The Application of Geostatistical Analysis on Radiometric Mapping Data to Recognized the Uranium and Thorium Anomaly in West Sulawesi, Indonesia.

Abstract Mamuju Region in West Sulawesi, Indonesia is one of prospect area of uranium/thorium in Indonesia. High radiometric concentrations were located in Adang Volcanic Rocks. This formation is grouped as basaltic to intermediate rock and composed by lava, pyroclastic rocks, and tuff. Regional field radiometric mapping, including radiation dose rates, potassium, uranium, and thorium contents of soil and rock was conducted to identify the existence of radioactive minerals and prospect zones. Some radiometric anomalies are detected and probably related to hydrothermal alteration, leaching, and precipitation processes. Uranium anomaly (97,261 ppm) located in Mamuju River upstream, Botteng, Takandeang and Ahu area. The anomaly related to uranium leaching and precipitation processes in leucite basalt lava. Thorium anomaly (369,461 ppm) located in Pangasaan, Takandeang, Ahu, and Taan area. To expand this radiometric mapping, we characterized the reflectance of Landsat-8 imagery based on field measurement data. Based on circular structures identification, uranium/thorium anomaly are related to the existence of volcano vents on Adang Volcanic. Based on band rationing, high uranium contents distributed in the area with less ferromagnesian mineral, while thorium did not affect. These field based and remote sensing characterization results could be used as preliminary parameters to identify wide and detail prospects.