Umber and manganese deposits in the Northern Shimanto Belt, west Kii Peninsula, Japan, with special reference to sedimentary environment and rare earth resources.

Abstract

Abstract:To evaluate resource potential of rare earth elements (REE), umber (ferromanganese sediment), manganese ore and associated rocks such as basalt, chert and shale in the Itogo, Misoigawa, Usugaokayama, Komoridani and Ryujin areas in the Northern Shimanto Belt, SW Japan were examined. The umber in the Itogo area and manganese ore in the Ryujin area occur between a basaltic footwall and a hanging wall shale.The basalts from the five areas are altered, resulting in addition of water and alkaline elements. Chondrite-normalized REE patterns of the basalts have slightly LREE-depleted and flat-shaped patterns. The REE patterns and trace element compositions of the basalt indicate that they are MidOceanic Ridge Basalt in origin. Chemical compositions of umber are characterized by enrichments in REE and negative Ce anomalies relative to post-Archean average shale (PAAS). Manganese ores are depleted in REE and show positive Eu anomalies. Geochemical features and geological evidences suggest that both the umber and the manganese ores were formed by precipitation of iron and manganese from submarine hydrothermal solution near the Mid-Oceanic Ridge.The umber contains up to 1,441 ppm of total REE contents, while the manganese ores have less than 100 ppm in total REE. These umber are equivalent in HREE contents compared with those of the "ion-adsorption" deposits (weathered granite) in southern China, which is the present major HREE producer. Although the total amount of REE resources in the Itogo area is quite small, basalt-chert and basalt-shale successions are common in accretionary complexes of Japan, and REE potential of ferromanganese deposits deserve to be inverstigated.

Manganese formations in the accretionary belts of Japan: Implications for subduction–accretion process in an active convergent margin

“…The mineralogy and texture of these ores are different from those of the cherthosted manganese ores. Rare earth, major and trace element geochemistry on these deposits showed that the geochemical features of these ores are similar to those of modern submarine hydrothermal deposits suggesting that they were precipitates by submarine hydrothermal activity (Choi and Hariya, 1992;Nozaki et al, 2004;Kato et al, 2005a,b;Fujinaga et al, 2006;Moriyama et al, 2007).…”

“…The Ryujin deposits occur between basalt and red or black shale. Moriyama et al (2007) measured the rare earth and trace element compositions of the basalt and manganese ore, and suggested that basalt is mid-oceanic ridge basalt in origin and the manganese ore was formed from hydrothermal solution near the mid-oceanic ridge. The manganese ore consists of rhodochrosite, caryopilite, braunite and hematite (Yoshimura, 1969;Takimoto and Ishigaki, 1973).…”

Rare Earth Element Enrichment in Late Archean Manganese Deposits from the Iron Ore Group, East India

“…The composition of stratiform manganese and ferromanganese ores from Phanerozoic accretionary complexes in the Japanese Islands (Kato et al , 2005a, b; Fujinaga et al , 2006; Moriyama et al , 2007a, b) is notably different to that of the IOG ores (Fig. 3).…”

“…Data sources: Mahapatra et al (1996), Mishra et al (2006) and the present study for the Iron Ore Group (IOG) ores. Choi and Hariya (1990), Kato et al (2005a, b), Fujinaga et al (2006) and Moriyama et al (2007a, b) for the Japanese ore data.…”

“… Post‐Archean average shale (PAAS)‐normalized rare earth element (REE) patterns. (a) Iron Ore Group (IOG) ores (Mohapatra et al , 1996; Mishra et al , 2006; present study); (b) Phanerozoic stratiform manganese and ferromanganese ores from Japan (Kato et al , 2005a, b; Fujinaga et al , 2006; Moriyama et al , 2007a, b); (c) modern oceanic ferromanganese and manganese sediments (Barrett & Jarvis, 1988; Hodkinson et al , 1994); (d) modern hydrothermal solution and seawater (Douville et al , 1999). …”