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In this work we present progress obtained in analysis airborne geophysicalsurvey data for the north-central region of the state of Goias (Brazil). Theresults obtained indicate that most of the subtropical soil types arecharacterized by Uranium contents of greater than one parts per million (ppm).Only ultisol and oxisol soils are found to have Uranium contents lower than oneppm. Thorium and Potassium abundances also display trends similar to those ofUranium. The K/U ratios fall in the expected range of values for common soilswhile the Th/U ratios are higher than normal. This latter observation mayindicate a characteristic feature of subtropical soils. Alternatively it may beconsidered as indicative of disequilibrium conditions in radioactive series andconsequent underestimation of Uranium in soil layers of the study area. In thiscontext we point out the possibility of using results of radiometric surveys asa convenient complementary tool in identifying geochemical zoning of soils insubtropical environments. Analysis of aeromagnetic data reveals the presence ofa large number of magnetic lineaments. The analytic signal values point to theexistence of substantial small scale variations related to lithologic changes.There are indications that deposition of soil types are controlled to a largeextent by the system of NE-SW trending faults and fracture systems. Accordingto results of radiogenic heat production calculations the cambisol soil in thisregion are found to have a mean heat production of 3.32 \pm 5.9 \mu Wm-3 whilethat of ultisol soil is only 0.36 \pm 0.3 \mu Wm-3. The mean heat production ofsoil layers at the surface is 0.68 \pm 0.4 \mu Wm-3. Heat production values ofbasement rocks are estimated to be more than 1.3 \muWm-3, after corrections fordensity changes and non-equilibrium conditions of Uranium series.

Airborne Geophysical Surveys in the North-Central Region of Goias (Brazil): Implications for Radiometric Characterization of Subtropical Soils