Munni Munni / history29 Apr 2022 13:18
Well worth a read just for info?
The complex is found in the West Pilbara Block of east-west trending granite-greenstone terranes consisting of domal granitic batholiths, separated by belts of greenschist to lower amphibolite facies meta-sedimentary and meta-volcanic rocks of the Mount Bruce Supergroup.
A significant mineralised PGE-Au horizon was discovered here by John Ferguson in the 1980's. Hunter Resources Limited explored the area in the mid 1980's and Helix Resources in late 2000. In 2013 three companies held exploration tenements over the Munni Munni Complex.
It is one of the best preserved mafic-ultramafic intrusives in Australia, consisting of a 1.8 kilometre ultramafic zone overlain by a 3.6 kilometre gabbroic zone.
The ultramafic zone is rythmically layered in nine zones of minor dunite, with iherzolite, olivine websterite, clinopyroxene, norite, with chromitic and platiniferous websterite near the top of the zone. Some zones are olivine dominant. The dominant three cumulus mineral phases are augite, bronzite and olivine. Inter-cumulus minerals are plagioclase, biotite, magnetite, ilmenite, pyrite, pyrrhotite, chalcopyrite, pentlandite, and minor phases traped in inter-cumulus liquid. Uppermost in the ultramafic zone is a mineralised horizon of mediium to coarse grained porphyritic websterite containing PGE. Olivine serpentinization and talc alteration is pervasive in the ultramafic zone. Plagioclase shows in the basal area of this zone.
https://www.mindat.org/loc-187867.html