Volcanic and Volcano-Sedimentary Facies Analysis of the Viscaria D-zone Fe-Cu Occurrence, Kiruna District, Northern Sweden

• Main Author: Masurel, Quentin
• Format: Bachelor Thesis
• Language: English
• Published: 2011
• Subjects: Life Earth Science; Bio- och geovetenskaper; Kiruna; Northern Sweden; Norrbotten
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-53913

The northern Norrbotten area in northern Sweden, is an important mining district and hosts several deposits of Fe-oxide Cu-Au type as well as epigenetic Cu-Au deposits. The Viscaria Cu-deposit is a major sulfide deposit in this area. The ore is hosted by the Paleoproterozoic Kiruna Greenstones. Since 1982, 12.54 Mt of ore with 2.29% Cu has been produced, mostly from A-zone and in less extent B-zone, the C-zone being barren. The Viscaria Cu-deposit has been interpreted as a syngenetic copper ore of exhalative origin (Martinsson, 1997). Recent drilling of the historic deposit by the company Avalon Minerals has identified a potentially economic resource at D-zone which has not yet been studied in detail. The master thesis main objective was to perform a first study of the D-zone Fe-Cu occurrence to help on-going exploration. Facies analysis has been applied to Viscaria D-zone. It comprised 4 steps: 1. Facies identification; 2. Facies associations, interpretation and discussion; 3. Stratigraphy and structural interpretation; and 4. Relationship between alteration and mineralization. The stratigraphy and the petrology of ore and host rocks are based on detailed logging of 1450m of drill cores and geochemical-petrographical study of the ore and associated alterations. The stratigraphy at Viscaria D-zone is fairly simple. Basalt flows that belong to the Pikse Fm. are overlain by an andesitic volcaniclastic sequence including minor carbonate horizons that belong to the Viscaria Fm. Relatively thick basaltic sills and dykes cut the stratigraphy in proximity to ore zone and belong to the Peuravaara Fm. The Viscaria D-zone comprises one steeply dipping ore lense. The host rocks consist of altered basaltic sills and tuffaceous siltstones. The main ore minerals are magnetite and chalcopyrite, magnetite being by far the most common at Viscaria D-zone. The location of the ore follows a NE-SW-oriented linear array. A shear zone appears to be the most important ore-controlling factor. In detail, the position of individual ore ...