Atomic numbers and accuracy
The GeoCore X10 uses a unique patented X-ray technology to provide concentrations of a wide range of elements in the drill core.
As X-rays with different energies pass through the rock, the radiation may interact with atoms yielding characteristic X-rays for each element. The signal is picked up by an XRF spectrometer. X-rays transmitted through the sample are detected at the opposite side of the core, yielding the materials ability to block x-rays. This provides further information about the material distribution in the sample. Since the interaction probabilities are different for each atom, it is possible to mathematically calculate the number of specific atoms with a unique atomic number.
Some common element groups
Some elements are easier to differentiate and count than others, and that’s why the GeoCore X10 exhibits different elemental detection levels across the periodic table.
The distribution of elements in the drill core can also affect detection levels, e.g., a dense cluster of an element has a better detection level than when it’s distributed uniformly in the rock. This is an advantage for geological applications since we are mostly interested in rock where we find clustered elements. Given this complexity, the stated detection limits should be considered indicative.
Base metals and rare earth elements (REE)
Around 10 ppm
The GeoCore X10 is particularly suited to measure economically interesting elements such as Mo, Ag, Sn, and Te where a detection limit of 10 ppm or better may be achieved.
Around 100 ppm
The GeoCore X10 is first and foremost designed to measure a wide range of elements in the base metal category, including for example Cu, Ni, Zn, Pb, and Mn. Additionally, rare earth elements, Y and Zr exhibit similar detection limits.
Gold, platinum group elements (PGE), and Rhenium
These elements typically occur in lower concentrations and are not suitable for the current version of GeoCore X10. Stay tuned for the successor that is aimed to detect these elements at sub-ppm levels.
Overview of detection limits
The following periodic table is a graphical representation of detection limits across all elements.
The GeoCore X10 exhibits a comprehensive detection capability across the periodic chart. Detection limits vary from very high (~10 ppm), to high (~100 ppm), and elements which require even higher concentrations to be detected.
The concentration of these elements are not detected directly but estimated based on a common set of geological rules defined in nature. Identified minerals, in combination with sample density, are used to calculate the lighter elements using stoichiometry.
For example, the presence of hematite (Fe2O3) would infer a certain amount of oxygen.
Elements not available
These elements do not occur naturally in significant concentrations in the earth’s crust. Hence, concentrations of elements belonging to this group are not available.