There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
In this paper we present maps of K, eU, and eTh abundances of Elba Island (Italy)
obtained with a multivariate spatial interpolation of airborne {\gamma}-ray data using
the constraints of the geologic map. The radiometric measurements were performed by
a module of four NaI(Tl) crystals of 16 L mounted on an autogyro. We applied the collocated
cokriging (CCoK) as a multivariate estimation method for interpolating the primary
under-sampled airborne {\gamma}-ray data considering the well-sampled geological information
as ancillary variables. A random number has been assigned to each of 73 geological
formations identified in the geological map at scale 1:10,000. The non-dependency
of the estimated results from the random numbering process has been tested for three
distinct models. The experimental cross-semivariograms constructed for radioelement-geology
couples show well-defined co-variability structures for both direct and crossed variograms.
The high statistical correlations among K, eU, and eTh measurements are confirmed
also by the same maximum distance of spatial autocorrelation. Combining the smoothing
effects of probabilistic interpolator and the abrupt discontinuities of the geological
map, the results show a distinct correlation between the geological formation and
radioactivity content. The contour of Mt. Capanne pluton can be distinguished by high
K, eU and eTh abundances, while different degrees of radioactivity content identify
the tectonic units. A clear anomaly of high K content in the Mt. Calamita promontory
confirms the presence of felsic dykes and hydrothermal veins not reported in our geological
map. Although we assign a unique number to each geological formation, the method shows
that the internal variability of the radiometric data is not biased by the multivariate
interpolation.