Identification and Determination of the Elements in Ore at Trace Levels

Detailed Ore Analysis using micro-XRF on SEM

Detailed elemental mapping using micro-XRF on SEM (also known as SEM XRF) can used to quickly identify the elements present in ore samples and to determine their distribution. This application example shows the fast, 2D elemental analysis of an ore-bearing sample from the Erzgebirge region and another from near Freiberg. 

The presence of valuable elements, such as silver (Ag), copper (Cu), nickel (Ni), cobalt (Co) in the Erzgebirge sample, and zinc (Zn) and lead (Pb) in the Freiberg sample can be easily determined. In addition, penalty elements, trace elements, and those that can complicate mineral processing, such as arsenic (As) and mercury (Hg) from Erzgebirge or iron (Fe) and cadmium (Cd) from Freiberg, can also be observed. Trace elements are observable due to the low analytical background and high signal-to-noise ratio, for example Hg, and Bi, or Fe and Cd. Such knowledge combined with mineralogical compositions, allows users to determine how the ore could be efficiently processed. 

Micro-XRF on SEM allows for the direct analysis of a cut rock sample with minimal sample preparation. In this example the ore-bearing sample was cut so that it had a flat surface and was analyzed without polishing or coating. Bruker's QUANTAX micro-XRF system was able to analyze the sample with no charging effects. The results clearly showed the distribution of the high-value elements that have made the Erzgebirge region an area of intense mining activity throughout modern history. 

The X-ray source used in QUANTAX micro-XRF, XTrace 2, uses a 50 kV Rh Tube, allowing users to access high-energy lines from elements such as silver, providing more confidence in their measurement

Micro-XRF on SEM elemental intensity map of an Erzgebirge Co-Ni ore. The benefits of micro-XRF analysis, such as trace element sensitivity and high-energy X-ray line detection, yields the ability to observe the distribution and relationship between important ore elements.  
Micro-XRF on SEM elemental intensity map of a Freiberg Pb-Zn ore. The sphalerite (ZnS) contains numerous trace elements, such as Fe, Cd, and P, which are clearly observably in enriched areas or in distinct bands within the sphalerite.  

High Signal-to-Noise Ratio for Trace Element Analysis

Micro-XRF analysis using QUANTAX micro-XRF is the ideal analytical tool for identifying base metal elements, as shown in the analysis of these ore samples from the Erzgebirge and Freiburg regions. X-ray excitation generates a high fluorescence yield for these elements, with a very low background, thus providing the ability to detect trace levels as well as the ability to easily deconvolute any overlapping peaks.  

Micro-XRF on SEM total map spectra that has been deconvoluted to show the correct determination of overlapping major and trace elements within the ore.

A More Accurate Elemental Analysis with High Energy Elemental Lines

QUANTAX micro-XRF uses a 50 kV X-ray source that is able to excite the high energy x-ray lines of elements that are not normally detectable via electron beam excitation. This is in turn provides more confidence in element identification, especially in regions where complex peak overlaps may occur.  In this example, the higher energy elemental lines for Ag (Kα = 22.1) are clearly observable.  

Spectrum captured using micro-XRF on SEM showing the presence of high-energy silver elemental lines as well as the rhodium tube signal.