The early Permian Royal, Crown and Roses Pride Shoots are recent discoveries made by the Cracow Joint Venture in the Cracow Goldfield in south-east Queensland. The shoots contribute at least one million ounces of gold to the Cracow Goldfield, which more than doubles the previous inventory of approximately 850,000 ounces of gold mined between 1933 and 1993. The gold shoots are structurally controlled, within steeply dipping low sulphidation epithermal quartz vein structures that are hosted by the early Permian Camboon Volcanics, a sequence of shallow, south-westerly dipping andesitic flows, fragmentais and volcaniclastic rocks. Mining of the Royal and Crown Shoots commenced in 2005. Ongoing exploration by the Cracow Joint Venture has been successful in discovering additional gold mineralised structures such as the Sovereign, Empire, Sterling, Phoenix and Kilkenny Structures. As a result of these exploration successes, the Cracow Goldfield is emerging as a world class epithermal system.
The ongoing challenge to discover and define additional resources led to the initiation of this study, to further understand and characterise the Royal, Crown and Roses Pride Structures and the high grade gold mineralisation and to assist in effective future exploration of the Goldfield. The epithermal structures are characterised in terms of geology, multi-element geochemistry, epithermal vein textures, paragenesis, hydrothermal alteration and hydrothermal fluid geochemistry (fluid inclusion microthermometry and oxygen, hydrogen and carbon stable isotopes). Age dating constrains the age of the gold mineralisation in the context of Queensland metallogenesis. The characteristics of the Royal, Crown and Roses Pride Structures are considered relative to each other, the Cracow Goldfield and global epithermal deposits.
The significant gold depositional events in the Royal, Crown and Roses Pride Shoots occur late in the history of the epithermal quartz vein system. While four phases of veining are identified in the paragenetic sequence, the banded phase (Phase 2) and the breccia channel phase (Phase 3) contribute to the gold inventory. Principal ore and sulphide minerals include electrum, pyrite, chalcopyrite, sphalerite, galena, bomite, arsenopyrite, tetrahedrite, hessite, petzite and argentite. Gangue minerals in the epithermal veins are quartz with minor calcite, adularia and illite. Gold is very fine grained and occurs predominantly as high fineness electrum, typically within the finest grained quartz. Vein textures are.......