review of copper occurrences in the "lower sandstone" unit by Cochrane (1982) showed that these were contained within a single sub- unit 19 m thick. This unit consists of lenticular erosion channels which are not ordered and are not laterally continuous. Where they crop out, cupriferous beds are typically 0.2–0.3 m thick and can be traced for up to 8 m. Mineralisation, which consists of malachite with minor chrysocolla and sulphide, averages 1–1.5% Cu.

Copper is reported in a discrete 10 km interval of the "lower sandstone" unit adjacent to the main road southwest of Tolmie (Meyer, 1973). Beds in this area are folded into a gently south- plunging anticline. Copper occurrences may in part be related to this structure which may have acted as a trap for migrating fluid.

Another control on copper distribution may be basement structures which may have carried GEOLOGY AND PROSPECTIVITY - WANGARATTA 55

mineralising fluids. Southern continuations of feldspathic and micaceous and contain faults under the Mansfield Basin which bound carbonaceous plant material. Drilling failed to and truncate Cambrian rocks at Tatong are of intersect significant mineralisation, and showed particular interest. These may have channelled the grey-green to buff sandstone was up to metal-bearing fluids derived from the 1.3 m thick, with a shoestring geometry within greenstones and were active just prior to a sequence of red sandstone and mudstone. deposition of sediments of the Mansfield Basin. The Devils Plain Formation here has a Cochrane (1982) showed that copper relatively elevated K and Th response in occurrences in shale occur at three levels of the airborne radiometric data. Northern Mining "upper cupriferous shale". Outcrops of this unit Corporation NL. (1975) reported that the within WANGARATTA are rare and mostly radiometric response over mineralisation is covered with Quaternary alluvium and associated with barite intergrown with the colluvium, and there are no recorded copper mineralisation, and that soil-covered occurrences within WANGARATTA. South of mineralisation has a response twice that of the WANGARATTA, mineralised beds are typically background. thin and calcareous and formed in a reducing environment. Mineralisation consists partly of 7.11 Placer diamond malachite and partly of disseminated chalcopyrite associated with pyrite, rare occurrences bornite, covellite and digenite, some of which lines joints and bedding planes. This is In excess of 78 diamonds were recovered during generally lower grade than mineralisation in mining of deep lead deposits of gold and tin sandstone. Uranium values are elevated for within the Eldorado, Beechworth and Chiltern- some copper occurrences. Rutherglen goldfields.

Cochrane (1982) concluded that it was unlikely Birch and Henry's (1997) comprehensive review that any major outcropping expression of of gemstone occurrences in Victoria shows these mineralisation had been overlooked as horizons were chiefly taken from alluvial gravels in that contain copper had been systematically Reedy Creek (parts of which are also known as mapped, and soil and drainage sediments Wooragee Creek, Youngs Creek, and Woolshed sampled. New airborne radiometric data Creek) from Wooragee to Eldorado. Many of indicate a small region with a high K, U and Th these diamonds were recovered from the radiometric response within the anticline Woolshed Creek portion of Reedy Creek. At containing the sandstone-hosted copper Eldorado, the western limit of diamond occurrences, 6 km northwest of Tolmie. The occurrences, stones were found in the bottom source of this response is not known and may be level of the alluvial deposits, on granite bedrock uranium ± copper mineralisation in outcrops of (Birch & Henry, 1997). Further east at prospective beds which cap hills in the area, or Sebastapol, Dunn (1871) reported diamonds Tertiary phonolite and trachyte plugs mapped cemented in Pliocene gravels. Diamonds within by Meyer (1973). the Chiltern-Rutherglen goldfield came principally from a patch of wash at 115 m depth In the Mount Typo Syncline along the on the Prentice Lead worked by the Great eastern margin of the Mansfield Basin, Southern Gold Mining Co. Diamond have also anomalous copper values were recorded from been reported from Pilot Creek, the Indigo Lead drainage sediment samples at 25 locations close and the Lancashire Lead. to the base of the Devils Plain Formation (informally named "Mount Pleasant Formation" Birch and Henry (1997) determined locations in EL reports). This work was reported by for 78 diamonds within these two fields. Of Northern Mining Corporation NL. (1975) under these, the two largest stones (6 & 8.2 carats) EL 412. Anomalies were located at Mount were taken from Black Sands and Old Hands Pleasant, Mount View, Mount Thomas and creeks within the Beechworth goldfield. Most Mount Ralph. Malachite and azurite within other diamonds weighed less than 0.5 carats. grey-green to buff sandstone at Mount Pleasant was identified by follow-up soil sampling and Diamonds mostly occur in deep leads and trenching. Copper carbonates occur in seams a gravels from streams which have drained few millimetres thick parallel to bedding, and granite of the Pilot Range. Birch and Henry have average grades of 4.65% Cu, 38 ppm Ag, (1997) found differences in features of diamonds 539 ppm U and 290 ppm V. Sandstones are recovered south of the Pilot Range from the 56 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Beechworth and Eldorado goldfields, and north was in the opposite direction, towards the north of the Pilot Range from the Great Southern and northeast. mine, and concluded they have different histories and origins. Diamonds from the Great Exploration programs in the late 1970s to early Southern mine are more abraded and lack 1990s were designed to target placer deposits radiation spots, reflecting high-energy around historic occurrences and the sources of transportation and deposition in alluvial those diamonds. Companies undertaking deposits with low zircon concentrations. significant programs were Northern Mining Radiation spots in diamonds from the Corporation NL and Freeport of Australia Beechworth and Eldorado goldfields can be (EL 619), Pennzoil of Australia Limited explained if the stones were deposited in older (EL 676), Duval Mining Ltd, Picon Exploration placer deposits, and redeposited into Recent P/L and Jan Resources P/L (EL 1225), Triad alluvial gravels. Minerals NL (EL 3213), and Normanby Poseidon Exploration Ltd (EL 3247). These The most simple explanation for the programs failed to locate significant diamond distribution of placer diamonds is an placer deposits and a primary source for known unrecognised diamond-bearing volcanic pipe on diamonds (Wilkie & Brookes, 1997). Limited the divide east of Mount Pilot. Lamproite and stream sediment sampling was undertaken for kimberlite have not been recognised within the indicator minerals by Freeport of Australia and Tasman Fold Belt, and lithosphere thicknesses Triad Minerals NL at Eldorado and south of are generally considered to be insufficient for Chiltern. Of the 100 samples, two yielded diamond formation. The subduction diamond microdiamonds. One of these, taken from model of Barron et al. (1994) predicts a shallow Commissioner Creek west of Reedy Creek, also diamond stability field in a long-lived contained phlogopite and picroilmenite subduction zone. In this model, diamonds are suggesting proximity to source. Chromite was "carried" by basanite, nephelinite and leucite recorded in many samples, while pyrope, magmas. Indicators, which also form in this picroilmenite and phlogopite are very rare. stability field, include corundum and Na garnet. 7.12 Coal

Birch and Henry (1997) record common Significant exploration programs undertaken sapphire (corundum), spinel and zircon from by Western Mining Corporation Ltd (EL 627), multiple sources with diamonds in CRA Exploration P/L (ELs 824, 1063 & 1064) WANGARATTA, while phlogopite, and the SECV have failed to identify economic picroilmenite, pyrope and other indicators of coal deposits within WANGARATTA (Wilkie & lamproite and kimberlite are uncommon. Brookes, 1997).

There is a spatial association of diamonds and The Oaklands Infrabasin lies within the Ovens Cainozoic alkali basalt in the Tasman Fold Belt, Graben, and straddles the State border. This although this is not obvious within basin contains the Late Permian Coorabin Coal WANGARATTA. Jurassic and Cainozoic Measures which has been mined intermittently alkaline rocks include breccia-filled volcanic in NSW since 1917. This unit is high in the pipes similar to kimberlite intrusives. Jaques Permian succession and does not persist into et al. (1985) concluded these rocks were olivine Victoria where the graben is relatively shallow. nephelinite and alkali basalt–related diatremes. The coal measures consist of fluvial to While these are unrecognised within lacustrine shale, coal and minor sandstone WANGARATTA, they occur nearby at Delegate (Holdgate, 1995). and Koetong (Tan, 1982). Late Permian coal deposits have also been Dunn (1913) proposed that diamonds were identified in the Numurkah Basin near transported to WANGARATTA from Delegate Deniliquin in NSW (Brown & Stephenson, by "Permian" (= Late Carboniferous) glaciers, 1991). The Permian succession in the and shed from glacial conglomerate deposits Numurkah Basin is mostly untested in into Cainozoic drainage. Birch and Henry WANGARATTA, and may be prospective for (1997) point out that these Late Carboniferous similar deposits. deposits must have been more extensive than at present to account for the distribution of placer Large uneconomic deposits of mostly soft low- diamonds. In addition, glacial striations show rank lignitic brown coal occur in the Eocene that ice movement in the Late Carboniferous GEOLOGY AND PROSPECTIVITY - WANGARATTA 57

Olney Formation of the Murray Basin, but do not persist into WANGARATTA. Large quantities of Glenrowan Granite are extracted by Glenrowan Quarries P/L (WA 235) 7.13 Non-metallics at Glenrowan for aggregate, road base, armour and fill. A small quantity of this granite was Construction materials extracted for dimension stone in 1990/91. Taminick Gap Granite is extracted for road base, aggregate and fill at Chesney Vale, west Modern mining has been dominated by the of Glenrowan. Mawson & Sons P/L (WA 319) is development of construction material resources. the only significant producer. Small quantities Construction materials worth approximately of Youarang Granite are extracted at Youarang $20.5M were extracted in 1994/95 under the for fill. Extractive Industries Act 1966 (Department of Natural Resources & Environment records). Cambrian metasediments are extracted at Cosgrove South and Killandra for road base and Coonambidgal Formation clay and sand is fill. Boral Resources P/L (WA 79) is the only extracted from the Murray River, Broken River significant producer. and Ovens River valleys close to Albury, Benalla, Everton and Wangaratta. This is used Additional operations, primarily sand and for aggregate, concrete and fine sand, and fill gravel pits operated by the Department of and road base. Significant producers are CSR Natural Resources and Environment, are an Ltd (WA 185), Pioneer Concrete P/L (WA 386), important source of local road surfacing Wodonga Quarries Ltd (WA 474) and A.P. material. Delaney & Co P/L (WA 205). Small quantities of clay were extracted by G.C. Douglas from WA 475 and Wodonga Quarries Ltd from Feldspar WA 474 for brick manufacture. Feldspar is used in the glass and ceramics Hotham beds material is extracted close to industries as a source of alumina and alkalis. Glenrowan, Chiltern, Youarang and Benalla. This is used for aggregate, road base, armour At Sheep Station Creek, 3 km east of and fill. Significant producers are CSR Ltd Beechworth, ACI Resources Ltd (ML 1657) are (WA 185), E.B. Mawson & Sons P/L (WA 320 & developing an orthoclase feldspar resource in 325), Pioneer Concrete P/L (WA 390) and the leucocratic Beechworth Granite. A proven Extons P/L (WA 223). Contact-metamorphosed reserve of 3 Mt of suitable granite has been Hotham beds (mostly hornfels) adjacent to delineated by the company, and recent pilot granites is commonly used as aggregate, and plant tests have yielded a relatively clean, low was trialed as dimension stone by Mawson & iron, quartz-feldspar product suited to glass Sons P/L in 1986/87. manufacture. Development of this resource is planned in the near future. Newer Volcanics basalt is extracted from Cosgrove for aggregate, road base and fill. Industrial tests indicate that massive Boral Resources P/L (WA 76) is the only orthoclase feldspar in a pegmatite dyke at significant producer. Tallangalook is suitable for use in the manufacture of ceramics. Similar pegmatite Siluro-Devonian sandstone is extracted close to dykes have been reported from Huon Hill, Cosgrove South, Euroa and Karn, south of Mount Pilot and Mount Lady Franklin in Benalla. This is used for aggregate, fill and northeast WANGARATTA. Small-scale road base. B. North (WA 366) is the only production is reported from feldspar-rich dykes significant producer. which intrude schist of the Omeo Metamorphic Complex at Huon Hill. These are up to 30 m Upper Devonian rhyodacite ignimbrite is thick and can be traced for 550 m (McHaffie & extracted close to Violet Town for road base, Buckley, 1995). aggregate and armour. Violet Town Quarries P/L (WA 471) is the only significant producer. 58 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Table 10 Gemstone occurrences

Locality Agate Amethyst Chalcedony Chert Corundum Diamond Emerald

Beechworth X X X X X Chiltern X X Tatong/Toombullup X X X Glenrowan/ X X Taminick/Greta

Locality Garnet Jasper Quartz Sapphire Topaz Tourmaline Zircon

Beechworth X X X X X X X Chiltern X X X X X Tatong/Toombullup X X X X X Glenrowan/ X Taminick/Greta

Source: McHaffie and Buckley (1995).

A resource of 750 t has been inferred for two alloy practice, and as a flux in the ceramics parallel, near-vertical pegmatite dykes at industry (McHaffie & Buckley, 1995). Kookaburra Creek (Tan & Atkinson, 1988). Dykes contain very large feldspar crystals, with Low-grade fluorite occurs in quartz veins up to accessory tourmaline and muscovite. The 10 m wide in the Mount Warby area, southwest largest dyke is 150 m long and averages 60 cm of Wangaratta. Minor amounts of pyrite, thick (McHaffie & Buckley, 1995). galena and sphalerite are also present. These were estimated to be 20 m by 30 m in area at Gemstones vein intersections, but drilling showed that this decreased significantly with depth. Fluorite is Table 10 lists gemstone occurrences in an accessory mineral in many quartz veins in WANGARATTA. Dunn (1913) thought that granitic intrusions of the Warby Ranges amethyst, jasper, carnelian and zircon at (McHaffie & Buckley, 1995). Woolshed Valley, near Beechworth, came from the nearby Pilot Range Batholith. These Calcite minerals are accompanied by agates and massive corundum pebbles derived from Late At Boxwood a large calcite vein in Cambrian Carboniferous glacial deposits (Dunn, 1913). dolerite has been worked by a series of pits over Gemstones in deep leads at Chiltern probably 360 m. The vein is about 3.5 m thick at the have a similar source. Diamonds from Reedy surface. Calcite was burned to produce lime for Creek and leads at Chiltern have been use in agriculture and plaster (McHaffie & discussed above. Buckley, 1995).

Birch (1988) described well-formed bladed Wollastonite ferroaxinite crystals up to 1 cm in size from cavities and veins in Cambrian dolerite in a Wollastonite is most commonly formed by quarry 3 km west of Dookie (Laing et al., 1977). contact metamorphism or metasomatic The ferroaxinite is associated with andradite replacement of limestone, siliceous limestone or and actinolite crystals. calcareous sandstone. It is used in the manufacture of paint, plastics, ceramics and Fluorite electrical insulation. Contact metamorphism of calcareous sandstone is reported along the The main use of fluorite is in the manufacture margin of the Strathbogie Granodiorite north of of hydrofluoric acid. It is less commonly used Bonnie Doon, and at Chesney Vale. as a fluxing agent in iron foundry and ferro- Wollastonite has only been recognised within the cordierite-muscovite contact metamorphic GEOLOGY AND PROSPECTIVITY - WANGARATTA 59

isograd about the Strathbogie Granodiorite traced intermittently for about 30 km. The (McHaffie & Buckley, 1995). Greta South turquoise fields occur in similar rocks near Greta South. Turquoise occurs in Quartz crystals small veinlets or as patches in brecciated slate and has been worked from a series of small Laing et al. (1977) report mining of quartz workings spread over a distance of 500 m crystals from coarse-grained biotite granite at (McHaffie & Buckley, 1995). the Crystal King Mine near Tallangalook for use in radio transmitters during the 1940s. A IMC Development Corporation (ELs 37 & 53) recent upsurge in interest in quartz crystals for considered these and other deposits not to be of ornamental and "new-age healing" purposes economic significance (Wilkie & Brookes, 1997). has led to reworking of this deposit (McHaffie & Buckley, 1995). Dimension stone

Talc Dimension stone is natural stone that is cut to specific dimensions for use in building, Talc is soft and smooth; has a perfect basal construction and monumental industries. The cleavage, is easily ground to an extremely fine major stones used are marble, limestone, white powder, is a good lubricant and is granite, gneiss, basalt, sandstone and slate. chemically inert. It has high absorption, a high McHaffie and Buckley (1995) recognised four fusion point, low shrinkage when fired and low granites with potential for dimension stone thermal and electrical conductivity. These production within WANGARATTA. characteristics make it useful in the manufacture of paint, plastics, rubber and The various intrusions in the Pilot Ranges have ceramics. It is also widely used in the cosmetics been used extensively as "Beechworth granite" industry (McHaffie & Buckley, 1995). for building at Beechworth between 1857 and 1864. They display a range of colours and Talc is recorded at several localities in the textures. King and Weston (1997) reported Cambrian rocks at Dookie. At Ascot Hills, talc good potential for dimension stone sites based replacing pyroxene constitutes about 75% of the on limited inspection and past production. rock in an outcrop area of 0.5 ha. Near Dookie, talc also occurs in mudstone and within a The Yackandandah Granite was used last narrow fault zone (McHaffie & Buckley, 1995). century for building in and around Yackandandah. The rock has a number of Phosphate colours and textures, including a mylonitic foliation in the Kancoona Fault zone. King and Apatite is the major commercial phosphate Weston (1997) noted the rock is worthy of mineral and is common in some marine further investigation. sedimentary deposits and igneous rocks. Phosphate ore is processed to give Glenrowan Granite and Taminick Gap Granite superphosphate, triple superphosphate, within the Warby Ranges were quarried for phosphoric acid or super phosphoric acid. Most dimension stone used in buildings in phosphate produced is used in the manufacture Glenrowan, Wangaratta and Melbourne as of fertiliser (McHaffie & Buckley, 1995). recently as 1991. The rock is pyritic, and irregular jointing means blocks are generally "Phosphate Minerals of Victoria” (Birch et al., small. These properties, together with the 1993) describes the distribution, geological exclusion of quarrying in large outcrop areas setting and history of discovery of Victorian covered by the Warby Ranges State Park, make phosphate occurrences. Two significant development potential low (King & Weston, occurrences lie in WANGARATTA. 1997).

Several belts of Ordovician carbonaceous black The Strathbogie Granodiorite is a large granite shale and slate, containing primary and intrusion which has local variations in colour secondary phosphate minerals, crop out near and jointing characteristics. There is no known Cheshunt. These are called the Edi-Cheshunt use of the rock, and common xenoliths mean it turquoise fields, and were worked between 1893 has just moderate potential for dimension stone and 1921. Turquoise occurs as compact veins (King & Weston, 1997). up to 2 cm thick in these belts, which can be 60 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Results of trials of hornfels adjacent the Strathbogie Granodiorite as dimension stone by Mawson & Sons P/L in 1986 were not followed by production, and hence probably indicated that the rock was unsuitable. GEOLOGY AND PROSPECTIVITY - WANGARATTA 61

8 Soil and stream sediment Stream sediment samples collected for diamond indicator minerals cover small areas in the geochemistry Eldorado goldfield and south of the Chiltern goldfield. Of about 100 samples collected, 2 Soil and stream sediment geochemical (and yielded microdiamonds. Others contained diamond indicator mineral) surveys conducted chromite, pyrope, picroilmenite and phlogopite. since the Exploration Licence system was established in 1965 are discussed briefly in this Figures 15–17 show the distribution and type of chapter to give a regional perspective of the soil samples collected, and which samples were distribution and type of geochemical sampling analysed for gold. Extensive soil sampling covering WANGARATTA. programs cover Cambrian greenstone at Dookie and Tatong, Siluro-Devonian sequences north of Open file stream sediment and soil geochemical the Strathbogie Granodiorite, Ordovician black (and diamond indicator mineral) data reported shale sequences about phosphate occurrences, in all expired EL reports have been captured the Pilot Range Batholith, and the Everton digitally and are available from the Geological molybdenite field. Most samples at Dookie and Survey of Victoria in the following formats: within the Everton molybdenite field were not analysed for gold. Small surveys cover parts of · themes in the WANGARATTA GIS data set; the Mansfield Basin, and the Chiltern- Rutherglen, Beechworth, Eldorado, Bright- · Explorer 3 database Ó Terra Search P/L; Wandiligong, Tallangalook and Merton and goldfields. Large parts of all goldfields are · ASCII files. untested by soil sampling.

The data set consists of location and assay Detailed analysis of these data has not yet been information on more than of 6000 soil and 5000 attempted, but will be undertaken as part of a stream sediment samples collected within regional analysis for the whole of eastern WANGARATTA. Victoria in 1998.

Stream sediment sampling programs cover most Palaeozoic rocks. Figures 11–14 show the distribution and type of stream sediment samples collected, and which samples were analysed for gold.

Only stream sediment samples covering Cambrian greenstones at Dookie, Ordovician Hotham beds south of Glenrowan, and Late Devonian Mansfield Group were not analysed for gold. Areas with no sampling are northeast and southwest of Mount Buffalo, north and east of the Yackandandah Granite, the Violet Town Volcanics, and central WANGARATTA north of Glenrowan. No stream sediment samples have been collected from the Chiltern-Rutherglen goldfield which include mostly placer gold deposits, and the Toombullup, Buckland River and Bright-Wandiligong-Freeburgh goldfields.

The coverage of stream sediment samples analysed for gold by bulk cyanide leaching (BCL) is similar, except for the Beechworth goldfield where samples have a low density. BCL analysis gives very low detection limits, and offers the best potential of detecting coarse- grained gold in drainage. 62 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Figure 11 Distribution of stream sediment samples analysed for gold (excluding samples analysed with the bulk cyanide leach method).

Figure 12 Distribution of stream sediment samples analysed for gold by bulk cyanide leaching (BCL). GEOLOGY AND PROSPECTIVITY - WANGARATTA 63

Figure 13 Distribution of stream sediment samples not analysed for gold.

Figure 14 Distribution of diamond indicator stream sediment samples. 64 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Figure 15 Distribution of soil samples analysed for gold (excluding samples analysed with the bulk cyanide leach method).

Figure 16 Distribution of soil samples analysed for gold by bulk cyanide leaching (BCL). GEOLOGY AND PROSPECTIVITY - WANGARATTA 65

Figure 17 Distribution of soil samples not analysed for gold. 66 GEOLOGY AND PROSPECTIVITY - WANGARATTA

9 Mineral resource potential Aeromagnetic data covering goldfields shows possible bedding, magnetic dykes and faults. and prospectivity Detailed interpretation of the data may be helpful in identifying prospective, gold-bearing Mining has a 146 year history within structural settings. WANGARATTA, producing significant quantities of gold and minor quantities of other A brief regional overview of the data covering minerals. New resources continue to be defined goldfields shows: by modern exploration programs. East of Beechworth, ACI Resources Ltd are planning · Domains in moderately magnetic Ordovician development of a glass-grade orthoclase Hotham beds of the Buckland River goldfield feldspar resource with a proven reserve of 3 Mt which trend north-northwest, parallel to the of suitable granite. Proven mineral resources trend of most gold-bearing quartz veins. are shown in Figures 6 and 7, and described in · Moderately magnetic responses from detail in Chapter 7 and the Wangaratta Mine bedding and possible dykes in the Bright- Database. They are also shown with a TMI Wandiligong goldfield. Also dislocations image background in Figure 18. probably corresponding to faults. Regional-scale evaluation of new geophysical · Some bedding, faults and dykes in the information, together with compilation of Stanley and Beechworth goldfields have information on mineral resource, geochemistry magnetic responses. Granites which host and exploration, has identified potential for minor mineralisation have well defined new mineral resources. This is discussed under magnetic responses. mineralisation style headings. Further · Northwest-trending bedding and faults, and potential will be recognised by more detailed northeast-trending faults are apparent in evaluation of this information. the data covering the Chiltern-Rutherglen goldfield. These have the same trend as Orogenic gold most gold-bearing quartz veins.

New geophysical and recompiled geochemical Concentration of gold by supergene processes data may indicate extensions to historic has been demonstrated within the Chiltern- mineralisation, or indicate undiscovered Rutherglen goldfield, and offers excellent, repetitions of this mineralisation. largely untested, bulk mineable potential. Exploration methods that recognise Investigation of historically profitable gold groundwater migration and composition, and deposits has resulted in the identification of the geochemical controls on dissolution and new reserves for many gold miners in Victoria. aggregation, will improve the ability to identify these deposits and source rocks. Within WANGARATTA, many mines produced moderate amounts of gold, and were abandoned Hotham beds underlying local high-grade at shallow depths despite high grades and sections in deep leads, and northwest-trending untested potential at depth. In more remote sections of leads (possibly reflecting recessive goldfields of the Harrietville-Dargo gold faults controlling drainage) may be prospective province this probably reflects the high for primary gold. O'Shea et al. (1994) noted operating costs associated with remote potential for disseminated gold deposits in operations. To date, very little modern granites, particularly close to the rich Chiltern- exploration has been undertaken within these Rutherglen, and Beechworth and Eldorado goldfields, and improved access makes these alluvial goldfields. exciting development prospects. Detailed annual production records and information on Placer gold mine history are provided for most mines in the WANGARATTA Mine Database. The magnetic data show both fossil and present-day drainages, and may be useful in Some high-grade stockwork and multiple vein defining the course of shallow and deep leads. deposits previously mined underground within Terraces along the Buckland and Ovens rivers the Harrietville-Dargo gold province may be have distinctive moderate magnetic responses suited to bulk, open cut mining. which can be traced for several kilometres. Within the Beechworth and Eldorado goldfields, GEOLOGY AND PROSPECTIVITY - WANGARATTA 67

magnetic data indicates late faults which may the nearby Toombullup goldfield is uncertain, be responsible for local thickening of alluvium. and may be veins and dykes within the Complex. Radiometric data clearly show present-day and fossil drainages at the surface. The response Porphyry gold-copper-molybdenite around the Chiltern-Rutherglen goldfield shows deposits recent drainage becoming disorganised— probably due to very low gradients—along Potential for economic gold-copper porphyry- Black Dog Creek west of the 450 000 mE style mineralisation, similar to deposits in gridline. This has produced broad alluvial Boggy Plain Supersuite rocks in NSW, is deposits. This setting may be analogous to the indicated by patchy gold intersections in the setting at the time gold was deposited in broad recessively weathered/hydrothermally altered deep leads. An understanding of this Murmungee Granite. Aeromagnetic data palaeosetting may help identify extensions to, suggest the Everton Granodiorite is a late and repetitions of buried deposits. phase of the Murmungee Granite. The Everton Granodiorite has a strong potassium response Thermal aureole gold in radiometric data, and hosts low-grade porphyry-style molybdenite mineralisation. Variably contact-metamorphosed Silurian and Other magnetic granites have not been fully Devonian siltstone, sandstone and tested and may be similarly prospective. conglomerate close to the Strathbogie Granodiorite host significant bulk mineable Copper deposits in the Mansfield disseminated deposits near Tallangalook. The Group Glen Creek Cambrian greenstone inlier is close to these deposits, and may also be important in New airborne radiometric data show high their genesis. Areas close to Cambrian responses in the Late Devonian Mansfield greenstones at Tatong and Dookie may also be Group, and may indicate significant uranium ± prospective for similar styles of mineralisation. copper mineralisation. The high response corresponds to hill cappings of the "lower VHMS and epigenetic gold deposits in sandstone" unit of the Devils Plain Formation. Cambrian greenstones Reduced zones of this unit host small, low-grade copper deposits nearby. Aeromagnetic data show large areas of Cambrian greenstone at the surface and under These occurrences may be related to a gentle, shallow cover within WANGARATTA. shallowly south-plunging anticline, which may Unmineralised banded pyrrhotite-rhodonite- have acted as a trap for migrating fluids. chert with characteristics of VHMS-style Another control on copper distribution may be deposits occurs in greenstone at Samaria Creek. basement structures. Southern continuations Significant VHMS-style Au-Cu and Au-Ag-Ba of faults which bound and truncate Cambrian mineralisation occurs in the Cambrian rocks at Tatong were active just prior to Jamieson Volcanics south of WANGARATTA at deposition of sediments of the Mansfield Basin, Hill 800 and Rhyolite Creek. Small epigenetic and may have channelled metal-bearing fluids gold deposits are also recognised in greenstones derived from the greenstones. Similar south of WANGARATTA. Cambrian structural settings in the "lower sandstone" greenstones in WANGARATTA are prospective unit may be prospective for repetitions of this by analogy with these deposits, and have not mineralisation. been fully tested, especially under shallow cover. By analogy with the Kupferschiefer and other shale-hosted base metal deposits, reduced Antimony-?gold deposits in the Tolmie Ordovician black shales within WANGARATTA Igneous Complex may be prospective for base metal deposits.

Stibnite-bearing veins in rhyolite and rhyodacite ignimbrite of the Upper Devonian Tolmie Igneous Complex are similar to deposits with minor gold associated with ring dykes around the Cerberean caldera south of WANGARATTA. The source of alluvial gold in 68 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Diamond deposits

The origin of rare diamonds in the deep lead at Eldorado, Chiltern and Rutherglen is uncertain. Numerous small aeromagnetic anomalies may represent unrecognised diamond-bearing mafic intrusions.

The subduction diamond model of Barron et al. (1994) predicts a diamond stability field compatible with WANGARATTA's crustal thickness and predicts basanite, nephelinite and leucitite "carrier" magmas. Lavas derived from such magmas occur in the Newer Volcanics in WANGARATTA. Corundum, which is common at Eldorado, Chiltern and Rutherglen, is an indicator to this style of deposit.

Only a single sample from limited diamond indicator mineral sampling at Eldorado and south of Chiltern suggested a nearby kimberlite or lamproite source. This sample was from a catchment within the mostly untested Omeo Zone close to the Kiewa Fault.

Coal

Upper Permian coal deposits have been identified in the Numurkah Basin near Deniliquin in NSW. The Permian sequence of the Numurkah Basin is mostly untested in WANGARATTA, and may be prospective for similar deposits.

Industrial minerals

Testing of the Beechworth Granite has shown it has glass-grade feldspar and quartz; development of this resource is planned in the near future.

King and Weston (1997) reported that the Beechworth and Yackandandah Granites have good potential for dimension stone sites. Hornfels adjacent the Strathbogie Granodiorite may also be suited to dimension stone quarrying. GEOLOGY AND PROSPECTIVITY - WANGARATTA 69

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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 northwest of Victoria, Eastern Highlands, central Victoria and the Otway Basin.

The surveys are outlined in Table 11.

Table 11 Status of VIMP airborne surveys

Line Survey Contractor Kilometres spacing Status (metres)

Eastern Highlands (Mt Geo Instruments 7 369 200 Released Wellington) Eastern Highlands (Orbost) Geo Instruments 16 170 200 Released Bendigo NGMA AGSO/GSV 53 700 200/400 Released North West Area (Murray Kevron Geophysics and 122 800 200/400 Released Basin) World Geoscience North West (Glenelg) World Geoscience 23 595 200 Released Eastern Highlands Geo Instruments 33 358 200 Released (Mallacoota) Eastern Highlands Geoterrex 52 397 200 Released (Tallangatta) Eastern Highlands (Omeo) Geo Instruments 13 780 200 Released Eastern Highlands (Corryong) Geoterrex 17 444 200 Released Eastern Highlands (Dargo Geo Instruments and 27 886 200 Released Kevron Geophysics Eastern Highlands Geo Instruments and 14 555 200 Released (Murrindal) Kevron Geophysics Wangaratta (south) Geo Instruments and Des 46 954 200 Released Fitzgerald & Associates Wangaratta (north-infill) AGSO 22 236 200 Released Shepparton North (east) AGSO 987 200 Released Yea Geo Instruments and Des 15 803 200 Released Fitzgerald & Associates Castlemaine-Woodend World Geoscience 37 788 200 Released Otway Basin (Offshore) Kevron Geophysics 44 379 500 Released

TOTAL 551 201 78 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Appendix 2 Navigation Novatel 951R receivers VIMP Survey specifications and differential GPS. data processing Ground base magnetometer The following is a summary of survey specifications and data processing for the Geometrics, model G856AX magnetometers Wangaratta (VIMP and NGMA) surveys. (local and remote), located at base camps (local) and generally 3 km east (remote) of base camp, VIMP Wangaratta airborne geophysical survey sampling at 5 seconds, to record the diurnal variation. Area Buffalo, Euroa (part), Whitfield (part) and Albury Magnetic data processing (part) 1:100 000 mapsheets Job no. 9628 The magnetic data have been corrected for Client Department of Natural regional gradient by subtraction of IGRF model Resources and Environment 1997.0 and secular variation model 1990–1995. Flown December 1996 to March Diurnal variations have been removed. System 1997 parallax has been removed. Tieline levelling Survey company Geo Instruments P/L and microlevelling have been applied. The mean diurnal value and IGRF base value have Area falls within sheets: been added to the data. 1:250 000 WANGARATTA SJ55-2 Gamma spectrometer data processing Survey specifications The coefficients for the following corrections Aircraft Bell 206B helicopter have been derived from using AGSO's VH-JWF radiometric calibration pads in Canberra and Magnetometer Stinger mounted the Bairnsdale calibration range (Grasty & Geometrics G-822A Minty, 1995). Caesium Vapour Automatic compensator RMS Instruments Standard windows processing has been applied. AADCII Corrections have been applied for: Resolution 0.01 nanoTesla Cycle rate 0.1 seconds - instrument deadtime Sample interval approximately 4 m - cosmic and aircraft background Spectrometer 256 channel - height correction to 80 m AGL Exploranium GR-820 temperature corrected Crystal volume 16.8 l - stripping to give c/s for K-40, Bi-214 and Cycle rate 1.0 second Tl-208 Sample interval approximately 40 m Calibration: Real time automatic Sensitivity constants stabilization based on tracking of the 1% potassium = 54.48 cps Thorium peak. 1 ppm uranium = 6.21 cps 1 ppm thorium = 3.14 cps Traverse line spacing 200 m Traverse line direction 090–270 degrees The influence of radon has been minimised by Traverse line kilometres 40 238 km the application of a spectral ratioing technique. Tie line spacing 2000 m Tie line direction 180–360 degrees Gridding Tie line kilometres 6 716 km Magnetic and radiometric data were gridded Total line kilometres 46 954 km using a 50 m square grid mesh. Filtering was not applied to the grids.

Mean terrain clearance 80 m Digital terrain model GEOLOGY AND PROSPECTIVITY - WANGARATTA 79

A digital terrain model was generated from the GPS data and the radar altimeter data. The Navigation Ashtec Ranger data were error-corrected and microlevelled and differential GPS. converted to AHD. The grid was generated using a 50 m mesh and was not filtered. Ground base magnetometer

NGMA Survey specifications and Geometrics, model G856AX magnetometer, located at Albury airport, sampling at 5 data processing seconds, to record the diurnal variation.

NGMA Wangaratta airborne geophysical Magnetic data processing survey The magnetic data have been corrected for Area Dookie, Wangaratta, Euroa regional gradient by subtraction of IGRF model (part) and Albury (part) 1997.3 and secular variation model 1990–1995. 1:100 000 mapsheets Diurnal variations have been removed. System Job no. 624 parallax has been removed. Tieline levelling Client Australian Geological and microlevelling have been applied. A value Survey Organisation of 62 214 nT was removed from the data to give (AGSO) and Department of a mean of 5000 nT. Natural Resources and Environment Gamma spectrometer data processing Flown March to May 1997 Survey company AGSO The coefficients for the following corrections have been derived from tests using AGSO's Area falls within sheets: radiometric calibration pads in Canberra. 1:250 000 WANGARATTA SJ55-2 Standard windows processing has been applied. Survey specifications Corrections have been applied for:

Aircraft Aero Commander VH- - instrument deadtime BGE - cosmic and aircraft background Magnetometer Geometrics G-822A - height correction to 80 m AGL Caesium Vapour temperature corrected Automatic compensator RMS Instruments - stripping to give c/s for K-40, Bi-214 and AADCII Tl-208 Resolution 0.01 nanoTesla Cycle rate 0.1 seconds Sensitivity constants Sample interval approximately 7 m Spectrometer 256 channel 1% potassium = 110.42 cps Exploranium GR-820 1 ppm uranium = 8.33 cps Crystal volume 33.6 l 1 ppm thorium = 5.79 cps Cycle rate 1.0 second Sample interval approximately 70 m The influence of radon has been minimised by Calibration: Real-time automatic the application of the spectral ratioing stabilization based on technique. tracking of the Thorium peak. Gridding

Traverse line spacing 200 m Magnetic and radiometric data were gridded Traverse line direction 090–270 degrees using a 40 m square grid mesh. Filtering was Traverse line kilometres 41 106 km not applied to the grids. Tie line spacing 2000 m Tie line direction 180–360 degrees Tie line kilometres 4 353 km

Total line kilometres 45 459 km

Mean terrain clearance 80 m 80 GEOLOGY AND PROSPECTIVITY - WANGARATTA

Digital terrain model

A digital terrain model was generated from the GPS data and the radar altimeter data. The data were error-corrected and microlevelled and converted to AHD. The grid was generated using a 40 m mesh and was not filtered. GEOLOGY AND PROSPECTIVITY - WANGARATTA 81

Appendix 3 Digital The data are provided on five-gigabyte Exabyte VIMP Products tape or Compact Disc and contains the following information: The following products may be purchased from: Located data in ASCII format: Geological Survey of Victoria Located total magnetic intensity; Geophysics section Located radiometrics. 3 rd Floor, 115 Victoria Pde P O Box 2145 Grids in ERMapper format: Fitzroy, Victoria, 3065 Total magnetic intensity; Ph: (03) 9412 7816 Fx: (03) 9412 7803 First vertical derivative; Total count; Hardcopy Potassium; Thorium; Maps Uranium; Digital terrain model. The following hardcopy products are available. These may be purchased as map sets or as GIS dataset: individual items. Towns, roads, National Parks, map boundaries; 1:100 000 scale black and white products (paper Current and expired Exploration Licences or transparency): and Mining Licences; Geology, mineral occurrences; Flight path maps; Magnetic, radiometric and digital terrain Total magnetic intensity profiles; model images. Total magnetic intensity contours (1 nT contour interval); NGMA Products Maps for individual 1:25 000 mapsheets are The following products may be purchased from: also available. Australian Geological Survey Organisation 1:100 000 scale colour products (paper): (AGSO) Map Sales Centre Total magnetic intensity contours Cnr Constitution Ave and Anzac Pde (1 nT contour interval); GPO Box 378 Total magnetic intensity first vertical Canberra, ACT, 2601 derivative contours (0.005 nT/m contour Ph: (06) 249 9519 Fx: (06) 249 9982 interval). Total count radiometrics contours (25 cps contour interval); Hard copy Potassium contours (0.05% eK contour interval); Maps Thorium contours (0.5 ppm eTh contour interval); 1:250 000 scale, 1:100 000 scale and 1:50 000 Uranium contours (0.1 ppm eU contour scale black and white products (paper or interval). transparency): Digital terrain model contours (5 m contour interval) Total magnetic intensity contours; Dose rate contours; 1:100 000 scale colour products (pixel image): Total magnetic intensity with relief shading; 1:250 000 scale black and white products (paper Total magnetic intensity greyscale; or transparency) Total magnetic intensity first vertical gradient greyscale; Digital elevation model contours; Total count radiometrics; Radiometrics RGB (K, Th, U); Digital terrain model with relief shading. 82 GEOLOGY AND PROSPECTIVITY - WANGARATTA

1:50 000 scale black and white products (paper or transparency)

Flight path maps; Total magnetic intensity profiles;

1:250 000 scale and 1:100 000 scale colour products (pixel images):

Total magnetic intensity; Gamma-ray;

1:250 000 scale colour products (pixel image):

Digital elevation model;

Digital

The following data are available:

Located data in ASCII format:

Located total magnetic intensity; Located Gamma-ray.

Gridded data:

Total magnetic intensity; Total count; Potassium; Thorium; Uranium; Digital terrain model. GEOLOGY AND PROSPECTIVITY - WANGARATTA 83

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., NOT RELEASED WILLOCKS, A.J. and O'SHEA, P.J., 1995. The geology and prospectivity of 21 SARMA, S., 1995. Seismic the Mallacoota 1:250 000 sheet, Eastern interpretation of the offshore Otway Highlands VIMP area. Basin, Victoria. 9 SANDS, B.C., 1995. A geological 22 MEHIN, K., and LINK, A.G., 1995. interpretation of the geophysical data Early Cretaceous source rocks of the from the Orbost 1994 airborne survey. Victorian onshore Otway Basin. 10 OPPY, I.D., CAYLEY, R.A. and 23 PARKER, G.J., 1995. Early Cretaceous CALUZZI, J., 1995. The geology and stratigraphy along the northern margin prospectivity of the Tallangatta of the Otway Basin, Victoria. 1:250 000 sheet. 24 MOORE, D.H., 1996. A geological 11 CALUZZI, J., 1995. Mineral exploration interpretation of the geophysical data of history of the Tallangatta 1:250 000 the Horsham 1:250 000 map sheet area. sheet. 25 VANDENBERG, A.H.M., HENDRICKX, 12 SIMONS, B.A., 1995. An appraisal of M.A., WILLMAN, C.E., MAGART, new airborne geophysical data over the A.P.M., ORANSKAIA, A.N., ROONEY, Tallangatta 1:250 000 map area, S. and WHITE, A.J.R.,1996. The Victoria. geology and prospectivity of the Orbost 1:100 000 map area, eastern Victoria. 84 GEOLOGY AND PROSPECTIVITY - WANGARATTA

26 HENDRICKX, M.A., WILLMAN, C.E., 41 LAVIN, C. J., and MUSCATELLO, T. MAGART, A.P.M., ROONEY, S., 1997. The petroleum prospectivity of VANDENBERG, A.H.M., ORANSKAIA, the Casterton Petroleum System in the A. and WHITE, A.J.R. The geology and Victorian Onshore Otway Basin. prospectivity of the Murrungowar 42 CHIUPKA, J. W., MEGALLAA, M., 1:100 000 map area, eastern Victoria. JONASSON, K. E., and FRANKEL K., 27 BOYLE, R. J., 1996. Mineral 1997. Hydrocarbon plays and play exploration history of the Omeo fairways of four vacant offshore 1:100 000 map area. Gippsland Basin areas, 1997 acreage release. 28 HAYDON, S.J., 1996. An appraisal of airborne geophysical data from the 1995 43 MEHIN, K., and LINK, A.G., 1997. Omeo survey, Victoria. Late Cretaceous source rocks offshore Otway Basin. 29 MAHER, S., 1996. Mineral resources of the Dunolly 1:100 000 map area. 44 WILLOCKS, A.J., 1997. An appraisal of airborne geophysical data from the 30 CHIUPKA, J.W., 1996. Hydrocarbon Castlemaine-Woodend survey, Victoria. Play Fairways of the Onshore Gippsland Basin, Victoria. 45 HUTCHINSON, D.F., 1997. Mineral exploration history of the Heathcote and 31 MEHIN, K., and LINK, A.G., 1996. Nagambie 1:100 000 map areas. Early Cretaceous source rock evaluation for oil and gas exploration, Victorian 46 MAHER, S., VANDENBERG, A.H.M., Otway Basin. McDONALD, P.A and SAPURMAS, P., 1997. The Geology and prospectivity of 32 SLATER, K.R., 1996. An appraisal of the Wangaratta 1:250 000 map sheet new airborne geophysical data over the area. Dargo region, Victoria. 47 ORANSKAIA, A.N., 1997. Geological 33 McDONALD, P.A., 1996. An appraisal interpretation of geophysical features of new airborne geophysical data over Bendoc 1:100 000 sheet. the Corryong region, northeastern Victoria. 48 ORANSKAIA, A.N., 1997. Geological interpretation of geophysical features 34 TWYFORD, R., 1996. An appraisal of Cann, Mallacoota and Victorian part of airborne geophysical data from the Eden 1:100 000 sheets. Murrindal survey, Victoria. 49 WILKIE, J.R., and BROOKES, D.J., 35 HUTCHINSON, D.F., 1996. Mineral 1997. Mineral exploration history of the exploration history of the Dunolly Wangaratta 1:250 000 map area. 1:100 000 map area. 50 McDONALD, P.A., 1997. An appraisal 36 BROOKES, D.J. and BOYLE, R.J., of airborne geophysical data from the 1996. Mineral exploration history of the Yea survey, Victoria. Bairnsdale 1:250 000 map area. 51 EDWARDS, J.E., WILLMAN, C.E., 37 MAHER, S., HENDRICKX, M.A., McHAFFIE, I.W., OLSHINA, A. and BOYLE, R.J. and BROOKES, D.J., WILLOCKS, A.J., 1997. The geology 1996. Geology and prospectivity of the and prospectivity of the Castlemaine, Bairnsdale 1:250 000 map sheet area. Woodend, Yea and part of Bacchus 38 McDONALD, P.A. and WHITEHEAD Marsh 1:100 000 map sheets. M.L., 1996. Geological interpretation of 52 MAHER, S., MOORE, D.H., geophysical data over the Ararat CRAWFORD, A.J., TWYFORD, R. and 1:100 000 map sheet. FANNING, F.M., 1997. Test drilling 39 MOORE D.H. 1996. A geological onthe southern margin of the Murray interpretation of the geophysical data of Basin. the Ouyen 1:250 000 map sheet area. 40 BROOKES, D.J., 1996. Mineral exploration history, Ararat and Grampians 1:100 000 map areas.