Identification of paleo-channel based on radon and thoron anomalies in the Pompong Valley, Toboali, South Bangka.

To support U, Th and REE exploration, in 2020 and 2021 radon and thoron gas measurements have been carried out in the Pompong valley, Toboali, South Bangka to see the pattern of radon and thoron gas in paleo-channel deposits which are believed to contain monazite. On Bangka Island, monazite, which is a by-product of tin mining, cassiterite, both primary tin mining in granite rocks and secondary tin mining in alluvial deposits. Geologically, monazite is formed in acidic to medium igneous rocks, moderate to high grade metamorphic rocks and sedimentary rocks, especially sandstones and alluvial deposits resulting from detrital of the three rock groups. In general, monazite contains uranium, thorium, phosphate and rare earth metals so that at this time it is considered to have significant economic value, especially its rare earth element content. Radon and thoron are the natural decay products of naturally occurring radioactive materials, uranium and thorium. Radon comes from the decay of 238U and thoron from 232Th. Measurement of the intensity of radon and thoron on the surface can be used as a pathfinder for the location of monazite trapped in the paleo-channel below the surface which is paleo-river deposits in a braided environment. Identification of the presence of monazite by mapping of radon and thoron gases provides an overview of the distribution pattern of monazite in this location and at the same time the presence of cassiterite as a tin-bearing mineral can be mapped well. As for achieving these objectives, the methodology used includes reviewing the results of previous studies including geological data and the presence of monazite (U, Th) both surface and subsurface, mapping of radon gas, data processing and analysis and evaluation. From the resulting of radon gas iso map, it showed that in general the pattern of radon and thoron gases in Pompong Valley area has a relative pattern of SSW –NNE and WNW-ESE to EW with the highest reading of radon gas reaching 28,000 Bq/m³ while for thoron it is 110,000 Bq/m³. This pattern was not much different from the paleochannel distribution in the Pompong Valley, especially in the south region. It remarked that the using of radon and thoron measurement can be a pathfinder for tin and monazite-bearing paleochannel, although further direct exploration still should be conducted. [ABSTRACT FROM AUTHOR]