Hydrocarbon fluid inclusions in authigenic quartz from the Jurassic Torinosu Limestone and associated sediment at Sakawa town, Japan, were studied by microthermometry, ultraviolet (UV) fluorescence, and Raman spectroscopy. The quartz contained abundant liquid hydrocarbon and subordinate vapor hydrocarbon fluid inclusions, and tiny solid inclusions of bitumen, calcite, and rarely pyrite. Aqueous fluid inclusions and aqueous components in hydrocarbon inclusions were absent. Under UV irradiation, most of the liquid inclusions from the limestone and associated sediment displayed intense whitish-blue and deep-blue luminescence, respectively. Further, these liquid inclusions were homogenized at around 24 °C and 53 °C, respectively. Small numbers of liquid inclusions from the associated sediments contained a liquefied gas-condensate. Raman measurements indicated the presence of aromatic compounds and the absence of H₂O or CO₂ molecules in the liquid and vapor inclusions.

Katoite, ideally denoted as {Ca₃}[Al₂](□_xSi_3−x)(OH)_4xO_12−4x, where 1.5 < x ≤ 3, was found in skarn xenoliths from Tadano, Fukushima Prefecture, Japan, and investigated by electron microprobe analyses, X-ray single crystal structure refinement, and infrared (IR) spectroscopy. Katoite characteristically contains up to 0.18 atoms per formula unit (apfu) of S and has a range of compositions, wherein Si = 0.96-1.25 apfu, Al = 1.47-1.74 apfu, Fe = 0.13-0.28 apfu, and Mg = 0.01-0.10 apfu. A difference Fourier map revealed the residual electron density near the octahedral Y site (Wyckoff position = 16a), and we interpreted that S with three-fold coordination occurs at the position of the residual electron density, which is represented as the Y’ site (Wyckoff position = 32e). The final refinement introduced the Y’ site to yield R1 [F² > 2σ(F²)] = 0.0353 with space group Ia3d and unit cell parameter a = 12.24095(8) Å. The IR spectrum in the range of 800-1200 cm⁻¹ shows a band at 1124 cm⁻¹ due to ν₃(SO₄) and doublet bands at 879 and 931 cm⁻¹ with different absorbances interpreted as ν₃(SiO₄) overlapping with ν₃(SO₃). The combined results of IR spectroscopy and structure refinement imply that in the Tadano katoite, S⁴⁺ and S⁶⁺, forming (SO₃)²⁻ and (SO₄)²⁻ coordinations, are placed at the Y’ and tetrahedral Z sites, respectively. Assuming that S is preferentially allotted to the Y’ site as S⁴⁺ to compensate for the deficiency of the octahedral cations Al, Fe, Mg, Mn, and Ti at the Y site, chemical formulae, including possible S⁴⁺ and S⁶⁺ contents, may be calculated. The average chemical formula for 14 different spots is as follows: {Ca₃}[(Al_1.614Fe³⁺_0.208Mg_0.063Ti_0.019)_Σ1.90S⁴⁺_0.096]_Σ2.00(□_1.867Si_1.120S⁶⁺_0.013)_Σ3.00[(OH)_7.192O_4.612F_0.147Cl_0.048]_Σ12.00.

We conducted single-crystal X-ray diffraction experiments on kulanite [Ba(Fe²⁺, Mn²⁺, Mg)₂(Al, Fe³⁺)₂(PO₄)₃(OH)₃] to investigate the potential orientational ordering of its hydroxy groups. Structural refinements showed no sign of a phase transition between 120 and 353 K. Additionally, the orientation of the hydroxy group was determined uniquely along the c-axis for the measured temperature range of 120-353 K.

The metamorphic and plutonic rocks within a serpentinite mélange in the Nagato Tectonic Zone, Yamaguchi prefecture, southwest Japan have been known as a part of the early Paleozoic rock record in Japan. Thus, they play an important role in deciphering the tectonic evolution of proto-Japan. This study determined their U-Pb zircon ages to deduce the origin and geological significance of the Nagato Tectonic Zone. The results of the petrographic observation and LA-ICP-MS U-Pb zircon dating revealed the occurrences of the massive amphibolite originated from the 460 Ma mafic igneous rock, two-mica tonalites formed at 470-460 Ma in association with some xenocrystic zircon grains, and low-grade metasedimentary rocks including detrital zircon grains of 2460-400 Ma. The lithology, petrographic characteristics, and U-Pb zircon ages of these constituent rocks in the Nagato Tectonic Zone are well comparable with the blocks within serpentinite mélange in the Kurosegawa Tectonic Belt, rather than the Hida Gaien Belt which has been considered to form a single geological unit with the Nagato Tectonic Zone as the Sangun-Renge metamorphic belt or Nagato-Renge belt. It implies the Nagato Tectonic Zone could be regarded as an isolated fragment of the Kurosegawa Tectonic Belt. The features of detrital age spectra and Ordovician magmatism in the Nagato Tectonic Zone and Kurosegawa Tectonic Belt provide the possibility of the development of their granitoids and protoliths of metamorphic rocks at the active continental margin of the South China craton.

Serpentinization is a widely observed hydration process in the earth’s crust. In this study, hydrothermal experiments were performed at different temperatures, times, and pH values to explore the geochemical processes of serpentinization in forsterite. The results indicated that forsterite converts to serpentine after reacting with SiO₂ at 200 °C and a pH of 13 for 20 days in a hydrothermal system. X-ray diffraction patterns showed that the serpentine is lizardite, with lamellar and leaf-like micro-morphology. Furthermore, hydroxyl absorption peaks, which represent the formation of lizardite, were observed in the Fourier-infrared spectroscopy spectra. The newly formed serpentine showed high crystallinity and a relatively perfect crystal form. High-resolution electron microscopy indicated that the serpentine crystal layer only appeared on the forsterite surface. The transformation was a process of the coupling of dissolution and precipitation where the forsterite was replaced from the surface; [SiO₄]⁴⁻ and [MgO₆]¹⁰⁻ units were attached in situ to the forsterite surface, reacted, and formed a serpentine structure. These results are of fundamental significance for exploring the transformation and controllable synthesis between olivine group and serpentine group minerals as well as understanding the genesis, geochemical behavior, and geological environment of ultrabafic rock alteration deposits.