Porphyry copper, gold and molybdenum deposits - new geochemical exploration methods to aid discovery

Abstract

In the past decade, significant research efforts have been devoted to mineral chemistry studies to assist porphyry exploration. These activities can be divided into two major fields of research: (1) porphyry indicator minerals (PIMS), which aims to identify the presence of, or potential for, porphyry-style mineralization based on the chemistry of magmatic minerals such as plagioclase, zircon and apatite, or resistate hydrothermal minerals such as magnetite; and (2) porphyry vectoring and fertility tools (PVFTS), which use the chemical compositions of hydrothermal minerals such as epidote, chlorite and alunite to predict the likely direction and distance to mineralized centres, and the potential metal endowment of a mineral district. This new generation of exploration tools has been enabled by advances in laser ablation-inductively coupled plasma mass spectrometry, short wave length infrared data acquisition and data processing, and the increased availability of microanalytical techniques such as cathodoluminescence. PVFTS and PIMS show considerable promise for porphyry exploration, and are starting to be applied to the diversity of environments that host porphyry and epithermal deposits around the circum-Pacific region. Industry has consistently supported development of these tools, in the case of PVFTS encouraged by several successful blind tests where deposit centres have successfully been predicted from distal propylitic settings. Industry adoption is steadily increasing but is restrained by a lack of the necessary analytical equipment and expertise in commercial laboratories.

Biography

ARC Centre of Excellence in Ore Deposits
University of Tasmania

Professor David Cooke’s main research theme is the geological, chemical and fluid processes that produce the world’s major copper–gold deposits, known as ‘porphyry copper deposits’. His recent research has focused on documenting changes in the chemistry of minerals surrounding these magmatic copper–gold deposits. Particular minerals retain trace elements in relative abundances which vary in patterns set by the temperature gradient and wall rock compositions. Systematic, rapid sampling of a prospective area can define mineral chemical vector techniques that companies can employ to assist targeting of drill holes designed to discover deeply buried deposits.

The importance of this work has been recognised by many companies that now employ the techniques as a routine procedure in exploration for magmatic copper–gold deposits. Professor Cooke’s other significant contribution has been the mentoring of a large number of PhD students who have gone on to fill important geoscience roles in many mineral exploration companies worldwide.

Venue

Room 309, Steele Building (#03)