Bancroft (uraniferous pegmatites)
Ontario, Bancroft district, Canada
UraniumU
- Type
- Uraninite-bearing granitic pegmatites and alaskites (IAEA class 1.1)
Uranium ore sample from the Queen's University collection analysed by Voinot et al. (2024) for U, Mo and Tl; ε205Tl and δ238U decrease together in metamorphic and unconformity deposits (U reduction and Tl redox change), whereas δ97Mo is strongly modified by late remobilisation. Grenvillian pegmatites (about 953 Ma); uraninite with very low ε205Tl (-8.2), in the light population of intrusive deposits (-9.1 to -8.0). Indicative coordinates (Bancroft). Uvarova et al. (2014): δ238U (normalisation offset by about +0.60 ‰) and δ234U of samples from the Queen's University collection (Table 2).
δ238U in ‰ (per mil) Values of the same system
Standard : NBL CRM 112-A
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −0.25 ‰ | 1 | pegmatite uraninite Single analysis; per-sample uncertainty not published; sample U402; IAEA class 1.1. Anatectic: Pegmatite - alaskite (intrusive); average age used 953 Ma; 57.3 % U, 0.78 µg/g Tl, 1.77 µg/g Mo. | Voinot et al. (2024), Tl, Mo and U isotopes in U-ore deposits record Earth's fundamental … | |
| 0.29 ± 0.1 ‰ | 1 | Th-rich uraninite Single analysis; ± 0.10 ‰ (2 SD, reproducibility); sample Cardiff M6639, Cardiff, Ontario; bracketing-only δ238U at +0.25; 238U/235U of 137.877; about -0.31 ‰ after removing the 0.60 ‰ offset specific to this study. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… | |
| 0.47 ± 0.1 ‰ | 1 | Th-rich uraninite Single analysis; ± 0.10 ‰ (2 SD, reproducibility); sample M20798, Wilberforce, Haliburton County, Ontario; bracketing-only δ238U at +0.32; 238U/235U of 137.902; about -0.13 ‰ after removing the 0.60 ‰ offset specific to this study. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… | |
| 0.36 ± 0.1 ‰ | 1 | Th-rich uraninite Single analysis; ± 0.10 ‰ (2 SD, reproducibility); sample M22301A, Nu-age property, Haliburton County, Ontario; bracketing-only δ238U at +0.41; 238U/235U of 137.886; about -0.24 ‰ after removing the 0.60 ‰ offset specific to this study. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… | |
| 0.33 ± 0.1 ‰ | 1 | Th-rich uraninite Single analysis; ± 0.10 ‰ (2 SD, reproducibility); sample M22299, Nu-age property, Haliburton County, Ontario; bracketing-only δ238U at +0.36; 238U/235U of 137.882; about -0.27 ‰ after removing the 0.60 ‰ offset specific to this study. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… |
δ234U in ‰ (per mil) Values of the same system
Standard : équilibre séculaire
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 33 ‰ | 1 | pegmatite uraninite Single analysis; per-sample uncertainty not published; sample U402; IAEA class 1.1. Anatectic: Pegmatite - alaskite (intrusive); average age used 953 Ma; 57.3 % U, 0.78 µg/g Tl, 1.77 µg/g Mo. | Voinot et al. (2024), Tl, Mo and U isotopes in U-ore deposits record Earth's fundamental … | |
| 5 ‰ | 1 | Th-rich uraninite Single analysis; per-sample uncertainty not published; sample Cardiff M6639, Cardiff, Ontario. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… | |
| 2 ‰ | 1 | Th-rich uraninite Single analysis; per-sample uncertainty not published; sample M20798, Wilberforce, Haliburton County, Ontario. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… | |
| 0 ‰ | 1 | Th-rich uraninite Single analysis; per-sample uncertainty not published; sample M22301A, Nu-age property, Haliburton County, Ontario. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… | |
| −5 ‰ | 1 | Th-rich uraninite Single analysis; per-sample uncertainty not published; sample M22299, Nu-age property, Haliburton County, Ontario. | Uvarova et al. (2014), Variations in the uranium isotopic compositions of uranium ores fr… |
ε205Tl in ε units (parts per 10,000) Values of the same system
Standard : NIST SRM 997
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −8.2 ± 0.7 ε | 1 | pegmatite uraninite Single analysis; ± 0.7 (2 SD); sample U402; IAEA class 1.1. Anatectic: Pegmatite - alaskite (intrusive); average age used 953 Ma; 57.3 % U, 0.78 µg/g Tl, 1.77 µg/g Mo. | Voinot et al. (2024), Tl, Mo and U isotopes in U-ore deposits record Earth's fundamental … |
Deposits of the same type
- Faraday Canada
- Madawaska Canada
- Denison Canada
- Milliken Lake Canada
- Stanleigh Canada
- Stanrock Canada
- Grafton Center (pegmatites, New Hampshire) United States
- Ingersoll Mine (Black Hills) United States
Cite this page
IsoFind Atlas (2026). Bancroft (uraniferous pegmatites), isotope signatures. https://www.isofind.tech/isotopes/en/deposits/bancroft-pegmatites-uraniferes/ (accessed 2026-10-16).
@misc{isofind2026bancrofturaniferouspegmatites,
title = {Bancroft (uraniferous pegmatites), isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/bancroft-pegmatites-uraniferes/},
note = {Accessed 2026-10-16}
}Updated : 2026-10-16