Jornal de Geologia e Geofísica
Acesso livre

Abstrato

Thermodynamic-Geophysical Modeling of the Interior Structure of the Siberian Cratonic Mantle along Cross-Cutting Profiles Kimberlite and Meteorite

Kuskov OL, Kronrod VA and Pavlenkova NI

Using a thermodynamic-geophysical approach, we map the 2-D interior structure of the Siberian cratonic mantle along the ultra-long cross-cutting seismic profiles Kimberlite and Meteorite carried out in Russia with peaceful nuclear explosions. There is a systematic decrease in temperature from west to east for the Kimberlite profile and a weak decrease from NW to SE for the Meteorite profile. Cratonic mantle shows a significant heterogeneity in the distribution of seismic velocities, temperature and density, topography of seismic boundaries and degree of layering at depths up to ~200 km reflecting somewhat different thermal state along both seismic profiles. Temperatures in the central part of the craton are somewhat lower than those at the periphery and 300-400°C lower than the average temperature in the surrounding mantle. A change of composition from depleted to fertile material reveals a negligible effect on seismic velocities that is practically unresolved by seismic methods, but remains the most important factor for the density increase of cratonic root. The distribution of density in the mantle cannot be attributed to any single composition, either depleted or enriched in basaltic components. This finding suggests a significant fertilization with depth and is compatible with the chemical stratification in the root of the craton. The thickness of the thermal boundary layer (TBL, conductive lid + transition layer) can be estimated as 300 ± 30 km thick along the Kimberlite and Meteorite profiles. At the base of the TBL, the temperature is close to 1450 ± 100°C isotherm; the calculated density corresponds to the PREM model density