Advertisement

Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Sulfide composition and phase relations in the Fe-Ni-Cu ore deposits of the Ivrea-Verbano basic complex (western Alps, Italy)

Abstract

The bulk composition, mineralogy and mineral chemistry of base-metal sulfides have been investigated in the Fe-Ni-(Cu) ore deposits of the Ivrea-Verbano basic complex.

The sulfide ores mostly display textural evidence of having been primarily deposited as an immiscible melt. Bulk compositions of the ores indicate that considerably low Ni/Fe and Ni/Co ratios are found in deposits developed close to metasedimentary country rocks, possibly as a result of mixing with sedimentary sulfur.

Phase relations of primary sulfides indicate that early crystallization of the ore was dominated by a monosulfide solid solution (Mss) with a pyrrhotite composition, from which pentlandite and chalcopyrite were formed through subsolidus exsolution. Pentlandite from contaminated ores is typically enriched in Co. Troilite and hexagonal intermediate pyrrhotite intergrowths frequently occur due to low-temperature equilibration of metal-rich pyrrhotites, suggesting a low S fugacity of the original sulfide melt.

The sulfides may be locally mobilized and redeposited along shear zones within the same host rock, giving rise to fairly massive ores having a typical cemented-breccia texture. Bulk composition and assemblages suggest that mobilization occurred at various temperatures during the cooling history of the ore, when sulfides were still in the molten state or at a lower temperature under the influence of abundant deuteric fluids. In this last case, growth of pyrite is seen as being possibly due to sulfurization and/or oxidation.

This is a preview of subscription content, log in to check access.

References

  1. Arnold, R.G.: Pyrrhotite phase relations below 304.6 °C at 1 atm. total pressure. Econ. Geol. 64:405–419 (1969)

  2. Arnold, R.G., Reichen, L.E.: Measurement of the metal content of naturally occurring metal-deficient, hexagonal pyrrhotite by an X-ray spacing method. Am. Mineral. 47:105–111 (1962)

  3. Bertolani, M.: Studio microscopico a luce riflessa sui minerali dei giacimenti cupro-nicheliferi della Val Sesia. Rend. SIMP, 8:67–86 (1952)

  4. Bertolani, M.: Le manifestazioni metallifere della Val Strona (Novara). Atti Soc. Nat. Mat. Modena, 95:3–22 (1964)

  5. Bigioggero, B., Brigo, L., Ferrario, A., Gregnanin, A., Montrasio, A., Zuffardi, P.: Strona Valley (Fe-Ni-Cu) and (Fe-Ba) ore deposits: Excursion book. Mem. Ist. Geol. Min. Univ. Padova, 33:33–39 (1979)

  6. Buchnan, D., Nolan, J.: Solubility of sulfur and sulfide immiscibility in synthetic tholeitic melts and their relevance to Bushveld-complex rocks. Can. Mineral. 17:483–494 (1979)

  7. Campbell, I.H., Naldrett, A.J.: The influence of silicate:sulfide ratios on the geochemistry of magmatic sulfides. Econ. Geol. 74:1503–1506 (1979)

  8. Craig, J.R.: Pyrite-pentlandite assemblages and other low temperature relations in the Fe-Ni-S system. Am. Jour. Sc., 273-A:496–510 (1973)

  9. Craig, J.R., Naldrett, A.J., Kullerud, G.: Succession of mineral assemblages in pyrrhotite-rich Ni-Cu ores. Carnegie Inst. Washington, Year Book 67:431–434 (1967)

  10. Desborough, G.A., Carpenter, R.H.: Phase relations of pyrrhotite. Econ. Geol. 60:1431–1450 (1965)

  11. Durazzo, A., Taylor, L.A.: Exsolution in the Mss-pentlandite system: textural and genetic implications for Ni-sulfide ores. Mineral. Deposita 17:313–332 (1982)

  12. Ferrario, A., Garuti, G., Sighinolfi, G.P.: Platinum and palladium in the Ivrea-Verbano basic complex, Western Alps, Italy. Econ. Geol. 77:1548–1555 (1982)

  13. Ferrario, A., Garuti, G., Rossi, A., Sighinolfi, G.P.: Petrographic and metallogenic outlines of the “La Balma-M. Capio” Ultramafic-Mafic Body (Ivrea-Verbano Basic Complex, NW Italian Alps). Mineral Deposits of the Alps and of the Alpine Epoch in Europe, H.J. Schneider, Ed., pp 28–40. Berlin-Heidelberg: Springer (1983)

  14. Garuti, G., Rinaldi, R.: Mineralogy of melonite-group PGM and other tellurides from Ivrea-Verbano basic complex, Western Italian Alps. Fourth International Platinum Symposium, Abstracts, Can. Mineral. 23:303 (1985)

  15. Hawley, J.E.: The Sudbury ores: their mineralogy and origin. Can. Mineral. 7:1–207 (1962)

  16. Heilmann, H., Lensch, G.: Sulfur isotope investigation of sulfides and rocks from the main basic series of the Ivrea-Zone. Schweizer Min. Petr. Mitt. 57:445–456 (1977)

  17. Hunziker, J.C., Zingg, A.: Lower Paleozoic amphibolite- to granulite-facies metamorphism in the Ivrea zone (Southern Alps, Northern Italy). Schweizer Min. Petr. Mitt. 60:181–213 (1980)

  18. Hüttenlocher, F.: Die Erzlagerstättenzonen der Westalpen. Schweizer Min. Petr. Mitt. 14:22–149 (1934)

  19. Irvine, T.N.: Crystallization sequence in the Muscox Intrusion and other layered intrusions. II. Origin of chromite layers and similar deposits of other magmatic ores. Geochim. Cosmochim. Acta 39:991–1020 (1975)

  20. Kissin, S.A., Scott, S.D.: Phase relations involving pyrrhotite below 350 °C. Econ. Geol. 77:1739–1754 (1982)

  21. Kullerud, G.: Phase relations in the Fe-S-O system. Carnegie Inst. Washington, Year Book 56:198–200 (1957)

  22. Misra, K.C., Fleet, M.E.: The Chemical Compositions of synthetic and natural pentlandite assemblages. Econ. Geol. 68:518–539 (1973)

  23. Naldret, A.J.: A portion of the system Fe-S-O between 900° and 1080 °C and its application to sulfide ore magmas. Jour Petrology 10:171–201 (1969)

  24. Naldrett, A.J., Craig, J.R., Kullerud, G.: The central portion of the Fe-Ni-S system and its bearing on pentlandite exsolution in iron-nickel sulfide ores. Econ. Geol. 62:826–847 (1967)

  25. Omenetto, P., Brigo, L.: Metallogenesi nel quadro dell'orogene ercinico delle Alpi (con particolare riguardo al versante italiano). Mem. Soc. Geol. It. 13:1–24 (1974)

  26. Rivalenti, G., Garuti, G., Rossi, A.: The origin of the Ivrea-Verbano basic formation (Western Italian Alps). Whole rock geochemistry. Boll. Soc. Geol. It. 94:1149–1186 (1975)

  27. Rivalenti, G., Garuti, G., Rossi, A., Siena, F., Sinigoi, S.: Existence of different peridotite types and of a layered igneous complex, Western Alps, Italy. Jour. Petrology 22:127–153 (1980)

  28. Rivalenti, G., Rossi, A., Siena, F., Sinigoi, S.: The Layered Series of the Ivrea-Verbano Igneous Complex, Western Alps, Italy. TMPM, 33:77–99 (1984)

  29. Suardi, M.: I risultati della ricerca geomineraria nella zona Ivrea-Verbano (Piemonte). Relazione RIMIN s.p.a. — Ministero Ind. Comm. Artig., Div. Gen. Miniere. L'industria mineraria, 2:1–14 (1983)

  30. Vaasjoki, O., Hakli, T.A., Tontti, M.: The effect of cobalt on the thermal stability of pentlandite. Econ. Geol. 69:549–551 (1974)

  31. Yund, R.A., Kullerud, G.: Thermal stability of assemblages in the Cu-Fe-S system. Jour. Petrology 7:454–488 (1966)

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Garuti, G., Fiandri, P. & Rossi, A. Sulfide composition and phase relations in the Fe-Ni-Cu ore deposits of the Ivrea-Verbano basic complex (western Alps, Italy). Mineral. Deposita 21, 22–34 (1986). https://doi.org/10.1007/BF00204358

Download citation

Keywords

  • Sulfide
  • Pyrite
  • Shear Zone
  • Bulk Composition
  • Cooling History