Neil Phillips University of Melbourne & Phillipsgold P/L, Australia Adding value in gold exploration 28 October 2010 London UK 30 +th SirJulius Wernher Memorial Lecture Institute of Materials, Minerals and Mining

Gold supply shortfall Discoveries Discovery – why it matters Exploration in the future Repeated discoveries – learning from these.

Supply and demand for gold Discover gold Mine gold Sell gold to meet demand

Supply and demand for gold Discover gold Mine gold Sell gold to meet demand 4000t pa 2500t pa

Supply and demand for gold Discover gold Mine gold Sell gold to meet demand Central banks Individuals hoarding

Supply and demand for gold Discover gold Mine gold 2500 Sell gold to meet demand 4000 Central banks Individuals hoarding ~30000

New Generation Gold Conference 2009, 2007, 2005, Also previously 2001, 1999, 1997, 1995.

Recent discoveries - conclusions Mature gold provinces – Archaean of Australia, Canada Established gold regions – Ghana Less-traditional gold areas (wrt 20th century) – Mali, Peru, China.

Recent discoveries - conclusions Decreasing dominance of gold-only Increasing role of gold-plus – Copper-gold – Larger tonnage – Longer life ( years) – Lower gold grade.

Witwatersrand 1886 and : Rand (George Harrison) Klerksdorp 1930s: Carletonville 1940s: Welkom 1951: Evander.

Witwatersrand 1951 to to 2010: no new goldfields.

Gold production: South AfricaWorld

Future exploration focus

Lots of dollars, projects, drilling or Raise discovery rate (σ)

Discovery rate (σ) Adds real value σ Ounces discovered per exploration dollar

Future exploration focus Country? Technique? Idea? Who? How to add value.

Which country? Appetite for risk Particular knowledge or expertise Special opportunity geology or commercial deal But not everywhere.

What techniques? Classic success stories -Ground magnetics in Witwatersrand -EM in Noranda, Canada (Cu, Zn, Au) -Regolith methods, Western Australia.

What ideas? – Gold genesis Syngenetic on seafloor -Follow horizons, stratigraphy -Only for Cu-Pb-Zn-Ag-Au (VMS).

What ideas? – Gold genesis Epigenetic (after rocks have formed) -Host rocks – mechanical & chemical -Alteration – CO 2 +K+H 2 S -Orogenic – role of structural geology Hogan 2004

New ideas – Gold genesis Hydrothermal gold deposits do not form at 700 o C -Continuum model is inappropriate.

Future exploration focus – Who? Discovery is a rare event Within exploration it is atypical

Future exploration focus – Who? Rarely is a discovery so obvious that everyone can ‘see it’, and agrees that it should be drilled.

Future exploration focus – Who? It follows then that.. -Harmonious group, consensus -Large collaborative team -May not correlate with discovery.

Reproduced from Antrobus (1986) 5 km Welkom Goldfield

Hydrothermal model

Wits formation Since 1900 two ideas Placer dominates exploration - no source, no universal sorting mechanism

Reproduced from Antrobus (1986) 5 km Welkom Goldfield No gold in source area No special sedimentary sorting

Witwatersrand gold - ideas A winner was selected Commitment to idea, not to discovery No alternatives. What would Wernher do?

Sir Julius Wernher Rand goldfields of Johannesburg Wernher, Beit and Co. Imperial College

Development of Yandal gold 1894 Alluvial gold 1987 Mt McClure

Yandal Perth

Yandal story – field work Fe-rich host rocks Structural style Carbonate, mica, pyrite alteration Quartz veining Anomalous gold Akin to prospective gold areas. Minsaco Resources 1986

Development of Yandal gold 1894 Alluvial gold 1987 Mt McClure 1992 Bronzewing 1993 Jundee, Nimary 1996 Jundee deeps- Barton, Centenary 1999 Thunderbox

Future exploration focus – Who? Smart, motivated Directed – we are here to make a discovery.

Future exploration focus – Who? Line-of-sight (priorities).

Future exploration focus – Who? Confidentiality

Confidentiality? “Good! I will use your idea in my next talk”.

Don’t worry about someone else stealing your idea; if it is any good you will have to ram it down their throat. (Kerr Wan-Tass, 1997)

Opportunities Ballarat - 10 Moz Au - immediately north along strike

Conclusion Discovery – the magic may lie in the people.

An epigenetic origin for Archean banded iron ‑ formation ‑ hosted gold deposits. Economic Geology, 79, 162 ‑ 171. Phillips, G N, Groves, D I and Martyn, J E, Geology and alteration in the Golden Mile, Kalgoorlie. Economic Geology, 81, 779 ‑ 808. Phillips, G N, Problems with the placer model for Witwatersrand gold. Geology, 15, 1027 ‑ Phillips, G N, Myers, R E and Palmer, J A, The Witwatersrand goldfields. II: An origin for Witwatersrand gold during metamorphism and associated alteration. Economic Geology Monograph, 6, Phillips, G N and Myers, R E, Link between gold provinces. Economic Geology, 88, Phillips, G N and Powell, R, Hydrothermal origin for Witwatersrand gold. Society of Economic Geologists Newsletter, 31, Phillips, G N and Law, J D M, Yandal greenstone belt, Western Australia: 12 million ounces of gold in the 1990s. Mineralium Deposita, 33, Phillips, G N, Vearncombe, J R and Eshuys, E Witwatersrand goldfields: geology, genesis and exploration. SEG Reviews, 13, Phillips G N and Law J D M Role of CO 2 in the formation of gold deposits. Nature 429: Phillips G N and Evans K E, Hydrothermal replacement model for Witwatersrand gold. Economic Geology, One hundredth anniversary volume, Law J D M and Phillips G N Formation of gold deposits: Review and evaluation of the continuum model. Earth-Science Reviews, 94, Phillips G N and Powell R, Formation of gold deposits: a metamorphic devolatilization model. Journal of Metamorphic Geology. 28, Phillips G N and Powell R, West African map: Gryphon Minerals Limited. Ballarat exploration target: Dr Martin Hughes & Oroya Mining Limited. Source of figures and some concepts

Author contact neil at phillipsgold.com.au [at neil at phillipsgold.com.au School of Earth Sciences University of Melbourne & Phillipsgold P/L, PO Box 3, Central Park, 3145, Australia Articles available on request.

Economic elements beyond gold Gold-only Many gold deposits have no co-product Gold-plus Co-products and by-products – Cu, Zn, Pb, Ag.

Gold Only DepositsWitwatersrand Greenstone Slate Placer(Other) Epithermal Massive Sulfide Cu-Au

Yandal story and message 50km from large goldfields Bronzewing, Jundee, Darlot, Thunderbox, Mt McClure