Average composition of the crust in the Australian, Fennoscandian, and Ukrainian shields from refraction seismic studies and petrophysical modelling

Abstract

Seismic velocity models of the Australian, Fennoscandian, and Ukrainian shields fall into two broad categories: one has thin (35-44 km) crust; the other, thick (>45 km). In the Australian shield, Archaean crust is identified as thin; Proterozoic crust, as thick. The Ukrainian shield is the only one whose average models of both thick and thin crust show remarkably similar velocities in the upper 44 km of the crust. Velocities in the upper 20 km of the Ukrainian shield are noticeably higher than in other regions. The hottest assumed geotherm among the regions analysed is that of the Australian Proterozoic crust. Differences in seismic velocity distribution in the crust of the three Precambrian domains do not necessarily translate into marked differences in composition of the differences in geothermal regimes are considered. Show more