Remote Sensing Identification of Uranium Exploration Targets - Laguna Sirven Project, Santa Cruz, Argentina

The Laguna Sirven uranium-vanadium deposit belongs to the surficial geological type. The presence of uranium minerals, mainly carnotite, has been detected between 0.5 to 3 m depths, within the calcrete level which serves as cement to a polimictic matrix. Uranium target areas were identified by means of the processing and interpretation of multispectral satellite imagery and SRTM data. LandSat 7 ETM+ and ASTER generated products indicated mainly two types of non-pedogenic mineral patterns related to the precipitation of uranium and vanadium minerals, showing two different depositional pathways, one related to carbonate minerals and another to sulfate minerals. The present contribution briefly describes the methodology and results of the application of remote sensing techniques for the identification of uranium exploration targets in this type of geological model. Laguna Sirven corresponds to a surficial deposit formed by rich uranium precipitations at the water table interface, creating calcretes of a large extent and typically tabular form. In most of these deposits, uranium comes from the weathering of volcanic rocks and sandstones. Uranium solubility is closely linked to oxidation potential, whereby under oxidizing conditions uranium is found as U⁶⁺ cation in the uranyl ions, highly soluble and therefore very mobile. However, in a reducing environment, the U⁶⁺ ion is converted to the insoluble form U⁴⁺. Thus, the uranium in solution flows through permeable strata until it meets conditions to precipitate, such as the sediments of the Deseado River. As previously studied, soils are important fixing materials due to the content of clay minerals, organic matter, iron hydroxides, manganese or aluminum hydroxides.