The Neoproterozoic Dalradian Supergroup contains widespread diagenetic pyrite, in both carbonaceous shales and glacial diamictites, deposited in relatively reducing and oxidizing conditions respectively. The trace element compositions of the pyrite, and consequently the whole rock compositions, contrast between the two lithologies. The highest amounts of selenium, tellurium and gold are all found in diamictite-hosted pyrite. The data suggest that increased mobility of these elements in oxidizing conditions led to greater uptake when pyrite was precipitated. As one model for the formation of orogenic gold ore deposits assumes a pyrite-rich protolith, pyrite formed during relatively oxidizing conditions could make a contribution, including the widespread pyrite precipitated during the Neoproterozoic ‘Snowball Earth’ glaciations.
- Dalradian supergroup
- snowball earth