Geochemistry and Origin of Ananai Stratiform Manganese Deposit in the Northern Chichibu Belt, Central Shikoku, Japan

Fujinaga, Koichiro; Nozaki, Tatsuo; Nishiuchi, Takazumi; Kuwahara, Kiyoko; Kato, Yasuhiro

doi:10.1111/j.1751-3928.2006.tb00293.x

Cited by 24 publications

(26 citation statements)

References 33 publications

(27 reference statements)

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“…1b). The massive basaltic lava contains Ti-rich augite, Ti-rich biotite, K-rich kaerusutite and apatite as relict igneous minerals in addition to pseudomorphs after olivine, feldspar and titanomagnetite, in agreement with the alkaline affinity of metaigneous rocks in the Kamiyoshida unit (Fujinaga et al, 2006).…”

Section: Geologysupporting

confidence: 49%

“…In contrast, Murata et al (2009) suggested that the region of high-P/T metamorphism extends further south from the Sasagatani fault based on the widespread occurrence of sodic amphibole (magnesioriebeckite to riebeckite) in metabasite. Metabasites in the Mikabu and Kashiwagi units are mostly derived from tholeiitic oceanic-floor basalts, whereas those in the Kamiyoshida unit include within-plate alkaline basalt (Suzuki and Ishizuka, 1998;Fujinaga et al, 2006). Formation of single phase magnesioriebeckite/riebeckite in alkaline basalt does not require high-P/T conditions, and thus it remains unclear whether or not the Kamiyoshida unit in the study area underwent the Sanbagawa metamorphism.…”

Section: Geologymentioning

confidence: 99%

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Jadeite–bearing metaigneous rocks from the Northern Chichibu belt, SW Japan: implications for the lowest–grade Sanbagawa metamorphism

Endo

2015

Journal of Mineralogical and Petrological Sciences

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Multiple generations of Na-Ca and Na pyroxenes (aegirine-augite, aegirine and jadeite) were found in a metamorphosed monzonitic dike from a coherent mafic layer of the Northern Chichibu belt in central Shikoku, Japan. The mafic layer was derived from alkaline basalt magma and its derivatives, and belongs to the Kamiyoshida unit (Middle Jurassic accretionary complex). The earliest-stage sodic pyroxene (jadeite-free Ti-rich aegirine-augite to aegirine) in the dike probably crystallized during a post-magmatic hydrothermal stage. Igneous Ti-rich augite phenocrysts were almost completely pseudomorphed by chlorite + phengite + Al-OH-rich titanite + sodic pyroxene (aegirine-augite with jadeite component) during early stages of subduction metamorphism. The earliest-stage sodic pyroxene and pseudomorphed Ti-rich augite were further overgrown by jadeite/ aegirine fringes during high-P/T metamorphism. Jadeite/aegirine pyroxene also occurs as small (~50 µm long) neoblasts within pseudomorphs (albite + phengite + pumpellyite ± Ba-rich K-feldspar) after igneous plagioclase. Individual grains of the fringe/neoblastic pyroxene are zoned with a jadeite core (up to 98% jadeite content) and an aegirine rim (down to 25% jadeite content). Jadeite-rich pyroxene (up to 92% jadeite content) was also found in basaltic rock from the mafic layer. The absence of quartz and the alkaline affinity of the protoliths suggest that the jadeite formation can be explained by the reaction analcime = jadeite + H 2 O. If H 2 O fluid was present, the decrease in jadeite content in the fringe/neoblastic pyroxene implies decompression from 0.6-0.7 GPa at 300°C to~0.4 GPa at 210-260°C. The formation of the jadeite-to-aegirine pyroxene during exhumation probably resulted from the lowest-grade Sanbagawa metamorphism.

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Section: Geologysupporting

confidence: 49%

Section: Geologymentioning

confidence: 99%

Jadeite–bearing metaigneous rocks from the Northern Chichibu belt, SW Japan: implications for the lowest–grade Sanbagawa metamorphism

Endo

2015

Journal of Mineralogical and Petrological Sciences

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“…The other is the stratiform Mn deposit that is mainly distributed in the Jurassic accretionary complex (Mino-Tanba, Chichibu and Northern Kitakami Belts) and is interbedded with chert or associated with greenstone. The Mn deposit is considered to have been formed by inflow of oxic deepwater into a stagnant anoxic ocean floor Komuro and Wakita, 2005) or by hydrothermal activity related to hotspot volcanism (Fujinaga et al, 2006). In addition to these Fe-Mn and Mn oxide deposits, volcanogenic massive sulfide (VMS) deposits, termed as Besshi-type deposits, occur in the Sanbagawa highpressure metamorphic belt, southwest Japan.…”

Section: Introductionmentioning

confidence: 99%

Whole-rock Geochemistry of Basic Schists from the Besshi Area, Central Shikoku: Implications for the Tectonic Setting of the Besshi Sulfide Deposit

et al. 2006

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Whole-rock chemical compositions of the Besshi basic schist closely associated with the Besshi massive sulfide deposit from the Sanbagawa Belt are reported. Studied samples were collected from four outcrops around the Dozan-goe, central Shikoku. Common metamorphic mineral assemblage of the basic schist is albite + epidote + actinolite + chlorite ± muscovite ± quartz. Major element contents are similar to those of typical tholeiitic basalts. Trace element patterns of the basic schist normalized to normal mid-ocean ridge basalt (N-MORB) are generally flat, although concentrations of highly mobile large-ion lithophile elements are quite variable. Chondrite-normalized rare earth element (REE) patterns are flat to slightly light REE-depleted patterns. In the Hf-Th-Ta and Nb-Zr-Y discrimination diagrams, basic schist samples closely associated with the sulfide deposit are plotted within the N-MORB field. The Th/Nb ratios of the basic schist are also comparable to those of N-MORB. These geochemical lines of evidence indicate that the protolith of the Besshi basic schist is N-MORB and the Besshi sulfide deposit was formed by hydrothermal activity in conjunction with MOR volcanism.

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“…This result is supported by lithological, chemical and isotopic evidence. Fujinaga et al (2006) suggested that the deposit associated with basic volcanic rock of the Ananai deposit in the Chichibu Terrane formed hydrothermally due to hot-spot volcanism. Thick carbonate layers and specific stratigraphic succession similar to those of the stratiform manganese deposits in the accretionary complexes are not recognized in the ODP cores, suggesting that carbonate layers did not form in the Cenozoic oxic pelagic environment.…”

Section: Implications For Manganese Mineralization In Accretionary Comentioning

confidence: 99%

Paleoceanographic Setting and Preservation of Buried Manganese Deposits in DSDP/ODP Cores

Ito¹,

Komuro

2006

Resource Geology

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Abstract:The occurrence, lithology, and stratigraphic setting of buried manganese deposits and associated host sediments in cores obtained on Legs 123-210 of the Ocean Drilling Program (ODP) are examined in order to establish the formative environment and conditions of preservation. Fossil manganese nodule and crusts are found to have formed or deposited throughout the period from 100 Ma to the present, with an additional example of formation near 137 Ma, suggesting that the deepsea environment has been oxic and suitable for the formation of manganese nodules and crusts since the Cretaceous. Many manganese nodules and crusts occur on horizons corresponding to hiatuses in sedimentation or periods of slow sedimentation, consistent with the environment in which modern nodules form (sedimentation rate less than 10 m/m.y.). Sediments overlying the fossil nodules and crusts are oozes or biogenic sediments with sedimentation rates of 1-18 m/m.y. Low total organic carbon (<0.1 wt%) in the overlying sediments and high sulfate content (>25 mM) in interstitial water around the manganese horizon suggest that no strong reduction occurred within the overlying sediments. Coverage by biogenic sediments containing only small amounts of organic matter is therefore considered important for the preservation of manganese nodules and crusts. Manganese carbonate occurs sporadically as nodules, concretions or thin layers in various host sediments, including clay, calcareous ooze and siliceous ooze with sedimentation rates of 6-125 m/m.y. Hiatuses are rare around the host sediments of manganese carbonate. Higher total organic carbon (0.2-1.8 wt%) in the host sediments and lower sulfate content (0-25 mM) in interstitial water around the manganese carbonate horizon suggest that reduction in association with decomposition of organic matter would have proceeded in the host sediments.

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Geochemistry and Origin of Ananai Stratiform Manganese Deposit in the Northern Chichibu Belt, Central Shikoku, Japan

Cited by 24 publications

References 33 publications

Jadeite–bearing metaigneous rocks from the Northern Chichibu belt, SW Japan: implications for the lowest–grade Sanbagawa metamorphism

Jadeite–bearing metaigneous rocks from the Northern Chichibu belt, SW Japan: implications for the lowest–grade Sanbagawa metamorphism

Whole-rock Geochemistry of Basic Schists from the Besshi Area, Central Shikoku: Implications for the Tectonic Setting of the Besshi Sulfide Deposit

Paleoceanographic Setting and Preservation of Buried Manganese Deposits in DSDP/ODP Cores

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