Duluth Complex, PGM-bearing basal troctolites
Minnesota, Duluth Complex (basal zone), United States
Magmatic (Ni-Cu-PGE, carbonatites)Cu-Ni (Pt, Pd)
- Type
- Magmatic Cu-Ni-PGE sulphides (late-magmatic hydrothermal remobilisation)
Cu-Ni-mineralised gabbroic troctolites of the basal zone of the Duluth Complex (Midcontinent Rift, about 1100 Ma), drill holes W9, BA1, II-1, 34872, DU-15 and BI-144: Pd bismuthotellurides (moncheite, michenerite, froodite), sperrylite, taimyrite and Fe-Pt alloys associated with hydrous silicates (prehnite, serpentine, chlorite, biotite, actinolite), graphite and the rims of zoned spinels; Os 3-15, Ir 0.1-25.1, Pt 25-390, Pd 5-1300 ppb; serpentine up to 1.1 wt% Cl. Narrow δ34S (+4 to +9 ‰, +13.8 ‰ in a graphite-rich troctolite), different from Cu-rich troctolites without PGM and close to the PGE-rich zone at Babbitt; late-magmatic chlorine-bearing C-O-H-S fluids and a second Cu mineralisation episode according to Mogessie and Stumpfl (1992). Drill holes spread over several sectors of the basal zone, hence an entry separate from Dunka Road and Babbitt. Coordinates not given.
δ34S in ‰ (per mil) Values of the same system
Standard : V-CDT
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 6.13 ± 1.56 ‰ | 4.61 / 9.1 ‰ | 13 | sulphides of PGM-bearing basal troctolites (whole rock) Mean and standard deviation recalculated from 13 analyses, 13 samples from drill holes W9, BA1, 34872, DU-15 and BI-144; narrower than the Cu-rich troctolites of Dunka Road (+0.2 to +15.3 ‰). | Mogessie et Stumpfl (1992), Platinum-group element and stable isotope geochemistry of PGM… |
| 13.83 ‰ | 1 | sulphides of a graphite-rich troctolite (II-1-220.5, 15 % S) Single analysis; 40 to 60 modal % graphite, V-rich oxides, arsenides and pyrrhotite. | Mogessie et Stumpfl (1992), Platinum-group element and stable isotope geochemistry of PGM… |
δ18O in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 5.68 ± 1.79 ‰ | 2.107 / 7.318 ‰ | 9 | PGM-bearing basal troctolites (whole rock) Mean and standard deviation recalculated from 9 analyses, values below +5 ‰ in magnetite-rich samples, normal according to Ripley; BA1-2636.5 and BI-144-670.5 share the same value (+7.318 ‰). | Mogessie et Stumpfl (1992), Platinum-group element and stable isotope geochemistry of PGM… |
Deposits of the same type
- Bayan Obo China
- Norilsk-Talnakh Russia
- Bushveld, Merensky Reef South Africa
- Bushveld, UG2 chromitite South Africa
- Bushveld, Platreef South Africa
- Sudbury Canada
- Voisey's Bay Canada
- Rössing Namibia
Cite this page
IsoFind Atlas (2026). Duluth Complex, PGM-bearing basal troctolites, isotope signatures. https://www.isofind.tech/isotopes/en/deposits/complexe-de-duluth-troctolites-basales-a-mineraux-du-groupe-du-platine/ (accessed 2026-10-15).
@misc{isofind2026duluthcomplexpgmbearingbasalt,
title = {Duluth Complex, PGM-bearing basal troctolites, isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/complexe-de-duluth-troctolites-basales-a-mineraux-du-groupe-du-platine/},
note = {Accessed 2026-10-15}
}Updated : 2026-10-15