Gold-copper-bismuth deposits of the Tennant Creek district, Northern Territory, Australia, are distinctive as some of the highest grade deposits within the Fe-oxide Cu-Au global family. They are unified by an association with epigenetic magnetite ± hematite - rich 'ironstones' that are hosted by a sequence -I860 Ma, low metamorphic grade, Fe-oxide rich greywacke, siltstone and shale. While many of the high grade gold orebodies are dominated by magnetite - chlorite ± minor hematite, muscovite and pyrite, there are significant variations representing a spectrum of styles from reduced (pyrrhotite-bearing) Cu-Au-Bi deposits to oxidised hematitic Au-Bi(Cu) deposits. Shear-hosted Au-Cu mineralisation outside ironstones further adds to the diversity of styles present in the district. Ironstones predated syn- to late-deformational ~1825-1830 Ma introduction of Au, Cu and Bi in ~-300-350°C, acidic, low-moderate salinity or hypersaline fluids, which were in places carbonic and nitrogenous. The very wide range of oxidation-reduction conditions during ore deposition across the district is interpreted as the product of both reduced (magnetite ± pyrrhotite stable, H2S > S04=) and oxidised (hematite stable, S04= > H2S) fluids reacting with ironstones and/or mixing. Oxygen and hydrogen isotope data point to an hybrid ore fluid source with input of evolved surficial or formation waters, whereas Sm-Nd reconnaissance data and sulfur isotope compositions are consistent with contributions from igneous sources.

GAROFALO, P. S. & RIDLEY, J. R. Gold-transporting hydrothermal fluids in the Earth’s crust: an introduction
POKROVSKI, G. S., AKINFIEV, N. N., BORISOVA, A. Y., ZOTOV, A. V. & KOUZMANOV, K. Gold speciation and transport in geological fluids: insights from experiments and physical-chemical modelling
GAROFALO, P. S., FRICKER, M. B., GU¨ NTHER, D., BERSANI, D. & LOTTICI, P. P. Physical-chemical properties and metal budget of Au-transporting hydrothermal fluids in orogenic deposits

Gondwana Five is not a large or pretentious volume because our resources are not large and we are too aware of our limitations to have any pretensions. The editors are very grateful to those many authors who cheerfully and gracefully accepted cuts in their scripts, sometimes outright mutilation, in order to meet space restrictions. We hope that the volume fairly represents the proceedings of the Fifth Gondwana Symposium and that the papers still contain enough information to be useful. 

Near the southern margin of the African continent, a ringwall of mountains holds up a vast interior desert known as the Great Karoo. It is far from anywhere, in both space and time. The Karoo is a Lost World.

In the Khoikhoi language, Karoo means "land of thirst." It is a broad plateau that is either too hot or too cold for human comfort and always too dry; a place where water is a rarity and where your skin dries and ages even at night.