Lignite and tin ores exploration in southern part of Thailand by using nuclear track-etch detectors

Abstract

Both lignite and tin mines in Southern of Thailand are associated with uranium ore. In lignite exploration, Bangpudum Lignite Mine at Krabi Province was chosen for this studied because we know the exact location and deposition of coal seam by using other geophysical technique and also confirm by borehole. The size 1x2 cm2 of cellulose nitrate CN-85 films were used, each film was stuck at the inner bottom of a softdrink cup. Each cup was put up side down at the bottom of a borehole about 75 cm depth from the earth surface and laid about 10 m apart. All the cups were put in the hole along the line in order to cover about 280 metre in the cross sectional direction long of the known coal seam. After one month, all the film detectors were collected and etched with 6.25N NaOH at 60°C about 25 minutes long in order to enlarge the latent alpha registration tracks. These alpha particles were emitted from radon gas (Rn-222) which was generated from uranium associated with lignite ore. The registration track density per area of each CN-85 film was studied by optical microscope at 400x magnifications. We found that the track densities of the films have high correlation with the depth of the known coal seam while high and low track densities will correspond to the shallow and deep coal seam respectively. Also, track density was significantly higher than background. A similar manner of experiment was designed for tin ore exploration at Ronpibul district, Nakorn Si Thammarat province. The result is in progress and will present at the conference.