Replacement of pyrrhotite by pyrite and marcasite under hydrothermal conditions up to 220  C: An experimental study of reaction textures and mechanisms

Characterization of porosity in sulfide ore minerals: A USANS/SANS study

“…In all cases the product mineral showed evidence of reaction generated porosity. The ore-forming reactions that have been studied include the replacement of pentlandite by violarite (Tenailleau et al 2006;Xia et al 2009Xia et al , 2008Xia et al , 2007, pyrrhotite by marcasite and pyrite (Qian et al 2011;Xia et al 2010Xia et al , 2007, hematite by chalcopyrite (Zhao et al 2014b), chalcopyrite by bornite (Zhao et al 2014a), magnetite by pyrite (Qian et al 2010) and by arsenian-pyrite (Qian et al 2013), calaverite by gold (Zhao et al 2009, and sylvanite and krennerite by gold-silver alloy (Xu et al 2013;Zhao et al 2013). In all these replacement reactions, porosity was generated in the daughter minerals regardless whether the reaction involves volume contraction or expansion.…”

Textural and compositional complexities resulting from coupled dissolution–reprecipitation reactions in geomaterials

“…showed that the reaction pathway can control the chemistry of the product.Arsenic in cationic form replaces Fe rather than substituting for S in anionic form, as is the case for most natural arsenian pyrite (i.e., ((Fe,As)S 2 ) vs. (Fe(S,As) 2 ), in arsenian pyrite formed experimentally via the replacement of magnetite under mild hydrothermal conditions (T = 125 and 220 ˚C; P sat ) in the presence of S(-II) and various As-containing species. This M A disulfide polymorph that forms via the replacement of pyrrhotite is closely related to the degree of supersaturation at the interface Qian et al (2011;. their Figure 8) identify pH and external S(-II) sources as being critical to the nature of the Fe disulfide phase that forms.Low supersaturation favors the epitaxial nucleation of marcasite as a result of having a Slattice similar to that of pyrrhotite.…”

Factors controlling the precipitation of copper and cobalt minerals in sediment-hosted ore deposits: Advances and restrictions

“…Reprecipitation replacement reactions can nicely be simulated in hydrothermal experiments (Qian et al, 2011;Xia et al, 2008). Xia et al (2008) used hydrothermal coupled dissolution-reprecipitation reactions to synthesise violarite (Ni,Fe) 3 S 4 and linnaeite (Co 3 S 4 ) using pentlandite (Fe,Ni) 9 S 8 and cobaltpentlandite (Co 9 S 8 ) as precursors.…”

“…The replacement of cobaltpentlandite by linnaeite causing an enrichment of cobalt is comparable to the replacement of cattierite by linnaeite in the reactive transport model. Also the replacement of pyrrhotite to Fe disulfide under hydrothermal conditions occurred by a dissolution-reprecipitation mechanism (Qian et al, 2011). The nature of the products was controlled by the supersaturation level of the solution with respect to Fe disulfide minerals.…”