The Cretaceous high‐P/T metamorphic complex such as Sanbagawa schists and Mikabu greenstones is located in the outer zone of the Median Tectonic Line in the Shibukawa area, northwestern Shizuoka Prefecture, central Japan. In this area, a 2 × 1 km Shibukawa ultramafic body, a member of the Mikabu greenstones, occurs within the chlorite zone of the low‐grade Sanbagawa schists. The upper part of this ultramafic body is covered by...

Carbonaceous material undergoes changes in its maturity mainly in response to its thermal history. Among the various geothermometers based on Raman spectra of carbonaceous material, those proposed by Kouketsu et al. (2014) have been employed to investigate the temperatures experienced by terrestrial rocks that undergo low‐ to medium‐grade metamorphism. Although their geothermometers use spectral parameters that can be determin...

We determined the mineralogical and petrological characteristics of ultramafic rocks dredged from two oceanic core complexes: the Mado Megamullion and 23°30′N non‐transform offset massif, which are located within the Shikoku back‐arc basin in the Philippine Sea. The ultramafic rocks are strongly serpentinized, but can be classified as harzburgite/lherzolite or dunite, based on relict primary minerals and their pseudomorphs. St...

Garnet grains in Sanbagawa quartz eclogites from the Besshi region, central Shikoku commonly show a zoning pattern consisting of core and mantle/rim that formed during two prograde stages of eclogite and subsequent epidote–amphibolite facies metamorphism, respectively. Garnet grains in the quartz eclogites are grouped into four types (I, II, III, and IV) according to the compositional trends of their cores. Type I garnet is mo...

This report describes an investigation of the composite metamorphic history recorded in garnet porphyroblasts of S ambagawa metasediments, and presents discussions of the possible distribution of eclogite facies lithologies in the Besshi region, central S hikoku, southwest J apan. Garnet grains usually show chemically composite zoning with resolved inner and overgrown outer segments, respectively. The inner segment usually con...

The R aman spectra of carbonaceous material ( CM ) from 19 metasediment samples collected from six widely separated areas of S outhwest J apan and metamorphosed at temperatures from 165 to 655°C show systematic changes with metamorphic temperature that can be classified into four types: low‐grade CM ( c. 150–280° C ), medium‐grade CM ( c. 280–400°C), high‐grade CM ( c. 400–650°C), and well‐crystallized graphite (> c. 650°C). T...

Aragonite and omphacite‐bearing metapelite occurs in the albite–biotite zone of the Togu (Tohgu) area, Besshi region, Sambagawa metamorphic belt, central Shikoku, Japan. This metapelite consists of alternating graphite‐rich and graphite‐poor layers that contain garnet, phengite, chlorite, epidote, titanite, calcite, albite, and quartz. A graphite‐poor layer contains a 1.5‐cm ivory‐colored lens that mainly consists of phengite,...