VEIN GRAPHITE FROM THE BOGALA AND KAHATAGAHA-KOLONGAHA MINES, SRI LANKA: A POSSIBLE ORIGIN

We report results on the physicochemical attributes and geological context of vein graphite from the Bogala and Kahatagaha-Kolongaha mines, Sri Lanka, according to their morphology and texture. Each type has been characterized with means of X-ray diffraction, Raman spectrometry, oxyreactive and differential thermoanalysis, and measurements of the ratio of the carbon isotopes, C-13/C-12. The carbon isotopic data for the Bogala graphite, expressed as delta C-13, are in the range of -8.3 and -10.4%, and the data for the Kahatagaha-Kolongaha graphite are in the range of -7.9 and -9.3%. These values of delta C-13 values are not consistent with graphite mineralization due to granulite metamorphism, but rather with a magmatic origin. In a single vein of Bogala graphite, we can observe successive morphologies from the wallrock to the central part of the vein. In this textural transition, the delta C-13 decreases as the carbon content increases from 93 to 98%.