ESTUDO DA TERMOLUMINESCÊNCIA NATURAL DO QUARTZITO, EM UMA ZONA MINERALIZADA EM OURO E URÂNIO (CANAVIEIRAS, JACOBINA, BAHIA)

The quartzite of the Canavieiras gold mine (Jacobina, Bahia, Brazil) exhibits a high temperature peak (280 ± 2)°C in its natural thermoluminescence glow curve. It was experimentally determined that the amount of light in this peak could be reproduced to within 5% for grain sizes between 80 and 100 mesh (0.149 and 0.177 mm). A positive correlation was found between the amount of this thermoluminescence and the uranium content with saturation beginning to be detected at the maximum (700 ppm) amounts of uranium found. Assuming that the thermoluminescence peak used is at a temperature high enough to permit accumulation and stability at room temperatures, the thermoluminescence found could have accumulated in (12.1 ± 0.3) X 10 6 years. This may date a complete liberation of trapped electrons in conjunction with a well documented initiation of weathering.