Hydrothermal mixing, carbonate dissolution and sulfide precipitation in Mississippi Valley-type deposits

Research output: Contribution to journalArticleResearchpeer-review

82 Citations (Scopus)

Abstract

A large number of Mississippi Valley-Type (MVT) deposits are located within dissolution zones in carbonate host rocks. Some genetic models propose the existence of cavities generated by an earlier event such as a shallow karstification, that were subsequently filled with hydrothermal minerals. Alternative models propose carbonate dissolution caused by the simultaneous precipitation of sulfides. These models fail to explain either the deep geological setting of the cavities, or the observational features which suggest that the dissolution of carbonates and the precipitation of minerals filling the cavities are not strictly coeval. We present a genetic model inspired by the textural characteristics of MVT deposits that accounts for both the dissolution of carbonate and precipitation of sulfides and later carbonates in variable volumes. The model is based on the mixing of two hydrothermal fluids with a different chemistry. Depending on the proportion of the end members, the mixture dissolves and precipitates carbonates even though the two mixing solutions are both independently saturated in carbonates. We perform reactive transport simulations of mixing of a regional groundwater and brine ascending through a fracture, both saturated in calcite, but with different overall chemistries (Ca and carbonate concentrations, pH, etc). As a result of the intrinsic effects of chemical mixing, a carbonate dissolution zone, which is enhanced by acid brines, appears above the fracture, and another zone of calcite precipitation builds up between the cavity and the surrounding rock. Sulfide forms near the fracture and occupies a volume smaller than the cavity. A decline of the fluid flux in the fracture would cause the precipitation of calcite within the previously formed cavities. Therefore, dissolution of carbonate host rock, sulfide precipitation within the forming cavity, and later filling by carbonates may be part of the same overall process of mixing of fluids in the carbonate host rock. © Springer-Verlag 2004.
Original languageEnglish
Pages (from-to)344-357
JournalMineralium Deposita
Volume39
DOIs
Publication statusPublished - 1 May 2004

Keywords

  • Carbonate dissolution
  • Fluid mixing
  • Hydrothermal karst
  • Mississippi Valley-type deposits

Fingerprint

Dive into the research topics of 'Hydrothermal mixing, carbonate dissolution and sulfide precipitation in Mississippi Valley-type deposits'. Together they form a unique fingerprint.

Cite this