Ti-rich hydroandradites from the Sanbagawa metamorphic rocks of the Shibukawa area, central Japan

Onuki, Hitoshi; Akasaka, Masahide; Yoshida, Takeyoshi; Nedachi, Munetomo

doi:10.1007/bf00374894

Cited by 16 publications

(8 citation statements)

References 12 publications

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“…TiO 2 ‐CaO‐FeO t ternary diagram comparing the hydroschorlomite compositions from Hole 1256D with Ti‐rich andradite and schorlomite from various locations. Same symbols as Figure 18; On is data from Onuki et al [1982].…”

Section: Discussionmentioning

confidence: 99%

“…celadonite (medium gray), hydroschorlomite (very light gray), and a silica mineral globule (medium gray, lined by dark gray) in thin section from Sample 206-1256D-67R-3, 5 -8 cm (Figures 13a, 13b, and 13d are back scattered electron images; Figure 13c Manning and Harris, 1970;Dowty, 1971] have been carried out but could not provide accurate values for Fe 2+ /Fe 3+ or Ti 3+ /Ti 4+ . Mössbauer studies suggest that significant Ti 3+ is generally present in Ti-rich garnets [Burns and Burns, 1971;Burns, 1972;Whipple, 1973;Onuki et al, 1982], although the Ti 3+ content of one schorlomite is negligible. From their investigation of eleven natural melanites and schorlomites by Mössbauer spectroscopy, Huggins et al [1977b] show that Ti 3+ /Ti total exceeds 0.10 in only one sample, for which this ratio is as high as 0.25.…”

Section: Composition Of Hydroschorlomitementioning

confidence: 99%

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Hydroschorlomite in altered basalts from Hole 1256D, ODP Leg 206: The transition from low‐temperature to hydrothermal alteration

Laverne

Grauby

Alt

et al. 2006

Geochem Geophys Geosyst

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[1] Hydroschorlomite, a Ti-, Ca-, Fe-rich andraditic garnet present in the deepest cores of basalts (661-749 mbsf) drilled in Hole 1256D during Ocean Drilling Program (ODP) Leg 206 (equatorial east Pacific), is reported here for the first time in oceanic crust. Detailed petrological and mineralogical studies by optical microscope, electron microprobe, scanning and transmission electron microscope, and micro-Raman spectroscopy are used to characterize this hydrogarnet and its relationships with other minerals. Hydroschorlomite occurs in Hole 1256D as small (5-50 mm) anhedral or euhedral crystals associated either with celadonite in black halos adjacent to celadonite veins or with brown saponitic phyllosilicate in brown alteration halos adjacent to veins of saponite and iron oxyhydroxides. Both types of halos are formed at low temperature (less than about 100°C). Textural observations suggest that hydroschorlomite formation is contemporaneous with the phyllosilicates. Hydroschorlomite is rich in CaO (22.5-26.5 wt%), TiO 2 (22.0-28.6 wt%), and FeO t (6.2-12.9 wt%) and contains significant F (up to 0.85 wt%) and Zr 2 O 3 (up to 0.34 wt%). The presence of OH suggested by the low total percentages of oxides (95.2-97.3 wt%) is confirmed by the OH vibration at 3557 cm À1 in the micro-Raman spectrum. Chemical mapping indicates that hydroschorlomite is not zoned and is always associated with either celadonitic or saponitic phyllosilicates. Some hydroschorlomite crystals partly include tiny (<10 mm) skeletal titanomagnetite. The occurrence of hydroschorlomite in Hole 1256D basalts coincides with a general downward increase in temperatures and overall intensity of alteration manifest by the alteration of plagioclase and the occurrence of small amounts of mixed-layer chlorite-smectite. The titanium necessary to form hydroschorlomite is provided by the breakdown of primary tiny (<10 mm) titanomagnetite, while calcium is provided by the replacement of plagioclase by albite. Hydroschorlomite is thus an indicator of alteration of titanomagnetite under conditions transitional from low-temperature alteration to hydrothermal metamorphism with formation of titanite and may affect magnetic properties of the rocks.

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Section: Discussionmentioning

confidence: 99%

Section: Composition Of Hydroschorlomitementioning

confidence: 99%

Hydroschorlomite in altered basalts from Hole 1256D, ODP Leg 206: The transition from low‐temperature to hydrothermal alteration

Laverne

Grauby

Alt

et al. 2006

Geochem Geophys Geosyst

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“…For (Ti-bearing) andradite, the associated defect of hydrogarnet substitution is expressed as four (OH) − group substituting for a SiO4 4− group, in which the incorporation of four protons (H + ) is charge-compensated by a Si 4+ vacancy, making it incorporate H 2 O (e.g. Onuki et al, 1982;Lager et al, 1987Lager et al, , 1989Libowitzky and Bern, 2006).…”

Section: Raman Spectroscopymentioning

confidence: 99%

The Formation and Evolution of Uvarovite in UHP Serpentinite and Rodingite and its Constraints on Chromium Mobility in the Oceanic Subduction Zone

Zhang

Shen

Zhang

et al. 2021

Acta Geologica Sinica (Eng)

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The uvarovite-andradite and uvarovite-andradite-grossular solid-solution series are rare in nature. The discovery of uvarovite-andradite in serpentinite and rodingite from the ultra-high pressure (UHP) metamorphic belt in southwestern Tianshan provided an opportunity to investigate its behavior in the subduction zone. Uvarovite (defined as chromiumgarnet) from serpentinite is homogeneous in a single grain, covering compositions in the uvarovite-andradite solid solution series of Adr 58-66 Uv 33-41 , with few grossular components. Uvarovite from rodingites contain various Cr 2 O 3 contents (1.7-17.9 wt%) and mineral compositions being in the range of Adr 21-31 Uv 41-50 Grs 22-37 , Adr 52-90 Uv 5-25 Grs 0-21 and Adr 19-67 Uv 3-63 Grs 13-42 . Discontinuous chemical variation of uvarovite from core to rim indicates that uvarovite formed by consuming andradite and chromite, which could provide Ca, Cr, Al and Fe. Raman signals of water were identified for uvarovite from both serpentinite and rodingite, with high water content in uvarovite from serpentinite. The high pressure mineral assemblage, as well as the association with perovskite, indicated that the studied uvarovite from serpentinite and rodingite was formed through high pressure metamorphism, during the subduction zone serpentinization and rodingitization. High alkaline and highly reduced fluids released from serpentinization or rodingitization in the oceanic subduction zone promote the mobility of chromium and enable its long-distance migration.

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“…Clinopyroxene is a rather rare mineral as a product during serpentinization, but has been sometimes reported in serpentinites of the Mikabu greenstone belt (e.g. Onuki et al, 1982;Mouri and Enami, 1988). Magnetite is disseminated in mats of serpentine and fibrous clinopyroxene.…”

Section: Mineralogicalmentioning

confidence: 99%

Ilvaite from a serpentinized peridotite in the Asama igneous complex, Mikabu greenstone belt, Sambagawa metamorphic terrain, central Japan

Agata

Adachi

1995

Mineral. mag.

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Ilvaite is sparsely disseminated in a serpentinized plagioclase wehrlite of the Asama igneous complex that underwent the Sambagawa regional metamorphism of pumpellyite-actinolite to greenschist facies. Ilvaite in the Asama complex is monoclinic (a = 13.019(5), b = 8.808(2), c = 5.850(4) A, 13 = 90.19(4)~ and its composition is similar to the ideal end-member composition (CaFe~+Fe3+SizO8OH). Ilvaite occurs in mats of serpentine (chrysotile); it probably formed during serpentinization, which might have accompanied the Sambagawa metamorphism. The associated secondary minerals include salitic clinopyroxene, magnetite and andradite. The ilvaite-free mineral assemblage that formed during the serpentinization is usually serpentineclinopyroxene-magnetite, which is widespread in the complex. The phase relations between coexisting minerals suggest that the conditions during the formation of the ilvaite-bearing assemblage were reducing when compared to those of the assemblage serpentine-clinopyroxene-magnetite. The reducing conditions during the ilvaite formation were presumably brought about by hydrogen gas thatl was generated during the serpentinization of olivine.

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Ti-rich hydroandradites from the Sanbagawa metamorphic rocks of the Shibukawa area, central Japan

Cited by 16 publications

References 12 publications

Hydroschorlomite in altered basalts from Hole 1256D, ODP Leg 206: The transition from low‐temperature to hydrothermal alteration

Hydroschorlomite in altered basalts from Hole 1256D, ODP Leg 206: The transition from low‐temperature to hydrothermal alteration

The Formation and Evolution of Uvarovite in UHP Serpentinite and Rodingite and its Constraints on Chromium Mobility in the Oceanic Subduction Zone

Ilvaite from a serpentinized peridotite in the Asama igneous complex, Mikabu greenstone belt, Sambagawa metamorphic terrain, central Japan

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