Skip to main content
U.S. flag

An official website of the United States government

Thermal and chemical variations in subcrustal cratonic lithosphere: Evidence from crustal isostasy

November 6, 2003

The Earth's topography at short wavelengths results from active tectonic processes, whereas at long wavelengths it is largely determined by isostatic adjustment for the density and thickness of the crust. Using a global crustal model, we estimate the long-wavelength topography that is not due to crustal isostasy. Our most important finding is that cratons are generally depressed by 300 to 1500 m in comparison with predictions from pure crustal isostasy. We conclude that either: (1) cratonic roots may be 50 to 300 °C colder than previously suggested by thermal models, or (2) cratonic roots may be, on average, less depleted than suggested by studies of shallow mantle xenoliths. Alternatively, (3) some combination of these conditions may exist. The thermal explanation is consistent with recent geothermal studies that indicate low cratonic temperatures, as well as seismic studies that show very low seismic attenuation at long periods (150 s) beneath cratons. The petrologic explanation is consistent with recent studies of deep (>140 km) mantle xenoliths from the Kaapvaal and Slave cratons that show 1–2% higher densities compared with shallow (<140 km), highly depleted xenoliths.

Publication Year 2003
Title Thermal and chemical variations in subcrustal cratonic lithosphere: Evidence from crustal isostasy
DOI 10.1016/j.lithos.2003.07.004
Authors Walter D. Mooney, John E. Vidale
Publication Type Article
Publication Subtype Journal Article
Series Title LITHOS
Index ID 70210110
Record Source USGS Publications Warehouse
USGS Organization Earthquake Science Center