Structural controls on the shear zone hosted, IOCG-style Kiskamavaara Cu-Co-Au mineralization

• Main Author: Metzger, Nicolai
• Format: Bachelor Thesis
• Language: English
• Published: Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser 2019
• Subjects: Geology; Geologi; Kiruna; Lynch; Gällivare; Nautanen; Norrbotten
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-74068

Sweden is the largest producer of iron ore in the European Union, as well as amongst the top producers for base and precious metals. Much of its mineral wealth derives from northern Norrbotten, type locality of the Kiruna-type-magnetite-apatite ores. Besides the massive iron ore bodies, the region is further recognized as important iron-oxide-copper-gold (IOCG) province, with the world class, Aitik Cu-Au-Ag-(Mo) deposit as its most prominent example (1061 Mt with 0,22% Cu; 0,15ppm Au; 1.3ppm Ag), (Wanhainen et al. 2012, Boliden 2017). The close spatial relation between Aitik, further IOCG style mineralization and the Nautanen Deformation Zone (NDZ), a crustal-scale, approximately N-S trending shear system provides important insights into the complex connection between deformation, reactivated fault systems and the different mineralizing events affecting the area during the Svecofennian period (1.9-1.8 Ga). Whereas this connection is well constrained within the Gällivare mining district (c.f. Martinsson and Wanhainen 2004, Wanhainen et al. 2012, Bauer et al. 2018, Lynch et al. 2018), the northern and southern continuations of the NDZ and its potential to host further mineralization remain unknown. During this study, an area around the Kiskamavaara Cu-Co-Au mineralization was investigated to link its tectonic evolution with regional metallogenic events and compare its alterations and structural regime to that of the highly prospective NDZ. It is suggested that the region was affected by at least two deformation events, D1 and D2, both causing a characteristic alteration assemblage, structural patterns and related mineralization. The identification of pseudotachylitic structures and supergene mineralization argues for a late, brittle, upper crustal event with hydrothermal character during D2. Constraining the Kiskamavaara Cu-Co-Au mineralization to this event allows to propose a genetic link to the known IOCG-style mineralization in the Nautanen area that are generally related to a late, 1.80 Ga period of ...