Delineation of permissive tract for 3-part quantitative undiscovered resources assessment of uranium and thorium in Mamuju, West Sulawesi

Mamuju is one focus area of radioactive mineral exploration in Indonesia. For almost a decade, geology, geochemistry, and geophysical exploration activities were conducted in the area. To estimate the uranium and thorium undiscovered resources in the area, a quantitative 3-part assessment is applied. The 3-part form of assessment assumes that mineral resources, contained in undiscovered deposits of a particular geological type, can be quantified using statistical distributions that characterize grades, tonnages, and the spatial distribution of known deposits of the same type. The 3-part assessments include three stages: (1) determination models of grades and tonnages of deposits, (2) delineation of permissive tracts, (3) estimation of the likely number of undiscovered deposits, and finally the estimation of the total undiscovered metal endowment. This paper focused on the delineation of permissive tracts from a regional to local geology point of view. Permissive tracts represent extended frontiers of terrains for which geologic environments permit a deposit type to form. Based on the geological analysis, volcanogenic uranium represents the deposit model for uranium in the area, while alkaline represents the deposit model for thorium. From the analysis of geology, geochemistry, and geophysical data, the permissive tract is delineated for further undiscovered resource assessment. Compared to the previous permissive tract delineation, the method integrating statistically processed radiometric and geochemical data, as well as geological map and deposit model was better and more effective for delineating permissive tract for undiscovered resources assessment.