Alexandrinka
Southern Urals, East Magnitogorsk island-arc zone, Russia
Volcanogenic massive sulfidesZn-Cu (Ag, Au)
- Type
- Polymetallic volcanic-hosted massive sulphide
Medium-sized Middle Devonian massive sulphide (9.8 Mt at 5.5 % Zn, 4.4 % Cu, 57 g/t Ag and 2.2 g/t Au) in the Givetian Karamalytash Formation, an island-arc dacite-basalt volcanic series. Sulphide mound almost completely degraded on the seafloor: coarse breccias near the mound, graded sediments on the flanks, metalliferous sediments in the hanging wall. Tessalina et al. (2008): Os increases and initial 187Os/188Os decreases from chimneys to stockwork, massive and clastic sulphides then metalliferous sediments, reflecting increasing mixing between reduced hydrothermal fluid and oxidised seawater; metalliferous sediments (0.17 to 0.2) would record Devonian seawater.
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 |
|---|---|---|---|---|
| 8.705 ± 4.646 | 5.419 / 11.99 | 2 | stockwork sulphides (hydrothermal-metasomatic facies), present-day ratio Mean and standard deviation recalculated from 2 analyses, 5.419 to 11.990 (A12 (Sp) 5.419; Al2 (Py) 11.990). Initial ratios at 355 Ma: A12 0.485 (Re 11.4 ppb, Os 103.2 ppt); Al2 0.992 (Re 17.7 ppb, Os 98.6 ppt). The table gives A12 (sphalerite) and Al2 (pyrite): probably the same stockwork sample spelled two ways. Errorchron of 355 ± 15 Ma (2σ), poorly constrained initial of 0.12 ± 0.19. | Tessalina et al. (2008), Osmium isotope distribution within the Palaeozoic Alexandrinka s… |
| 6.241 ± 6.416 | 2.029 / 13.625 | 3 | seafloor chimney and massive sulphides (pyrite, chalcopyrite, sphalerite), present-day ratio Mean and standard deviation recalculated from 3 analyses, 2.029 to 13.625 (5978/148.7 13.625; 6025/185.5 2.029; 6025/185 3.070). Initial ratios at 355 Ma: 5978/148.7 1.324 (Re 11.8 ppb, Os 69.8 ppt); 6025/185.5 0.128 (Re 12.5 ppb, Os 216.3 ppt); 6025/185 0.184 (Re 12.2 ppb, Os 154.8 ppt). Chimney 5978/148.7 gives the most radiogenic initial (1.324), taken by the authors as a minimum value for the Devonian hydrothermal fluid. Errorchron of 355 ± 15 Ma (2σ), poorly constrained initial of 0.12 ± 0.19. | Tessalina et al. (2008), Osmium isotope distribution within the Palaeozoic Alexandrinka s… |
| 1.198 | 1 | fine-clastic ore (pyrite, chalcopyrite, sphalerite), present-day ratio Single analysis (6025/162.3). Initial ratios at 355 Ma: 6025/162.3 0.321 (Re 31.2 ppb, Os 1071.9 ppt). 10 cm clastic cycle on the southern flank of the orebody, highest Os content of the deposit. Errorchron of 355 ± 15 Ma (2σ), poorly constrained initial of 0.12 ± 0.19. | Tessalina et al. (2008), Osmium isotope distribution within the Palaeozoic Alexandrinka s… | |
| 0.631 ± 0.433 | 0.339 / 1.49 | 6 | seafloor-altered metalliferous sediments (barite, chlorite, hematite, carbonate), present-day ratio Mean and standard deviation recalculated from 6 analyses, 0.339 to 1.490 (Ba1 0.484; 6025/168 0.339; 6019/48.6 1.490; 5999/102.8 0.3825; 5906/475 0.630; 6022/122.9 0.460). Initial ratios at 355 Ma: Ba1 -0.280 (Re 0.8 ppb, Os 29.4 ppt); 6025/168 0.222 (Re 2.0 ppb, Os 45.6 ppt); 6019/48.6 0.229 (Re 1.9 ppb, Os 46.5 ppt); 5999/102.8 0.067 (Re 0.2 ppb, Os 13.2 ppt); 5906/475 -0.173 (Re 0.6 ppb, Os 21.2 ppt); 6022/122.9 0.174 (Re 0.5 ppb, Os 50.3 ppt). Two initials are negative (Ba1 -0.280, 5906/475 -0.173), a sign of an open Re-Os system. For 6025/168, the published common Os (443.8 ppt) exceeds total Os (45.6 ppt), probably a typo for 43.8. Errorchron of 355 ± 15 Ma (2σ), poorly constrained initial of 0.12 ± 0.19. | Tessalina et al. (2008), Osmium isotope distribution within the Palaeozoic Alexandrinka s… |
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- Kidd Creek Canada
- Flin Flon Canada
- Rio Tinto Spain
- Cyclades (Kondaros-Katsimouti and Triades) Greece
- Boliden Sweden
- Tharsis Spain
Cite this page
IsoFind Atlas (2026). Alexandrinka, isotope signatures. https://www.isofind.tech/isotopes/en/deposits/alexandrinka/ (accessed 2026-10-20).
@misc{isofind2026alexandrinkaisotopesignatures,
title = {Alexandrinka, isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/alexandrinka/},
note = {Accessed 2026-10-20}
}Updated : 2026-10-20