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