Stavely Project – Regional 3D Geological Model R.A. Cayley, M.A. McLean, P.B. Skladzien & C.P. Cairns Stavely Project Report 3 Authorised by the Director, Geological Survey of Victoria Department of Economic Development, Jobs, Transport and Resources 1 Spring Street Melbourne Victoria 3000 Telephone (03) 9651 9999 © Copyright State of Victoria, 2018. Department of Economic Development, Jobs, Transport and Resources 2018 Except for any logos, emblems, trademarks, artwork and photography this this work is made available under the terms of the Creative Commons Attribution 4.0 Australia licence. To view a copy of this licence, visit creativecommons.org/licenses/by/4.0/. It is a condition of this Creative Commons Attribution 4.0 Licence that you must give credit to the original author who is the State of Victoria. Bibliographic reference: Cayley, R.A., McLean M.A., Skladzien P.B & Cairns C.P., 2018. Stavely Project – Regional 3D Geological Model. Stavely Project Report 3. Geological Survey of Victoria. Department of Economic Development, Jobs, Transport and Resources. ISSN 2207-8681 – Online (pdf / word) ISBN 978-1-925734-18-8 (pdf/online/MS word) GSV Catalogue Record #154990 Keywords: 3D geological modelling, potential field, gravity, magnetic, Stavely Project, Stavely Arc, Grampians Group, Cambrian, porphyry, volcanic massive hosted sulphide, mineral exploration, copper, Victoria. Acknowledgements: The development of the STAVELY 3D model has significantly benefited from the data and findings from the Southern Delamerian deep seismic reflection survey in 2009, a collaboration between the Geological Survey of Victoria, Geoscience Australia, AuScope Limited and the Department of Primary Industries and Regions (South Australia), and pre-competitive stratigraphic drilling undertaken as part of the Stavely Project, a collaboration between the Geological Survey of Victoria and Geoscience Australia. The skills, knowledge and expertise brought by individuals to these projects was fundamental in their successful delivery. Chris Osborne constructed the Rocklands Volcanic Group surface and refined the Newer Volcanic Group surface. James Goodwin (Geoscience Australia) completed early fault analysis and delineation and commenced modelling of the Grampians Group. Sarlae McAlpine (Geoscience Australia) identified, reviewed and compiled Newer Volcanic Group intersections from historical drill holes. David Taylor participated in technical discussions regarding the location and timing of faults and their influence on the regional geology. Lauren Wolfram, Ken Sherry and Taylor Ogden assisted in drafting figures. Stewart Govett assisted in preparation of the geological cross sections for publication. Navarre Minerals Ltd provided airborne magnetic data for modelling of the volcanic belts in the Black Range. Cover photo: Ross Cayley taking portable XRF measurement of botryoidal and vuggy silica alteration in Buckeran Diorite at the Lexington prospect, merged with image taken from the STAVELY 3D model (Phil Skladzien, Geological Survey of Victoria). Disclaimer: This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. The Victorian Government, authors and presenters do not accept any liability to any person for the information (or the use of the information) which is provided or referred to in the report. For more information about earth resources in Victoria visit the website at www.earthresources.vic.gov.au. Contents Executive summary ................................................................................................................................. xi Key findings for mineral exploration and targeting .................................................................................................................... xii 1. Introduction ............................................................................................................................................ 1 1.1 Background .......................................................................................................................................................................................................... 1 1.2 Geological context ......................................................................................................................................................................................... 5 1.3 Aims ......................................................................................................................................................................................................................... 6 1.4 Scientific and economic justification .............................................................................................................................................. 6 1.5 Philosophy ........................................................................................................................................................................................................... 9 2. Modelling methodology ................................................................................................................... 10 2.1 Geological rationale................................................................................................................................................................................... 10 2.2 Model extent .................................................................................................................................................................................................... 10 2.3 Software ............................................................................................................................................................................................................... 11 2.4 Inputs and constraints ............................................................................................................................................................................... 11 2.4.1 Regional geological mapping and drilling .................................................................................................................... 13 2.4.2 Potential field data, processing and enhancement............................................................................................... 13 2.4.2.1 Magnetic data ................................................................................................................................................................................ 13 2.4.2.2 Gravity data ..................................................................................................................................................................................... 13 2.4.2.3 Data processing ........................................................................................................................................................................ 13 2.4.2.4 Image enhancement ............................................................................................................................................................. 20 2.4.3 Key sites of constraint ................................................................................................................................................................ 20 2.4.4 Rock properties ................................................................................................................................................................................ 31 2.4.5 Regional 2D seismic lines ......................................................................................................................................................... 32 2.4.6 Existing 3D models ..................................................................................................................................................................... 35 2.5 Modelling workflow ..................................................................................................................................................................................... 37 2.5.1 Modelling workflow summary................................................................................................................................................ 39 2.6 Interpretation methodology................................................................................................................................................................. 39 2.6.1 Fault timing ......................................................................................................................................................................................... 41 2.6.2 Fault shape and orientation ................................................................................................................................................... 41 2.6.3 Blind faults ......................................................................................................................................................................................... 44 2.6.4 Interpretation of geophysical data .................................................................................................................................. 44 2.6.4.1 Interpretation of fault network .................................................................................................................................