Finding of prehnite-pumpellyite facies metabasites from the Kurosegawa belt in Yatsushiro area, Kyushu, Japan

Kamimura, Kenichiro; Hirajima, Tsuyoshi; Fujimoto, Yoshiyuki

doi:10.2465/jmps.111020c

Cited by 6 publications

(5 citation statements)

References 24 publications

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“…Recently, we confirmed that the LBS reported by Ueta (1961) is extremely fresh and almost free from hydration reactions suffered during the exhumation stage, which are common in the Sanbagawa metamorphic rocks (e.g., Uno et al, 2014). Kamimura et al (2012) confirmed that LBS is predominant in the zone 1 of Ueta (1961), but prehnite and/or pumpellyite occur in metabasites in zone 2 of Ueta (1961) except for the Shimotake Formation, and then they proposed a new metamorphic zonal mapping, such as LBS zone mainly occurred in the Hakoishi sub-unit and PrP facies unit mainly developed in the Tobiishi subunit, corresponding with the eastern half of the Tobiishi Formation of Kanmera (1952). As metabasites of LBS and PrP facies rocks are generally lacking in the Sanbagawa belt, they considered that these metabasites belong to the Kurosegawa belt.…”

Section: Geologic and Metamorphic Background Of The Hakoishi And Tobisupporting

confidence: 68%

“…2b of Kamimura et al (2012)], because this rock has many amygdules,~2.0-0.2 mm in diameter, including greenish-mica . Under the microscope, dendritic igneous clinopyroxene and plagioclase occupy the matrix of the rock.…”

Section: Tobiishi Sub-unitmentioning

confidence: 99%

“…

White mica K-Ar age dating was carried out for metapelites in the Hakoishi sub-unit and a meta-pillow basalt in the Tobiishi sub-unit of the Kurosegawa belt (Kamimura et al, 2012), Yatsushiro district, Kyushu, Japan. The Hakoishi sub-unit suffered the lawsonite-blueschist facies metamorphism with peak conditions of 0.7-0.9 GPa and <300°C.

…”

mentioning

confidence: 99%

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White mica K–Ar ages from lawsonite–blueschist facies Hakoishi sub–unit and from prehnite–pumpellyite facies Tobiishi sub–unit of the Kurosegawa belt, Kyushu, Japan

Sato

Hirajima

Kamimura³

et al. 2014

Journal of Mineralogical and Petrological Sciences

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White mica K-Ar age dating was carried out for metapelites in the Hakoishi sub-unit and a meta-pillow basalt in the Tobiishi sub-unit of the Kurosegawa belt (Kamimura et al., 2012), Yatsushiro district, Kyushu, Japan. The Hakoishi sub-unit suffered the lawsonite-blueschist facies metamorphism with peak conditions of 0.7-0.9 GPa and <300°C. Phengite separate with K content of 5.323 wt% from OD 28 gives 299.0 ± 6.1 Ma and those with K content of 1.222 wt% and 2.142 from OD 113 give 280.2 ± 5.8 Ma and 245.3 ± 5.1 Ma, respectively. The Tobiishi sub-unit suffered the prehnite-pumpellyite facies metamorphism with the peak conditions round <0.4 GPa and <350°C. White mica named as alumino-celadonite with a composition range of Si from 3.79 to 3.94 and Fe 3+ from 0.30 to 0.48 for Oxygen = 11 basis is developed in amygdules of meta-pillow basalts, closely associated with pumpellyite and chlorite. Alumino-celadonite separates obtained from pillow basalt, SOD01-B, vary K content from 5.601 to 2.343 wt% and give K-Ar ages from 181 to 173 Ma. The peak P-T conditions of the all studied samples were much lower than the closure temperature of Ar in white micas, so those data can be interpreted as the peak metamorphic timing of each sub-unit, i.e., the existence of both late Paleozoic (299-245 Ma) lawsonite blueschist facies metamorphic rocks and Mesozoic (181-173 Ma) prehnitepumpellyite facies metamorphic rocks are newly identified from the Kurosegawa belt in Kyushu, although Mesozoic epidote-blueschist facies metamorphic rocks have been reported in the relevant area. Obtained metamorphic ages and grade from the Hakoishi and Tobiishi sub-units are almost similar with those of the Osayama area in the Renge belt (Tsujimori and Itaya, 1999) and of the Katsuyama area in the Suo belt of the Inner Zone of Southwest Japan, respectively (Hashimoto, 1968;Nishimura, 1998). These data support the Inner Zone origin of the Kurosegawa belt proposed by Isozaki and Itaya (1991).

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Section: Geologic and Metamorphic Background Of The Hakoishi And Tobisupporting

confidence: 68%

Section: Tobiishi Sub-unitmentioning

confidence: 99%

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White mica K–Ar ages from lawsonite–blueschist facies Hakoishi sub–unit and from prehnite–pumpellyite facies Tobiishi sub–unit of the Kurosegawa belt, Kyushu, Japan

Sato

Hirajima

Kamimura³

et al. 2014

Journal of Mineralogical and Petrological Sciences

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“…The formation of pumpellyite, irrespective of its chemistry, denotes the transition between the zeolite and greenschist facies (e.g. Kamimura et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Major and rare earth element mineral chemistry of low-grade assemblages inform dynamics of hydrothermal ocean-floor metamorphism in the Dinaridic Neotethys

Šegvić

Slovenec²,

Badurina³

2022

Geol. Mag.

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This contribution provides insights into ocean-floor hydrothermal metamorphism of the fast-evolving Dinaridic Neotethys. Mineralogical, geochemical and Sr isotope data collected from altered ophiolites and non-ophiolite basalts/andesites and tuffs of the active continental margin are consistent with hydrothermal alteration trajectories that reflect the host-rock composition. This suggests that hydrothermal fluxes were restricted within a simple closed seawater-fed system. Based on the initial isotopic ratios of Sr, two fluid–rock interaction trends are established: (a) low-to-medium degrees of metasomatism in pre-Middle Jurassic anorogenic ophiolites that progressively abated, and (b) increased intensities of metasomatism in post-Middle Jurassic orogenic ophiolites. This agrees with chlorite thermometry and Ca-Al-(Fe)-silicate phase chemistry. The metamorphic assemblages belong to the zeolite, prehnite-pumpellyite, prehnite-actinolite and greenschist facies. The facies is reliant on the temperature of hydrothermal systems and their fluid chemistry. Rare earth element (REE) phase geochemistry shows (a) variable fluid–rock ratios in chlorite and pumpellyite dependent on fluid temperatures, (b) prominent Eu and Ce anomalies that reflect the fluid oxidation state, (c) light REE/heavy REE mobilization attributed to prevalent ligand complexation, and (d) multi-phase fluid percolation across reaction zones of heterogeneous permeability. This study proposes initiation of simple hydrothermal system(s) at or near a spreading centre(s) in the infancy of the Dinaridic Neotethys. Such a system became more complex during Middle Jurassic and Early Cretaceous time with reactive hydrothermal fluids passing the recharge area and reaching the hot reaction zone. An abrupt obliteration of the established high-temperature regime ensued, following the final closure of the Neotethys.

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“…Subsequent work has shown that low‐grade minerals may form in a variety of other rock types and tectonic settings. Low‐grade minerals occur in subduction settings (Kamimura et al, 2012), at the ocean floor (Spooner & Fyfe, 1973), in island arcs (Miron et al, 2012), in gneiss terrains (Morad et al, 2011; Möller & Søderlund, 1997; Zeck, 1971), as veins in metadolerite (Sansone & Rizzo, 2012) and as veins in amphibolite facies basement gneisses (Weisenberg & Bucher, 2011). Already Eskola (1939) recognized that these minerals formed by hydrothermal processes and therefore questioned if the zeolite and prehnite‐pumpellyite facies should indeed be referred to as metamorphic facies.…”

Section: Introductionmentioning

confidence: 99%

Low‐grade prehnite‐pumpellyite facies metamorphism and metasomatism in basement rocks adjacent to the Permian Oslo rift: The importance of displacive reactions

Austrheim

Engvik

Ganerød

et al. 2022

Journal Metamorphic Geology

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The Kongsberg and Bamble lithotectonic domains of SE‐Norway are known as classical Precambrian high‐grade metamorphic terrains. The area has undergone extensive metasomatism with formation of albitites and scapolite‐rich rocks and numbers of previously economically important deposits including the Kongsberg Silver and the Modum Cobalt mines. We demonstrate here that the central part of the Bamble lithotectonic domain (Kragerø area) has locally developed low‐grade metamorphic minerals (prehnite, pumpellyite, analcime, stilpnomelane and thomsonite) belonging to the prehnite‐pumpellyite and zeolite facies. Structurally, the low‐grade minerals occur as fracture fills, in the alteration selvages around fractures where the rock is albitized, and along shear zones and cataclastic zones. The fracture fill and the alteration selvages vary from millimetres scale to 1 m in thickness. The fractures with low‐grade minerals are part of larger fracture systems. The low‐grade minerals typically formed by both displacive (swelling) and replacive reactions and in a combination of these. Prehnite together with albite, K‐feldspar, quartz, epidote and hydrogarnet form lenses along (001) faces in biotite and chlorite leading to bending of the sheet silicates through a displacive reaction mechanism. Numerous replacement reactions including the earlier minerals as well as the low‐grade minerals occur. As albite, K‐feldspar, talc, quartz, actinolite, titanite, calcite and hydrogrossular form in the same veins and in the same biotite grain as the classical low‐grade minerals, they probably belong to the low‐grade assemblage and some of the albitization in the region presumably occurred at low‐grade conditions. Alteration of olivine (Fo69) at low‐grade conditions results in the formation of clay minerals including ferroan saponite. Reconnaissance studies at the east (Idefjord lithotectonic domain) and the northwest (Kongsberg lithotectonic domain) sides of the Oslo rift together with reports of low‐grade assemblages in south‐western Sweden along the continuation of the rift into Skagerrak suggest that the low grade assembles occur in rocks adjacent to the Oslo rift along its full extent. Ar‐Ar dating of K‐feldspar from the low‐grade assemblages gave an age of 265.2 ± 0.4 Ma (MSWD = 0.514 and P = 0.766), suggesting that the low‐grade metamorphism and some of the metasomatism is induced by fluids and heat from the magmatic activity of the Permian Oslo rift, which requires transport of fluid over distances of several kilometres. The metamorphic conditions are constrained by stability fields of prehnite, pumpellyite and analcime to be less than 250°C and at a pressure less than 5 kbars. The displacive reactions created micro‐fractures and porosity in the adjacent minerals that enhance fluid flow and low‐grade mineral formation on a local scale. On a thin section scale, the displacive growth of albite in biotite results in a local volume increase of several 100%. Whether the opening of the larger, horizontally oriented fracture systems...

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Finding of prehnite-pumpellyite facies metabasites from the Kurosegawa belt in Yatsushiro area, Kyushu, Japan

Cited by 6 publications

References 24 publications

White mica K–Ar ages from lawsonite–blueschist facies Hakoishi sub–unit and from prehnite–pumpellyite facies Tobiishi sub–unit of the Kurosegawa belt, Kyushu, Japan

White mica K–Ar ages from lawsonite–blueschist facies Hakoishi sub–unit and from prehnite–pumpellyite facies Tobiishi sub–unit of the Kurosegawa belt, Kyushu, Japan

Major and rare earth element mineral chemistry of low-grade assemblages inform dynamics of hydrothermal ocean-floor metamorphism in the Dinaridic Neotethys

Low‐grade prehnite‐pumpellyite facies metamorphism and metasomatism in basement rocks adjacent to the Permian Oslo rift: The importance of displacive reactions

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