107 / 2023-04-13 21:40:28

Towards a comprehensive understanding of electrical discontinuities in the cratonic lithosphere

Continental lithosphere,Craton,High conductivity anomaly,Thermal structure

高压物理与材料科学 > 高压地球科学-海报

Craton is an important geological unit of the continental lithosphere, which can provide significant information about the Earth's geological history, composition, structure and evolution of continental lithosphere. Magnetotellurics (MT) is a useful tool to image the composition and structure of continental lithosphere because electrical conductivity is sensitive to temperature, bulk composition, volatile (H₂O or CO₂) and/or melt/fluid content, and the presence of highly conductive minerals. In this study, we reviewed the electrical discontinuities revealed by MT surveys in the worldwide cratonic lithospheres. By integrating various geophysical and petrological observations, the thermal structure and conductivity-depth profiles were constructed in the continental lithosphere. The plausibility of water in nominally anhydrous minerals (NAMs), silicate melt, and carbonate melt to account for the high conductivity anomalies observed in the cratonic lithosphere was evaluated based on the geothermal structure and composition within the cratonic lithosphere. Our modelled results indicate that the thermal structure of the cratonic lithosphere acts as a primary control on its internal melting state and electrical conductivity and thereby its dynamic evolution. When the craton has anomalous high surface heat flow, the origin of the enhanced conductivity may be explained by the presence of silicate melt or carbonate melt. However, because of low temperature, silicate melt can be ruled out as a candidate for cratons with relatively low surface heat flow. Instead, either a small amount of carbonate melt or water in NAMs may explain the high conductivity anomalies observed in the deep part of the cratonic lithosphere.