Mg-amesite and Al-serpentine with cylindrical microstructures were found in white patches near the edge of rodingite, which were mixtures of white and opaque parts comprising fine grains and light-brown transparent parts comprising coarse grains, in a serpentinite body in the Yakiyama area of Iizuka, Fukuoka Prefecture, Japan. In the transmission electron microscopy images, the white parts comprised a cylindrical structure with a large hollow in the center (cylindrical Mg-amesite), space-filling irregular grains, and fibrous grains. Cylindrical Mg-amesite may have one or more lath grains with widths close to the diameter of the hollow or none at all. The selected area electron diffraction pattern of cylindrical Mg-amesite shows diffraction spots on b* and c* aligned in a straight line. Therefore, we conclude that the cylindrical Mg-amesite has a cylindrical structure elongated along the a-axis, similar to chrysotile or polygonal serpentine. Although the lath grain inside the cylindrical Mg-amesite shows mainly 7 Å reflections, slight reflections are present, indicating the presence of a long-period structure. The chemical composition shows trends corresponding to the microstructure, which can be roughly divided into three phases: most parts of the cylinder and some space-filling irregular grains are of Mg-amesite composition, whereas the inner wall of the cylinder and irregular grains are of Al-serpentine composition; lath grains inside the cylinder and fibrous grains show compositions that can be explained by serpentine–kaolin substitution or a mixed layer of serpentine–amesite and talc.

The distributions of Mn²⁺, Fe²⁺ and Fe³⁺ in babingtonite Ca_2.00Fe_0.64²⁺Fe_0.98³⁺Mn²⁺_0.27Mg_0.09Al_0.02Si₅O₁₄(OH) from the Yakuki mine, Fukushima, Japan are revealed via single-crystal anomalous X-ray scattering (AXS). The ordered distribution of Mn²⁺ at the Fe1 site is readily confirmed via Mn-AXS analysis based on the intensity difference observed in a pair of datasets measured at E_M1 = 6.388 keV and E_M2 = 6.513 keV below the Mn K absorption edge. The distributions of Fe²⁺ and Fe³⁺ are quantitatively determined for the first time using a dataset measured at E_F3 = 7.116 keV, where a significant difference in the anomalous scattering factor is observed between Fe²⁺ and Fe³⁺. This study quantitatively determines the site occupancies of Mn²⁺, Fe²⁺, and Fe³⁺ in babingtonite based on experimental evidence obtained from advanced AXS analysis. The present AXS analysis confirms the structural-chemical formula Ca_2.00(Fe_0.64²⁺Mn²⁺_0.27Mg²⁺_0.09)^Fe1(Fe_0.98³⁺Al³⁺_0.02)^Fe2Si₅O₁₄(OH) for babingtonite from the Yakuki mine.

Elastic wave velocities of sodium disilicate (Na₂Si₂O₅; NS2) glass were determined up to 7 GPa using an ultrasonic pulse–echo overlap technique combined with synchrotron X-ray imaging in a Kawai-type multi-anvil apparatus. NS2 glass represents an intermediate degree of polymerization (NBO/T = 1), bridging the compositional gap between fully polymerized and depolymerized silicate glasses. The compressional wave velocity (V_P) increases monotonically with pressure, whereas the shear wave velocity (V_S) remains nearly constant up to ∼4 GPa before rising at higher pressures. In comparison with fully polymerized (silica, jadeite, albite) and depolymerized (diopside, enstatite) glasses, the pressure dependence of NS2 glass resembles that of depolymerized compositions. These results indicate that the transition between polymerized and depolymerized elastic behavior occurs near NBO/T = 1. Consequently, mafic melts (NBO/T < 1) may exhibit anomalous elastic properties under upper-mantle conditions, whereas ultramafic melts (NBO/T > 1) are expected to stiffen monotonically with increasing pressure.

This study presents petrological and whole-rock geochemical data on basaltic lavas from the Tewa Zobar region of the northwestern Ethiopian plateau to investigate their petrogenesis, with petrographic analysis indicating the lavas consist of plagioclase, pyroxene, olivine, and Fe-Ti oxide minerals, exhibiting aphanitic, porphyritic, and glomeroporphyritic textures. Most of the basaltic samples (MgO = 7.4 wt. % - 7.9 wt. %) show alkaline composition, with the exception of one sample with lower MgO content of 6.4 wt.% showing a sub-alkaline nature. The alkaline basalts show steep primitive mantle-normalized trace element patterns with elevated high-field strength elements (HFSE) and heavy rare earth element (REE) profiles, including higher (Sm/Yb)_N, (La/Yb)_N, and (La/Sm)_N values, whereas the sub-alkaline rock sample #Z56 has flatter heavy-REE profiles with lower (Sm/Yb)_N, (La/Yb)_N, and (La/Sm)_N values. Based on the REE model, the sub-alkaline basalt suggests a melt fraction of 3-4%, while the alkaline basalt indicates a lower melt fraction of 1-2%, accompanied by approximately 1-2% residual garnet of enriched mantle source. These basalts also exhibit enriched trace element patterns, with the (Nb/Th)_PM ratios typically showing a higher range, while the sub-alkaline basalt displays a notably lower Nb/Th ratio. Additionally, the alkali basalts generally have a higher Nb content relative to La, with (Nb/La)_PM ratios showing a narrow range, while the sub-alkaline basalt presents a lower Nb/La ratio. The alkaline basalts analyzed, with element ratios such as La/Nb, Ba/Nb, and Ba/La —excluding Sample Z56, which shows distinct values—fall within the range of mantle-derived basalts, indicating the absence of crustal contamination. The middle rare earth element (MREE)/heavy rare earth element (HREE) and light rare earth element (LREE)/HREE ratios indicate that the basaltic magma was derived from a mantle source in the garnet-spinel transition zone at ∼80 km depth, with small degree of melting and significant contributions from both subcontinental lithospheric mantle (SCLM) and asthenospheric sources. Elevated Zr/Hf values and high incompatible trace element enrichment suggest that small-volume metasomatic fluids may have enhanced the source region. The elevated Nb/Ta ratio in the mafic lavas suggests the magma likely originated from a SCLM, potentially modified by metasomatic processes involving carbonatite-like component, while the geochemical similarities between the alkaline basalts and high-Ti 1 (HT1) magmatism point to a connection with mantle plume activity, which may have influenced the recent eruptions on the northwestern Ethiopian plateau.