Analysis of petrophysical properties of some granitoids in Sweden

Variations seen in the airborne magnetic, airborne spectrometry and ground gravity data are used as a base to study some granitoids with various outcrop distributions in two areas in Sweden. The ground gamma-ray spectrometry data as well as density and magnetic susceptibility of rock samples are then used to study the details of changes in the petrophysical properties of the granitoid suites. The variation of petrophysical properties is even studied within an individual suite. We have observed that in a given suite of granitoid, various rock types, namely mafic and felsic, can be discriminated using airborne and ground geophysical data. Airborne spectrometry and ground gravity data show that a more granitic composition has a higher concentration of K, U and Th and also a lower Bouguer anomaly signature. The measured concentrations on the outcrops and the densities of the rock samples support these results very well. The lower densities of the more felsic rocks with higher K concentrations are very well correlated. The geophysical data cover large areas and thus are also cost-effective to use.