Favourable conditions for the formation of basal type uranium deposits

Basal type uranium deposits or anomalies are wide-spread in Tertiary formations in Japan, but only a few of them are workable. Favourable conditions for accumulation of uranium in basal sediments are presence of basement granite, tributary channels on unconformity plane, traps for ground water, finely disseminated organic matter or adsorbent minerals, and impermeable cap layers. The site that meets all those conditions may be optimum for the formation of basal type uranium deposits. (auth.)