No abstract

is endowed with high purity vein graphite deposits with extensive mineralization in the tectonically weakened zones of the basement high-grade rocks. Distinctly different crystal shapes of graphite are found even within a single vein and it is controversial in interpreting prevailed fluid activities and crystallization process to form such a variation. Therefore, this study was carried out to interpret the origin of vein graphite using geochemistry, crystal-morphology, and structure of the crystals. Sampling was conducted on four different depths at the Kahatagaha-Kolongaha mine, Sri Lanka. Characterizations of graphite were carried out by micro-Raman spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, and inductive couple plasma mass spectroscopy. The results indicate that the genesis of the vein graphite is related to a single phase of fluid activity and the fluid was mostly pure with possible trace impurities. Further, it was revealed that the thickness of the veins, interaction with host rocks and mobility of the impurity elements have influenced the formation of different morphologies of graphite in a single vein.

Sri Lanka is well known for high-quality gemstones and approximately 25% of the total land area is liable for potential gem fields. Despite of that identification of new promising gem bearing areas is essential. In Sri Lanka, such investigations are mostly based on the sedimentological and geochemical analysis rather than in-situ radioactive surveys which are common in global contest. Information derived from sporadic studies and gem miners revealed that Godakawela gem field has interesting radioactiveness. Hence, this study focuses on the presence of radioactive minerals, their distribution and the origin of the gem deposit in Godakawela gem field. The ambient gamma dose rate was measured by the plastic scintillation detector from 40 points in random walk mode and gamma energy value was recorded in the NaI scintillation detector. Results have proved that Godakawela region has high radioactiveness with respect to the average baseline value Sri Lanka. The radioactive anomaly pattern and the presence of zircon and tourmaline like associated minerals, together with the surrounded geological aspects have suggested that the radioactive minerals may have a primary origin. Further, X-ray diffractogram shows the corresponding peaks for euxenite as a radioactive mineral but to confirm recrystallization analysis with heat treatment is needed.