Kunimiyama
Central Shikoku, Northern Chichibu Belt (Sumaizuku Unit), Japan
OtherFe-Mn
- Type
- Hydrothermal-hydrogenetic ferromanganese umber on mid-ocean ridge basalt, within an accretionary complex
Early Permian umber (Sakmarian, 293.5 to 290.5 Ma) at the contact between mid-ocean ridge basalt and red chert, in the ocean plate stratigraphy of the Sumaizuku Unit; Anagawa, Asahi, Kagami (the largest, 4 m thick on average and up to 12 m), Akatsuki and Noboru ore bodies. Hematite-dominated ore with minor caryopilite and calcite veinlets. Mined from 1941 to 1961, about 0.12 Mt of ore at 25-30 % Fe and 15-25 % Mn; samples taken from mine dumps. Prehnite-pumpellyite facies metamorphism.
187Os/188Os isotope ratio, no unit Values of the same system
Standard : Rapport absolu, sans standard de référence
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 0.6235 ± 0.0465 | 0.5463 / 0.6758 | 6 | umber (bulk), Kagami ore body, initial ratio (187Os/188Os)i at 292 Ma Mean and standard deviation recalculated from 6 analyses, 0.5463 to 0.6758 (04ku076 0.5463; 04ku078 0.6246; 04ku080 0.6653; 04ku081 0.6246; 04ku085 0.6046; 04ku150 0.6758). Initial ratios recalculated by the authors at 292.015 Ma (mid-Sakmarian). Duplicates averaged: 04ku081 0.6257 and 0.6234. | Yano et al. (2023), Marine osmium isotopic composition reconstructed from the early Permi… |
| 0.6027 ± 0.0416 | 0.5228 / 0.6484 | 11 | umber (bulk), Noboru ore body, initial ratio (187Os/188Os)i at 292 Ma Mean and standard deviation recalculated from 11 analyses, 0.5228 to 0.6484 (04ku120 0.5904; 04ku121 0.5835; 04ku122 0.6484; 04ku123 0.6358; 04ku124 0.6143; 04ku125 0.6353; 04ku126 0.5804; 04ku127 0.6410; 04ku128 0.5464; 04ku129 0.5228; 04ku130 0.6318). Initial ratios recalculated by the authors at 292.015 Ma (mid-Sakmarian). Duplicates averaged: 04ku127 0.6230 and 0.6590. 04ku127 and 04ku128 carry 44 to 49 ppt Re, against 1.3 to 14 ppt elsewhere. | Yano et al. (2023), Marine osmium isotopic composition reconstructed from the early Permi… |
| 0.6038 ± 0.0264 | 0.5787 / 0.6437 | 5 | umber (bulk), Akatsuki ore body, initial ratio (187Os/188Os)i at 292 Ma Mean and standard deviation recalculated from 5 analyses, 0.5787 to 0.6437 (04ku138 0.5995; 04ku139 0.6437; 04ku140 0.5827; 04ku141 0.5787; 04ku142 0.6143). Initial ratios recalculated by the authors at 292.015 Ma (mid-Sakmarian). Duplicates averaged: 04ku140 0.5834 and 0.5819. The table spells "Akatusuki". | Yano et al. (2023), Marine osmium isotopic composition reconstructed from the early Permi… |
| 0.6114 ± 0.0392 | 0.5239 / 0.6768 | 22 | umber (bulk), measured present-day ratio Mean and standard deviation recalculated from 22 analyses, 0.5239 to 0.6768 (04ku076 0.5466; 04ku078 0.6255; 04ku080 0.6659; 04ku081 0.6251; 04ku085 0.6049; 04ku150 0.6768; 04ku120 0.5915; 04ku121 0.5849; 04ku122 0.6506; 04ku123 0.6371; 04ku124 0.6156; 04ku125 0.6368; 04ku126 0.5813; 04ku127 0.6542; 04ku128 0.5619; 04ku129 0.5239; 04ku130 0.6341; 04ku138 0.6014; 04ku139 0.6457; 04ku140 0.5862; 04ku141 0.5791; 04ku142 0.6214). 22 samples from the Kagami, Noboru and Akatsuki ore bodies, duplicates averaged. Os 42 to 183 ppt, Re 1.3 to 49 ppt, 187Re/188Os 0.06 to 3.2: the age correction stays small, and the published mean initial ratio is 0.608 ± 0.039 (1 SD). The authors read it as early Permian seawater, Os being mostly hydrogenetic. Duplicates of 04ku127: 0.6357 and 0.6727 (initial 0.6230 and 0.6590), far beyond the 2 SE (0.0012 to 0.0014). Duplicates of 04ku140: 187Re/188Os of 0.988 and 0.450 for almost identical Re and Os contents (6.51 and 6.23 ppt; 70.60 and 70.69 ppt), which suggests an error in the table. | Yano et al. (2023), Marine osmium isotopic composition reconstructed from the early Permi… |
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Cite this page
IsoFind Atlas (2026). Kunimiyama, isotope signatures. https://www.isofind.tech/isotopes/en/deposits/kunimiyama/ (accessed 2026-10-20).
@misc{isofind2026kunimiyamaisotopesignatures,
title = {Kunimiyama, isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/kunimiyama/},
note = {Accessed 2026-10-20}
}Updated : 2026-10-20