Geological implications of the thermochemical plume model

摘要

This paper reviews available the mantle plume models and formulates seven questions, which can be solved using geological and geochemical data in terms of the thermochemical plume model. The main features of thermochemical plumes, including calculated plume parameters, are presented. It has been estimated how the power of a plume depends on water concentration in melt at variable melt portions and diffusion coefficients (Lewis numbers). A correlation between the latter and temperature drop at the base of a plume has been shown. The obtained plume parameters are compared with model plume localities, such as the Hawaiian and East African plumes, Siberian and Emeishan flood basalts, etc. Based on the oceanic plate movement pattern and He, Os, and Sr isotope data, the Hawaiian plume was proved to be generated within the D2 lower mantle layer; the diameter of the plume channel is about 100 km, the plume channel rotated and migrated to 100-200 km every 2 Ma; the plume power is about 3.10(8) kW, changing each 15 Ma. The reconstruction of complex core material-plume melts and Layer C-asthenosphere interactions is possible only by isotopic data and primary olivine composition. The plume model was applied to large igneous provinces (Siberian, Emeishan, and Ontong Java LIPs) using detailed mechanisms of plume head interaction with the lithosphere. Taking into account the similar age and evolution of the Tunguska syncline (Siberian LIP) and West Siberia, the plume-lithosphere interactions are deduced from the relationships between sedimentary and magmatic units, different modes of rifting, and variations of Sr and Nd isotopes.