The South Australian Approach to Exploration Under Cover

Transcription

1 The South Australian Approach to Exploration Under Cover Dr Tim Baker Director, Geological Survey of South Australia, PIRSA, Adelaide 5001, South Australia, Australia

2 The South Australian Approach to Betts et al (2009) Exploration Under Cover The Challenge & Advantage of Cover in South Australia The Success & Limitations of a Geophysical Approach Understanding the Mineral Systems A Holistic Approach New Technologies for Regional Alteration & Geochemical Footprints Deep Exploration Technologies Cooperative Research Centre Technology Push & Market Pull

3 The Challenge & Advantage of Cover in South Australia Moon Plain, Stuart Shelf, SA Courtesy of Steve Hill

4 Betts et al (2009) The Challenge & Advantage of Cover in Australia

5 The Challenge & Advantage of Cover in South Australia Betts et al (2009) 0 km -4 km

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7 South Australia A Decade of Cu Success Source: MinEx Consulting Feb 2010 Olympic Dam (1976) Prominent Hill (2001) Carrapateena (2006) Hillside (2009) Deposit Style Year Age (Ma) Depth (m) Size (Mt) Cu (%) Au (g/t) U (ppm) Olympic Dam Gawler Prominent Hill Gawler Carrapeteena Gawler Hillside Gawler IOCG Breccia IOCG Breccia IOCG Breccia IOCG Skarn ?

8 South Australia A Decade of Cu Success South Australia hosts the 3 most significant new Cu discoveries in past 10 yrs in Australia (GA, 2010) Carrapateena, Prominent Hill and Hillside. Olympic Dam has increased by a massive 48 Mt of contained Cu in this time More than the aggregate of all significant Australian Cu discoveries. South Australia attracted largest share of Cu exploration in Australia in FY ($101m) Queensland ($96m) & Western Australia ($78m) Cu is the commodity most explored for within South Australia 40% of the state s exploration expenditure in FY South Australia anticipates producing around one third of Australia s forecast t of the total t of copper in Australia in

9 The Success of a Geophysical Approach: Betts et al (2009) Olympic Dam, 1975, WMC

10 Olympic Dam Geophysics Total Magnetic Intensity

11 Olympic Dam Geophysics Bouger Gravity

12 Keys to OD Success (Haynes, 2006) New conceptual model Multi-disciplinary team High level support Recent (at the time) regional pre-competitive geoscience data (BMR gravity & magnetics) To test model needed to go at least 50m into basement Perseverance encouragement in first hole % Cu over 10 s metres; subsequent holes disappointing until RD10: 2.12% Cu, 12 months after program began

13 IOCG Geological Models IOCG deposits: structurally controlled hem-mag-copper sulfide systems Mixing of deep volatile-rich magmatic fluids with basinal/metamorphic brines IOCG deposits formed 100 to 200 my after supercontinent assembly & metasomatized early Precambrian subcontinental lithospheric mantle (SCLM) Common subalkaline to alkaline mafic-felsic A-type magmatism Commonly contain evaporite & mafic rocks in host sequences Associated with large scale alkali metasomatism Alteration broadly zoned; varies with depth of emplacement Shallow hematite-sericite-chlorite; deeper magnetite-feldspar-calcsilicate

14 IOCG Exploration Criteria: Geophysical Enhanced density hematite +/- magnetite +/- sulphide Enhanced magnetic susceptibility magnetite +/- pyrrhotite Increased chargeability & conductivity within well-connected sulfide systems Higher heat flows/thermal conductivities with U enrichment

15 Carrapeteena Geophysics Bouger Gravity & TMI

16 Carrapateena: A PACE Funded Discovery CAR002: % Cu, 0.64g/t Au me me me me mn CAR mn CAR015 CAR014 CAR001 CAR013 CAR009 CAR020 CAR021 CAR007 CAR008 CAR mn CAR016 CAR004 CAR018 CAR002 CAR005 CAR012 CAR017 CAR003 CAR mn CAR022 CAR024 CAR025 CAR CAR027 CAR mn metres CAR029 CAR030

17 Carrapateena: A PACE Funded Discovery

18 IOCG Prospectivity Eastern Gawler Province Residual Gravity Residual RTP TMI Coincident anomalies Anomaly contours

19 IOCG Prospectivity Eastern Gawler Province Residual Gravity Residual RTP TMI Coincident anomalies Anomaly contours

20 IOCG Prospectivity Eastern Gawler Province Residual Gravity Residual RTP TMI Coincident anomalies Anomaly contours

21 Prospectivity Eastern Gawler Province Residual Gravity Residual RTP TMI Coincident anomalies Anomaly contours Regional 3D Inversions Acknowledgement: Nick Williams & Geoscience Australia (geophysical inversion mesh)

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23 Betts et al (2009) The Success & Limitations of a Geophysical Approach But a lot of coincident anomalies.. Can we be either smarter with our models & data Or improve our drilling technology Or do both.

24 Deep Exploration Technologies Cooperative Research Centre Three main programs 1. Drilling Technologies 2. Data Fusion Technologies 3. Deep Targeting Technologies

25 New Technologies for Regional Alteration & Geochemical Footprints Existing Open File Holes Existing regional holes Hylogger technology for alteration systems Basement & cover sequence geochemistry DET CRC technology development

26 IOCG Geological Models

27 Fe oxide-cu-au Hematite-Sericite Breccia Deposit Carrapeteena Olympic Dam Prominent Hill Vulcan

28 Sodic-Calcic, Kspar-Bt, & Magnetite Veins & Skarns 1586±11Ma

29 HILLSIDE COVER GEOCHEMICAL PROFILE Reduced/Oxidised clays & sands Regolith Carbonates Basal Gravels Barren aeolian sands Weathered Granite Supergene Cu zone Joints / Faults Gossans Primary Ironstone Ferricrete

30 Understanding the regional mineralogy and chemistry PIRSA Glenside Core Library CSIRO HyLogger TM

31 New Thermal Infrared Increased Range of Minerals VIS-SWIR Spectrometer clays, carbonates, oxides, micas etc. TIR - Tectosilicates quartz, feldspar, garnet, pyroxenes Carbonates more reliable Compatible with high temperature alteration systems Requires significant validation work

32 HyLogger Data

33 New identify tool to access multiple datasets within query area Identify results Drillhole data Geophysical data Mines and deposits Previous exploration Digital geological maps Identify

34 Download analysis summary Select to see high resolution image New Hylogger details screen with core images and analysis summary

35 High resolution Hylogger imagery

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37 Initial Results Spectral logs to aid vectors to mineralisation Combined Fe alteration minerals as a vector The sum of: Siderite Phengite Fe-Chlorite Fe3+ Goethite Alan Mauger (NVCL project)

38 Stuart Shelf Targeting Cover Sequence Footprint Historic assay & new Niton geochemistry & relogging historic holes identified: Hematitic clasts with IOCG-like signature in basal pebble conglomerates Possible dispersion halo of ~10km around Carrapeteena Additional anomalies found at base of Mesoproterozoic Carriewerloo Basin & Neoproterozoic Stuart Shelf Basement-cover sequence targeting with hand held XRF cheaper more rapid first pass prospecting

39 Stuart Shelf Targeting Cover Sequence Footprint NW 5km SE Carrapeteena Historic Cu assays capped 500ppm Niton IOCG signature

40 Deep Exploration Technologies Cooperative Research Centre Greenfields Coiled Tubing Drill Rig for MinEx & Regional Drilling Market Pull

41 Challenge: Coil Tubing Rig But Smaller and Faster for Greenfields MinEx

42 Small, Greenfields Coil Tube Rig Positives No rod handling (reduce exploration LTIs 50%) Fast easy set up (reduced environmental impact) Data and power possible (tube for comms) Steel tube may last 136 trips More stable holes in unconsolidated materials High speed drilling possible Problems Down hole motors have low RPM = low penetration rate for diamond composite. No coring tool available. Needs integrated technologies to change game

43 Indicative Costs for CT Drilling Item Ave Cost for 300m hole Tube ($40 metre) 6 trips per hole (136 trip life) $500 Rig cost ($2M over 1,000 days) $2,000 Mud, water & fuel $2,000 Mobilisation $2,000 Transport of rig $2,000 Bits and down hole motor ($30K for a motor) $1,000 Labour (2 men) $3,000 Contingency $2,500 Target: One 300m $50/metre $15,000/hole with improved OH&S, environmental impact and hole stability

44 PACE Type Contract to drill X,000m on grid through cover for basement and/or unconformity sample at $50/m Existing Holes Commercialisation (Suppliers) Program 1 CT Rig capable of drilling through cover at $50/metre and sampling basement and/or unconformity Market Pull (Mining Companies) R&D Providers Mining Companies DISCO- VERY Suppliers Technology Push (R&D Providers) Program 3 Dispersion &/or alteration vector that increases halo to 5km x 5km

45 PACE Type Contract to drill 130,000m on 10km x 10km grid through cover for basement and unconformity sample at $50/m: $6.5M PACE Type Contract to drill 520,000m on 5km x 5km grid through cover for basement and unconformity sample at $50/m: $26M Combined with 5km x 5km vectoring (lab-on-the-rig) technologies, potential for large IOCG-type system to be discovered Aim to produce regional top of basement and unconformity geochemical, alteration & geological map

46 The South Australian Approach to Betts et al (2009) Exploration Under Cover The Challenge & Advantage of Cover in South Australia The Success & Limitations of a Geophysical Approach Understanding the Mineral Systems A Holistic Approach New Technologies for Regional Alteration & Geochemical Footprints Deep Exploration Technologies Cooperative Research Centre Technology Push & Market Pull