Rock characterisation

Whole Rock Analysis

Whole rock analysis determines major rock forming oxides using fusion decomposition followed by analysis via an XRF or ICP-AES instrument. The use of fusion to decompose the sample is to ensure all minerals are broken down fully. We offer a choice of methods for analysing rock forming elements, trace elements, or both in a single package.

Complete Characterisation Packages

Complete characterisation packages have been developed that combine a number of methods into one cost-effective group designed to provide a complete sample characterisation. These packages were developed to include analysis for major elements, exploration pathfinder elements, and resistive elements. By carefully selecting methods for certain elements, issues such as volatilisation and incomplete recovery are minimised. Carbon and sulphur by combustion analysis are included along with several detection limit options for the base and trace elements. Precious metals and halogens are not included in these packages but can be added separately if required.

Expertise in method selection

Our in-house expertise on the behaviour of elements during digestion and measurement has been used to combine analytical methods into the offered packages. There is continual development and review of methods based on instrument and digestion improvements.

Sulphur & Carbon Analysis

Accurate sulphur speciation can be crucial to early identification of recovery and environmental issues on many projects. Likewise, carbon has important metallurgical and environmental implications for many types of mineral deposits. Carbonates may consume acid, impact leach process design and mine waste remediation, while preg-robbing by organic carbon can interfere with the cyanidation of gold and silver ores.

Isotopes

Many important mineralising fluid parameters of mineralising fluids may be determined by measuring the stable isotope ratios of minerals that crystallised from the fluids. Isotopic alteration may form a halo that extends beyond visible mineralogy changes, creating a larger deposit footprint for exploration vectoring. Similarly, radiogenic isotope methods provide insight into provenance, character of hydrothermal fluids, and rock genesis. This helps unravel geological history for a more sophisticated understanding of your ore body.

Stable and radiogenic isotopes

ALS partners with multiple academic institutions to provide an extensive range of stable and radiogenic isotopic methods in support of our own in-house methods. By using ALS as a centralised contact for isotopic investigations, the logistics of moving samples internationally and billing is simplified.

Geochronology

These methods may be used to date the ages of specific minerals, hydrothermal alteration events, and emplacement of igneous units. Age constraints on important events can help refine a deposit and regional exploration model, and to identify important events in mineralisation development.

Minerals used for geochronology

A range of minerals can be used for geochronological determinations; zircon and monazite by U-Pb, molybdenite by Re-Os, and potassium bearing minerals by Ar-Ar. Most commonly, a mineral is used for dating if the relationship of the mineral to the rock formation or alteration event can be determined clearly.

Mineral Chemistry

The composition of minerals is a function of their formation conditions which in turn can be used to infer information about the fluid or magma from which they crystallised. Research into the chemistry of minerals in ore and associated alteration systems suggests that spatial changes in mineral composition may make an effective exploration tool. ALS partners with CODES Centre for Ore Deposit and Earth Sciences at the University of Tasmania to offer Laser Ablation Inductively Couple Plasma Mass Spectrometry (LA-ICP-MS) to provide mineral characterisation by trace-element point analyses.

Trace-element mineral chemistry for exploration

In a single mineral type, measurable trace element variation has been observed between the distal and proximal parts of the alteration halo in fertile mineralising systems. Such examples are dominantly available for porphyry systems. However, similar changes in mineral chemistry would be expected in other hydrothermal ore systems where alteration cells exceed the visible alteration distribution or where similar alteration systems are associated with both fertile and infertile systems.

Hyperspectral Scanning

Spectral mineralogy is a useful tool to identify difficult mineral phases that may be missed by conventional visual logging. For geochemistry-style sampling density, handheld mineral analysers like TerraSpec® 4 HR spectrometer provide rapid, high-quality spectra. TerraSpec® spectra allow identification of minerals in the visible and short-wave infra-red (VIS-SWIR).

Interpretation of hyperspectral scans

One of the major hurdles in implementing a routine spectral analysis program is interpretation. ALS has partnered with AusSpec/IMDEX to offer the aiSIRIS™cloud-based automated mineral interpretation service. aiSIRIS™ uses coded expert methods for an accurate first pass interpretation of spectra on any project.