REPORT GEOCHEMISTRY OF VOLCANIC ROCKS 104 OF THE NORTHERN PILBARA CRATON WESTERN AUSTRALIA by R. H. Smithies, D. C. Champion, M. J. Van Kranendonk and A. H. Hickman Keep 3 mm border around photo. Resize white box as required. GEOLOGICAL SURVEY OF WESTERN AUSTRALIA REPORT 104 GEOCHEMISTRY OF VOLCANIC ROCKS OF THE NORTHERN PILBARA CRATON by R. H. Smithies, D. C. Champion1, M. J. Van Kranendonk, and A. H. Hickman 1 Geoscience Australia, GPO Box 378, Canberra, ACT 2601 Perth 2007 MINISTER FOR ENERGY; RESOURCES; INDUSTRY AND ENTERPRISE Hon. Francis Logan MLA DIRECTOR GENERAL, DEPARTMENT OF INDUSTRY AND RESOURCES Jim Limerick EXECUTIVE DIRECTOR, GEOLOGICAL SURVEY OF WESTERN AUSTRALIA Tim Griffi n REFERENCE The recommended reference for this publication is: SMITHIES, R. H., CHAMPION, D. C., VAN KRANENDONK, M. J., and HICKMAN, A. H., 2007, Geochemistry of volcanic rocks of the northern Pilbara Craton, Western Australia: Western Australia Geological Survey, Report 104, 47p. National Library of Australia Cataloguing-in-publication entry (Geochemistry of volcanic rocks of the northern Pilbara Craton, Western Australia) Bibliography. ISBN 978-1-74168-122-2 (web) 1. Geochemistry — Western Australia — Pilbara 2. Volcanic ash, tuff, etc. — Western Australia — Pilbara 3. Rocks, Igneous — Analysis I. Smithies, Robert Hugh, 1962– II. (Title. (Series: Report (Geological Survey of Western Australia); 104). 552.06 ISSN 0508–4741 Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the text are referenced using Map Grid Australia (MGA) coordinates, Zones 50 and 51. All locations are quoted to at least the nearest 100 m. Copy editor: J. F. Johnston Cartography: A. Blake, S. Dowsett Desktop publishing: K. S. Noonan Published 2007 by Geological Survey of Western Australia This Report is published in digital format (PDF), and is available online at www.doir.wa.gov.au/GSWA/publications. Laser-printed copies can be ordered from the Information Centre for the cost of printing and binding. Further details of geological publications and maps produced by the Geological Survey of Western Australia are available from: Information Centre Department of Industry and Resources 100 Plain Street EAST PERTH, WESTERN AUSTRALIA 6004 Telephone: +61 8 9222 3459 Facsimile: +61 8 9222 3444 www.doir.wa.gov.au/GSWA/publications Cover photograph: Mafi c globules within a basalt at the transition zone between the tholeiitic basalts and the F1 series, Coonterunah Subgroup, Warrawoona Group. Specimen is from a locality about 6.8 km south-southwest of Table Top Well (MGA Zone 50 711949E 7663602N) Contents Abstract ..................................................................................................................................................................1 Introduction ............................................................................................................................................................1 Nomenclature and terminology .......................................................................................................................4 Analytical details .............................................................................................................................................4 Regional geology ...................................................................................................................................................5 East Pilbara Terrane ........................................................................................................................................5 West Pilbara Superterrane ...............................................................................................................................5 De Grey Superbasin ........................................................................................................................................7 East Pilbara Terrane and the De Grey Superbasin in the east Pilbara ....................................................................7 Traverse geology .............................................................................................................................................7 Warrawoona Group ..................................................................................................................................7 Coonterunah Subgroup .....................................................................................................................7 North Star Basalt ...............................................................................................................................8 Mount Ada Basalt .............................................................................................................................8 Duffer Formation ..............................................................................................................................9 Apex Basalt .......................................................................................................................................9 Panorama Formation .........................................................................................................................9 Kelly Group ..............................................................................................................................................9 Euro Basalt ........................................................................................................................................9 Sulphur Springs Group ..........................................................................................................................10 Soanesville Group ..................................................................................................................................10 De Grey Supergroup ..............................................................................................................................10 Bookingarra Formation ...................................................................................................................10 Units of unknown stratigraphic position ................................................................................................10 Pilbara Well greenstone belt ...........................................................................................................10 Wodgina greenstone belt .................................................................................................................10 Geochemistry ................................................................................................................................................11 Komatiites and komatiitic basalts ..........................................................................................................11 Basaltic rocks .........................................................................................................................................11 Warrawoona Group .........................................................................................................................11 Kelly Group ....................................................................................................................................13 Sulphur Springs Group ...................................................................................................................15 Soanesville Group ...........................................................................................................................16 Croydon Group ...............................................................................................................................16 Samples of unknown stratigraphic position ....................................................................................16 Secular compositional trends ..........................................................................................................16 Possible tectonic settings inferred from the geochemistry of the basaltic rocks ............................16 Use of geochemistry as an indication of stratigraphic affi nity .......................................................18 Felsic volcanic rocks and felsic series ...................................................................................................18 Secular compositional trends ..........................................................................................................22 Use of geochemistry as an indication of stratigraphic affi nity .......................................................22 West Pilbara Superterrane and the De Grey Superbasin in the west Pilbara .......................................................22 Roebourne Group — Ruth Well Formation ..................................................................................................22 Geochemistry .........................................................................................................................................22 Whundo Group ..............................................................................................................................................22 Geochemical stratigraphy ......................................................................................................................23 Geochemistry .........................................................................................................................................24 Boninite-like rocks ..........................................................................................................................24