U-Pb age constraints on the host rocks of the Barsele Norra Volcanogenic Massive Sulphide deposit, northern Sweden

• Main Author: Sandlund, Maria
• Format: Bachelor Thesis
• Language: English
• Published: Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser 2021
• Subjects: Geochronology; Skellefte district; Barsele; VMS; LA-ICP-MS; SEM; Environmental Engineering; Naturresursteknik; Avan; Avan’; Norra Sverige; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-87042

The Barsele area is located in the "Gold Line", southwest of the volcanogenic massive sulphide (VMS) Skellefte district which hosts more than 85 known VMS-deposits where some are gold-bearing. The Barsele area consists of the Central, Avan and Skiråsen intrusion hosted gold deposits, the Norra gold-bearing VMS-deposit and the Risberget zone. This study includes a geochronological study of two coherent volcanic rocks from the Norra zone using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry and Scanning Electron Microscope images of zircons and also includes petrographic microscopy of thin sections and lithogeochemical data used in classification diagrams. This study presents two new LA-ICP-MS zircon U-Pb ages for VMS-hosting volcanic rocks from the Barsele area: o 1956.8 ± 6.47 Ma (n: 17, MSWD: 0.99), sample A from a hydrothermally altered volcanic rock o 1952.2 ± 14.5 Ma (n: 6, MSWD: 1.1), sample B from a rhyolite-dacite The new U-Pb age constraints presented in this study indicate that the volcanic rocks of the Norra zone are older than the volcanic rocks in the Skellefte Group. The results presented in this report together with the earlier dated c. 1.96 Ga metadacite suggests that the volcanic rocks of the Barsele area are located at a lower chronostratigraphic level than the Skellefte Group, i.e., at the chronostratigraphically lower Bothnian Supergroup. Additionally, the results presented here conclude that two VMS-events can be delineated by geochronological data which further opens up for the question if the Barsele area belong to an older arc system (e.g., the Knaften arc) or were part of an arc system evolving continuously between 1.95-1.88 Ga (e.g., the Knaften-Skellefte arc). Barsele, Västerbottens län, norra Sverige, ligger i ett område som kallas för Guld linjen och är beläget sydväst om Skelleftefältet där mer än 85 kända förekomster av massiva sulfidmalmer (VMS), vissa guldförande, förekommer. Barseleområdet är uppdelat i Central, Avan och Skiråsen zonen, Norra zonen och Risberget ...