Revolutionize ore body analysis with ELEMISSION’s ECORE LIBS drill core scanner

EliminationThe ECORE LIBS drill core scanner provides detailed mineralogical and textural information quickly.

Exploration, mining and mineral processing account for a significant proportion of global GDP. A comprehensive and robust ore body analysis is essential information to determine the viability and profitability of ore deposits.

Characterization of the mineralogy of a deposit is a reliable way to improve mineral physical knowledge through validation and refinement of genetic samples, which can support exploration efforts and lead to new discoveries.

Traditional ore physical analysis methods

Traditionally, a combination of techniques has been used to better understand the mineralogy of ore deposits. Thin sections for representative lithologies throughout a deposit are prepared and characterized by a geologist using a petrographic microscope. These interpretations usually need to be verified and further extended by secondary and tertiary methods such as scanning electron microscopy (SEM) or electron probe microanalysis (EPMA).

For more in-depth studies, trace element and isotopic analyzes using methods such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) or secondary ion mass spectrometry (SIMS) can better understand the mixing zone or timing of mineralization. .

In more recent years, automated mineralogy solutions have been developed that use technologies such as SEM-EDS and X-ray Fluorescence (XRF) to produce mineral maps of thin sections or epoxy resin blocks.

While these techniques are useful for better understanding the mineralogy of ore deposits, the scale of these analyzes is very small and limited by sampling. A standard thin section size of 27 x 46 mm requires a large volume to generate a dataset representative of an entire deposit.

In addition, small sample sizes increase the likelihood of biased sampling, which, according to sampling theory, can induce sampling error. These traditional analyzes are often very expensive and time-consuming (both in terms of analysis time and required sample preparation), and limit how much of the deposit can be truly characterized. In an effort to overcome some of these challenges, commercial drill core scanners using infrared hyperspectral imaging (IR-HSI) have become popular over the past decade to provide high-resolution mineralogy.

These machines are capable of providing large amounts of textual and mineralogical information quickly and at relatively low cost. While this significantly reduces scaling issues associated with traditional methods, this technology has several limitations that result in reduced data quality. Metal oxides, quartz and sulphide minerals are not spectrally active with IR-HSI and, therefore, cannot be distinguished from each other.

Additionally, the spot size of each analysis is ~1 mm, resulting in mixed results on finer lithologies. Infrared hyperspectral imaging (IR-HSI) is a molecular spectroscopy technique characterized by multiple spectral interferences, resulting in many minerals being indistinguishable from each other.

ECORE – the ideal solution for large-scale mineralogy

ECORE (Fig. 1), ELEMISSION Inc. (Montreal, QC, Canada), is a fully automated, high-speed, commercial laser-induced breakdown spectroscopy (LIBS) commercial drill core scanner that provides rapid automated mineralogical and chemical evaluations. While providing high quality and accurate information.

ECORE is capable of providing SEM-EDS-level mineralogy directly on the drill core with a spot size of 30 µm and a resolution (distance between analysis spots) that is fully adjustable by the user. With ELEMISSION’s proprietary and user-friendly LIBS control software and smart automated mineralogy (SAM) algorithm, users can access fast and accurate quantitative mineralogy in minutes (five minutes per core box at standard resolution).

The A unique application of LIBS technology Allows you to locate every naturally occurring element on the periodic table (from hydrogen to uranium). LIBS is an atomic emission spectroscopy technique that minimizes spectral interferences due to ultra-thin emission lines (less than 100 picometers), enabling accurate and precise characterization of minerals and elemental compositions in rock samples. The high selectivity of LIBS elemental spectra means that users can see individual elements within minerals and understand elemental interactions.

The unique combination of microscale probe points and the high selectivity of atomic emission spectroscopy brings the data needed for high-fidelity quantitative automated mineralogy. It allows users to distinguish minerals that contain the same elements in different amounts and to see compositional variations within the same mineral.

ECORE can provide quick access to chemical and mineralogical information with high-resolution and detailed text images. The following studies demonstrate how ECORE’s unique features can be used to unlock deposit potential and provide largely inaccessible information to improve ore body analysis.

Case study one: distinguishing between arsenic-bearing pyrite and arsenopyrite

For many gold deposit types, the presence of arsenic-bearing minerals is known to be associated with gold mineralization. Systematically controlling the release of arsenic within a deposit provides invaluable insight into understanding the constraints on gold mineralization to facilitate decision-making and develop future drilling targets.

The orogenic gold deposit that is the focus of this case study consists of gold mineralization that is almost exclusively refractory and associated with disseminated sulfide mineralization and associated hydrothermal alteration. Typically, gold particles are primarily entrapped within fine-grained arsenopyrite or arsenic-rich pyrite crystals. High concentrations of arsenic are generally associated with high gold concentrations.

The selectivity and sensitivity of ECORE technology allows users to distinguish between arsenopyrite, as-bearing pyrite and as-bearing pyrite. Using a combination of mineralogy and elemental mapping (Fig. 2), the distribution of As throughout the core can be traced, and mineralogical, textural, and chemical correlations between As-bearing pyrite and non-bearing pyrite can then be established. .

The textural and chemical properties of these minerals can be used to better understand the mechanisms and timing of gold deposition. Access to detailed mineralogy promotes easy and accurate deposit characterization and identification of alteration assemblages, allowing informed decisions for future exploration.

Case study two: detailed mineralogical mapping used to reconstruct events associated with VMS mineralization

Understanding the paragenesis (the sequence in which the minerals that comprise the rock formed) of a deposit is important for establishing the context of the different phases within a deposit. This understanding allows mineralization to be associated with distinct fluid episodes and associated characteristic phase assemblages, which can then be used to develop strategies for geochemical exploration.

Paragenesis is usually determined by examining polished thin sections or resin blocks using various techniques (eg, SEM, EPMA, LA-ICP-MS). However, the representation of a thin section/block decreases significantly with increasing deposit size, where vein and dike systems can be hundreds of meters or kilometers long.

This, combined with the heterogeneous phase distribution often observed during various fluid injections, increases the challenge of model representation.

ECORE has the ability to provide mineralogical results comparable to SEM-EDS over the entire core compartment in minutes, creating the opportunity to maximize sample representativeness. ECORE provides rapid access to automated mineralogical and textural information at the macroscale and can be used for entire drilling projects.

ECORE technology was used to characterize drill core (Fig. 3) and thin section off-cuts (Fig. 4) from strongly metamorphosed and metamorphosed VMS deposits. The deposit has two styles of mineralization, mineralogically and texturally distinct, that are characteristic of VMS deposits. The high-resolution automated mineralogical mapping performed by ECORE allowed for accurate visualization and correlation of structure and phase relationships, contributing to overall paragenetic knowledge.

LIBS technology detects and differentiates between different sulfide and metal oxide phases, eliminating the ambiguity common when using hyperspectral imaging. With ECORE, resolution can be adjusted down to 30µm at the touch of a button. Any area of ​​interest can be rescanned at ultra-high resolution to highlight ultra-fine features that might be missed at lower resolution.

The mineral physical analysis revolution

ECORE is a unique tool that greatly enhances ore body analysis by empowering geologists with detailed mineralogical and textural mapping. Users can gain a better understanding of elemental distribution within a deposit, which has implications for pathfinder and indicator mineralogy, while increasing sample representativeness with the ability to scan entire core boxes in minutes.

Please note, this article appears in the 19th edition of our quarterly publication.