Granite Creek (Osgood Mountains)
Potosi district, Osgood Mountains, Humboldt County, Nevada, United States
SkarnsW (Cu, Mo)
- Type
- Calcic scheelite skarn (garnet-pyroxene) at a granodiorite contact
Massive grandite garnet-pyroxene skarn between the Late Cretaceous Osgood Mountains granodiorite stock and marbles of the Preble Formation, mined underground (levels 200 to 500). Stage I with mostly magmatic fluid (δ18O +9.0 ‰, δD -30 to -45 ‰), stage II replacement by quartz, Fe-rich amphibole, epidote and calcite at 480-550 °C with 20 to 50 % meteoric water, stage III pyrite and calcite up to an entirely meteoric water (Late Cretaceous: δ18O -14.0 ‰, δD -107 ‰). Coordinates from Mindat (Granite Creek mine).
δ18O in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 6.97 ± 0.36 ‰ | 6.2 / 7.5 ‰ | 13 | skarn grandite garnet Mean and standard deviation recalculated from 13 samples, Samples from levels 200 to 500 in the part of Table 5 before the 'other mines'; assigned to Granite Creek from the levels and the text. One value per sample; fractions of different composition averaged (72-76-2, 72-105-4, 73-249). δ18O decreases as andradite content rises (apparent 2.5 ‰ end-member difference). Other mines: 7.2 to 8.8 ‰ (Alpine, Moly). | Taylor et O'Neil (1977), Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and ass… |
| 8.8 ± 0.29 ‰ | 8.5 / 9.1 ‰ | 4 | skarn pyroxene Mean and standard deviation recalculated from 4 samples, Samples from levels 200 to 500 in the part of Table 5 before the 'other mines'; assigned to Granite Creek from the levels and the text. Stage I. | Taylor et O'Neil (1977), Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and ass… |
| 14.11 ± 0.33 ‰ | 13.7 / 14.7 ‰ | 7 | skarn quartz (stage II) Mean and standard deviation recalculated from 7 samples, Samples from levels 200 to 500 in the part of Table 5 before the 'other mines'; assigned to Granite Creek from the levels and the text. Quartz-amphibole pairs: 480-550 °C (mean 523 ± 25 °C, Bottinga and Javoy, 1973). | Taylor et O'Neil (1977), Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and ass… |
| 9.27 ± 0.25 ‰ | 8.8 / 9.5 ‰ | 10 | Fe-rich tremolitic amphibole (stage II) Mean and standard deviation recalculated from 10 samples, Samples from levels 200 to 500 in the part of Table 5 before the 'other mines'; assigned to Granite Creek from the levels and the text. Narrow range: formation over about 70 °C. | Taylor et O'Neil (1977), Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and ass… |
| 13.01 ± 0.56 ‰ | 12.2 / 14.1 ‰ | 15 | skarn calcite Mean and standard deviation recalculated from 15 samples, Samples from levels 200 to 500 in the part of Table 5 before the 'other mines'; assigned to Granite Creek from the levels and the text. Calcite mostly from stage III, in pods and interstitial. Narrow range: composition buffered by a constant fluid; carbon mostly magmatic according to the authors. | Taylor et O'Neil (1977), Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and ass… |
δD in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −122.2 ± 16.9 ‰ | −152 / −95 ‰ | 13 | Fe-rich tremolitic amphibole (stage II) Mean and standard deviation recalculated from 13 samples, Samples from levels 200 to 500 in the part of Table 5 before the 'other mines'; assigned to Granite Creek from the levels and the text. 60 ‰ spread, against 20 ‰ for granodiorite amphiboles: exchange with deuterium-depleted meteoric water, lower δD for more abundant and coarser amphiboles. | Taylor et O'Neil (1977), Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and ass… |
δ13C in ‰ (per mil) Values of the same system
Standard : V-PDB
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −7.66 ± 1.09 ‰ | −10.2 / −5.8 ‰ | 15 | skarn calcite Mean and standard deviation recalculated from 15 samples, Samples from levels 200 to 500 in the part of Table 5 before the 'other mines'; assigned to Granite Creek from the levels and the text. Calcite mostly from stage III, in pods and interstitial. Narrow range: composition buffered by a constant fluid; carbon mostly magmatic according to the authors. | Taylor et O'Neil (1977), Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and ass… |
Deposits of the same type
- CanTung (E zone) Canada
- Buck Creek United States
- Antamina Peru
- Cobriza Peru
- Azegour Morocco
- Los Santos Spain
- Morille Spain
- Scalittas Italy
Cite this page
IsoFind Atlas (2026). Granite Creek (Osgood Mountains), isotope signatures. https://www.isofind.tech/isotopes/en/deposits/granite-creek-monts-osgood/ (accessed 2026-10-13).
@misc{isofind2026granitecreekosgoodmountainsis,
title = {Granite Creek (Osgood Mountains), isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/granite-creek-monts-osgood/},
note = {Accessed 2026-10-13}
}Updated : 2026-10-13