Optical Cathodoluminescence

The cathodoluminescence system of the PARI platform reveals in minutes the internal structures of minerals that are invisible under conventional optical microscopy, enabling precise targeting of zones for geochemical analysis.

Cathodoluminescence (CL) is an imaging technique that exploits the emission of light by certain materials when subjected to an electron beam. The colour and intensity of this emission are governed by the concentration of trace activator elements and by crystalline defects within the material, making CL a qualitative to semi-quantitative chemical mapping tool, complementary to direct chemical analyses.

The Cathodyne system (Newtec Scientific), coupled to a Leica optical microscope, enables the observation and mapping of the natural luminescence of minerals under electron excitation, from the centimetre down to the micrometre scale. The technique reveals chemical, structural and textural heterogeneities – growth zoning, oscillations, recrystallisation, grain organisation – that are invisible under conventional optical microscopy.

Main analytical capabilities

• High spatial resolution CL imaging of textures and internal structures
• Optical and luminescence mapping of polished sections or thin sections
• Detection of growth zoning, oscillations and grain morphology
• Qualitative identification of mineral phases: quartz, feldspars, carbonates, zircon, apatite, fluorite…
• Targeting of zones of interest for downstream geochemical analyses (ICP-MS, electron microprobe, SEM)

Accepted sample types

• Sedimentary, igneous and metamorphic rocks: limestones, sandstones, volcanic rocks, metamorphic rocks
  
• Mineral separates and polished sections: quartz, feldspars, calcite, zircon, apatite, fluorite, volcanic glass
  
• Biological and environmental materials: speleothems, shells, biominerals
  

Why use the PARI platform CL system?

Cathodoluminescence is the instrument of choice for visualising and interpreting internal structures that are inaccessible by other optical imaging techniques. It is routinely used as a preliminary reconnaissance step: by rapidly identifying zoning patterns, mineral phases and heterogeneities within a sample, it enables precise selection of target areas for higher-resolution analyses – scanning electron microscopy (SEM), electron microprobe, or geochemical analyses on the PARI platform (ICP-MS, LA-ICP-MS).

CL thus constitutes an essential complementary tool for investigating textures, crystallisation processes and the diagenetic or magmatic history of geological materials.