Geology and mineralogy of the Mae Than ball clay deposit, Ampohoe Mae Tha, Changwat Lampang

The study area is covered an area approximately 50 square kilometres in Amphoe Mae Tha, changwat Lampang in the northern part of Thailand. This study is focusing upon the appraisal of the geological aspects of the Mae Than area, including the characteristics, distribution, and possible genesis of the Mae Than ball clay. The Mae Than basin is the Cenozoic intermontane basin infilled with medium- to fine-grained clastic associations and carbonaceous sediments. Considering the distribution of pre-Cenozoic rocks surrounding the Mae Than basin, the Permo-Triassic volcanic associations are exposed in the western part of the basin whereas the clastic sediments of Lampang Group cover the eastern part of the basin. Characteristics and distribution of the Mae Than ball clay have revealed that the mineralogical composition are mainly disordered kaolinite with minor amount of illite, quartz and traces of interstratified illite-smectite. The organic matters content in terms of total carbon is averaged about 0.26 per cent. The important chemical composition of the ball clay is approximately 74 per cent Si02, 20.3 per cent A1203, and 1.29 per cent Fe203. The ball clay in the Mae Than basin is mainly discovered in the SW part of the basin as layers with the thickness ranging from 5-20 metres within the average depth range of 0-100 metres below the ground surface. The ball clay layers are associated with coal seams and other medium- to fine-grained clastic sequences. They are believed to be deposited under the fluvio-lacustrine environment. The potential source rocks of the ball clay are identified to be the Permo-Triassic volcanic association exposed it the western margin of the basin and probably underlying the Cenozoic sequence in the SW part of the basin.