Applications of Cathodoluminescence Microscopy to Ore Deposits and Petroleum Exploration



Cathodoluminescence microscopic view of the Dewey Limestone near Bartlesville, Oklahoma. Fossil fragments (Calc-1) can be readily distinguished from sparry calcite (Cals-2). The sparry calcite has formed as bands of calcite deposited on the walls and eventually completely filling original pores in the limestone. It is characterized by bands that differ strongly in their strength and colors of cathodoluminescence due varying amounts of trace element activators, probably mainly manganese. This micrograph illustrates the value of cathodoluminescence microscopy to the petroleum industry where it is routinely used to assess original porosity of carbonate units at the time of petroleum migration. Low magnification (20X in original slide).



Cathodoluminescence microscopic view of sillimanite-microcline-plagioclase-biotite gneiss from the Adirondack Mountains, New York. Sillimanite (Sill; medium to dark red) crystals are disseminated through areas of predominantly microcline (Mc; dark bluish purple). Plagioclase (Pl; light bluish green) and biotite (Bio; black non-CL; platy) also are present. In contrast to this sillimanite-bearing gneiss away from the Benson iron mine, sillimanite in iron ore-bearing gneisses at the mine cathodoluminesce blue and may provide a guide to the presence of iron ore. A single crystal of apatite (bright yellow) is present at the bottom center of the micrograph. Low magnification (20X in original slide).



Cathodoluminescence microscopic view of tremolite schist from Gouvenour Talc-Tremolite Mining District in the Adirondack Mountains, New York. Tremolite (Tm; deep red) is intergrown with another amphobole (cummingtonite or anthophyllite)((Amp; light yellow). Low magnification (20X in original slide).



Emerald (chromium-bearing beryl) crystals (Br; deep red) and plagiclase (Pl; green) from the Gravelotte emerald mine in South Africa. The beryl has crystallized within a chromium-bearing komatiite (extrusive peridotite) immediately adjacent to a pegmatite intrusion, suggesting that beryllium was derived from the pegmatite intrusion and chromium from the komatiite. The trace amounts of chromium present in the beryl act as the activator for the strong red CL. Cathodoluminescence microscopy, low magnification (20X in original slide).