Using XRF for Ore Grade Control in Mining
Ore deposits are inconsistent in nature, having high concentrations of metals in one area but much lower concentrations in others. Mining geologists perform ore grade control in underground mining operations to figure out where the most profitable ore bodies are, in terms of location and mineral concentration variability. By performing ore grade control, mining operators are also reducing risk because they are checking for quality and variability of an ore, which gives them a better understanding of their material.
Portable XRF instruments provide fast acquisition of geochemical data for ore deposit modelling, easily determining elemental constituents for most natural low concentration samples, as well as high grade ore concentrates. XRF (X-ray fluorescence) is a non-destructive analytical technique used to determine the elemental composition of materials.
XRF analysers determine the elemental composition of a sample by measuring the fluorescence (or secondary) X-ray emitted from elements in a sample when those are excited by a primary X-ray source. Each of the elements present in a sample produces a set of characteristic X-ray lines (“a fingerprint”) that is unique for that specific element, which is why XRF spectroscopy is an excellent technology for qualitative analysis and quantitative determination of material composition. (For more information about XRF, download this ebook: Portable XRF Technology for the Non-Scientist.)
Ore-grade assessment utilising XRF technology helps manage blasting, excavation, and hauling activities, optimising the site blend provided to the concentrator while preventing grade dilution or the erroneous transport of ore to the waste dump. One can rapidly delineate ore boundaries and quickly identify increasingly low-grade deposits as well as instantly flag grade, sub-grade, and waste.
According to one technical note abstract entitled Grade control geological mapping in underground gold vein operations*:
The foundation of all grade control programmes should be that of geological understanding led by clear and accurate mapping and representative sampling to drive appropriate estimation strategies and mining. Gold veins show features relating to erratic grade distribution (nugget effect), and variable geometry and internal architecture. These features include variations in dip, strike and width, late-stage faulting/shearing effects and vein continuity and type. Variations generally require close geological understanding to ensure optimum grade, minimal dilution and maximum mining recovery. A well-designed grade control programme will prove to management and stakeholders that by applying geological knowledge, the mining process can be both efficient and cost effective.
Miners seek solutions for rapid geochemical analysis that will enable them to increase discovery success rates, identify drill targets quickly, make on-site decisions about whether to stop or continue drilling, and decide where to focus on the grid. Using XRF technology can give mining operations real-time geochemical data to guide drilling decisions, enable high-productivity operations, and gain a competitive advantage.
* S C Dominy & I M Platten (2012) Grade control geological mapping in underground gold vein operations, Applied Earth Science, 121:2, 96-103, DOI: 10.1179/1743275812Y.0000000019