Significant contribution of subseafloor microparticles to the global manganese budget

Ferromanganese minerals are widely distributed in subseafloor sediments and on the seafloor in oceanic abyssal plains. Assessing their input, formation and preservation is important for understanding the global marine manganese cycle and associated trace elements. However, the extent of ferromanganese minerals buried in subseafloor sediments remains unclear. Here we show that abundant (108–109 particles cm−3) micrometer-scale ferromanganese mineral particles (Mn-microparticles) are found in the oxic pelagic clays of the South Pacific Gyre (SPG) from the seafloor to the ~100 million-year-old sediments above the basement. Three-dimensional micro-texture, and major and trace element compositional analyses revealed that these Mn-microparticles consist of poorly crystalline ferromanganese oxides precipitating from bottom water. Based on our findings, we extrapolate that 1.5–8.8 × 1028 Mn-microparticles, accounting for 1.28–7.62 Tt of manganese, are globally present in oxic subseafloor sediments. This estimate is at least two orders of magnitude larger than the manganese budget for nodules and crusts on the seafloor. Subseafloor Mn-microparticles thus contribute significantly to the global manganese budget.This study was supported in part by the Japan Society for the Promotion of Science (JSPS) Strategic Fund for Strengthening Leading-Edge Research and Development (to JAMSTEC and F.I.), the JSPS Funding Program for Next Generation World-Leading Researchers (GR102 to F.I.), JSPS Grant-in-Aid for Scientific Research (24687004 and 15H05608 to Y.M., 25871219 to G.-I.U., 15H02810 to R.W., 18H04134, 17H06458 and 17H04582 to Y.T., and 26251041 to F.I.), JSPS Grant-in-Aid for JSPS Fellows (14J00199 to G.-I.U.), and Ministry of Education, Culture, Sports, Science, and Technology (MEXT) Fund Leading Initiative for Excellent Young Researchers (to Kochi University and G.-I.U.)

Relativistic Effect on the Bistability of Bi {012} Nanofilms

金沢大学理工研究域数物科学系We perform fully-relativistic first-principles calculations on Bi{012}films which are stable when the film thickness is very small. We find that the 2ML free-standing film has bistability, i,e, the two top atoms are buckled in one geometry and they are nearly flat in the other geometry. The calculated amplitude of the buckling in the buckled structures is 0.17 Å whereas the amplitude is 0.41 Å when the spin-orbit interaction (SOI) is not included in the calculation. Furthermore, the bond lengths between the top and the second top atoms in the buckled structure are alternant when the SOI is included in the calculation. Therefore, the SOI has a significant effect on the geometry. The total energy difference between the two structures is less than 1 meV. Therefore, we expect that one of the two structures appears depending on circumstance such as the interaction between the substrate and the film. [DOI: 10.1380/ejssnt.2009.13