Change search
ReferencesLink to record
Permanent link

Direct link
Metabasalts as sources of metals in orogenic gold deposits
Stockholm University, Faculty of Science, Department of Geological Sciences.
2015 (English)In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 50, no 3, 373-390 p.Article in journal (Refereed) Published
Abstract [en]

Although metabasaltic rocks have been suggested to be important source rocks for orogenic gold deposits, the mobility of Au and related elements (As, Sb, Se, and Hg) from these rocks during alteration and metamorphism is poorly constrained. We investigate the effects of increasing metamorphic grade on the concentrations of Au and related elements in a suite of metabasaltic rocks from the Otago and Alpine Schists, New Zealand. The metabasaltic rocks in the Otago and Alpine Schists are of MORB and WPB affinity and are interpreted to be fragments accreted from subducting oceanic crust. Gold concentrations are systematically lower in the higher metamorphic grade rocks. Average Au concentrations vary little between sub-greenschist (0.9 +/- 0.5 ppb) and upper greenschist facies (1.0 +/- 0.5 ppb), but decrease significantly in amphibolite facies samples (0.21 +/- 0.07 ppb). The amount of Au depleted from metabasaltic rocks during metamorphism is on a similar scale to that removed from metasedimentary rocks in Otago. Arsenic concentrations increase with metamorphic grade with the metabasaltic rocks acting as a sink rather than a source of this element. The concentrations of Sb and Hg decrease between sub-greenschist and amphibolite facies but concentration in amphibolite facies rocks are similar to those in unaltered MORB protoliths and therefore unaltered oceanic crust cannot be a net source of Sb and Hg in a metamorphic environment. The concentrations of Au, As, Sb, and Hg in oceanic basalts that have become integrated into the metamorphic environment may be heavily influenced by the degree of seafloor alteration that occurred prior to metamorphism. We suggest that metasedimentary rocks are much more suitable source rocks for fluids and metals in orogenic gold deposits than metabasaltic rocks as they show mobility during metamorphism of all elements commonly enriched in this style of deposit.

Place, publisher, year, edition, pages
2015. Vol. 50, no 3, 373-390 p.
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:su:diva-116644DOI: 10.1007/s00126-014-0547-yISI: 000351178000007OAI: diva2:807060


Available from: 2015-04-22 Created: 2015-04-22 Last updated: 2015-04-22Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Pitcairn, Iain K.
By organisation
Department of Geological Sciences
In the same journal
Mineralium Deposita
Earth and Related Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 11 hits
ReferencesLink to record
Permanent link

Direct link