DEPOSIT, SKELLEFTE DISTRICT, NORTHERN SWEDEN

• Main Authors: Mineralogy Of, Sulfosalt-rich Vein-type Ores, Boliden Massive Sulfide, Thomas Wagner, Erik Jonsson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: sulfosalts; kobellite; laitakarite; Te incorporation; solid solution; decomposition reaction; Boliden; Skellefte district; Sweden. SOMMAIRE; Northern Sweden
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.583.9762; http://rruff.info/doclib/cm/vol39/CM39_855.pdf

Sulfosalt-rich vein-ores, which form an important mineralization type of the Paleoproterozoic metavolcanic-hosted Boliden Au–Cu–As massive sulfide deposit, in the Skellefte district, in northern Sweden, have been investigated by a combination of ore microscopy, electron-microprobe analysis and balanced reactions. The sample material contains a variety of ore minerals, includ-ing Au–Ag alloy, gudmundite, selenian galena, kobellite, tetrahedrite, bournonite and laitakarite. The vein ores display structures indicative of extensive deformation. Three distinct decomposition-induced assemblages, which postdate the deformation, have formed at the expense of kobellite: (i) selenian galena + laitakarite, (ii) tetrahedrite + laitakarite, and (iii) bournonite + laitakarite. Both kobellite and bournonite are unusually Se-rich, with concentrations in the range of 3.16–4.55 wt. % and 3.37–4.73 wt.%, respectively. Laitakarite, Bi4(Se,S)3, is characterized by substantial incorporation of Te, in the range of 0.94–9.64 wt.%. Compa-rable compositions have not been reported before and are indicative of extensive solid-solution within the system Bi4S3–Bi4Se3– Bi4Te3. Pb, with concentrations in the range of 3.01–4.56 wt.%, constitutes an essential component of laitakarite. The amount of Pb incorporation is approximately constant over the entire compositional range. Construction of balanced reactions for the prin-cipal types of decomposition textures demonstrates that these fluid-assisted replacement processes are controlled by individual pairs of immobile elements.