The Tjarrojakka Fe-oxide Cu (-Au) occurrence, Kiruna area, northern Sweden

摘要

The Tjarrojakka area is located 50 km WSW of Kiruna and hosts several Fe-oxide and Cu (-Au) mineralisations. They are mainly hosted by strongly altered 1.9 Ga Svecofennian metaandesites overlain by metabasalts and show a spatial correlation to faults and shear zones. The Tjarrojakka Fe-oxide Cu (-Au) occurrence consists of an Fe-oxide deposit and a Cu (-Au) mineralisation located close to each other. The Fe-ore is characterised by a massive magnetite core surrounded by a magnetite-amphibole breccia and a low-grade Cu-mineralisation in the wall rock. The host rock has been affected by albite, K-feldspar and scapolite alteration. Chalcopyrite and bornite are the main ore minerals in the Tjarrojakka Cu-mineralisation occurring disseminated and in veinlets. The mineralised zone is dominated by potassic alteration expressed by the formation of K-feldspar. The footwall is characterised by magnetite-apatite veining spatially related to albitisa-tion, while scapolite alteration accompanied by biotite is mainly developed in the hanging wall. The close spatial relation and the similarity in host rock and alteration suggest a genetic relation between the Tjarrojakka Fe-ore and the Tjarrojakka Cu-occurrence.