QUEENSLAND GEOLOGICAL RECORD 2008/04 Diamonds, diamond indicator minerals and a review of exploration for diamonds in Queensland L C Cranfield & G Diprose Queensland the Smart State ADDRESS FOR CORRESPONDENCE: Geological Survey of Queensland Department of Mines and Energy Block A, 80 Meiers Road, Indooroopilly, QLD 4068 Telephone: (07) 3362 9364; International +61 7 3362 9364 Facsimile: (07) 3362 9343; International +61 7 3362 9343 Internet: www.dme.qld.gov.au © The State of Queensland, Department of Mines and Energy 2008 ISSN 1039-5547 ISBN 978-1-921489-33-4 Graphics: G. Nuttall Issued: October, 2008 REFERENCE: CRANFIELD, L.C. & DIPROSE, G., 2008: Diamonds, diamond indicator minerals and a review of exploration for diamonds in Queensland. Queensland Geological Record 2008/04. i CONTENTS SUMMARY....................................................................... 1 INTRODUCTION .................................................................. 2 PROPERTIES AND USES OF DIAMONDS............................................. 3 ORIGIN OF DIAMOND............................................................. 5 AGE OF DIAMONDS............................................................ 5 CARBON SOURCES ............................................................ 6 CARBON ISOTOPIC COMPOSITION OF DIAMONDS ................................6 DIAMOND OCCURRENCES AND EXPLORATION TECHNIQUES .......................11 HISTORICAL DIAMOND MINING IN AUSTRALIA....................................14 NEW SOUTH WALES .......................................................... 14 VICTORIA ................................................................... 14 TASMANIA .................................................................. 15 SOUTH AUSTRALIA........................................................... 15 WESTERN AUSTRALIA ........................................................ 15 NORTHERN TERRITORY ...................................................... 16 QUEENSLAND................................................................ 16 DISTRIBUTION OF DIAMONDS AND INDICATOR MINERALS IN QUEENSLAND ........17 EXPLORATION FOR DIAMONDS IN QUEENSLAND 1960–2008 ........................28 NORTH-WEST QUEENSLAND .................................................. 28 COEN AREA.................................................................. 41 LAURA AREA ................................................................ 44 PALMER RIVER AREA......................................................... 45 COOKTOWN AREA ........................................................... 47 ATHERTON TABLELAND ...................................................... 51 CROYDON AREA ............................................................. 56 GEORGETOWN AREA ......................................................... 59 MOUNT SURPRISE AREA ...................................................... 60 GREENVALE AREA ........................................................... 65 RICHMOND–HUGHENDEN AREA ............................................... 67 WINTON AREA .............................................................. 67 BOULIA AREA................................................................ 68 BEDOURIE AREA ............................................................. 68 DIRRANBANDI AREA ......................................................... 68 ROLLESTON AREA ........................................................... 70 MOUNT COOLON AREA ....................................................... 70 CLERMONT AREA ............................................................ 71 ANAKIE AREA ............................................................... 72 PROSTON AREA .............................................................. 72 PITTSWORTH AREA .......................................................... 74 STANTHORPE AREA .......................................................... 75 CONCLUSIONS .................................................................. 75 ACKNOWLEDGEMENTS.......................................................... 75 BIBLIOGRAPHY ................................................................. 76 TABLE 1. World wide occurrences of diamond-bearing host rocks with known age dates ............7 FIGURE 1. Garnet compositions in diamond occurrences by origin ..............................6 2. Carbon isotopic composition in diamondiferous rocks ...............................8 3. Subduction origin for diamonds ................................................ 9 4. Schematic cross-section of a kimberlite pipe .....................................10 5. The 57 open file mineral exploration permits EPMs) that contain diamond exploration ....18 6. The number of microdiamonds found at each location ..............................19 7. The location of diamond indicator minerals found in Queensland .....................20 8. The number of chromite grains found at each location ..............................21 9. The number of pyrope grains found at each location................................22 10. The number of garnet grains found at each location ................................23 ii 11. The number of picro ilmenite grains found at each location ..........................24 12. The number of chrome diopside grains found at each location ........................25 13. Niobium (Nb) concentrations in ppm............................................26 14. The location of grains that underwent microprobe analysis...........................27 Queensland Geological Record 2008/04 1 SUMMARY Exploration for diamonds in Queensland has continued to be influenced by the South African approach, modified by the discovery of diamonds in lamproite in Western Australia. This approach is to explore for kimberlite and lamproite bodies using indicator minerals that are dispersed from these rocks by fluvial and colluvial processes. Exploration for diamonds in Australia has increased since the discovery and exploitation of the Argyle Mine in Western Australia. The New South Wales Geological Survey has produced a digital data product on the prospects for diamond exploration in that State as have the Northern Territory Geological Survey (as a grouping of Microsoft Excel spreadsheets with data on diamond indicator minerals) and the Geological Branch of PIRSA in South Australia. As part of the Smart Mining Initiative (2006–2010), the Geological Survey of Queensland has compiled a database of micro-diamonds and diamond indicator minerals from open file company data in the Department of Mines and Energy’s QDEX system. Much of the exploration for diamonds in Queensland has been patchy and has proceeded along with exploration for other commodities. There has been no commercial exploitation of diamonds in Queensland and only rare occurrences of microdiamonds have been reported. This report also outlines the properties of diamonds and geological models for their formation. There appears to be a regional difference in diamond occurrences in Queensland, with the kimberlite and lamproite models favoured for the north-western regions of the State and the subduction (S-type model) favoured for the eastern coastal and sub-coastal zones, linked to Cainozoic alkalic basalt volcanism. Sapphire is commonly associated with diamonds in these areas. Studies in New South Wales indicate that diamonds do occur in economic quantities in alkali basaltic intrusions and further exploration in Queensland is warranted on diamond indicator minerals and their composition. The main occurrences of microdiamonds have been in the Mount Isa region, where they have been reported from stream sediment samples. Microdiamonds have been found in the Stanthorpe, Proston, Herberton and Lakeland Downs areas of eastern Queensland. Keywords: Diamonds, diamonds indicator minerals, diamond indicator mineral spreadsheets, macrodiamonds. microdiamonds, diamond exploration, exploration techniques, properties and uses of diamonds, origin of diamonds, age of diamonds, potassic-ultramafic, kimberlite, serpentine,xenoliths, lherzolite, picroilmenite, titanium- and magnesium-rich chromite, chrome diopside, magnesium-rich olivine, pyrope and eclogitic garnets, mineral geochemistry, niobium, phosphorous, nickel, chromium, peridotite, P-type, eclogite, E-type, lamproite , carbon isotopes, light rare earth elements, Archaen, Tertiary, basalt, subduction, aeromagnetic surveys, ground magnetic surveys, diamond mining, air photo interpretation, electromagnetic surveys, northwest Queensland, Coen, Laura, Palmer River, Cooktown, Atherton tableland, Croydon, Georgetown, Mount Surprise, Greenvale, Richmond-Hughenden, Winton, Boulia, Bedourie, 2 Cranfield & Diprose Dirranbandi, Rolleston, Mount Coolon, Clermont, Anakie, Proston, Brigooda, Pittsworth, Stanthorpe, Queensland. INTRODUCTION Based on the popularity of the Northern Territory’s Diamond Mineral Indicator database, a similar database was constructed for Queensland. This Diamond Indicator Mineral and Geochemistry database was created to provide an overview of where diamonds and diamond indicator minerals have been found throughout Queensland. Data was extracted by the Geological Survey of Queensland from company reports held in the Departmental QDEX system, which includes reports mentioning diamond exploration as far back as 1968. The data from these reports was extracted and entered in the diamond database. Of the 220 company reports initially extracted from QDEX, some did not contain information on diamond exploration but were selected by the query used due to mentions of ‘diamond’ in