Tohoku University · Earth and Planetary Sciences
Professor Tatsuki Tsujimori's research lab specializes in high-pressure and low-temperature metamorphism, with a focus on subduction zone processes, eclogite and blueschist formation, and the petrology of HP/UHP rocks. The lab investigates the P–T conditions, mineralogical transformations, and tectonic evolution of metamorphic terranes, particularly in orogenic belts such as the Circum-Pacific, Alpine-Himalayan, and Caledonian regions. Key research directions include the petrology of jadeitite and lawsonite-bearing rocks, zircon geochronology in subduction-related settings, and the role of fluids and trace elements in metamorphic reactions. The lab integrates fieldwork, microtextural analysis, and high-precision geochronology (e.g., SHRIMP-RG U/Pb dating) to reconstruct deep Earth processes in convergent margins.
Figures are computed from collected data and may differ slightly.
Abstract Lawsonite‐bearing metamorphic/metasomatic rocks form at high‐pressure–ultrahigh pressure (H P –UH P ) and low‐temperature (L T ) conditions, commonly in Pacific‐type subduction zones. The P–T stability fields of lawsonite blueschists and lawsonite eclogites represent subfacies of the blueschist and eclogite facies, respectively. Although the lawsonite–epidote transition boundary has a positive Clapeyron ( d P / d T ) slope, the blueschist‐to‐eclogite transformation within the lawsonite
Jadeitite-bearing serpentinite-matrix melange is distributed in the Caribbean (Guatemala, Cuba, and Dominican Republic), circum-Pacific (Japan, Western USA, and Papua New Guinea), Alpine-Himalayan (Italy, Iran, Greece, and Myanmar), and Caledonian (Russia and Kazakhstan) orogenic belts, and always contains high-pressure, low-temperature (H P -L T ) metamorphic rocks. There are also jadeitite xenoliths in kimberlitic pipes in the Colorado Plateau (USA). The oldest occurrences of jadeitite are Ear
Blueschist‐bearing Osayama serpentinite melange develops beneath a peridotite body of the Oeyama ophiolite which occupies the highest position structurally in the central Chugoku Mountains. The blueschist‐facies tectonic blocks within the serpentinite melange are divided into the lawsonite–pumpellyite grade, lower epidote grade and higher epidote grade by the mineral assemblages of basic schists. The higher epidote‐grade block is a garnet–glaucophane schist including eclogite‐facies relic minera
Late Paleozoic glaucophane eclogite and garnet glaucophane schist are intercalated with pelitic schist from the Omi eclogitic unit in the Renge metamorphic belt, Hida Mountains, southwestern Japan. Eclogite and garnet glaucophane schist have MORB-like bulk compositions (major and trace), but garnet glaucophane schist is free from omphacite, reflecting a higher Mg/(Mg+Fe) ratio bulk-rock composition. In the eclogite, three different metamorphic stages (stages I to III) are defined on the basis of
Early Cretaceous lawsonite eclogites and related high-pressure rocks occur as tectonic inclusions within serpentinite mélange south of the Motagua fault zone, Guatemala. Petrologic and microtextural analyses of mafic high-pressure rocks reveal three metamorphic stages linked to several deformational textures. The prograde stage represents an incipient eclogitization and is preserved in prograde garnet, along with an older S1–S2 foliation. The prograde assemblage is garnet (X Mg = ∼0.22) + omphac
Crystals of zircon up to 3 mm in length occur in jadeitite veins in the Osayama serpentinite mélange, Southwest Japan. The zircon porphyroblasts show pronounced zoning, and are characterized by both low Th/U ratios (0.2-0.8) and low Th and U abundances (Th = 1-81 ppm; U = 6-149 ppm). They contain inclusions of high-pressure minerals, including jadeite and rutile; such an occurrence indicates that the zircon crystallized during subduction-zone metamorphism. Phase equilibria and the existing fluid
Coexisting jadeite and omphacite were found as retrograde minerals in a jadeite-bearing lawsonite- eclogite from the Motagua Fault Zone, Guatemala. The lawsonite-eclogite is characterized by the occurrence of garnet porphyroblasts up to 2.5 cm in size, and the eclogite-facies parageneses, almandine- rich garnet + impure jadeite + lawsonite + rutile + quartz; garnet contains inclusions of impure jadeite, phengite, ferroglaucophane, chlorite, lawsonite, rutile, ilmenite, and quartz. Textural relat
蓮華変成帯, 新潟県青海町上路(あげろ)地区湯ノ谷にエクロジャイト質藍閃石片岩が産する.この岩石は主として藍閃石(37%), ざくろ石(21%), オンファス輝石(19%), 緑れん石(19%)と少量の石英, 曹長石, フェンジャイト, 緑泥石, ルチル, チタン石から構成される.エクロジャイト相鉱物組み合わせ 'ざくろ石+オンファス輝石+藍閃石+緑れん石+石英+ルチル' はマトリクスの片理(S1)を構成し, わずかに二次的な緑泥石, 曹長石, 方解石に置換され, S1片理形成以前の緑れん石青色片岩相の鉱物組み合わせ '藍閃石+緑れん石+チタン石+石英+曹長石' の包有物列(S0)がざくろ石のコアに観察される.蓮華変成帯では, これまでにも残存エクロジャイト相鉱物の報告はあったが, 今回, 岩石組織と鉱物化学組成・累帯構造から, 初めて, 緑れん石青色片岩相からエクロジャイト相への累進変成作用を読みとることができた.
Abstract Early Palaeozoic kyanite–staurolite‐bearing epidote–amphibolites including foliated epidote–amphibolite (FEA), and nonfoliated leucocratic or melanocratic metagabbros (LMG, MMG), occur in the Fuko Pass metacumulate unit (FPM) of the Oeyama belt, SW Japan. Microtextural relationships and mineral chemistry define three metamorphic stages: relict granulite facies metamorphism (M1), high‐ P (HP) epidote–amphibolite facies metamorphism (M2), and retrogression (M3). M1 is preserved as relict
Abstract Omphacite (Jd 46.1–52.0 Ae 0–8.4 Aug 48.0–51.2 ) and diopside (Jd 4.3–6.3 Ae 0–0.4 Aug 93.6–95.6 ) coexist in a vein cutting an omphacitite block in a serpentinite melange of the Oeyama ophiolite, central Chugoku Mountains. The compositional gap between omphacite and diopside is significantly wider than for other omphacitediopside pairs reported in the literature. The intergrowth texture of the omphacite-diopside vein suggests that the clinopyroxene pair was contemporaneously crystalliz
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