The Mechanisms Responsible for Translating Impulses from Depth to the Outer Shells of the Modern Earth: The Late Cenozoic Global Tectonomagmatic Increase in Activity on Our Planet

Abstract

We know that tectonomagmatic activity periodically increased during the Earth’s history without any visible external factors to cause these occurrences. This is obviously related to the evolution of petrological processes at depth that produce events in the outer shells of the modern Earth (the tectonosphere). However, the essence of these processes and the mechanisms that translate them to the tectonosphere remain little known. We have examined this problem for the particular case of the Late Cenozoic (Neogene to Quaternary) global activation. We know that the modern Earth is a cooling body with a solidifying liquid iron core. The process must be accompanied by a number of thermodynamic, physical, and physicochemical effects, and it is these which might cause the inner activation of our planet. We have tried to shed some light on these problems using available modern geological, petrological, geochemical, and geophysical data on the activation that is just now occurring before our eyes. We have shown that the main active element on the modern Earth must be a thin crystallization zone that is constantly rising; that zone is between the wholly solidified part of the core (the solid inner core) and its completely liquid part (the outer liquid core). It is this zone which harbors various phase transitions in a cooling melt as the melt is passing bifurcation points. The phase transitions are both of the type like a change in released solid phases that accrete to the inner core and as retrograde boiling producing drops of core fluids. It is shown that the drops are rising in a high-Fe host melt and are accumulated at the base of the mantle. Once there, they participate in the generation of mantle plumes which are the chief translators of deep impulses to the outer geospheres, and leave the core for good simultaneously with impulses. It is supposed that at one such point, fluid solubility experienced a sharp drop in the cooling high-iron liquid of the outer core. This must have led to a simultaneous intensification of retrograde boiling of this melt throughout the entire surface of the core crystallization zone, that is to say, on a global scale. It is this phenomenon which must have supplied the excess of core fluids necessary for mass generation of mantle plumes and have served as a trigger for processes involved in the Late Cenozoic global tectonomagmatic activation of the Earth.