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

Abstract

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, 13 C/ 12 C. The carbon isotopic data for the Bogala graphite, expressed as δ 13 C, 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 δ 13 C 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 δ 13 C decreases as the carbon content increases from 93 to 98%.