I found that Fe-oxides were usually not used for vectoring Fe mineral deposits of skarn type in geochemical exploration. As an indicator element, the common practice told us Fe-oxides should be the most important indicator for Fe mineral exploration. Is there someone who can give an explanation? In addition, which elements can be used for prospecting skarn Fe mineralization?
Skarn is metamorphosed sedimentary rock, it's iron deposits are in the form of sulfides. This means two things;
- There almost certainly will be iron oxide contamination throughout the unit, at least I have never seen a sedimentary rock that didn't have staining from iron oxides. In my Earth Science classes we were always told that copper, and particularly iron oxide(s) were next to useless as diagnostic tools because tiny volumes of metal cause large and widespread colour signatures and sample contamination.
- The commercial iron ore deposits in skarn units are unusual in that they are normally sulfides rather than the more usual oxides, thus tracking oxides is not as useful as it would usually be.
You're looking for sulfur based mineralisation so Gypsum may be diagnostic, you're also looking for areas of metal concentration so lower mobility metals like Molybdenum may also be useful.