if the fugacity of S rises or fugacity of O drops, is it possible to precipitate magnetite and pyrite from a same hydrothermal fluid? Is there any case study?
Hello Trisrota,
Try this one:
Evans, K.A., 2010. A test of the viability of fluid-wall rock interaction mechanisms for changes in opaque phase assemblage in metasedimentary rocks in the Kambalda-St. Ives goldfeld, Western Australia. Miner. Deposita 45, 207–213.
Cheers,
We have also found this association (pyrite+magnetite) working with orogenic gold in NE Brazil. In this case, magnetite is apparently late in respect to pyrite. Fluid mixing, fluid–rock interaction and/or phase separation may have driven the evolving fluid to more oxidizing nature.
Please take a look in our paper:
Article Fluid inclusion and stable isotope (O, H, C) constraints on ...
https://www.sciencedirect.com/science/article/abs/pii/S0169136819303221
this paper shows pyrite mineralization associated with magnetite.
Yes, they can form together but in a sequential event.
Initially, the reduced fluid tends to cause the precipitation of pyrite, followed by a subsequent transition into a comparatively oxygenated state, attempting to precipitate magnetite.
Such type of occurrence has been reported by the following work,
Barla, Anmol, Sahendra Singh, and Rajarshi Chakravarti. "Genesis of metasomatic gold mineralization in the Pahardiha-Rungikocha gold deposit, eastern India: constraints from trace element signatures in chromite-cored magnetite and bulk rock geochemistry." Ore Geology Reviews 121 (2020): 103482.