AusGEO news No.68 - coral 12/20/02 5:36 PM Page 1 DECEMBER 2002 ISSUE No. 68 AUSGEOnews CORAL REEFS & hydrocarbon seeps Mineral provinces the geological evidence Geophysical tools for little Aussie digger PP 255003/00048 Also: Australian islands double in size, map maker honoured, demand up for spatial data AusGEO news No.68 - coral 12/20/02 5:36 PM Page 2 AUSGEO News December 2002 Issue no. 68 CONTENTS Editor Julie Wissmann Comment 3 Graphic Designer Karin Weiss Coral reefs and hydrocarbon seeps 4 This publication is issued free of charge. It is published six times a year Huge dust storm tracked in satellite images 8 by Geoscience Australia. The views expressed in AusGeo New isotope equipment proves News are not necessarily those of a gas for coal 9 Geoscience Australia, or the editor, and should not be quoted as such. Every Geochemical capabilities expanded 9 care is taken to reproduce articles as accurately as possible, but Geoscience Volcano doubles size of Australian islands 10 Australia accepts no responsibility for errors, omissions or inaccuracies. Field day for policy makers 11 © Commonwealth of Australia 2002 Events calendar 11 ISSN 1035-9338 Little Aussie digger makes waves Printed in Canberra by in the desert 12 National Capital Printing Map maker acknowledged for Geoscience Australia public service 14 GPO Box 378 Canberra ACT 2601 Australia cnr Jerrabomberra Ave & Hindmarsh Dr Symonston ACT 2609 Australia MINERAL SPECIAL… Internet: www.ga.gov.au In-depth study of mineral provinces evolution 16 Chief Executive Officer Dr Neil Williams Geoscience an asset to natural resource management 23 Subscriptions Mineral exports a near record, but 2nd Dave Harris for exploration 24 Phone +61 2 6249 9333 Fax +61 2 6249 9982 Major structures for gold in seismic E-mail [email protected] images of crust 26 Sales Centre National maps update 29 Dave Harris Phone +61 2 6249 9519 Fax +61 2 6249 9982 E-mail [email protected] Product news 29 GPO Box 378 Canberra ACT 2601 Australia Editorial enquiries An opal-hearted country that hides untold mineral wealth. Julie Wissmann Australia’s geology hosts much of the world’s lead, zinc Phone +61 2 6249 9249 and silver resources, and enormous deposits of gold, Fax +61 2 6249 9926 copper and uranium. What factors caused such riches? E-mail [email protected] Geoscience Australia comes up with some interesting findings in its search to understand the geological evolution of Australia and provide high-quality pre- AusGeo News is available competitive geoscientific information that attracts mineral on the web at www.ga.gov.au/ exploration Down Under. See pages 16–28. about/corporate/ausgeo_news.jsp Photo: Arthur Mostead AusGEO news No.68 - coral 12/20/02 5:36 PM Page 3 Australian mineral exploration is at its lowest level of expenditure in 20 years and Australia has lost its place as the world’s leading country for mineral exploration to Canada, despite continuing discoveries across the continent. The concern is whether the level of investment in mineral exploration in Australia is adequate to sustain the industry into the future. Gold is Australia’s major metal commodity export. If under investment in gold exploration continues, coupled with the very high rates of gold production, the resource could be depleted. The Commonwealth Government has taken action to address the issues and problems associated with current levels of exploration in Australia. Minister for Industry, Tourism and Resources, the Honourable Ian Macfarlane recently announced two initiatives: the House of Representatives Industry and Resources Committee Inquiry into ‘Resources exploration impediments’ and the Minerals Exploration Action Agenda. Already, the House of Representatives inquiry has attracted a considerable number of submissions. And the first meeting of the Strategic Leaders Group was held in November, under the leadership of the Minerals Action Agenda Chair, Mr Peter Lalor. High-quality pre-competitive geoscientific information is crucial to maintaining Australia’s competitive position in attracting mineral exploration investment and providing a basis for new resource discovery. Inside this issue of AusGeo News are some results of work by Geoscience Australia to support mineral discovery. Most of this work is done in collaboration with state and territory geological surveys, under the National Geoscience Agreement. Also in this issue is an article about the impact of the Commonwealth Government’s Spatial Data Access and Pricing policy, introduced in September 2001. This policy benefits the mineral resources industry, particularly junior explorers and consultants, by making data critical to project generation available at a very low cost or free via the web. There has been a big increase in the uptake and use of Geoscience Australia’s information and databases, especially airborne geophysical data, since the policy was introduced. Comment NEIL WILLIAMS CEO Geoscience Australia AusGEO News 68 December 2002 3 AusGEO news No.68 - coral 12/20/02 5:36 PM Page 4 CORAL REEFS &hydrocarbon seeps Some say oil and water don’t mix, yet on Australia’s North West Shelf they have an old and remarkable association, which led to the development of reefs and other coralline communities along Australia’s western and northern coast. Geoscience Australia sedimentologist, Kriton Glenn outlines what has been happening. 4 December 2002 AUSGEO News 68 AusGEO news No.68 - coral 12/20/02 5:36 PM Page 5 M Figure 1. Map showing the location of Ashmore Reef and the Indonesian Through Flow M Figures 2 a–c. A three-stage model illustrates how the geology is breached (a), hydrocarbons escape and corals colonise the hardened build-ups around the lip of the seep (b), and the reef builders keep up with rises in sea level (c). Sea level Sea-floor HydrocarbonHydrocarboydrocarb coc lumn bout 5.7 million years ago, the Australian plate collided with the Eurasian plate. The collision furthered the formation of the Timor ResidualR A Trough and focused the flow of a huge volume of hot, low column salinity water from the western Pacific Ocean through the Indonesian archipelago, and southwards to mix with the Indian Ocean (figure 1). As the plates collided, cracks formed in the crust and hydrocarbons seeped to the surface. Whenever sea levels are low, such as the last glacial maximum about 18 000 years ago, water is stored as ice at the Oil slicks poles and Australia’s north-west continental shelf is exposed. In these periods, the hydrocarbons seep onto the exposed land and gases are vented directly into the atmosphere. When sea levels are high, such as the present day, ocean covers the seeps and water pressure restricts the hydrocarbon flow. The thermocline traps some hydrocarbon, but a significant amount rises through the water column where it is digested by bacteria. The rest surfaces as gas or an oil Oil slick, which generally evaporates fairly quickly. Gas As the bacteria and other benthic organisms that are digesting the hydrocarbons die, their skeletal remains and sediments slowly form a solid mound around the seep. Coral spawn colonise this hard surface, rather than the adjacent loose sand and sediments (figure 2). The reef builders establish their robust architecture on the hard surfaces and keep up with sea level rise. Biological input There is no other place on Earth where a huge volume of tropical water banks up and flows from one ocean to another at more than 10 million cubic metres a second. It is called the Indonesian Through Flow, and it helps warm the Indian Ocean. It is a conduit for genetic material to Australia’s western coast. Although Ashmore Reef is in the Indian Ocean, it is surrounded by very warm Pacific Ocean water. The water’s salinity is diluted by heavy rainfall near the Equator before it flows south. Sometimes the water temperature is greater than 30 degrees Celsius, and this makes reef growth quite remarkable because most corals die out when water is 28–29 degrees Celsius. The water is rich with marine life including coral and fish spawn. Ashmore Reef is a marine protected area because of its rich biodiversity and range of endemic species. It is a stopping point for many migratory animals including birds and turtles, and is a critical habitat for dugong and other marine life. The area also has the highest population density of sea snakes in the world. Genetic components from both oceans and Ashmore Reef seed many reefs and other habitats along Australia’s western shores, some as far south as Perth. AusGEO News 68 December 2002 5 AusGEO news No.68 - coral 12/20/02 5:36 PM Page 6 M Figure 3. Coral terraces on the eastern side of Ashmore Reef. The youngest terraces are in red and the oldest are shown in bright green. The present-day reef is dark green. Image supplied by the Royal Australian Navy Hydrographic Office . Coral terraces Sea level has not risen steadily over time. It has been going up and down in stages, and the reef builders of Ashmore have kept pace, recording the changes in their architecture. When sea level is rising, corals grow upwards. When sea level is stable, corals grow outwards. As sea level falls, reefs die leaving cliffs of limestone. When sea level rises again, marine life re-inherits the limestone. Royal Australian Navy hydrographic vessels recently swath mapped the ocean floor near the eastern side of Ashmore Reef and passed the information to Geoscience Australia. The Navy M images reveal a series of submarine Figure 4. Sediments are pinched out, a chimney forms, and hydrocarbons leak coral terraces (figure 3). This is into the ocean. exciting new data for scientists because the terraces represent true sea level.