Bayan Obo
Inner Mongolia, China
Magmatic (Ni-Cu-PGE, carbonatites)Fe (REE, Nb)
- Type
- Carbonatite (Fe-REE-Nb deposit)
The largest rare earth deposit in the world, associated with a carbonatite complex. Iron is mineralised as massive magnetite.
δ56Fe in ‰ (per mil) Values of the same system
Standard : IRMM-014
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −0.03 ± 0.16 ‰ | 14 | fine iron ore (bulk) δ56Fe values close to zero, consistent with a magmatic origin and distinct from both sedimentary banded iron formations and hydrothermal ores. Uncertainty at 2 standard deviations. | Sun et al. 2013, Iron isotopic constraints on the genesis of Bayan Obo, Precambrian Resea… | |
| 0.01 ± 0.14 ‰ | 14 | magnetite | Sun et al. 2013, Iron isotopic constraints on the genesis of Bayan Obo, Precambrian Resea… | |
| 0.08 ± 0.18 ‰ | 3 | hematite Very small Δ56Fe fractionation between hematite and magnetite (about 0.07 ‰), indicating high-temperature equilibrium. | Sun et al. 2013, Iron isotopic constraints on the genesis of Bayan Obo, Precambrian Resea… | |
| −0.33 / −0.08 ‰ | siderite (carbonatite) Slightly negative δ56Fe values, consistent with a mantle source as in typical carbonatites, and distinct from Mesoproterozoic sedimentary carbonates. | Etude Fe-Mg-Sr-Nd-Pb-C-O isotopes des carbonatites a siderite de Bayan Obo, 2025 |
206Pb/204Pb isotope ratio, no unit Values of the same system
Standard : NIST SRM 981
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 15.992 / 16.482 | siderite (carbonatite) Measurements on siderite carbonatites, with a mantle signature, distinct from the unradiogenic lead of the Bolivian Andes. | Etude Fe-Mg-Sr-Nd-Pb-C-O des carbonatites a siderite de Bayan Obo, 2025 |
207Pb/204Pb isotope ratio, no unit Values of the same system
Standard : NIST SRM 981
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 15.271 / 15.412 | siderite (carbonatite) | Etude Fe-Mg-Sr-Nd-Pb-C-O des carbonatites a siderite de Bayan Obo, 2025 |
208Pb/204Pb isotope ratio, no unit Values of the same system
Standard : NIST SRM 981
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 36.701 / 51.566 | siderite (carbonatite) A very wide 208Pb/204Pb range, reflecting variability of the Th/Pb ratio in the carbonatite components. | Etude Fe-Mg-Sr-Nd-Pb-C-O des carbonatites a siderite de Bayan Obo, 2025 |
Deposits of the same type
- Jinchuan China
- Norilsk-Talnakh Russia
- Pechenga Russia
- Great Dyke (Main Sulfide Zone) Zimbabwe
- Bushveld, Platreef South Africa
- Bushveld, UG2 chromitite South Africa
- Bushveld, Merensky Reef South Africa
- Rössing Namibia
Cite this page
IsoFind Atlas (2026). Bayan Obo, isotope signatures. https://www.isofind.tech/isotopes/en/deposits/bayan-obo/ (accessed 2026-10-06).
@misc{isofind2026bayanoboisotopesignatures,
title = {Bayan Obo, isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/bayan-obo/},
note = {Accessed 2026-10-06}
}Updated : 2026-10-06