Lithology and mineralisation types of the Rockliden Zn–Cu massive sulphide deposit, north-central Sweden: Implications for ore processing

Abstract

The Rockliden Zn–Cu volcanic-hosted massive sulphide deposit is located approximately 150 km south of the Skellefte ore district, north-central Sweden. Most of the mineralisation is found at the altered stratigraphic top of the felsic volcanic rocks, which are intercalated in the metamorphosed siliciclastic sedimentary rocks of the Bothnian Basin. Mafic dykes cross-cut all lithological units, including the massive sulphides, at the Rockliden deposit. The relatively high Sb grade of some parts of the mineralisation results in challenges in handling of the Cu–Pb concentrate in the smelting process. The aim of this study is to characterise different host rock units and ore types by their main mineralogy, as well as by their trace mineralogy with focus on the Sb-bearing minerals. Ore types are distinguished largely on the basis of their main base-metal bearing sulphide minerals, which are chalcopyrite and sphalerite. Several Sb-bearing minerals are documented and differences in the trace mineralogy between rock and ore types are highlighted. Based on the qualitative ore characterisation, rock- and ore-intrinsic parameters, such as the pyrite, pyrrhotite and magnetite content of the massive sulphides, the trace mineralogy and its association with base-metal sulphide minerals, are outlined and discussed in terms of relevance to the ore processing.

Keywords:

• Rockliden
• North-central Sweden
• Base metal sulphide
• Ore characterisation
• Process mineralogy
• Impurity elements

Acknowledgements

This study is part of a PhD project financed by CAMM (Centre of Advanced Mining and Metallurgy). New Boliden AB is acknowledged for financing the analytical work in this study, and for permission to publish this paper. ALS Minerals Division (Piteå, Sweden) is thanked for financial support for preparation of chemical assays and analytical work. Hein Raat (Boliden Mines, Exploration Department) is thanked for advice about the geology of Rockliden and the personnel in the Boliden drill core archive for their help with finding and mounting drill cores which made it possible to obtain samples in an efficient way.

The authors also acknowledge the comments and corrections of three anonymous reviewers and our colleague Riia Chmielowski.

Notes

1 Rounded up to 5 cm wide non-sulphide spots within the massive sulphides. Please note that the term is not used in a strict sedimentary sense. As it is used here it has no implication on rock formation.