Bajo de la Alumbrera
Catamarca (Farallón Negro Volcanic Complex), Argentina
PorphyriesCu-Au
- Type
- Porphyry Cu-Au
Late Miocene gold-rich porphyry copper deposit in the Farallón Negro Volcanic Complex (intermontane basin of the Tucumán fault zone, between the Puna and the Sierras Pampeanas); 402 Mt at 0.54 % Cu and 0.64 g/t Au (Proffett, 2003). Biotite dacite porphyries dated (zircon U-Pb) at 7.98 ± 0.14 Ma (P2, main ore host) and 7.10 ± 0.07 Ma (P3). Mineralised potassic core (biotite, K-feldspar, quartz), propylitic halo, intermediate argillic alteration (chlorite-illite ± pyrite) overprinting the top and flanks, then phyllic (quartz-muscovite-illite ± pyrite). Fluid inclusions: chalcopyrite-bearing brines up to 845 °C and 65 wt% NaCl eq. in early veins, 300-550 °C and 25-57 % in mineralised potassic alteration, 250-390 °C and 2-12 % in intermediate argillic, 120-410 °C and up to 15 % in phyllic alteration. Magmatic fluids dominant at every stage according to the authors: early potassic δ18O +8.3 to +10.2 ‰ and δD -33 to -81 ‰, late potassic D-depleted (down to -123 ‰) by phase separation, intermediate argillic +4.8 to +8.1 ‰ and -31 to -71 ‰, phyllic -0.8 to +10.2 ‰ and -31 to -119 ‰. Coordinates from the sample GPS points (Table 3).
δ18O in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 10.23 ± 0.35 ‰ | 9.9 / 10.6 ‰ | 3 | early potassic (stage 1) vein quartz Mean and standard deviation recalculated from 3 analyses, ACH0125, ACH99105 and ACH9983; model fluid at 625 °C of +9.1 to +9.8 ‰, primary magmatic water. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 7.03 ± 0.57 ‰ | 6.4 / 7.5 ‰ | 3 | early potassic (stage 1) hydrothermal biotite Mean and standard deviation recalculated from 3 analyses, ACH9984, ACH9985 and ACH9987; model fluid at 625 °C of +9.0 to +10.1 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 9.75 ± 1.04 ‰ | 8.3 / 10.6 ‰ | 4 | late, mineralised potassic (stage 2) vein quartz Mean and standard deviation recalculated from 4 analyses, ACH9973, ACH9999, ACH99153 and ACH99157; model fluid at 450 °C of +5.2 to +7.5 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 8.8 ‰ | 1 | propylitic chlorite (BAL00/263) Single analysis; model fluid at 325 °C of +9.0 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… | |
| 6.25 ± 1.77 ‰ | 5 / 7.5 ‰ | 2 | intermediate argillic (stage 3) chlorite Mean and standard deviation recalculated from 2 analyses, ACH9987 and ACH0125; model fluid at 325 °C of +5.2 and +7.7 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 12.25 ± 2.05 ‰ | 10.8 / 13.7 ‰ | 2 | main-stage phyllic (stage 4) vein quartz Mean and standard deviation recalculated from 2 analyses, ACH9923 and ACH9994. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 8.94 ± 1.62 ‰ | 6.6 / 11.7 ‰ | 9 | main-stage phyllic (stage 4) illite Mean and standard deviation recalculated from 9 analyses, model fluid at 375 °C of +4.7 to +9.8 ‰, in two groups by δD. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 6.57 ± 0.47 ‰ | 6.2 / 7.1 ‰ | 3 | phenocrystic biotite of the late porphyries (Late P3) Mean and standard deviation recalculated from 3 analyses, water in equilibrium at 700 °C of +8.9 to +9.8 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 10.55 ± 0.07 ‰ | 10.5 / 10.6 ‰ | 2 | early potassic (stage 1) quartz (Ulrich et al., 2002) Mean and standard deviation recalculated from 2 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 2.95 ± 0.21 ‰ | 2.8 / 3.1 ‰ | 2 | early potassic (stage 1) magnetite (Ulrich et al., 2002) Mean and standard deviation recalculated from 2 analyses, model fluid of +8.3 and +8.6 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 6.8 ± 0.52 ‰ | 6.5 / 7.4 ‰ | 3 | late potassic (stage 2) biotite (Ulrich et al., 2002) Mean and standard deviation recalculated from 3 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 9.68 ± 1.19 ‰ | 8.5 / 11.3 ‰ | 4 | late potassic (stage 2) quartz (Ulrich et al., 2002) Mean and standard deviation recalculated from 4 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 10.25 ± 0.49 ‰ | 9.9 / 10.6 ‰ | 2 | propylitic albite (BLA55 and BLA64, Ulrich et al., 2002) Mean and standard deviation recalculated from 2 analyses, model fluid of +6.4 and +5.7 ‰, lower than that from chlorite. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 10.04 ± 1 ‰ | 8.3 / 10.7 ‰ | 5 | phyllic (stage 4) quartz (Ulrich et al., 2002) Mean and standard deviation recalculated from 5 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| 9.2 ‰ | 1 | phenocrystic quartz of the late LP porphyry (Ulrich et al., 2002) Single analysis. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
δD in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −58.67 ± 24.17 ‰ | −81 / −33 ‰ | 3 | fluid inclusion water in early potassic (stage 1) quartz Mean and standard deviation recalculated from 3 analyses, same samples. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −86 ± 15.1 ‰ | −102 / −72 ‰ | 3 | early potassic (stage 1) hydrothermal biotite Mean and standard deviation recalculated from 3 analyses, model fluid of -73 to -43 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −105.33 ± 27.21 ‰ | −123 / −74 ‰ | 3 | fluid inclusion water in late potassic (stage 2) quartz Mean and standard deviation recalculated from 3 analyses, D-depleted fluid through degassing and phase separation of the magmatic fluid according to the authors. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −69 ‰ | 1 | propylitic chlorite (BAL00/263) Single analysis; model fluid of -45 ‰. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… | |
| −75 ± 28.28 ‰ | −95 / −55 ‰ | 2 | intermediate argillic (stage 3) chlorite Mean and standard deviation recalculated from 2 analyses, model fluid of -31 and -71 ‰, magmatic water directly involved according to the authors. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −119 ‰ | 1 | fluid inclusion water in phyllic quartz (ACH9923) Single analysis. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… | |
| −81 ± 18.26 ‰ | −113 / −61 ‰ | 9 | main-stage phyllic (stage 4) illite Mean and standard deviation recalculated from 9 analyses, fluids of -66 to -88 ‰ (residual magmatic water) and -36 to -48 ‰ (poorer in 18O, close to Miocene meteoric waters at 200 °C). | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −95 ± 11.31 ‰ | −103 / −87 ‰ | 2 | phenocrystic biotite of the late porphyries (Late P3) Mean and standard deviation recalculated from 2 analyses, water of -78 and -62 ‰: magma that had already exsolved much water according to the authors. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −80 ± 7.97 ‰ | −90 / −68 ‰ | 5 | late potassic (stage 2) biotite (Ulrich et al., 2002) Mean and standard deviation recalculated from 5 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −55 ‰ | 1 | inclusion water in late potassic quartz (43-47.1/195, Ulrich et al., 2002) Single analysis. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… | |
| −77.5 ± 0.71 ‰ | −78 / −77 ‰ | 2 | propylitic chlorite (BLA55 and BLA64, Ulrich et al., 2002) Mean and standard deviation recalculated from 2 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −65.5 ± 19.09 ‰ | −79 / −52 ‰ | 2 | inclusion water in phyllic quartz (Ulrich et al., 2002) Mean and standard deviation recalculated from 2 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −71 ± 2 ‰ | −73 / −69 ‰ | 3 | probable illite of the phyllic alteration (Ulrich et al., 2002) Mean and standard deviation recalculated from 3 analyses. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
| −110 ‰ | 1 | biotite of the late LP porphyry (Ulrich et al., 2002) Single analysis. | Harris et al. (2005), Bajo de la Alumbrera Copper-Gold Deposit: Stable Isotope Evidence f… |
Deposits of the same type
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Cite this page
IsoFind Atlas (2026). Bajo de la Alumbrera, isotope signatures. https://www.isofind.tech/isotopes/en/deposits/bajo-de-la-alumbrera/ (accessed 2026-10-14).
@misc{isofind2026bajodelaalumbreraisotopesigna,
title = {Bajo de la Alumbrera, isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/bajo-de-la-alumbrera/},
note = {Accessed 2026-10-14}
}Updated : 2026-10-14