THE COMPOSITION OF THE CONTINENTAL CRUST

Abstract

A new calculation of the crustal composition is based on the proportions of upper crust (UC) to felsic lower crust (FLC) to mafic lower crust (MLC) of about 1:0.6:0.4. These proportions are derived from a 3000 km long refraction seismic profile through western Europe (EGT) comprising 60% old shield and 40% younger fold belt area with about 40 km average Moho depth. A granodioritic bulk composition of the UC in major elements and thirty-two minor and trace elements was calculated from the Canadian Shield data (Shaw et al., 1967, 1976). The computed abundance of thirty-three additional trace elements in the UC is based on the following proportions of major rock units derived from mapping: 14% sedimentary rocks, 25% granites, 20% granodiorites, 5% tonalites, 6% gabbros, and 30% gneisses and mica schists. The composition of FLC and MLC in major and thirty-six minor and trace elements is calculated from data on felsic granulite terrains and mafic xenoliths, respectively, compiled by Rudnick and Presper (1990). More than thirty additional trace element abundances in FLC and MLC were computed or estimated from literature data.