Preface for the article collection “High-Pressure Earth and Planetary Science in the last and next decade”

Preface A special session entitled “Early Earth from accumulation to formation-” was held on May 24, 2015 during the Japan Geoscience Union (JpGU) annual meeting. This session aimed to bring together high-pressure/hightemperature experiment on physics and chemistry of deep Earth materials, natural observation, and theoretical modeling within the principal subject areas of “Early Earth” research. Twenty-six oral and seven poster presentations were given at this session (Fig. 1). Two review and seven research articles from that session are included in this SPEPS. These articles cover Earth’s formation/evolution (de Vries et al. 2016; Kondo et al. 2016), magma and fluid in the interior of the Earth (Mysen 2015; Ohira et al. 2016; Poli 2016; Reynard 2016), Earth’s deep mantle (McCammon et al. 2016; Zhang et al. 2016), and methods using synchrotron radiation (Yu et al. 2016). Giant impact events during planetary accretion caused large degrees of melting of the early Earth. De Vries et al. (2016) simulated the volumes of melt, pressure, and temperature conditions of metal-silicate equilibration after each impact, and demonstrated that the pressure evolution during metal-silicate equilibration during accretion depends strongly on the lifetime of impactgenerated magma oceans compared to the time interval between large impacts. Kondo et al. (2016) estimated major element composition of an early Earth reservoir (EER) with the aid of Nd/Nd isotope systematics to determine the age and pressure–temperature conditions to form the EER. They concluded that the EER formed within 33.5 Myr of Solar System formation and at near-solidus temperatures and pressures of shallow upper mantle conditions. The picritic to komatiitic crust (EER) most likely would have been ejected from the Earth by the last giant impact or preceding impacts. They concluded, therefore, the EER was lost, leaving the Earth more depleted than its original composition. The existence of magma and fluid is one of the most unique features of the Earth. These materials are principal agents of mass and energy transfer in and on the Earth and are, therefore, responsible for the many unique features of formation, evolution, and present day processes of the Earth. In subduction zone environments, fluids are particularly important. With this consideration in mind, Poli (2016) studied the melting carbonated epidote eclogites. The subsolidus breakdown of epidote in the presence of carbonates at depths exceeding 120 km provides a major source of C–O–H volatiles at sub-arc depth. In warm subduction zones, the possibility of extracting carbonatitic liquids from a variety of gabbroic rocks and epidosites offers new scenarios on the metasomatic processes in the lithospheric wedge of subduction zones and a new mechanism for recycling carbon. Reynard (2016) reviewed the mantle hydration and Cl-rich fluids in the subduction forearc. Mysen (2015) reported the Zr transport capacity of water-rich fluids. His results imply that fluid released during high-temperature/high-pressure dehydration of hydrous mineral assemblages in the Earth’s interior under some circumstances may carry significant concentrations of Zr. In order to further our understanding of the nature of dense silicate melts that may be present at the base of the mantle, Ohira et al. (2016) used Brillouin scattering spectroscopic methods to pressures of 196.9 GPa to conduct in situ high-pressure acoustic wave velocity * Correspondence: [email protected] Department of Earth Science, Tohoku University, 6-3, Aramaki Aza-Aoba, Aoba-ku, Sendai 980-8578, Japan Full list of author information is available at the end of the article Progress in Earth and Planetary Science