The Kuosanen target is located within a volcanic belt prospective for both iron oxide-apatite (IOA) and iron oxide-copper-gold (IOCG) mineralisation in the northern Norrbotten metallogenic province. The Svecokarelian orogeny produced a complex, polyphase deformational evolution that is regionally recognised as a key control on the distribution and geometry of mineral deposits. This motivates a systematic structural investigation of the volcanic host succession of the poorly constrained Kuosanen IOA target. Through field mapping and microstructural analysis, this study defines the deformation history, evaluates the structural control on mineralisation, and integrates the local framework into the regional tectonic context.

The volcanic belt is characterised by a system of parallel, moderately steep, WSW-dipping high-strain zones that record oblique- to dip-slip, predominantly western-block-up movements consistent with c. ENE–WSW-directed crustal shortening. Two deformation events, D₁ and D₂, are recognised. Early D₁ is associated with the development of a continuous penetrative S₁ foliation, amphibole-magnetite-albite and quartz ± feldspar veins, and selective scapolite alteration. Subsequent D₂ deformation involved brittle-ductile reactivation of pre-existing structures and transposition of earlier fabrics into a moderately to steeply WSW-dipping composite S_0/1/2 cleavage. This event was accompanied by extensive hydrothermal activity, expressed by pervasive K-feldspar alteration, widespread veining, and syn- to late-tectonic infill of hematite and Cu-sulphides, consistent with a regionally recognised IOCG overprint.

The strong positive magnetic anomaly at Kuosanen coincides with a deformation zone splay, indicating a structural geometry that likely enhanced permeability and acted as a trap for mineralising fluids focused along reactivated high-strain zones. The polyphase deformation history of the IOA-hosting volcanic units further suggests that the Kuosanen mineralisation has undergone significant structural and hydrothermal reworking.

The defined structural framework provides new constraints on the continuity of deformation between Kiruna and Svappavaara. Inferred linkages to the Kiruna–Naimakka deformation zone (KNDZ) and, more speculatively, to the Nautanen deformation zone (NDZ) suggest that the Kuosanen structures form part of a broader interconnected system with a strong influence on fluid flow patterns and localisation of mineralisation. These results emphasise the significance of investigating structurally complex, reactivated deformation zones for mineral exploration targeting in northern Norrbotten.