Geology and 3D model of the Luikonlahti formation in North Karelia, eastern Finland

Abstract

The Luikonlahti Cu-Co-Zn deposit is located in the municipality of Kaavi in North Karelia, eastern Finland, 35 kilometers northeast from Outokumpuu. The polymetallic deposit is one of the Outokumpu-type sulphide deposits in the area. The ore deposit was exploited in 1968-1983, during which a total of 6.85 Mt of copper ore was mined. There is three main ore bodies in Luikonlahti; Asuntotalo, Pajamalmi and Kunttisuo, with Asuntotalo being the largest. There is possibly fourth mineralization, Tirronen, in the SW edge of the Luikonlahti deposit.

The Luikonlahti sulphide deposit is part of the 1.97 Ga Outokumpu assemplage, a distinct rock assemplage hosting several polymetallic Outokumpu-type Cu-Co-Zn-Ni-Ag-Au deposits in North Karelia. The massive-semimassive sulphide deposit is associated with an ultramafic serpentinite massive rimmed by metasomatic quartz-carbonate-calc-silicate rocks addition to black schists and mica schists. Subhorizontal granitic intrusions, originating from the nearby Maarianvaara granite batholith, are also abundant.

In this work all the geological data available from Luikonlahti area was combined to a valid drill hole database. Also some new geochemical and structural data were included. Based on the database a geological 3D model was created to study the regional geology of the Luikonlahti deposit and to identify possible areas lacking sufficient geological data. The 3D model reveals that the Outokumpu rock assemblage hosting the Luikonlahti sulphide deposit seems to continue below the large subhorizontal granite sheets. The geological 3D model also emphasise the importance of the granitic intrusions and major faults when studying the possible continuation of the mineralizations in the area. In the future, observations based on the geological model and geochemical analyses can be used when considering additional drillings in the area.