Accessible Silicate Earth (part of the silicate Earth from which we can obtain materials for analysis).
Using these novel approaches, we construct a plausible model of the formation of the EER and explain the difference in 142Nd/144Nd ratios between the ASE and chondrites, investigate the silicate differentiation of the early Earth, and constrain the composition of the bulk silicate Earth (BSE).
Kleine, T., Mezger, K., Palme, H. & Münker, C. The W isotope evolution of the bulk silicate Earth: Constraints on the timing and mechanisms of core formation and accretion.
Wood, B. J., Nielsen, S. G., Rehkämper, M. & Halliday, A. N. The effects of core formation on the Pb- and Tl- isotopic composition of the silicate Earth.
We argue that although such dense melts likely exhibit some 'primordial' geochemical signatures, they are not representative of the bulk silicate Earth.
Leading models of the kind known as bulk silicate Earth (BSE) assume that the mantle and crust contain only lithophiles ("rock-loving" elements) and the core contains only siderophiles (elements that "like to be with iron").
Here, we demonstrate that such an ancient mantle reservoir is likely composed of enriched and depleted dense melts, and propose a model for early global differentiation of the bulk silicate Earth that would produce two types of dense melts with distinctive chemical compositions in the deep Earth.
The Accessible Silicate Earth (ASE) has a higher 142Nd/144Nd ratio than most chondrites.
Finally, we dedicate this SPEPS to Dr. E. Ohtani (professor emeritus at Tohoku University), who made meaningful contributions to vast research areas from partial melting of deep silicate Earth, element partitioning, and role of hydrous circulation of water and hydrogen in the early deep Earth to core/mantle equilibria together with equation-of-state of silicate mantle and metal core materials.
The Th/U ratio in the deep CC of the LOC is typically approximately 5 as compared to a bulk silicate Earth ratio of 3.9 or a bulk CC ratio just greater than 4.0; the higher Th/U ratio in the deep CC is likely due to the greater upward mobility of U during dehydration reactions that accompany granulite facies metamorphism of the deep CC.
