Gacun
Western Sichuan, Baiyu (Yidun arc), China
Volcanogenic massive sulfidesZn-Pb-Cu (Ag)
- Type
- Rhyolite-hosted volcanogenic massive sulfide (VHMS)
Giant Triassic volcanogenic massive sulfide deposit in an intra-arc rift of the Yidun arc. It comprises a massive sulfide lens (UMO), a strata-bound stockwork (MSO) in a rhyolitic tuff and a lower stringer zone (LSO) in a rhyolitic dome. Lithium in quartz and its fluid inclusions shows a large input of magmatic fluid, dominant in the lower zone (80 to 90%) and smaller in the massive lens (less than 50%).
δ7Li in ‰ (per mil) Values of the same system
Standard : IRMM-016
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 4.1 / 22.5 ‰ | 41 | pure gangue quartz Published range for 41 samples; δ7Li increases laterally away from the feeder zone. Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… | |
| 0.8 / 4.2 ‰ | 12 | quartz with sericite (LSO and MSO zones) Published range for 12 samples; a mixed value, lowered by sericite. Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… | |
| 3.7 / 15 ‰ | 17 | fluid inclusions in pure quartz (crush-leach) Published range for 17 extracts. Mean fluid values increase from +5.4 ‰ (LSO) to +9.8 ‰ (UMO). The abstract gives +4.5 to +13.8 ‰ for fluid inclusions, a range the text also assigns to the quartz-fluid offset of the 9 samples with primary inclusions: an internal inconsistency of the paper. Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… | |
| 1.3 / 10.2 ‰ | 12 | fluid inclusions in quartz with sericite Published range for 12 extracts; considered by the authors as representative of the ore fluid. Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… | |
| −0.7 / 18.4 ‰ | 32 | calculated ore fluid (from pure quartz) Values calculated by the authors from quartz δ7Li and homogenisation temperature, using their empirical quartz-fluid equation (175 to 340 °C). The discussion also gives +18.5 ‰ for the upper bound. Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… | |
| 1 / 2.3 ‰ | 3 | fresh rhyolite outside the deposit Published range for 3 samples, close to continental crust; local unaltered reference. Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… | |
| 1.2 / 8.8 ‰ | 6 | altered rhyolite from the feeder zone Quoted values: +1.2 ‰ (rhyolitic dome), +3.4 ‰ (LSO host rock), +8.8 ‰ (MSO host rock), increasing upwards. The range for the 6 samples is inferred from these values. Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… |
δ18O in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 2.6 / 16.4 ‰ | 53 | gangue quartz (pure and with sericite) Published range for 53 samples; precision 0.2 ‰ (1σ). Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… | |
| 0.9 / 8.7 ‰ | 53 | calculated ore fluid (in equilibrium with quartz) Values calculated by the authors with the quartz-water equation of Matsuhisa et al. (1979) and homogenisation temperatures (117 to 368 °C). Means decrease from the dome (+7.6 ‰) and the LSO zone (+7.1 ‰) to the MSO zone (+5.4 ‰) and the massive lens (+2.8 ‰). Individual values in Table S1, not consulted. | Yang et al. (2015), Lithium isotope traces magmatic fluid in a seafloor hydrothermal syst… |
Deposits of the same type
- Honghai (Kalatag district) China
- Tangyin Mer de Chine orientale
- Yonaguni IV Mer de Chine orientale
- Iheya North Mer de Chine orientale
- Iheya Ridge Mer de Chine orientale
- Matsumine Japan
- Doyashiki (Kannondo) Japan
- Ezuri Japan
Cite this page
IsoFind Atlas (2026). Gacun, isotope signatures. https://www.isofind.tech/isotopes/en/deposits/gacun/ (accessed 2026-10-13).
@misc{isofind2026gacunisotopesignatures,
title = {Gacun, isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/gacun/},
note = {Accessed 2026-10-13}
}Updated : 2026-10-13