Deposit Geology The host rocks to the Malmberget mineralisation comprises a package of mafic to felsic, mildly alkaline, volcanoclastic to sub-volcanic metavolcanic rocks. The ore bodies and the metavolcanic rocks have been intruded by dolerite dikes, as well as, several generations of pegmatitic and aplitic dikes, and granitic bodies (Lund, 2013). U-Pb dating of oscillatory zoned zircons from the metavolcanic rock yields magmatic ages between 1.89 and 1.87 Ga and metamorphic ages between 1.80 and 1.77 Ga (Sarlus et al., 2020). Amphibolite facies metamorphism, deformation and several phases of hydrothermal alteration have transpositioned primary bedding, and partly to completely destroyed the primary features of the ore and the volcanic rocks (Skiöld and Cliff, 1984; Bauer et al., 2018). The high metamorphic grades have significantlly coarsened the grainsize of the Malmberget rocks. Alteration typically consists of pervasive K-feldspar and albite alteration, and patchy to disseminated amphibole-, biotite-, hematite- and magnetite-alteration. High temperature metamorphism is more prevalent in the western part of the deposit, proximal to the large Lina type granitic intrusion, typically evident as sillimanite- and muscovite-bearing gneisses. Massive biotite zones (i.e., biotite schist) occur in the proximity of the ore-zones and are interpreted to be mylonites that were formed as a result of strain partitioning between the metavolcanic host rock and the massive ore during de ........

Mineralisation at Malmberget mine has historically been identified to comprise 30 orebody areas which are either active, inactive or mined-out. The orebodies are distributed over an area of about 5.0 km by 2.5 km and are grouped into Eastern Field and Western Field. The mine is divided into an eastern and western part. The western part is a continuous ore horizon where the orebodies contain magnetite and hematite, with a high apatite content. The eastern part is made up of individual orebodies which consist of magnetite with a low amount of apatite. The orebodies are bound within geological strata and are frequently surrounded by ore breccia types. The orebodies are strongly affected by metamorphic recrystallisation and ductile deformation. Large granite intrusions of the granite-pegmatite association are situated near the deposit. The average width of the orebodies ranges from 20 m to 100 m, and iron mineralisation is comprised around 90% magnetite and 10% hematite. The host rocks are metamorphosed volcanic rock such as gneisses and fine-grained feldspar-quartz rock called leptite. Granite veins often intrude into the ore zones. Mining is by the sublevel caving (SLC) method which is selected for its suitability to the size, distribution, orientation, and dip of the orebodies. SLC at Malmberget uses a combination of transverse layouts of footwall drifts with crosscuts in wider sections of the orebody and longitudinal layouts with drifts set out on the strike for narrow ore ........

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