Fluid and metal sources in the Fäboliden hypozonal orogenic gold deposit, Sweden

Bark, G., Boyce, A. J. , Fallick, A. E. and Weihed, P. (2021) Fluid and metal sources in the Fäboliden hypozonal orogenic gold deposit, Sweden. Mineralium Deposita, 56, pp. 425-440. (doi: 10.1007/s00126-020-00977-7)

Abstract

To model the formation of orogenic gold deposits, in a global perspective, it is important to understand the ore-forming conditions not only for deposits hosted in greenschist facies rocks but also in amphibolite facies. The Paleoproterozoic Fäboliden deposit in northern Sweden belongs to the globally rare hypozonal group of orogenic gold deposits and, as such, constitutes a key addition to the understanding of amphibolite facies orogenic gold deposits. The Fäboliden deposit is characterized by auriferous arsenopyrite-rich quartz veins, hosted by amphibolite facies supracrustal rocks and controlled by a roughly N-striking shear zone. Gold is closely associated with arsenopyrite-löllingite and stibnite, and commonly found in fractures and as inclusions in the arsenopyrite-löllingite grains. The timing of mineralization is estimated from geothermometric data and field relations at c. 1.8 Ga. In order to constrain the origin of gold-bearing fluids in the Fäboliden deposit, oxygen, hydrogen, and sulfur isotope studies were undertaken. δ18O from quartz in veins shows a narrow range of + 10.6 to + 13.1‰. δD from biotite ranges between − 120 and − 67‰, with most data between − 95 and − 67‰. δ34S in arsenopyrite and pyrrhotite ranges from − 0.9 and + 3.6‰ and from − 1.5 and + 1.9‰, respectively. These stable isotope data, interpreted in the context of the regional and local geology and the estimated timing of mineralization, suggest that the sulfur- and gold-bearing fluid was generated from deep-crustal sedimentary rocks during decompressional uplift, late in the orogenic evolution of the area. At the site of gold ore formation, an 18O-enriched magmatic fluid possibly interacted with the auriferous fluid, causing precipitation of Au and the formation of the Fäboliden hypozonal orogenic gold deposit.

• Item Type: Articles
• Additional Information: Open access funding provided by Lulea University of Technology. This study is funded by Georange, being part of the Georange research project 89126: Genesis and tectonic setting of Aulode in the new Lycksele-Storuman ore province. S.U.E.R.C. is funded by NERC and the consortium of Scottish Universities. AJB is funded by the NERC support of the Isotope Community Support Facility at S.U.E.R.C.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Fallick, Professor Anthony and Boyce, Professor Adrian
• Authors: Bark, G., Boyce, A. J., Fallick, A. E., and Weihed, P.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Mineralium Deposita
• Publisher: Springer
• ISSN: 0026-4598
• ISSN (Online): 1432-1866
• Published Online: 04 April 2020
• Copyright Holders: Copyright © 2020 The Authors
• First Published: First published in Mineralium Deposita 56:425-440
• Publisher Policy: Reproduced under a Creative Commons License