Vitrinite Reflectance Lab

Principle of vitrinite reflectance measurements

The vitrinite reflectance (VR) method is an established standard approach to estimate the coal rank and the thermal maturity of natural organic matter contained in sediments. It relies on the fact that vitrinite (one of the most abundant constituent of coals, derived from woody tissue and cell-wall material of terrestrial plants) shows a quasi-linear increase of reflectance (measured against a set of standards of known reflectance) with increasing temperature. Routinely, the random reflectance (Rr%) of vitrinite particles is measured under monochromatic light (546 nm) on polished sample surfaces using oil-immersion objectives. Random reflectance describes the amount of incident light reflected from a particle in any 'random' orientation in which it is encountered, i.e., irrespective of polarization effects. Correspondingly, measurements of Rr% are performed under non-polarized light.

Analytical equipment

The VR lab at the Institute of Geosciences in Jena is equipped with a SpectraVision photomultiplier tube (PMT) system (manufactured by A.S. & Co.) attached to a Zeiss Axio Imager D1m microscope that rests on a shock-absorbing frame. Measurements are made using EPIPLAN Neofluar oil immersion objectives with magnifications of 50x and 100x and immersion oil with a refractive index n=1.518 at 23°C. An adjustable rectangular pinhole allows measuring dispersely distributed particles of variable size. For accurate alignment of the measuring spot, the pinhole image can be projected into the eyepiece. A Zeiss Axiocam 105 color video camera allows instantaneous documentation of microscopic observations. Six industrial reflectance standards with Rr% between 0.42 and 3.05 are currently available.

Contact: K. Ustaszewski (E-Mail)

G. Löwe performing vitrinite reflectance measurements in our lab.
Photomicrograph of disperse vitrinites in a Rotliegend sandstone from Thuringia under reflected light and oil immersion. On the left collinite (homogeneous without internal structures), on the right telinite (with distinguished cell structures). Pale yellow grains in the center of view are framboidal pyrite.

Qualification theses

Mareike Danigel, 2019: Rekonstruktion der Versenkungsgeschichte der Sächsischen Kreide auf Grundlage von Vitrinit- Reflektanzmessungen, 158 pp.

Christian Wagner, 2016: Mikroanalytische Untersuchungen zur thermalen Reife eines eozänen Sedimentbeckens der Pyrenäen, MSc thesis, Friedrich-Schiller-Universität Jena, 44 pp.