Gabbroid associations have the highest Au contents amongst ophiolite assemblages: 4 X 10-7% instead of the 3.3 X 10-7% found in hyperbasites. Pyroxenes, olivines and plagioclases 1.3-4.1 X 10-7% are the carrier minerals in the baryte sites and hyperbasites, while the concentrators are titanomagnetite, chromite, magnetite and ilmenite: 11.7-88.1 X 10-7%. The Au levels in gabbroids associated with Alpine-type hyperbasites are relatively low, which is due to the levels in the initial basite magmas arising in the partial melting of the undepleted mantle. Gabbroids in layered series are somewhat enriched in Au because of magmatite differentiation during evolution of the mantle material. The Au distribution with a tendency for the levels to fall is associated with the increase in plastic deformation of the hyperbasites. Substantial loss occurs in connection with metasomatic olivinization of the ultrabasites. Gabbroized hyperbasites and metasomatites (hornblendites and listvenites) related to the emplacement of orogenic granitic intrusions in ophiolite belts have levels of Au elevated by factors of 5-10 due to redistribution and influx of it with magmatic fluids. (Authors' abstract) -A.W.H.
|Number of pages||13|
|Publication status||Published - 1 Jan 1986|
ASJC Scopus subject areas
- Geochemistry and Petrology