Design and construction of infrastructure within and around mine sites requires effective ways of assessing whether there are additional ore zones nearby, or in the surrounding district. For example, construction of a tailings dam above an undiscovered ore zone will prevent that resource from ever being mined. Maximising knowledge gained during diamond drilling, both within known ore bodies, and in district-scale exploration, is the key to facilitating decision-making processes in mine design, planning and implementation. The two questions that must be answered relate to fertility (how big is the ore zone?) and vectoring (how far away is it, and in what direction?).
UTAS, in collaboration with AMIRA, currently leads the world in research pertaining to detecting far-field and proximal geochemical footprints of ore deposits, as demonstrated by the mining industry's strong and continued financial support of these research activities under the auspices of AMIRA research projects for porphyry copper and epithermal gold deposits, and sediment-hosted gold deposits. Our research has shown that most ore zones have subtle geochemical 'footprints' that can extend for kilometres away from the centre of mineralisation, much further than previously detected by conventional geochemical techniques. We have also shown that the size of the footprint relates to the size of the ore zone, whereas systematic changes in alteration mineral trace element compositions can provide vectors that can help determine the precise ore body location.
Critical to the success of this research program has been the breakthrough technological and analytical advances in laser ablation ICPMS by the CODES laser ablation laboratory, which can now perform in-situ spatially-resolved low-level chemical analysis of silicate, oxide and sulfide minerals for a large range of elements. Low-level trace element analyses have been combined with mapping of simple textural features, such as pyrite morphology, epidote vein intensity, and quartz textures, to provide explorers with new tools that provide indications of proximity to ore zones in near-mine and far-field environments, sensing ore deposits from 100s to 1000s of metres distant.
Theme 1 research will develop new geochemical and computational tools for detection of proximity to ore zones during automated core logging. Corescan have developed advanced imaging software that integrates high resolution reflectance spectroscopy, visual imagery and 3D laser profiling to map mineralogy, geochemistry and rock quality designation (RQD) parameters during automated core logging. Newcrest are currently collaborating with Corescan to develop technology that will allow bulk rock geochemical analyses to be acquired simultaneously with the hyperspectral data using a portable X-Ray Fluorescence device (pXRF). AMIRA P1060 confidential research results have shown that due to the limited sensitivity and spatial resolution of pXRF, the technique is unable to detect the subtle (1 – 100 ppb) trace element geochemical dispersion halos that are encapsulated within alteration minerals around ore deposits; low-level detection limits provided by LA-ICP-MS analyses of alteration minerals are essential for footprint detection in more distal parts of hydrothermal systems.
We propose two main research activities within Theme 1:
i) Development and testing of new tools that will allow low-level detection of hypogene geochemical anomalies on the periphery of hydrothermal systems, primarily using LA-ICPMS analysis of alteration minerals;
ii) Automation of textural and mineralogical logging tools that allow for rapid interpretation and modelling of footprint data from hyperspectral core logging data.
Geological and geochemical vectors to low sulfidation epithermal gold mineralization, Cerro Negro district, Deseado Massif, Argentina
Far-field and near-mine footprints: Finding and defining the next generation of Tier 1 ore deposits (AMIRA P1202): Modules 1-3
Identifying unique Resistate Indicator Mineral (RIM) chemistry as a guide in prospectivity for sediment-hosted copper mineralisation (AMIRA P1206)