Primary magmas and mantle temperatures through time

摘要: Chemical composition of mafic magmas is a critical indicator physicochemical conditions, such as pressure, temperature, and fluid availability, accompanying melt production in the mantle its evolution continental or oceanic lithosphere. Recovering this information has fundamental implications constraining thermal state physics convection throughout Earth's history. Here statistical approach applied to geochemical database about 22,000 samples from magma record. Potential temperatures (Tps) derived database, assuming melting by adiabatic decompression Ti-dependent (Fe2O3/TiO2 = 0.5) constant redox condition (Fe2+/∑Fe = 0.9 0.8) magmatic source, are thought be representative different “horizons” (or heterogeneities) ambient mantle, ranging depth shallow sublithospheric (Tp minima) lower boundary layer maxima). The difference temperature (ΔTp) observed between Tp maxima minima did not change significantly with time (∼170°C). Conversely, progressive but limited cooling ∼150°C proposed since ∼2.5 Gyr for which falls limit Herzberg et al. [2010] (∼150–250°C hotter than today). Cooling after 2.5 Ga preceded high-temperature plateau transition dominant plumes plate tectonics geodynamic regime, suggesting that subductions stabilized Archaean was warming mode at time.