Change search
ReferencesLink to record
Permanent link

Direct link
Contrasting geochemistry of orogenic gold deposits in Yukon, Canada and Otago, New Zealand
Stockholm University, Faculty of Science, Department of Geological Sciences.
Number of Authors: 4
2015 (English)In: Geochemistry: Exploration, Environment, Analysis, ISSN 1467-7873, Vol. 15, no 2-3, 150-166 p.Article in journal (Refereed) Published
Abstract [en]

The Yukon-Tanana Terrane (YTT) of western Yukon Territory in NW Canada and Otago Schist belt (OSB) of South Island, New Zealand share similar geological evolutionary histories as convergent orogenic belts. Both belts host orogenic gold deposits of mainly Jurassic to Early Cretaceous age. Jurassic mineralization in the YTT occurred during convergent orogenesis and stacking of previously-metamorphosed (Palaeozoic) greenschist-amphibolite facies metasediments, metavolcanic rocks, and metagranitoids. Early Cretaceous OSB mineralization occurred in the latter stages of terrane accretion of un-metamorphosed turbidites with minor basaltic rocks. Metamorphism of the OSB turbidites mobilised background levels of Au (0.6-1.3 ppb), As (2-20 ppm), Sb (0.1-1 ppm), and W (< 10 ppm), primarily under greenschist to lower amphibolite facies conditions when diagenetic pyrite (Au c.0.5-2 ppm; As c.500-10000 ppm) transformed to pyrrhotite on a regional scale. In contrast, the previously-metamorphosed YTT rocks had generally low background As contents (1-2 ppm) apart from some As-rich quartzites (up to 100 ppm As). Consequently, there was less As available for orogenic mobilisation, and YTT Au deposits generally have lower concentrations of this pathfinder element compared to the OSB. YTT host rocks, especially metagranitoids, have anomalous levels of Mo (10-300 ppm), and many orogenic deposits contain elevated Mo, locally including molybdenite. OSB turbidites have elevated Mo (2-200 ppm), along with elevated Au and As, in diagenetic pyrite, but this Mo became largely dispersed through the metamorphic pile as metamorphic grade increased and pyrite transformed to pyrrhotite. OSB orogenic deposits have only marginally elevated Mo (c.1 ppm), no molybdenite, and accessory scheelite in these deposits is distinctly Mo-poor. Only minor mobilisation of base metals occurred in these orogenic belts, and orogenic Au deposits contain sparse base metal sulphides. Orogenic deposits in the YTT and OSB differ in that Au (and other associated elements) in many of the orogenic deposits in the YTT was remobilised from relatively local sources (e.g. pre-existing Cu-Mo-Au porphyry or volcanogenic sulphide mineralization) whereas Au in the OSB was mobilised from larger volumes of homogeneous rock at depth.

Place, publisher, year, edition, pages
2015. Vol. 15, no 2-3, 150-166 p.
Keyword [en]
gold, arsenic, antimony, molybdenum, metamorphism, hydrothermal, graphite, orogenic
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:su:diva-119086DOI: 10.1144/geochem2013-262ISI: 000355850300006OAI: diva2:843347
Available from: 2015-07-28 Created: 2015-07-27 Last updated: 2015-07-28Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Pitcairn, Iain
By organisation
Department of Geological Sciences
In the same journal
Geochemistry: Exploration, Environment, Analysis
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: 19 hits
ReferencesLink to record
Permanent link

Direct link