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Record 2018/13 | eCat 117123Geological Survey of New South Wales Record GS2018/0199

Milcarpa 1 borehole completion recordSouthern Thomson Project

I. C. Roach, K. F. Bull, D. C. Champion, A. J. Cross, C. B. Folkes, P. Gilmore, R. Hegarty, S. L. Jones and D. B. Tilley

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Milcarpa 1 borehole completion record

Southern Thomson Project

GEOSCIENCE AUSTRALIA RECORD 2018/13 GEOLOGICAL SURVEY OF NEW SOUTH WALES RECORD GS2018/0199

I. C. Roach1, K. F. Bull2, D. C. Champion1, A. J. Cross1, C. B. Folkes2, P. Gilmore2, R. Hegarty3, S. L. Jones1 and D. B. Tilley2

1. Geoscience Australia. 2. Geological Survey of New South Wales 3. Formerly Geological Survey of New South Wales.

Department of Industry, Innovation and Science Minister for Resources and Northern Australia: Senator the Hon Matthew Canavan Secretary: Heather Smith PSM

Geoscience Australia Chief Executive Officer: Dr James Johnson

Department of Planning and Environment, New South Wales Minister: The Hon Don Harwin MLC Secretary: Ms Carolyn McNally

Geological Survey of New South Wales Executive Director: Dr Chris Yeats

This paper is published with the permission of the CEO, Geoscience Australia and the Executive Director, Geological Survey of New South Wales.

© Commonwealth of Australia (Geoscience Australia) 2018 and State of New South Wales (Geological Survey of New South Wales) 2018.

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ISSN 2201-702X (PDF) ISBN 978-1-925297-83-6 (PDF) eCat 117123

Bibliographic reference: Roach, I. C., Bull, K. F., Champion, D. C., Cross, A. J., Folkes, C. B., Gilmore, P., Hegarty, R., Jones, S. L., Tilley, D. B. 2018. Milcarpa 1 borehole completion record: Southern Thomson Project. Record 2018/13. Geoscience Australia, Canberra. Geological Survey of New South Wales Record GS2018/0199. http://dx.doi.org/10.11636/Record.2018.013

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http://dx.doi.org/10.11636/Record.2018.013

Milcarpa 1 borehole completion record iii

Contents

1 Introduction ............................................................................................................................................ 1 1.1 The Southern Thomson Project ....................................................................................................... 1

2 Borehole rationale, location and construction ....................................................................................... 3 2.1 Rationale and location ..................................................................................................................... 3 2.2 Borehole construction ...................................................................................................................... 6

3 Lithology, petrography, stratigraphy, igneous geochemistry and U-Pb isotopic age ..........................10 3.1 Introduction ....................................................................................................................................10 3.2 Lithology .........................................................................................................................................11 3.3 Basement rock petrography ...........................................................................................................13 3.4 Geochemistry and U-Pb isotopic age ............................................................................................14 3.5 Stratigraphy ....................................................................................................................................15 3.6 Synthesis within the regional stratigraphic framework ...................................................................17

4 Borehole and drill core rock properties ................................................................................................19 4.1 Introduction ....................................................................................................................................19 4.2 Rock properties measurements .....................................................................................................19 4.3 Results and interpretation ..............................................................................................................19

4.3.1 Natural gamma .........................................................................................................................19 4.3.2 Induction conductivity ...............................................................................................................20 4.3.3 Magnetic susceptibility .............................................................................................................22 4.3.4 Bulk density and apparent porosity ..........................................................................................23

4.4 Rock properties data package .......................................................................................................23

5 HyLogger data .....................................................................................................................................24 5.1 HyLogger data acquisition and processing ....................................................................................24 5.2 Results ...........................................................................................................................................25

5.2.1 Milcarpa 1 mud rotary chips .....................................................................................................25 5.2.2 Milcarpa 1 diamond drill core ...................................................................................................26

5.3 Comparison with other logging ......................................................................................................26 5.4 HyLogger data package .................................................................................................................29 5.5 HyLogger data reprocessing ..........................................................................................................29

6 Groundwater ........................................................................................................................................30

7 Acknowledgements .............................................................................................................................31

8 References ..........................................................................................................................................32

Appendix A Borehole construction .........................................................................................................36

Appendix B Drilling activities and consumables .....................................................................................38

Appendix C Petrophysical equipment details .........................................................................................40 C.1 Borehole wireline logging equipment ............................................................................................40 C.2 Hand-held magnetic susceptibility logging equipment ..................................................................40 C.3 Analytical balance equipment (density determination) ..................................................................40

Appendix D Petrophysical data acquisition and processing ...................................................................41 D.1 Data acquisition and processing ...................................................................................................41 D.2 Equipment calibration ....................................................................................................................41

iv Milcarpa 1 borehole completion record

D.3 Data processing ............................................................................................................................42

Appendix E Lithological and stratigraphic log.........................................................................................43 Appendix F Whole-rock geochemistry ....................................................................................................45

Appendix G Metallogenic and Igneous classifications ...........................................................................48

Appendix H Borehole log ........................................................................................................................51

Milcarpa 1 borehole completion record v

Figures

Figure 1.1: Location of the Thomson Orogen in eastern Australia. The red box encompasses the Southern Thomson Project area. ....................................................................................................... 1

Figure 1.2: Location map of all boreholes drilled as part of the Southern Thomson Project. Background: TOPO 250K topographic map mosaic, Geoscience Australia. ........................................... 2

Figure 2.1: Location map of the Milcarpa 1 borehole and local waterbores. Background: TOPO 250K mosaic of Australia, Geoscience Australia. .................................................................................... 4 Figure 2.2: Location map showing the Milcarpa 1 borehole and solid geological basement interpretation from Purdy et al. (2014) and Purdy et al. (2018), over a first vertical derivative of total magnetic intensity (1VD TMI) image of the Magnetic Map of Australia 2015. ................................. 5

Figure 2.3: The Milcarpa 1 borehole with AEM conductivity sections draped over surface geological mapping on the EULO and YANTABULLA 1:250,000 geological map sheets. Each AEM conductivity section depicts the modelled electrical conductivity model from surface to ~400 m depth, rotated into the plane of the map. Milcarpa 1 was drilled ~1.1 km south of 2014 AEM survey AEM flight line 1251 where the modelled geoelectrical stratigraphy indicates that there is at least 175 m of Eromanga Basin cover (see Roach, 2015). ..................................................... 6

Figure 2.4: The Milcarpa 1 borehole site prior to drilling, looking west. ................................................... 7

Figure 2.5: Mud rotary drilling operations at Milcarpa 1 showing safety barriers around the mud sumps, looking west. ................................................................................................................................ 8 Figure 2.6: Image showing the partial rehabilitation of mud sumps at Milcarpa 1. Sumps are fenced until such time as they dry out before backfilling with the original soil, looking southwest. Image courtesy Sebastian Wong GSNSW. .............................................................................................. 8

Figure 2.7: Image showing the partial rehabilitation of the site and mud sumps (right) at Milcarpa 1, looking east. ......................................................................................................................................... 9 Figure 3.1: Mud rotary chip sample layout at the Milcarpa 1 borehole site. Samples are laid out on hessian starting in the top right corner, moving left in runs of 10 m, with the sample from the deepest part of the borehole in the foreground at bottom left. Note the colour change in chips from the surface weathering zone (background) to unweathered Eromanga Basin rocks in the foreground. The chip sample piles were coated with a considerable amount of windblown red dust, which was removed during sampling. ............................................................................................10 Figure 3.2: Milcarpa 1 lithological and stratigraphic graphic log. Lithology is summarised form the detailed lithological log attached in Appendix E. ..............................................................................12

Figure 3.3: Dry (above) and wet (below) field photos of typical diamond drill core from Milcarpa 1. .............................................................................................................................................................13

Figure 3.4: Representative thin-section photomicrographs from the Milcarpa 1 borehole at ~289 m DL. ......................................................................................................................................................14

vi Milcarpa 1 borehole completion record

Figure 3.5: Geochemical discrimination plots for selected igneous rocks sampled as part of the Southern Thomson Project. Analyses include samples from Tongo 1 (Roach et al., 2018a), Congararra 1 (Roach et al., 2018d), Congararra 2 (Roach et al., 2018c), Janina 1 (Roach et al., 2018b) and Milcarpa 1. A: Plutonic rock classification of Debon and Le Fort (1983). X and Y axes correspond to proportions of quartz (Q) and plagioclase (P). B: K2O versus SiO2 classification plot. Boundary fields are from Le Maitre (2002). C: A plot of Fe2O3/FeO versus total Fe as FeO* (wt.%), after Champion and Heinemann (1994), showing the fields for strongly reduced, reduced, oxidised and strongly oxidised. Samples from New South Wales drill holes are also shown, which range from strongly reduced and reduced (Congararra 1 & 2, Janina 1) to oxidised (Milcarpa 1, Tongo 1). D: Rb-Ba-Sr triangular plot from El Bouseily and El Sokkary (1975) showing the fields for normal and fractionated granites. Samples show they are not significantly fractionated. E: Plot of Rb/Sr versus Fe2O3/FeO, from Blevin et al. (1996), with the field of Intrusion-related gold deposits (IRGD) from Blevin (2004).........................................................16

Figure 4.1: Lithology, stratigraphy, rock properties and borehole construction data for Milcarpa 1. The legend for lithology types and stratigraphy is the same as in Figure 3.2. For more detail on borehole construction refer to Appendix A. .......................................................................................21

Figure 5.1: Mineral spectra summary plot of Milcarpa 1 mud rotary drill chips. .....................................25

Figure 5.2: Mineral spectra summary plot of Milcarpa 1 diamond drill core. ..........................................26

Figure 5.3: The Fe-OH absorption feature within Milcarpa 1 – FeatEx Wvl, 2253+-10 nm plots as two discrete wavelengths, attributed to the coexistence of Fe-Mg chlorite and epidote within the core. ..................................................................................................................................................27

Figure 5.4A: comparison between spectral mineralogy, interpreted stratigraphy and borehole rock properties data from Milcarpa 1. The spectral mineralogy legends in the upper part of the log refer to the mud rotary drilled portion of the borehole < 246.9 m TVD, and in the lower part to the diamond drilled portion to EOH. .......................................................................................................28 Figure 8.1: Milcarpa 1 borehole construction. ........................................................................................37

Milcarpa 1 borehole completion record vii

Tables

Table 2.1: Details for the Milcarpa 1 borehole.......................................................................................... 3

Table 3.1: Whole-rock geochemical petrographic and metallogenic indicators and SHRIMP U-Pb age for Milcarpa 1 basement rocks. ..................................................................................................15

Table 3.2: Interpreted stratigraphy of the Milcarpa 1 borehole. .............................................................17

Table 4.1: Milcarpa 1 natural gamma stratigraphic interval statistics. ...................................................20

Table 4.2: Milcarpa 1 induction conductivity stratigraphic interval statistics. .........................................22 Table 4.3: Milcarpa 1 stratigraphic interval magnetic susceptibility statistics. .......................................22

Table 4.4: Density measurements on diamond drill core from Milcarpa 1. ............................................23

Table 6.1: Local waterbores within the Milcarpa 1 vicinity highlighting the overall sub-artesian water pressures present in the area. Refer to Figure 2.2 for locations. .................................................30

Table 8.1: Milcarpa 1 drilling times and production rates .......................................................................38

Table 8.2: Milcarpa 1 drilling consumables used. ..................................................................................39 Table 8.3: Borehole wireline data acquisition steps in Milcarpa 1..........................................................41

Table 8.4: Whole-rock major element geochemical data for Milcarpa 1. ...............................................45

Table 8.5: Whole-rock trace element geochemical data for Milcarpa 1. ................................................46

Milcarpa 1 borehole completion record 1

1 Introduction

1.1 The Southern Thomson Project The Thomson Orogen is a major component of the Paleozoic Tasmanides of eastern Australia that extends through large portions of central and southwest Queensland and northwest New South Wales (Figure 1.1). Much of the Thomson Orogen is buried under younger sedimentary basins (some up to several kilometres thick) and regolith cover, making it one of the most poorly understood elements of Australia’s geology. As a result, the mineral potential of the region is also poorly defined.

The Southern Thomson Project (the Project) is a collaborative investigation between the Commonwealth of Australia (Geoscience Australia) and its partners the State of New South Wales (Department of Planning and Environment, Geological Survey of New South Wales – GSNSW) and the State of Queensland (Department of Natural Resources, Mines and Energy, Geological Survey of Queensland – GSQ).

Figure 1.1: Location of the Thomson Orogen in eastern Australia. The red box encompasses the Southern Thomson Project area.

The Project aims to better understand the geological character and mineral potential of the southern Thomson Orogen region, focusing on the border between New South Wales and Queensland, by acquiring and interpreting multi-disciplinary geophysical, geochemical, geological and geochronological data. The primary intended impact of this work is to provide the mineral exploration

2 Milcarpa 1 borehole completion record

industry with pre-competitive data and knowledge that reduces risk and encourages mineral exploration in the region.

The pre-competitive data collection culminated in a drilling program of 12 boreholes within the project area of New South Wales and Queensland (Figure 1.2), targeting strategic basement rocks that will improve the understanding of the mineral potential of the southern Thomson Orogen and its geodynamic setting within the Tasmanides of eastern Australia.

Figure 1.2: Location map of all boreholes drilled as part of the Southern Thomson Project. Background: TOPO 250K topographic map mosaic, Geoscience Australia.


2 Borehole rationale, location and construction

I. C. Roach, R. Hegarty, C. B. Folkes and P. Gilmore

2.1 Rationale and location The Milcarpa 1 borehole was drilled approximately 9 km SSE of Hungerford, Queensland (which is located on the New South Wales-Queensland border), adjacent to the road between Hungerford and Wanaaring, NSW (figures 1.2, 2.1, Table 2.1). The borehole was designed to test aeromagnetic anomalies in the basement rocks (Figure 2.2), test the electrical conductivity properties of cover and basement rocks to validate airborne electromagnetic (AEM) data (Figure 2.3), and to test pre-drilling geophysical cover thickness estimates (Goodwin et al., 2017).

The Milcarpa 1 borehole was drilled as a vertical borehole, thus drilled length (DL) equates to True Vertical Depth (TVD) in the text and tables below.

Table 2.1: Details for the Milcarpa 1 borehole.

Hole ID Milcarpa 1

Site ID* Swamp Bore 2*

Contractor DRC Drilling Pty Ltd

Drilling rig Sandvik DE880

Landholder Milcarpa Station

Title EL 8443

Status Closed, cemented to surface, cement cap installed, site remediation earthworks were not completed at the time of publication

Location Longitude (GDA94): 144.448757° Latitude (GDA94): -29.072255° Easting (MGAZ55S): 251638 m Northing (MGAZ55S: 6781321 m Elevation (ellipsoidal): 125 m

Drilled length 290.9 m

Casing 0-80 m TVD steel 168.28 mm outside diameter (OD), cemented 0-246.9 m TVD steel 114.3 mm OD, cemented 246.9-290.9 m TVD (end of hole - EOH) open hole

Casing cut-off depth 0.5 m below surface

Grouting Cement, from EOH to surface

Mud rotary drilled length 0-246.9 m TVD (246.9 m TVD)

Diamond drilled length 246.9-290.9 m TVD (44.0 m TVD)

Commencement date 07.07.2017

Completion date 12.07.2017

Deviation Vertical hole

Deviation survey date No deviation survey

GA Boreholes ENO 620172

*Project pre-drilling internal reference to site.


Figure 2.1: Location map of the Milcarpa 1 borehole and local waterbores. Background: TOPO 250K mosaic of Australia, Geoscience Australia.


Figure 2.2: Location map showing the Milcarpa 1 borehole and solid geological basement interpretation from Purdy et al. (2014) and Purdy et al. (2018), over a first vertical derivative of total magnetic intensity (1VD TMI) image of the Magnetic Map of Australia 2015.


Figure 2.3: The Milcarpa 1 borehole with AEM conductivity sections draped over surface geological mapping on the EULO and YANTABULLA 1:250,000 geological map sheets. Each AEM conductivity section depicts the modelled electrical conductivity model from surface to ~400 m depth, rotated into the plane of the map. Milcarpa 1 was drilled ~1.1 km south of 2014 AEM survey AEM flight line 1251 where the modelled geoelectrical stratigraphy indicates that there is at least 175 m of Eromanga Basin cover (see Roach, 2015).

2.2 Borehole construction The Project team at this site included scientists from Geoscience Australia and the GSNSW, a licensed water bore driller, and the contractor’s drilling team. The borehole was drilled as a vertical mud rotary borehole using two small inter-connected sumps (approximately 3 x 5 x 1.5 m) to catch mud rotary drill cuttings to 246.9 m TVD before switching to a vertical diamond drilling operation, extending the borehole to 290.9 m TVD using a third small sump (approximately 2 x 4 x 1.5 m) to catch cuttings in the diamond drilling fluids. A fourth sump was added to take the remaining drill cuttings before site abandonment.


Before commencement the Project team reviewed the standing water levels in the area to assess the likelihood of artesian groundwater conditions within the borehole by assessing bore cards for local water bores (Figure 2.1) available from the NSW Department of Primary Industries Office of Water (http://allwaterdata.water.nsw.gov.au/water.stm).

The Project team worked to ensure that the drilling fluid was correctly weighted before aquifers were likely to be encountered to prevent the accidental escape of artesian groundwater. The borehole was fully cased with steel casing and partially cement grouted through the cover sequence into competent basement rock before commencement of diamond drilling operations. This was to prevent swelling clays in the Eromanga Basin sequence from closing the borehole, to prevent groundwater escape, to prevent groundwater mixing between aquifers and to prevent drilling fluids from contaminating groundwater in accordance with the requirements of the Minimum Construction Requirements for Water Bores In Australia (National Uniform Drillers Licensing Committee, 2011). More information regarding borehole construction and drilling consumables is available in Appendix A and Appendix B and images of the site before, during and after drilling are included in Figures 2.4 to 2.7.

Figure 2.4: The Milcarpa 1 borehole site prior to drilling, looking west.

http://allwaterdata.water.nsw.gov.au/water.stm


Figure 2.5: Mud rotary drilling operations at Milcarpa 1 showing safety barriers around the mud sumps, looking west.

Figure 2.6: Image showing the partial rehabilitation of mud sumps at Milcarpa 1. Sumps are fenced until such time as they dry out before backfilling with the original soil, looking southwest. Image courtesy Sebastian Wong GSNSW.


Figure 2.7: Image showing the partial rehabilitation of the site and mud sumps (right) at Milcarpa 1, looking east.


3 Lithology, petrography, stratigraphy, igneous geochemistry and U-Pb isotopic age

I. C. Roach, R. Hegarty, C. B. Folkes, P. Gilmore, D. C. Champion and A. J. Cross

3.1 Introduction Cuttings and drill core from Milcarpa 1 were logged on site by GSNSW and Geoscience Australia geologists. Cuttings were collected from the mud rotary-drilled cover sequence and the top of basement at 1 m intervals to 246.9 m TVD, after which diamond coring commenced through to 290.9 m TVD. The sampling of some intervals was incomplete due to problems with the drilling fluid mixture; however the overall cutting quality and volume was high. Most 1 m intervals were represented by an amount of cuttings sufficient to fill a chip tray and a 250 ml sample vial for future analysis. Cuttings were laid out to partially de-water (Figure 3.1) before washing, lithological logging, sampling and analysis with a hand-held magnetic susceptibility meter.

Key parameters of grainsize, colour and organic matter content, and any other major textural changes, were recorded. The basement diamond drill core interval (246.9 m TVD to 290.9 m TVD) was also logged and photographed on site.

Figure 3.1: Mud rotary chip sample layout at the Milcarpa 1 borehole site. Samples are laid out on hessian starting in the top right corner, moving left in runs of 10 m, with the sample from the deepest part of the borehole in the foreground at bottom left. Note the colour change in chips from the surface weathering zone (background) to unweathered Eromanga Basin rocks in the foreground. The chip sample piles were coated with a considerable amount of windblown red dust, which was removed during sampling.


3.2 Lithology Milcarpa 1 penetrated 246 m of cover sediments and sedimentary rocks before entering porphyritic volcanic rocks of the basement. Lithological types observed in the hole are described below and in Figure 3.2. A detailed lithological log is given in Appendix E.

Modern regolith at the Milcarpa 1 site includes fine, red-brown, unconsolidated silt and fine sand from 0 m to 1 m TVD. This overlies a ~2 m interval of indurated red-brown hardpan with dominantly sub-horizontal calcrete laminae up to 5 mm thick filling cracks within the hardpan. Below this, the regolith comprises gleyed clay to 6 m TVD, indurated bleached siltstone and fine sandstone with clear quartz grains to 2 mm diameter, a mottled zone of the same including ferruginised and manganiferous fragments between 19 m TVD and 32 m TVD and mottled to white indurated silt and fine sand with rounded quartz grains to 1 mm diameter to 61 m TVD. At 61 m TVD there is an abrupt transition from weathered silts and sands to puggy grey clay. From 61 m TVD to 75 m TVD regolith materials consist of white and gleyed, puggy, plastic silt and mud before the base of surface weathering is encountered, visible as a gradual increase in dark clay fragments, finally entering fresh grey-black clays at 80 m TVD (Figure 3.1). The base of surface weathering is also confirmed by an increase in electrical conductivity in the borehole wireline induction conductivity log coinciding with the colour change from pallid or mottled clays to dark grey clays.

Below 80 m TVD materials include a thick sequence of dark grey to grey mudstone. There was poor sample recovery between 80 m TVD and 85 m TVD, but the borehole wireline logging confirms this unit continues through this interval. The mudstone includes minor thin, white, clay-rich spots between 148 m TVD and 151 m TVD, which appear to be reduction spots, and a layer of <1 mm diameter pyrite framboids at 161 m TVD. At 190 m TVD there is an abrupt transition to consolidated, grey/gleyed sandstone and siltstone, dominantly sandstone, with 1-2 mm diameter quartz grains, lithic fragments, biotite flakes and pyrite framboids. This unit continues as interbedded sandstone, siltstone and some clay, darkening in colour to the base at 224 m TVD, becoming brown at the base. Between 224 m TVD and 243 m TVD a brown, slightly sandy claystone was encountered above the basement-cover interface at 246 m TVD.

Basement was indicated by a sharp increase in the abundance of coarse, angular quartz grains, brown mottled clay and the appearance of porphyritic volcanic rock fragments in cuttings. Hard basement rock stopped the progress of mud rotary drilling at 246.6 m TVD.

Basement rocks consist of green porphyritic igneous rocks with ~5% of 2-7 mm diameter subhedral to euhedral quartz crystals and 5-15% subhedral to euhedral, 6-sided green crystals in a siliceous aphanitic groundmass (Figures 3.3 and 3.4). The rocks have numerous fractures filled with dominantly white, rarely orange, apparent zeolite minerals, and quartz veins occasionally with thin hematitic selvages. Zones of intense fracturing and some shear zones occur in the core, particularly in the intervals 261.35 m TVD to 261.50 m TVD and 270.6 m TVD to 272.2 m TVD, and a 5 cm wide shear zone is seen at 273.3 m TVD, Pervasive hematite alteration of the groundmass becomes slightly more prevalent to the bottom of the core, as do phenocryst size and concentration. The rock was classified in the field as rhyodacite lava.


Figure 3.2: Milcarpa 1 lithological and stratigraphic graphic log. Lithology is summarised form the detailed lithological log attached in Appendix E.


Figure 3.3: Dry (above) and wet (below) field photos of typical diamond drill core from Milcarpa 1.

3.3 Basement rock petrography A representative thin-section was taken between 289.23 m TVD and 289.39 m TVD, with representative photomicrographs shown in Figure 3.4. The rock is described as an altered intermediate to felsic porphyritic rock with a very fine-grained groundmass. It is a coherent sample of volcanic (e.g. lava) or shallow intrusive origin. Phenocrysts of plagioclase feldspar, quartz, alkali-feldspar and altered Fe-Mg minerals total ~10 vol. % of the sample, and consist of two main size fractions: 0.5 mm to 1 mm and 2 mm to 4 mm. Quartz phenocrysts are rounded and embayed with the feldspar altered to a mixture of epidote, sericite and clays. The Fe-Mg minerals are acicular and prismatic, altered to epidote and chlorite and are likely to have been amphibole and possibly biotite. The groundmass (0.05 mm to 0.15 mm diameter) consists of quartz, feldspars, lesser amounts of


epidote and chlorite, and trace amounts of apatite. The rock is classified as a quartz dacite based on the observed mineral assemblage.

Figure 3.4: Representative thin-section photomicrographs from the Milcarpa 1 borehole at ~289 m DL.

3.4 Geochemistry and U-Pb isotopic age Samples of diamond drill core from Milcarpa 1 were analysed for whole-rock major and trace element geochemistry at the Bureau Veritas Laboratories in Perth, Western Australia. A sample was also processed for uranium-lead (U-Pb) age dating at Geoscience Australia in Canberra. A summary of whole rock geochemistry is presented in Table 3.1, complete geochemical analyses are given in Appendix F and metallogenic and igneous classifications used are discussed in Appendix G.

The basement rock from Milcarpa 1 was assessed as being an unfractionated dacite with affinity for Cu-Mo mineralisation based on the classification scheme of Blevin et al. (1996) and Blevin (2004) (Figure 3.5). A preliminary SHRIMP zircon U-Pb isotopic age of 396 Ma (Cross et al., in prep) is calculated for the rock.


Table 3.1: Whole-rock geochemical petrographic and metallogenic indicators and SHRIMP U-Pb age for Milcarpa 1 basement rocks.

Classification (Figure 3.5A): Dacite

K2O content (Figure 3.5B) Medium; Na2O/K2O ~2.0

A/CNK: Very weakly peraluminous (1.01–1.02)

Fractionation: • K/Rb: 262-272 • Rb/Sr: 0.23-0.3 • Ba-Rb-Sr: unfractionated

Eu/Eu*: Minor moderate negative anomalies ~0.86

Redox (Figure 3.5C): Fe2O3/FeO: 0.58-0.66: oxidised

Redox-Evolution plot (Blevin; Figure 3.5D):

Oxidised-unfractionated

Adakite signature: No; HREE flat (Gd/Yb)N 1.6–1.7; mildly elevated Sr/Y: 14–14.5

Classification: Oxidised, medium-K, Sr-depleted, dacite

Anomalous elements: • Whole Rock

• Aqua Regia

• One sample has slightly elevated Ag (0.2 ppm), and both have

slightly elevated Sb, As and Mo. Rocks may have disturbed alkalis (gained Na2O, lost K2O), consistent with elevated LOI (1.4–1.6 wt.%). Low measured magnetic susceptibility contrasts with suggested redox based on Fe2O3/FeO values. This may in part reflect magnetite-destructive alteration?

• Slightly elevated As, and Cu, other elements close to detection level.

Prospectivity (Figure 3.5E): Based on evolution–redox plot falls into the Cu-Mo

Preliminary U-Pb age 396 Ma (SHRIMP U-Pb zircon; Cross et al., in prep)

3.5 Stratigraphy The stratigraphy in the Milcarpa 1 borehole (Table 3.1) is interpreted based on geological mapping on the YANTABULLA (Wallis and McEwan, 1962) and the EULO (Senior et al., 1969; Senior, 1971) 1:250,000 scale geological maps, interpretations from regional water bores and regional stratigraphic boreholes described by Hawke and Cramsie (1984).

The upper unit encountered between the surface and ~3 m TVD in the borehole is described by Wallis and McEwan (1962) as ‘Qd, wind-blown sand with minor clay pans’, which is in keeping with the aeolian red-brown fine sand and silt sheets that cover the region and are part of the present-day Murray-Darling hydrogeological basin. This lies above 17 m interval of bleached clay, then coarse sand and gravel, interpreted here to be Cenozoic alluvial sediment of the Murray-Darling hydrogeological basin.

Below this lies 41 m thickness of bleached and mottled clay, siltstone and, rarely, well lithified fine-grained sandstone, which are interpreted here as belonging to the Winton Formation of the Eromanga Basin. Hawke and Cramsie (1984) report that the Winton Formation does not occur in the Hungerford area; however, in keeping with interpretations in boreholes and water bores north of the NSW-Qld border on EULO (Senior, 1971), and in BMR Eulo 2 to north (Mond and Senior, 1970), this unit is interpreted here to be terrestrial sandstones and siltstones of the Winton Formation, and is in keeping with stratigraphy interpreted in the GSQ Eulo 1 (Roach et al., 2017a) and GSQ Eulo 2 (Roach et al., 2017b) boreholes. This unit contains more source-proximal, labile sediments including larger quartz and granitic lithic fragments due to the close proximity of the Hungerford Granite, a palaeohigh, cropping out less than 9 km to the north, and probably closer in sub-crop.


Figure 3.5: Geochemical discrimination plots for selected igneous rocks sampled as part of the Southern Thomson Project. Analyses include samples from Tongo 1 (Roach et al., 2018a), Congararra 1 (Roach et al., 2018d), Congararra 2 (Roach et al., 2018c), Janina 1 (Roach et al., 2018b) and Milcarpa 1. A: Plutonic rock classification of Debon and Le Fort (1983). X and Y axes correspond to proportions of quartz (Q) and plagioclase (P). B: K2O versus SiO2 classification plot. Boundary fields are from Le Maitre (2002). C: A plot of Fe2O3/FeO versus total Fe as FeO* (wt.%), after Champion and Heinemann (1994), showing the fields for strongly reduced, reduced, oxidised and strongly oxidised. Samples from New South Wales drill holes are also shown, which range from strongly reduced and reduced (Congararra 1 & 2, Janina 1) to oxidised (Milcarpa 1, Tongo 1). D: Rb-Ba-Sr triangular plot from El Bouseily and El Sokkary (1975) showing the fields for normal and fractionated granites. Samples show they are not significantly fractionated. E: Plot of Rb/Sr versus Fe2O3/FeO, from Blevin et al. (1996), with the field of Intrusion-related gold deposits (IRGD) from Blevin (2004).


Between 61 m TVD and 190 m TVD, dark grey to grey, almost monotonously clay-rich, puggy claystones occur, here interpreted as rocks of the Wallumbilla Formation, part of the Mesozoic marine succession. This unit was observed in GSQ Eulo 1 at 189 m thick, and is known to be up to nearly 300 m thick in the region; 291 m thick in Wanaaring 1 (Hawke, 1971a) and 226 m thick in Yantabulla 1 (Hawke, 1971b). This unit thins towards the Eulo Ridge (see Roach, 2015) and is only 28 m thick in GSQ Eulo 2 above a basement palaeohigh (Roach et al., 2017b).

Below this, the Milcarpa 1 borehole enters a thick, occasionally clayey, grey-black, micaceous, massive sandstone unit between 190 m TVD and 224 m TVD, here interpreted as the Wyandra Sandstone Member of the Cadna-owie Formation (Senior et al., 1975). The Wyandra Sandstone Member is a moderately-productive aquifer described in water bores from around the region. Senior et al. (1975) suggested that the Wyandra Sandstone Member was up to 18 m thick in Queensland (Hawke and Cramsie, 1984); however, we suggest that the unit is locally thickened (~34 m in this case) in proximity to basement highs that can increase the local sediment supply.

Table 3.2: Interpreted stratigraphy of the Milcarpa 1 borehole.

Province Stratigraphic unit Top depth (m TVD)

Bottom depth (m TVD)

True thickness (m)

No province Quaternary sand sheet 0.00 3.00 3.00

No province Gravel 3.00 20.00 17.00

Eromanga Basin Winton Formation 20.00 61.00 41.00

Eromanga Basin Wallumbilla Formation 61.00 190.00 129.00

Eromanga Basin Wyandra Sandstone Member 190.00 224.00 34.00

Eromanga Basin Cadna-owie Formation 224.00 243.00 19.00

Thomson Orogen Basement 243.00 290.90 EOH 47.90

Below this the borehole encountered another grey, massive, puggy clay or claystone unit interpreted here to be the Cadna-owie Formation between 224 m TVD and 246 m TVD. It is speculative that the lower ~4 m of this unit, brown, puggy clay, could be a palaeosol on the basement rocks, representing the top of a palaeoweathering profile on basement rocks.

Basement rocks are interpreted to be rhyodacite porphyry of an as yet unknown association, but could potentially be related to granitic intrusions in the Hungerford area.

3.6 Synthesis within the regional stratigraphic framework The felsic nature of the igneous (volcanic) rock intersected in Milcarpa 1 differs to the interpreted geology for this area, currently listed as ‘Kerrininna Zone – relatively young intermediate to mafic intrusions’ (Purdy et al., 2014; Purdy et al., 2018). Based on the texture of this rock (coherent, porphyritic with a very fine-grained groundmass) observed in the field and in thin-section, it is likely to be an extrusive lava.

The preliminary U-Pb geochronology age of 396 Ma (Cross et al., in prep.) provides useful constraints and context for this igneous unit. It is younger than the surrounding Hungerford Granite (419.1 ± 2.5 Ma; Cross et al., 2015), the other igneous units sampled in the recent stratigraphic drilling campaign (Cross et al., in prep) as well as the extensive 420-430 Ma intrusive units across the region (Purdy et al., 2018). The 396 Ma age is more similar to units such as the Tinchelooka Diorite and Conlea


Porphyry (~400 Ma; Purdy et al., 2018 and references therein), and igneous units in the Paka Tank Trough (the Tuncoona hole intersected volcanics in the Paka Tank Trough; Fraser and Thorne, in prep). To the southeast in the northern Eastern Lachlan Orogen, high level intrusive rocks at Mount Foster are slightly younger at ~387 Ma (Walthenberg et al., in prep). A preliminary comparison of whole rock trace element geochemistry between the Tinchelooka Diorite, Conlea Porphyry and Milcarpa 1 rhyodacite show they are all very similar. This age data also provides constraints for the timing of faults that cut across the area, such as the Willara Fault (Purdy et al., 2018).

Geochemical results show that the igneous unit sampled by the Milcarpa 1 borehole is an oxidised, medium-K, Sr-depleted, dacite that is unfractionated. In terms of mineral prospectivity, it falls into the Cu-Mo mineralisation field based on the classification scheme of Blevin et al. (1996) and Blevin (2004) although there is limited evidence for any substantial mineral prospectivity (only slightly elevated levels of Cu, Mo, Ag and Sb).

Basement rocks intersected in Milcarpa 1 form part of a highly magnetic, arcuate belt extending approximately east-west (the currently mapped Kerrininna Zone) that cuts across regional trends defined by mainly Cambro-Ordovician metasedimentary rock units (Purdy et al., 2018). This poses the question: is this volcanic/intrusive belt related to the proposed Devonian volcanic province sampled by the Waihora Volcanics in Queensland in the GSQ Eulo 2 borehole (Roach et al., 2017b)? This province has been suggested to represent a volcanic equivalent to one of the Devonian Granites in this area (e.g. Currawinya Granite) or to be correlated with lower parts of the Devonian basin systems, e.g. the Gumbardo Formation of the Adavale Basin (Purdy et al., 2018).The Milcarpa 1 basement rocks are non-deformed, suggesting they could be related to a rifting event, possibly of the same age that produced the Paka Tank Trough.


4 Borehole and drill core rock properties

I. C. Roach, R. Hegarty and S. Jones

4.1 Introduction Rock properties data provide the petrophysical link between observed geophysics and under-cover geology. Rock properties data may be used to help constrain models and inversions of potential fields (magnetic, gravity) geophysical data, resulting in more accurate predictions of geology from geophysics. Electrical conductivity rock properties data can also be used to constrain inversions of airborne electromagnetic (AEM) data for regional geological and groundwater resources mapping.

4.2 Rock properties measurements Rock properties measurements were performed in situ using borehole wireline logging tools, using hand-held equipment on mud rotary drill chips and diamond drill core in the field, using hand-held and laboratory equipment in the GSNSW core repository at Londonderry, New South Wales and at the Coffey Services Pty Ltd laboratory in Fyshwick, Australian Capital Territory. Rock properties measurements include:

• dual channel induction (electrical) conductivity (borehole wireline)

• natural gamma (borehole wireline)

• magnetic susceptibility (hand-held on mud rotary drill chips and diamond drill core)

• bulk saturated density (drill core only).

Borehole wireline logging was performed in stages, where possible, between drilling and subsequent borehole casing installation owing to the necessities of safely drilling and casing boreholes through the Great Artesian Basin, and preventing the uncontrolled escape of artesian groundwater. Every attempt was made to obtain borehole wireline rock properties measurements from open, uncased sections of each borehole. This was in order to obtain induction conductivity data to help validate airborne electromagnetic data collected in 2014 and 2016, detailed by Roach (2015) and Brodie et al. (in prep). Details of the equipment used are provided in Appendix C.

No in situ density measurements were obtained.

Data acquisition, processing and quality control details are included in Appendix D and an enlarged-scale graphic log is included in Appendix H.

4.3 Results and interpretation

4.3.1 Natural gamma

Natural gamma data were obtained along the full length of the borehole (Figure 4.1), from uncased sections in stages as they became available, and through casing at the completion of drilling. The


statistics included in Table 4.1 are taken from a composite of data from the uncased borehole. Natural gamma data are processed according to the description in Appendix D and are presented using American Petroleum Institute (API) units.

Natural gamma data are generally subdued in the Eromanga Basin sequence, with small spikes or offsets signifying stratigraphic unit boundaries, e.g. between the Cenozoic sedimentary cover and the Winton Formation, and between the Winton Formation and the Wallumbilla Formation. The Wyandra Sandstone Member and the Cadna-owie Formation both have relatively high and variable natural gamma responses due to the fact that they are both composed of labile quartzose sediments including feldspar and granitic lithic fragments, and presumably accessory minerals like zircon and monazite, derived locally from sediment shedding from a palaeohigh of the Hungerford Granite within ~3 km of the site. The basement response is more subdued and reflects the feldspar- and accessory mineral-poor, homogeneous nature of the rhyodacite basement rock.

Table 4.1: Milcarpa 1 natural gamma stratigraphic interval statistics.

Strat unit Minimum (API) Maximum (API) Average (API) SD (API) Quaternary 0.15 64.71 45.99 10.08

Cenozoic 11.45 83.56 33.53 15.68

Winton Formation 8.17 212.35 41.67 21.15

Wallumbilla Formation 30.35 164.26 66.39 13.98

Wyandra Sandstone Member 52.87 417.24 188.44 65.19

Cadna-owie Formation 78.69 413.31 172.85 64.48

Basement 66.18 153.36 101.77 14.10

4.3.2 Induction conductivity

An almost complete profile of induction conductivity logging is available for Milcarpa 1. Small data gaps exist where drill cuttings filled the bottom of hole before casing was inserted, between ~78.3 m TVD and 82.0 m TVD, and 245.8 m TVD and 248 m TVD (Figure 4.1).

Induction conductivity data from Milcarpa 1 demonstrate that the borehole penetrated electrically conductive cover and electrically resistive basement, confirming the data obtained by the 2014 AEM survey (Roach, 2015) and audio frequency magnetotelluric (AMT) soundings along the Hungerford-Wanaaring Road made in 2014 (Wang et al., 2017). The detail in the electrical conductivity data reflects the presence of a brackish aquifer in the Cenozoic alluvium, and relatively fresh water in the Wyandra Sandstone Member and the Cadna-owie Formation. Surface weathering effects are illustrated by the gradual increase in electrical conductivity in the upper Eromanga Basin sequence, peaking at ~70 m TVD; surface weathering was seen in mud rotary drilled chips to ~ 80 m TVD.

Electrical conductivity statistics for stratigraphic units encountered within Milcarpa 1 are presented in Table 4.2.


Figure 4.1: Lithology, stratigraphy, rock properties and borehole construction data for Milcarpa 1. The legend for lithology types and stratigraphy is the same as in Figure 3.2. For more detail on borehole construction refer to Appendix A.


Table 4.2: Milcarpa 1 induction conductivity stratigraphic interval statistics.

Strat unit Minimum (mS/m) Maximum (mS/m) Average (mS/m) SD (mS/m) Medium channel Quaternary 41.02 101.646 68.88 18.50

Cenozoic 45.26 514.71 307.74 171.85





Basement 4.92 52.02 16.49 10.23

Deep channel Quaternary 46.37 126.39 83.34 24.67

Cenozoic 53.89 606.65 374.32 203.71





Basement 11.06 69.12 23.40 11.96

4.3.3 Magnetic susceptibility

Magnetic susceptibility measurements were obtained in the field on mud rotary drill chips and diamond drill core using a hand-held magnetic susceptibility meter (see Appendix A for more detail). Some of the mud rotary chips were found to be contaminated by steel particles from the drilling pipe wearing on the foot clamps of the drilling rig. After values related to steel particle contamination have been removed from the log, magnetic susceptibility in both mud rotary chips and diamond drill core is relatively subdued (Figure 4.1). The highest values for magnetic susceptibility in the Eromanga Basin sequence occur on the Wyandra Sandstone Member and are probably reflective of small amounts of detrital magnetite sourced from the nearby Hungerford Granite.

Table 4.3: Milcarpa 1 stratigraphic interval magnetic susceptibility statistics.

Minimum (SI x 10-5) Maximum (SI x 10-5) Average (SI x 10-5) SD (SI x 10-5) Quaternary 0.00 37.00 13.93 12.35

Cenozoic 0.00 15.00 1.00 3.02





Basement 2.88 50.00 16.56 7.50

The Milcarpa 1 borehole was drilled in an attempt to intersect a magnetic target, assumed to be an igneous intrusion (Figure 2.2). Pre-drilling Depth To Magnetic Source (DTMS) modelling described by Goodwin et al. (2017) indicated that the target magnetic body could be up to 367 m below surface, although the anomaly selected for the Targeted Magnetic Inversion Model (TMIM) result was ~3 km to the west of the actual borehole site. The borehole did not reach the magnetic target, but was instead halted in what is interpreted to be the relatively non-magnetic volcanic carapace to this body, because


the borehole had achieved the science objectives of retrieving good quality basement core capable of being isotopically age dated.

4.3.4 Bulk density and apparent porosity

Samples of fresh rock from the Milcarpa 1 diamond drill core were submitted to the Coffey Services Australia Pty Ltd laboratory in Fyshwick, Australian Capital Territory, for determination of dry bulk density, saturated bulk density, grain density and apparent porosity according to Australian Standard AS 1141.6.1-2000, presented in Table 4.4.

Saturated, dry and grain bulk density determinations average between 2.72 g/cm3 and 2.73 g/cm3 indicating that the rock is generally non-porous. Comparison average densities for similar rocks range from 2.52 g/cm3 (rhyolite) to 2.58 g/cm3 (dacite) (Telford et al., 1976), and 2.57 g/cm3 for rhyodacite and 2.63 g/cm3 for rhyolite from the Lachlan Fold Belt, although well lithified versions of these rocks could have a saturated bulk density of up to 2.91 g/cm3 (Wyatt et al., 1984; Skladzien, 2007). The slightly higher density of basement rock in Milcarpa 1 may be reflective of the highly siliceous and non-porous nature of this rock.

Table 4.4: Density measurements on diamond drill core from Milcarpa 1.

From (m TVD) To (m TVD) n samples Mean dry bulk density (g/cm3)

Mean saturated bulk density (g/cm3)

Mean grain density (g/cm3)

Mean apparent

porosity (%)

256.50 256.79 2 2.72 ± 0.01 2.72 ± 0.004 2.72 ± 0.001 0.08 ± 0.08

281.68 282.01 4 2.73 ± 0.03 2.73 ± 0.03 2.73 ± 0.03 0.00 ± 0.00

± error is calculated as 1 standard deviation of the sample population

4.4 Rock properties data package Rock properties data for Milcarpa 1 are compiled as a Log ASCII Standard (LAS) file available for free download from the Geoscience Australia website and through the Rock Properties Explorer discovery tool (http://www.ga.gov.au/explorer-web/rock-properties.html). Rock properties data are also included in a Web Mapping Service (WMS) and Web Feature Service (WFS) from (http://www.ga.gov.au/data-pubs/web-services/ga-web-services).

http://www.ga.gov.au/explorer-web/rock-properties.html

http://www.ga.gov.au/data-pubs/web-services/ga-web-services

http://www.ga.gov.au/data-pubs/web-services/ga-web-services


5 HyLogger data

D. B. Tilley and I. C. Roach

5.1 HyLogger data acquisition and processing Diamond drill cores and mud rotary chips were spectrally scanned using the CSIRO-developed HyLogger™ system at NSW Planning and Environment’s HyLogger™ facility in the W.B. Clarke Geoscience Centre, Londonderry, NSW. The resultant spectral data were analysed using The Spectral Geologist™ (TSG) software, also developed by the CSIRO. This instrument measures spectra in three different wavelength bands (Mason and Huntington, 2012):

• the visible-near infrared (VNIR) between 380 and 1072 nm • the short-wave infrared (SWIR) between 1072 and 2500 nm • the thermal infrared (TIR) from 6000 and 14,500 nm.

The HyLogger™ instrument collects spectral data and imagery of geological materials on a systematic basis. The near-continuous nature and abundance of the spectral data collected provides ideal datasets which can be processed to identify systematic changes in the overall mineral assemblage along diamond drill cores and chip trays. This can highlight shifts in the nature of individual mineral species present (particularly chlorite and white mica), and identify changes in the relative abundance of specific minerals.

Prior to scanning, the diamond drill core was cleaned with a vacuum cleaner and moistened cloth to remove dust, dirt and in-tray debris. Disjointed core pieces were realigned and reconnected within sections of a tray to make a continuous core stick. Following this, the core was allowed to dry to reduce H2O spectral interference prior to scanning. In contrast, the only preparation done on the chips was that they were allowed to dry within their trays for a few days in open air.

A number of specialised scalars were used for inferring changes in the composition of white mica and chlorite and for estimating their relative abundances in core and chips.

For white mica composition and relative abundance The Spectral Assistant (TSA™) batch scalars White Mica Wavelength v1.2 and White Mica Intensity v1.2 were used. These scalars are based on the wavelength and depth of the Al-OH absorption feature in the short-wave infrared (SWIR) spectrum. It has been noted by Pontual et al. (2008) that the absorption minimum ranges from 2184 nm for paragonite (Na-sericite), to 2202 nm for muscovite (“normal” potassic compositions) and 2225 nm for phengite compositions (Mg-Fe substituted sericites). Also, the scalar’s batch script specifies that any identification of montmorillonite by TSA™ will provide a null result, whilst samples classified by TSA™ as bearing highly crystalline and/or illitic white micas are included in the determinations. The highly crystalline white micas include muscovite, phengite and paragonite whilst the illitic white micas include illite, phengitic illite and paragonitic illite. The depth of the feature provides an estimation of the relative abundance of white mica within core and chips.

The inferred composition and relative abundance of chlorite group minerals were determined using the following TSG™ Feature Extraction (FeatEx) scalars:

• chlorite composition: FeatEx Wvl, 2253 nm ± 10 nm • chlorite relative abundance: FeatEx Depth, 2253 nm ± 10 nm.


These scalars were used to determine the wavelength and depth of the Fe-OH absorption feature in the SWIR spectrum. The chlorite Mg-OH feature can be affected by the presence of carbonate, which overlaps the chlorite Mg-OH absorption. Consequently, it is more reliable to use the Fe-OH absorption feature for inferring the composition of chlorite rather than the Mg-OH feature. Pontual et al. (2008) have shown that this feature varies from 2245 nm for Mg-chlorite to 2261 nm for Fe-chlorite. The depth of the feature provides an estimation of the relative abundance of chlorite within the core/chips.

5.2 Results

5.2.1 Milcarpa 1 mud rotary chips

The mud rotary chips from Milcarpa 1 are composed mainly of kaolin (kaolinite), smectite (montmorillonite), white mica, quartz, plagioclase (albite), K-feldspar (microcline/orthoclase), sulfate (gypsum) and trace carbonate (Figure 5.1).

The Al-OH absorption feature varies from a maximum of 2211 nm at 185.4 m TVD to a minimum of 2202 nm at 204.4 m TVD. This is inferred to be a localised change in composition from a phengitic white mica to muscovite. Alternatively, the coexistence of a kaolinite-rich zone at this depth could be influencing the change in wavelength. As mentioned earlier, the wavelength of the Al-OH feature at the top of the diamond cored portion of the borehole is 2211 nm, so this shortening of the wavelength from 200.6 m TVD to 228.4 m TVD is considered to be only a localised change.

A few data points at the bottom of the mud rotary-drilled portion reveal an Fe-OH absorption feature at around 2255 nm, indicative of Fe-Mg chlorite, which is similar to that observed in the diamond drill core.

Figure 5.1: Mineral spectra summary plot of Milcarpa 1 mud rotary drill chips.


5.2.2 Milcarpa 1 diamond drill core

The diamond drill core from Milcarpa 1 is principally a Rhyodacite and is composed of Na plagioclase (albite-oligoclase), quartz, white mica, chlorite and epidote. Trace prehnite (other-AlOH) is also detectable within the core (Figure 5.2). The core appears to have undergone weathering in the uppermost part of the core as evidenced by kaolinite and smectite (montmorillonite). In addition, weathering/alteration appears to have occurred along faults/fractures throughout much of the core as smectite is also apparent within these structures.

Figure 5.2: Mineral spectra summary plot of Milcarpa 1 diamond drill core.

White mica is generally phengitic, as suggested by the Al-OH absorption feature having an average wavelength of 2216 nm throughout most of the borehole, i.e. from 255 m TVD to the EOH. In the uppermost part of the borehole, from 246 m TVD to 255 m TVD, the white mica is less phengitic, with the Al-OH feature averaging 2211 nm.

Throughout the borehole the Fe-OH absorption feature plots as two discrete wavelengths; one at 2252 nm and another at 2255 nm. This is attributed to the presence of epidote and Fe-Mg chlorite within the core (Figure 5.3).

5.3 Comparison with other logging The stratigraphy in the Milcarpa 1 borehole was interpreted from lithological textures and mineralogy based on knowledge from other boreholes in the region, regional geological mapping in the EULO and YANTABULLA 1:250,000 geological map sheets and borehole wireline geophysical data. These interpretations are tested against the spectral mineralogy of returned mud rotary chips and diamond drill core from the borehole in Figure 5.4A, B.

The spectral mineralogy compares very favourably with the other logging data in that stratigraphic boundaries interpreted from the chip and core logging are generally within close agreement with changes in bulk mineralogy derived from the spectral mineralogy data in fresh rocks. There is a small


amount of downward smearing of stratigraphic boundaries, ~3 m to 5 m below the interpreted stratigraphic boundaries interpreted in the field; however, major changes in lithology, and therefore stratigraphy, are generally visible in the unweathered portion of the borehole at or near the boundary indicated by the spectral mineralogy.

Figure 5.3: The Fe-OH absorption feature within Milcarpa 1 – FeatEx Wvl, 2253+-10 nm plots as two discrete wavelengths, attributed to the coexistence of Fe-Mg chlorite and epidote within the core.

The mineral spectra are complicated by two weathering overprints:

1. From surface to ~80 m TVD, consisting dominantly of kaolinite-smectite related to surface weathering. The boundary between the Winton Formation and the underlying Wallumbilla Formation, over which the surface weathering extends, is however marked by the appearance of sulphate (gypsum) and a marked decrease in silica (quartz).

2. A palaeoweathering overprint on basement rocks from the basement-cover interface at 246 m TVD to ~260 m TVD, visible as a gradual increase in chlorite content and an abrupt loss of kaolinite.

The spectral logging also compares very favourably with borehole rock properties data including natural gamma and induction conductivity, especially in the region of the Wyandra Sandstone Member and the Cadna-owie Formation, where elevated natural gamma is responding to the appearance of plagioclase and (from the lithological logging) the presence of granite lithic fragments and potentially other radioactive accessory minerals like zircon and monazite derived from the nearby Hungerford Granite. The induction conductivity in these two units drops in response to relatively high quartz content and the presence of fresh to brackish groundwater in the Wyandra Sandstone Member aquifer, resulting in overall low bulk electrical conductivity in these units.

Magnetic susceptibility in the mud rotary chips and diamond drill core is quite subdued, and there is no strong correlation between this and spectral mineralogy.


Figure 5.4A: comparison between spectral mineralogy, interpreted stratigraphy and borehole rock properties data from Milcarpa 1. The spectral mineralogy legends in the upper part of the log refer to the mud rotary drilled portion of the borehole < 246.9 m TVD, and in the lower part to the diamond drilled portion to EOH.


Figure 5.4B: Legend for Figure 5.4A.

5.4 HyLogger data package The HyLogger data package consists of drill core data processed to Level 1F (all metadata tables updated, optimum database loadable level, further updates possible) that can be opened and viewed using The Spectral Geologist (TSG™) Viewer software. This software can be freely downloaded from CSIRO via the following link:

https://research.csiro.au/thespectralgeologist/support/downloads/

This package also contains individual core tray images in .JPG format, and a mosaic of all the core trays arranged it order also in .JPG format. These images are referenced images and can be interactively interrogated when opened in TSG program. The data will also be made available through the AuScope National Virtual Core Library (NVCL) portal (http://portal.auscope.org/portal/gmap.html) and Geoscience Australia’s AUSGIN portal (http://portal.geoscience.gov.au/gmap.html).

5.5 HyLogger data reprocessing Geoscience Australia commissioned CSIRO Mineral Resources to perform a quality assessment of the HyLogger data package by reprocessing the original dataset described above. The results of the assessment indicate that the original TSA-derived mineralogy for the Congararra 1 borehole was a good match for the scalar-derived mineralogy calculated during the reprocessing (Lau et al., in prep), except perhaps for epidote, which appears to have been erroneously identified by SWIR-TSA. After acceptance, the reprocessed dataset will be available through the NVCL and AUSGIN portals listed above.



http://portal.auscope.org/portal/gmap.html

http://portal.geoscience.gov.au/gmap.html


6 Groundwater

I. C. Roach

Local aquifers include Cenozoic gravels and the Mesozoic Wyandra Sandstone Member of the Cadna-owie Formation. Hydraulic heads around Milcarpa 1 are all below ground level, and appear to have been since they were originally drilled, resulting in only sub-artesian water pressures. Local waterbores and their measured Standing Water Level (SWL) are listed in Table 6.1, highlighting the sub-artesian water levels present in the region.

Table 6.1: Local waterbores within the Milcarpa 1 vicinity highlighting the overall sub-artesian water pressures present in the area. Refer to Figure 2.2 for locations.

Bore ID Distance & bearing

Depth to main aquifer (m)

SWL when drilled (year)

Most recent SWL (year)

GW006619 3.2 km N 13.7 -11.9 (1940) NA

GW006642 6.5 km NE 51.8 -35.1 (1940) NA

GW004019 6.5 km NNW 134.4 -6.1 (1894) NA

*Negative values indicate SWL below ground surface.

No artesian groundwater was detected in Milcarpa 1. The borehole intersected Cenozoic gravels between ~6 m and ~20 m (~14 m unit thickness) and the Wyandra Sandstone Member of the Cadna-owie Formation between ~190 m and ~ 224 m (~34 m unit thickness), but no groundwater was made. Instead, an estimated 5000 L of drilling fluid was lost to the Wyandra Sandstone Member during drilling operations, indicating that the aquifer has high transmissivity, but low water pressure that was overcome by the weight of the drilling fluids in the borehole during drilling.


7 Acknowledgements

Geoscience Australia and its project partners, the Geological Survey of New South Wales and the Geological Survey of Queensland, gratefully acknowledge the following organisations and people:

• Landholder Manuel Fernandes and subsequently Joe Baty (of Muella station)

• Traditional owners the Barkandji People for cultural heritage monitoring

• DRC Drilling Pty Ltd, Dubbo NSW

• Fox Drilling Services Pty Ltd (Fox Campbell, licensed waterbore driller) for overseeing drilling operations through the Great Artesian Basin and ensuring the technical success of boreholes

• Greg Swain and Daniel Gray (Geoscience Australia On-site Representatives) for in-field management of drilling activities and budget monitoring

• Reviewer: Tim Barton

• OPM Consulting Pty Ltd for cultural heritage clearance work with the traditional owner cultural heritage monitors

• Southern Thomson Project team:

o Geoscience Australia: Angela O’Rourke (Project Manager), Narelle Neumann (former Project Manager), Tim Barton (former Acting Project Manager), Sheree Armistead, Patrice de Caritat, David Champion, Michael Doublier, James Goodwin, David Huston, Subhash Jaireth, Sharon Jones, Peter Maher (EASS, for assistance with land access and cultural heritage clearances), David McInnes, Andrew McPherson, Malcolm Nicoll, Ian Roach (Activity Leader), Paul Rossiter (Contracts and Probity), Roger Skirrow, Matilda Thomas, John Wilford, Geoscience Australia Laboratory and Science Services staff for support and analyses.

o GSNSW: Astrid Carlton, Chris Folkes (Activity Leader), John Greenfield, Phil Gilmore, Rosemary Hegarty (former Activity Leader), Bob Musgrave, Ned Stolz.

o GSQ: Dominic Brown, Paul Donchak, Laurie Hutton, David Purdy (Activity Leader), Janelle Simpson, Ian Withnall.


8 References

Blevin, P. L., 2004. Redox and Compositional Parameters for Interpreting the Granitoid Metallogeny of Eastern Australia: Implications for Gold-rich Ore Systems. Resource Geology 54(3), 241-252.

Blevin, P. L. and Chappell, B. W., 1992. The role of magma sources, oxidation states and fractionation in determining the granite metallogeny of eastern Australia. Transactions of the Royal Society of Edinburgh: Earth Sciences 83, 305-316.

Blevin, P. L., Chappell, B. W. and Allen, C. M., 1996. Intrusive metallogenic provinces in eastern Australia based on granite source and composition. Transactions of the Royal Society of Edinburgh: Earth Sciences 87(1-2), 281-290.

Brodie, R. C., Ley-Cooper, Y., Crowe, M. C. A., McInnes, D. J. and Roach, I. C., in prep. The 2016 Southern Thomson AEM Survey: Southern Thomson Project. Geoscience Australia, Canberra. Record.

Champion, D. C. and Chappell, B. W., 1992. Petrogenesis of felsic I-type granites: an example from northern Queensland. Transactions of the Royal Society of Edinburgh: Earth Sciences 83, 115-126.

Champion, D. C. and Heinemann, M. A., 1994. Igneous Rocks of Northern Queensland: 1:500 000 map and GIS explanatory notes. Australian Geological Survey Organisation, Canberra. Record 1994/11.

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http://www.ga.gov.au/corporate_data/15156/Rep_244.pdf


Appendix A Borehole construction

The Milcarpa 1 borehole was constructed using a combination of mud rotary drilling to refusal into competent basement, then diamond drilling for the core tail. Drilling commenced with an 80.0 m TVD section of mud rotary drilling using a 215.90 mm (8½ inch) diameter polycrystalline diamond (PCD) mud rotary drill bit and installation of 80 m of 168.28 mm OD (6 5/8 inch) guard casing to prevent loose surface material from collapsing into the hole. This was cemented into place back to the ground surface. The borehole was deepened to 246.9 m TVD into competent basement rocks using a 149.23 mm (5 7/8 inch) PCD mud rotary drill bit and cased using 114.30 mm OD (4 ½ inch) SFJ screw-thread casing, which was not cemented into place and which was removed prior to abandoning the hole. Drilling then continued into basement using a 96 mm OD HQ3 diamond drill bit and 3.0 m triple-tube core barrel to the EOH at 290.9 m TVD.

The borehole was abandoned by removing the SFJ casing and progressively cementing the borehole from bottom to top in stages through HQ3 drill pipe to surface. The guard casing was cut off 0.5 m below surface and the borehole was rehabilitated by pushing surface soil back over the borehole cellar. The drilling mud sumps were fenced, left to dry out and were rehabilitated by the landholder by pushing the original surface soil back into the sumps.

Drilling equipment consisted of a Sandvik DE880 multi-purpose drilling rig, a National Oilwell skid-mounted mud pump, 20’ mud tank, jack-up rod sloops, 40’ mobile workshop/office/first aid room, lighting towers and support vehicles.


Figure 8.1: Milcarpa 1 borehole construction.


Appendix B Drilling activities and consumables

Table 8.1: Milcarpa 1 drilling times and production rates

Date Plod # Shift Hole Rotary mud drilling Diamond drilling

Siz

e

From

To

Tota

l

From

To

Tota

l

Dril

ling

Tim

e

Act

ive

time

tota

l

Inac

tive

time

tota

l

Non

-ch

arge

able

tim

e to

tal

Shi

ft to

tal

mm m m m m m m hr hr hr hr hr Total 246.7 44 49 53 27.65 21.25 150.9

42923 302114 Day Milcarpa 1 0 3 0 0 3

42923 302115 Night Milcarpa 1 215.90 0.00 60.00 60.00 0 5.5 2 3.9 4.5 15.9

42924 302116 Day Milcarpa 1 215.90 60.00 80.00 20.00 0 3 6.5 1.75 0.75 12

42924 302117 Night Milcarpa 1 0 0 7.5 4 0.5 12

42925 302118 Day Milcarpa 1 0 0 0 12 0 12

42925 302119 Night Milcarpa 1 149.23 80.20 146.60 66.40 0 8 2.5 0 1.5 12

42926 302120 Day Milcarpa 1 149.23 146.60 212.60 66.00 0 4 4.5 0 3.5 12

42926 302121 Night Milcarpa 1 149.23 212.60 246.90 34.30 0 5 3.5 3 0.5 12

42927 302122 Day Milcarpa 1 HQ3 0 246.9 252.3 5.4 3.5 8 0 0.5 12

42927 302123 Night Milcarpa 1 HQ3 0 252.3 270.3 18 9 2 0 1 12

42928 302125 Day Milcarpa 1 HQ3 0 270.3 288.3 18 10.5 1 0 0.5 12

42928 302126 Night Milcarpa 1 HQ3 0 288.3 290.9 2.6 0.5 8 3 0.5 12

42929 302127 Day Milcarpa 1 0 0 4.5 0 7.5 12


Table 8.2: Milcarpa 1 drilling consumables used.

Date Plod # Shift 165

mm

(6 5

/8 S

FJ)

Dar

by P

lug

Dar

by P

lug

Aus

-Gel

Xtr

a (b

ento

nite

)

Cem

ent

AM

C P

ac-L

AM

C P

ac-R

Aus

-Det

Xtr

a

Cla

y D

oc

Liqu

id P

ol

Bio

-Cid

e G

Torq

ue G

uard

/ m 6.625” HQ 25 kg 20 kg 25 L 25 kg 25 L 10 kg 25 L 25 L 25 L Total 80.2 1 3 17 325 2 2 5 2 1 2 2

42923 302114 Day 8 42923 302115 Night 7 1 42924 302116 Day 32.2 2 42924 302117 Night 48 1 49 42925 302118 Day 10 42925 302119 Night 1 2 1 42926 302120 Day 1 1 1 42926 302121 Night 42927 302122 Day 1 42927 302123 Night 1 1 1 42928 302125 Day 1 1 2 42928 302126 Night 1 90 42929 302127 Day 2 176


Appendix C Petrophysical equipment details

C.1 Borehole wireline logging equipment • Mt Sopris QL40 IND dual induction tool SN 6067, 50 cm (medium) and 80 cm (deep) coil

spacing

• Mt Sopris QL40 GRA natural gamma tool SN 6060

• Mt Sopris QL40 MS magnetic susceptibility tool SN 144804

• ALT Matrix data acquisition system SN 0D0D

• Auslog W2000-4 winch SN T199 with 1750 m of 4-conductor cable.

C.2 Hand-held magnetic susceptibility logging equipment • CoRMaGeo RT-1 magnetic susceptibility meter SN 1520239 (Geoscience Australia).

C.3 Analytical balance equipment (density determination) • A & D Instruments EP-41KA Industrial Balance, quoted accuracy ± 1.0 g. Last calibrated 20

September 2017.


Appendix D Petrophysical data acquisition and processing

D.1 Data acquisition and processing Borehole wireline petrophysical data were acquired during the mud rotary and diamond drilling operations, nominally in the open borehole as each section of the borehole was drilled and before steel casing was inserted. Data from each logging run in the borehole were assessed for quality and were then stitched together to create a final run of data for the length of the borehole where possible.

Table 8.3: Borehole wireline data acquisition steps in Milcarpa 1

Date Length logged (m TVD)

Borehole casing size Properties logged

08.07.2017 0-79.0 m TVD 215.9 mm open hole to 80.0 m TVD Natural gamma, induction conductivity

11.07.2017 0-246.5 m TVD 168.28 mm OD steel to 80.0 m TVD, then 149.23 mm open hole to 246.9 m TVD

Natural gamma, induction conductivity

12.07.2017 0-288.0 m TVD 168.28 mm OD steel to 80.0 m TVD, then 114.3 mm OD SFJ steel to 246.9 m TVD, then 96 mm open hole to 290.9 m TVD

Natural gamma, induction conductivity

Hand-held magnetic susceptibility data were acquired in the field along the entire length of the borehole from the mud rotary drilled chips at 1.0 m intervals and from the diamond drill core at 0.5 m intervals. These data were used to produce a final magnetic susceptibility log of the borehole. Measurements were made on mud rotary drilled chip samples by placing the sample vial on top of the magnetic susceptibility meter and repeatedly measuring the sample to obtain a repeatable value. For magnetic susceptibility measurements on diamond drill core the plastic diamond drill core trays used for the drilling program were elevated above the work tables on a stack of two empty core trays to ensure no interference from steel in the work tables. Point observations were then obtained at 0.5 m intervals by repeated measurements on the same point to obtain a repeatable value. Magnetic susceptibility measurements on core were multiplied by the recommended compensation factor for the core size according to the manufacturer’s instructions. Some steel particle contamination was visible in the mud rotary chip samples, resulting in elevated magnetic susceptibility values. Where verifiable, these values have been edited out of the final data.

D.2 Equipment calibration Borehole wireline tools were calibrated according to the manufacturer’s Standard Operating Procedures (SOPs) described in the user manuals, also described in Roach et al. (2017a), apart from the natural gamma tool which was calibrated in the factory and is not capable of being calibrated in the field. In the field equipment was connected to the ALT Matrix data acquisition system and energised for a period of at least 15 minutes in the borehole to equilibrate temperature with the bore fluid before commencing calibration. Equipment was fully tested in Canberra before commencing borehole wireline logging operations to ensure that it was stable and gave repeatable results prior to the field campaign, and calibration drift was checked in the field at every use to ensure data repeatability.


The primary handheld magnetic susceptibility meter used to obtain data on mud rotary drilling chips and diamond drill core (CoRMaGeo RT-1 SN1520239) was calibrated by the manufacturer before commencing the field operations.

D.3 Data processing Petrophysical data were processed using the following processing stream:

• Levelling raw borehole wireline data files to a common datum (ground level) and interpolating the sampling interval to even increments (0.05 m) using WellCAD.

• Combining data from different logging runs into a single data file and removing overlapping data.

• Removing spikes or bad data in induction conductivity and magnetic susceptibility data caused by steel casing and inserting null values.

• Bridging any single-sample data dropouts caused by transient telemetry errors during acquisition by averaging data across the gap, leaving larger data gaps between successive logging runs as nulls.

• Editing natural gamma data to remove the effects of gamma-ray attenuation due to casing and changes in borehole diameter in overlapping data from earlier and later logging runs by applying a bias to attenuated data to achieve a full run of apparent “open hole” natural gamma data.

• Editing handheld magnetic susceptibility data to remove the effects of verified steel particle contamination.

• Produce a final LAS-format data file of:

o Open hole natural gamma

o Medium- and deep-channel induction conductivity (including data gaps)

o Composite magnetic susceptibility.


Appendix E Lithological and stratigraphic log

FROM TO GA LITHOLOGY

GA QUALIFIER

COLOUR MUNSELL COLOUR

DESCRIPTION GRAINSIZE PROVINCE STRATNAME MAPSYMBOL

m DL = TVD

m DL = TVD

Cla

y

Silt

Vfin

e

Fine

Med

Coa

rse

Vcoa

rse

Gra

nule

Pebb

le

Cob

ble

0.00 1.00 Aeolian Rd-br 2.5 YR 4/6 Red-brown fine sand and silt. Windblown soil low in organic content

X X No province Quaternary sand Qs

1.00 3.00 Hardpan indurated, ferruginous, manganiferous, calcareous

Rd-br 2.5 YR 4/6 Partially indurated red-brown fine sand and silt hardpan with irregular veins and sheets of regolith carbonate. Hardpan is partially silicified with ferruginous and manganiferous coatings.

X X No province Quaternary sand Qs

3.00 8.00 Sandy silt indurated Gy-gr Gley1 8/1 Partially indurated silt and sand with subrounded to subangular lithic fragments and quartz grains in an opaque light-toned siliceous matrix. Also contains abundant free quartz grains, both clear and milky.

X X X X No province Cenozoic alluvium Cz

8.00 20.00 Clayey sandstone

L gy 5Y 8/1 Well sorted, texturally-mature, quartz-rich sandstone, grain- to clast-supported, with a white clay matrix.

X X X X No province Cenozoic alluvium Cz

20.00 32.00 Sandstone ferruginous L gy-rd SR 6/3 Ferruginous orange-red very fine-grained, indurated quartz sandstone with interbedded coarse-grained quartz sandstone. Colour changes down-profile to pink colours. Mottled zone of weathering profile.

X X X Eromanga Basin Winton Formation Kw

32.00 50.00 Sandstone L gy 7.1 YR 8/1 Indurated, well sorted, fine- to medium-grained quartz sandstone with minor ferruginous fragments

X X Eromanga Basin Winton Formation Kw

50.00 55.00 Sandstone mottled L gy-rd 5R 6/3 Mixed pallid and ferruginised quartzose sandstone


55.00 61.00 Sandstone L gy 7.1 YR 8/1 Fine-grained, clast-supported quartz sandstone with opaque, white siliceous matrix


61.00 66.00 Clay Wh White Puggy, white-toned, plastic grey clay X X Eromanga Basin Wallumbilla Formation Klu

66.00 72.00 Clay L gy Gley2 8/1 Puggy, light grey toned plastic clay. X Eromanga Basin Wallumbilla Formation Klu

72.00 80.00 Silty shale Gy Gley2 7/1 Dark grey siltstone within puggy plastic clay. Base of surface weathering

X Eromanga Basin Wallumbilla Formation Klu

80.00 135.00 Mudstone silty Gy Gley 2 3/1 Dark grey mudstone with minor siltstone fragments

X X Eromanga Basin Wallumbilla Formation Klu

135.00 148.00 Mudstone Gy Gley 2 3/1 Dark grey mudstone with occasional light grey (Gley2 6/1)chips


148.00 151.00 Mudstone Gy Gley 2 3/1 Dark grey mudstone with ~10% white clayey reduction spots as planar flecks that smear on touching.



FROM TO GA LITHOLOGY

GA QUALIFIER

COLOUR MUNSELL COLOUR

DESCRIPTION GRAINSIZE PROVINCE STRATNAME MAPSYMBOL

m DL = TVD

m DL = TVD

Cla

y

Silt

Vfin

e

Fine

Med

Coa

rse

Vcoa

rse

Gra

nule

Pebb

le

Cob

ble

151.00 181.00 Mudstone carbonaceous Gy Gley 2 3/1 Mudstone with greasy, carbonaceous mudstone interbeds between ~165 m and 170 m. Contains occasional ~1 mm diameter pyrite framboids below ~160 m


181.00 183.00 Mudstone pyritic Gy Gley 2 3/1 Dark grey mudstone with ~10% white clayey reduction spots as planar flecks that smear on touching. Contains occasional ~1 mm diameter pyrite framboids


183.00 190.00 Mudstone pyritic Gy Gley 2 3/1 Dark grey mudstone with occasional ~1 mm diameter pyrite framboids


190.00 198.00 Silty sandstone

pyritic, micaceous

Gy Gley2 5/1 Grey sandstone and minor siltstone containing 1-2 mm quartz grains and lithic fragments, ~2 mm diameter pyrite framboids and biotite flakes.

X X X X Eromanga Basin Wyandra Sandstone Member

Klws

198.00 200.00 Sandy siltstone

Dk gy Gley 2 3/1 Dark grey siltstone X X X Eromanga Basin Wyandra Sandstone Member

Klws

200.00 209.00 Sandstone lithic, pyritic, micaceous

L gy Gley 2 5/1 Medium- to coarse-grained sandstone with abundant clear and milky quartz grains, granitic lithics, pyrite framboids, siltstone lithic fragments and biotite flakes, all moderately to well-rounded.

X X X X Eromanga Basin Wyandra Sandstone Member

Klws

209.00 210.00 Clayey sand micaceous Dk gy-br 10YR 7/2 Sandstone and micaceous, silky, puggy clay X X Eromanga Basin Wyandra Sandstone Member

Klws

210.00 224.00 Arenite lithic, pyritic, micaceous

L gy Gley2 5/1 Medium- to coarse-grained sandstone with abundant clear and milky quartz grains, feldspar grains, granitic lithics, pyrite framboids, siltstone lithic fragments and biotite and muscovite flakes, all moderately to well-rounded.

X X X X X Eromanga Basin Wyandra Sandstone Member

Klws

224.00 238.00 Clayey sandstone

pyritic, lithic Dk bn Gley2 3/1 Dark brown muddy sandstone with occasional quartz grain-rich patches, pyrite framboids, granitic lithic fragments

X X X X Eromanga Basin Cadna-owie Formation Kco

238.00 243.00 Sandy claystone

Bn 10YR 4/1 Brown sandy, pliable claystone, quartz sand grains, possibly interbedded sandstone between 209 m and 210 m

X X Eromanga Basin Cadna-owie Formation Kco

243.00 246.00 Saprolite Gn 5Y 6/1 Green puggy clay and platy green, siliceous rock chips

X X Thomson Orogen

246.00 290.90 Rhyodacite Gn Gley1 4/1 Hard, siliceous, green, porphyritic rhyodacite with hematite alteration, subhedral to anhedral 2 mm diameter feldspar crystals and < 4 mm diameter quartz crystals, increasing in concentration towards the EOH, and faint flow alignment. Commonly fractured with < 1 cm thick white zeolite-filled veins

X X X Thomson Orogen


Appendix F Whole-rock geochemistry

Samples of diamond drill core from 246.9 m TVD to 290.9 m TVD were taken for whole-rock geochemical analysis. Analyses were performed by Bureau Veritas in Perth, Western Australia. Major element abundances were determined by X-Ray Fluorescence (XRF), with results shown in wt. %. Exceptions include FeO, which was determined volumetrically, and Loss-On-Ignition (LOI), which was determined using a robotic Trace Gas Analysis (TGA) system at 110°C and 1000°C. Fe2O3* is regarded as total Fe, as Fe2O3. Fe2O3 is calculated by difference (Fe2O3* - 1.11134*FeO). Trace element analysis is by laser ablation ICP-MS on the fused glass disk (lithium metaborate fusion), except for S, which has been calculated from the analysed SO3 value. Limits of Detection (LD) and units of measure (ppm or ppb) shown are in the columns). Analyses below detection are shown as negative LD, e.g., -0.2.

Table 8.4: Whole-rock major element geochemical data for Milcarpa 1.

SAMPLEID 17/1054 17/1056 ENTITYID Milcarpa 1 Milcarpa 1 ROCKTYPE rhyolite rhyolite Depth_top (m) 256.5 281.68 Depth_bottom (m) 256.79 282.01 Lab LD Veritas Veritas Major elements wt. % wt. %

SiO2 -0.01 68.58 68.64

TiO2 -0.01 0.47 0.47

Al2O3 -0.01 14.8 15

Fe2O3* -0.01 3.7 3.5

Fe2O3 -0.11 1.39 1.2

FeO -0.1 2.08 2.07

MnO -0.01 0.06 0.07

MgO -0.01 1.59 1.46

CaO -0.01 3.43 3.09

Na2O -0.01 4.03 4.01

K2O -0.001 1.62 2.17

P2O5 -0.001 0.15 0.15

SO3 -0.001 0.01 0.01

Cl -0.001 -0.001 -0.001

LOI -0.01 1.61 1.4

Total 99.81 99.73


Table 8.5: Whole-rock trace element geochemical data for Milcarpa 1.

SAMPLEID 17/1054 17/1056 ENTITYID Milcarpa 1 Milcarpa 1 ROCKTYPE rhyolite rhyolite Depth_top (m) 256.5 281.68 Depth_bottom (m) 256.79 282.01 Lab LD Veritas Veritas Trace elements ppm ppm

Ba -0.5 248 361

Rb -0.05 48.7 68.5

Sr -0.1 208 224

Pb -1 9 9

Th -0.01 7.94 8.99

U -0.01 2.17 2.41

Zr -0.5 154 169

Hf -0.01 4.06 4.57

Nb -0.01 11.9 13

Ta -0.01 1.19 1.35

Y -0.02 14.8 15.5

La -0.01 27.3 29

Ce -0.02 48.2 50.2

Nd -0.01 17.5 18.6

Sc -0.1 6.5 5.6

V -0.1 40.8 42.7

Cr -1 14 15

Ni -2 12 10

Ga -0.1 15.9 18.2

Pr -0.01 5.48 5.69

Sm -0.01 3.36 3.5

Eu -0.01 0.9 0.96

Gd -0.01 3.07 3.24

Tb -0.01 0.48 0.52

Dy -0.01 2.62 2.85

Ho -0.01 0.55 0.59

Er -0.01 1.44 1.58

Tm -0.01 0.22 0.25

Yb -0.01 1.46 1.64

Lu -0.01 0.22 0.22

Ag -0.1 0.2 -0.1

As -0.2 2.6 1.6

Be -0.2 1.4 1.2

Bi -0.02 -0.02 -0.02

Cd -0.1 -0.1 -0.1

Cs -0.01 4.79 4.85


SAMPLEID 17/1054 17/1056 ENTITYID Milcarpa 1 Milcarpa 1 ROCKTYPE rhyolite rhyolite Depth_top (m) 256.5 281.68 Depth_bottom (m) 256.79 282.01 Lab LD Veritas Veritas Trace elements ppm ppm

Cu -2 60 26

Ge -0.05 1 1.1

In -0.05 -0.05 -0.05

Mn -1 419 451

Mo -0.2 0.4 0.2

Re -0.01 -0.01 -0.01

S 28 28

Sb -0.1 0.6 0.7

Se -5 -5 -5

Sn -0.2 1.8 2

Te -0.2 -0.2 -0.2

Ti -1 2520 2560

Tl -0.2 -0.2 0.2

Zn -5 55 65


Appendix G Metallogenic and Igneous classifications

Metallogenic and igneous classifications here follow on from that used by Champion and Heinemann (1994), augmented by more recent petrogenetic schemes, including those of Blevin et al. (1996) and Blevin (2004). In addition, given the (controversial) suggestion, e.g. Sajona and Maury (1998) and Sun et al. (2010), that igneous rocks of adakitic composition may be associated with copper and gold mineralisation, we have included geochemical indicators of adakitic composition also (using parameters from Martin et al., 2005). All indicators are used to assist with both classifying the units in question and also with understanding the metallogenic potential of the units. These indicators are further explained below.

Rock type classification (Figure 3.5A): Igneous classification follows Streckeisen (1973); (1976), based on drill core and thin section observation, augmented by the plutonic rock classification of Debon and Le Fort (1983).

Igneous rock type: All igneous units were classified into one of 4 possible classes: I-, S-, or A-type (e.g. Collins et al., 1982; Chappell and White, 1992), or M-type for mafic igneous rocks with less than 52% SiO2 (Le Maitre (1989) suggests 52% SiO2 as the boundary between mafic and intermediate classes and this is adhered to). Igneous units were classified as I- or S-type based on the available petrographic descriptions (e.g. presence of hornblende) and whole-rock geochemistry, using the parameters listed by Chappell and White (1984), and White et al. (1986). A-type units were discriminated from I-type units on the basis of whole rock geochemistry following the guidelines of Collins et al. (1982) and Whalen et al. (1987). Units where the designation is uncertain are designated with a question mark, e.g., ‘S-type?’

Potassium content (Figure 3.5B): Potassium content of igneous rocks can be indicative of both compositional maturity of the igneous unit in question and of the nature of the source protolith, both of which may have implications of metallogeny, e.g., shoshonitic rocks may indicate mantle metasomatism, which has been implicated in copper and gold mineralisation. Previous studies on volcanic rocks, e.g. Peccerillo and Taylor (1976) and Ewart (1979), have utilised K2O-SiO2 plots to distinguish low-, medium- and high-K igneous rocks. Le Maitre (1989) reinforced the use of these terms as qualifiers for standard volcanic nomenclature. This concept has been extended here and applied to all igneous rocks (intrusive and extrusive).

A/CNK: A/CNK (= molecular (Al/(Ca+Na+K)) is a measure of the Aluminium saturation Index of the rock in question, i.e., metaluminous (A/CNK < 1.0) or peraluminous (A/CNK > 1.0). As outlined by Chappell (1999) this measure is useful in identifying igneous type. It also has metallogenic implications, e.g., porphyry copper deposits are not generally related to peraluminous granites. A/CNK is affected by alteration (mobility of alkalis) so care needs to be taken in interpretation.

Redox (Figure 3.5C): Champion and Heinemann (1994), based on work by Ishihara et al. (1979) and Blevin and Chappell (1992), used the Fe2O3/FeO ratio as a measure of the degree of oxidation. As shown by both Ishihara et al. (1979) and Blevin and Chappell (1992), the oxidation state of a magma can play an important role in associated metallogeny, e.g. Cu-Au with strongly oxidised magmas, Sn with reduced to strongly reduced magmas.


Magnetic susceptibility (in SI x 10-5 units): Is a proxy for the current oxidation state of the unit in question, as it is typically a measure of the presence of absence of magnetite, i.e. oxidised magma. Care needs to be taken as it may be indicative of other minerals, e.g. pyrrhotite, or, in the case of strongly oxidised systems with hematite and no magnetite, misleading. Note that the indicative oxidation state as indicated by Fe2O3/FeO and magnetic susceptibility may not be in agreement for other reasons also, commonly reflecting presence of alteration and/or weathering.

Redox-Fractionation: As discussed by Blevin and Chappell (1992), Blevin et al. (1996) and Blevin (2004), the interplay between the oxidation state and the compositional evolution of a magma (e.g. as indicated by fractionation) can play a significant role in associated metallogeny. This largely relates to the behaviour of ore elements such as Cu and Sn in the magma and when such elements are at their greatest concentration. For example, reduced conditions will favour Sn in the divalent state and hence make this element more incompatible, such that Sn contents will increase with increasing fractionation, and will be at maximum levels in reduced-fractionated magmas.

Fractionation (Figure 3.5D): As documented by Blevin and Chappell (1992) and Blevin et al. (1996), compositional evolution of magmas can be an important factor in metallogeny. There are a number of ways of constraining the degree of fractionation (e.g. Champion and Chappell, 1992; Champion and Heinemann, 1994; Blevin, 2004). We have used three ratios, based on relative behaviours of elements of differing compatibility, largely related to feldspars:

1. Rb/Sr: uses the ratio of the mostly incompatible element Rb over the strongly compatible element Sr (largely incorporated in plagioclase). The Rb/Sr ratio increases with increasing fractionation, from values much less than 1.0 to 10 to 100+ (e.g. Champion and Chappell, 1992). Blevin et al. (1996) used this ratio in their redox-fractionation metallogenic plot (e.g. Figure 3.5E).

2. Ba-Rb-Sr: The ternary relationship (Figure 3.5D) utilises the mostly incompatible Rb, the strongly compatible Sr, and the element Ba which with increasing fractionation changes from incompatible to compatible (reflecting K-feldspar and biotite crystallisation). We follow Champion and Heinemann (1994) in using the fields of El Bouseily and El Sokkary (1975).

3. K/Rb: Champion and Chappell (1992) showed that the K/Rb ratio strongly decreases in strongly fractionated felsic igneous rocks, from values around 150-200 and above, down to values <30. In addition, as discussed by Blevin (2004), for example, rocks from continental and island arcs tend to have elevated K/Rb ratios, e.g. around 250-350 and 400-700+, respectively, illustrating that K/Rb can also be utilised, like K content, as an indicator of source protolith, i.e., tectonic regime.

Adakite signature: Recent authors, e.g. Sajona and Maury (1998) and Sun et al. (2010), have suggested that adakitic rocks may be associated with Cu-Au mineralisation. Although this association is controversial and strongly disputed by some, e.g. Richards and Kerrich (2007), it is included in the current metallogenic analysis for completion. As discussed by many authors, e.g. Martin et al. (2005), adakitic rocks have a characteristic signature—elevated Sr, Sr/Y, LREE/HREE, MREE/HREE, low HREE, Y—which is consistent with derivation from mafic protoliths at high pressures leaving a garnet-bearing and plagioclase-free residue (although alternative origins have been proposed). Accordingly, we have utilised a number of indicators:

• (Gd/Yb)N (=primitive mantle (PM)-normalised Gd/PM-normalised Yb): this variable provides an indication of the fractionation of the heavy rare earth elements (HREE). This value will be elevated for rocks with an adakitic heritage, but generally low (~1-2 for non-adakitic rocks).


• Sr/Y: this ratio can be used a direct measure of the elevated Sr, low Y (& HREE) nature of adakitic rocks, which have Sr/Y values of 20–25 and greater. Unfortunately, this is non-unique and rocks derived from adakitic protoliths can also inherit similar ratios.

• Eu/Eu* (= Eu/ square root (Sm + Gd)): this ratio measures the mismatch between the actual Eu contents of the unit and what the Eu contents would have been if present at the same levels (normalised to chondrite) as the rare earth elements of slightly smaller and higher atomic numbers (e.g., Sm, Gd). Unlike other rare earth elements, Eu is commonly present in the divalent form in most magmatic systems and behaves compatibly (commonly substituting into plagioclase). As such the Eu/Eu* is a direct measure of whether or not plagioclase has played a significant role in the genesis of an igneous unit. Adakitic rocks typically have values of 1 (or greater). Eu/Eu* can also be used as an indicator of fractionation as this ratio can decrease to low levels (<0.1) in very strongly fractionated rocks.

• Na2O/K2O: adakitic rocks are typically characterised by low K2O contents (Low-K to medium-K) with elevated Na2O/K2O ratios greater than, often much greater than, 1.0.

It is noted that many of these parameters can be directly affected by alteration as well as weathering so care needs to be taken with their use. Importantly, the presence of alteration may be indicated by variable results using the above parameters, for example, the combination of high-K coupled with high Na2O/K2O, is unusual and immediately raises suspicions of alteration.


Appendix H Borehole log

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Milcarpa 1

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Lithology Stratigraphy

Longitude / easting: 144.448757° / 251638 mLatitude / northing: -29.072255° / 6781321 mDatum: GDA94 / MGA94Z55S

Location: 9 km SSE of Hungerford, QueenslandOperator: Geoscience Australia for the Geological Survey of New South Wales

Date completed: 12.07.2017Borehole orientation: VerticalAHD elevation (AUSGeoid2020): 102 m

Arenite

Clay

Clayey sand

Clayey sandstone

Claystone, carbonaceous

Hardpan

Mudstone

Rhyodacite

Sand

Sandstone

Sandy claystone

Sandy silt

Sandy siltstone

Saprolite

Silty sandstone

Silty shale

Lithology Stratigraphy

Qs - Quaternary sand

Kw - Winton Formation

Klu - Wallumbilla Formation

Klws - Wyandra Sandstone Member

Kco - Cadna-owie Formation

Bas - Basement

Cz - Cenozoic alluvium

Cement

Casing

Open hole

Construction

Sur

face

wea

ther

ing

Pal

aeow

eath

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