Volcanic setting of the 1.89 Ga Petiknäs South massive sulfide deposit, Skellefte district, Sweden

• Petiknäs South is a producing underground mine in the eastern part of the Skellefte district. The massive sulfide deposit, which consists of several stacked ore lenses, is hosted by altered, deformed and metamorphosed volcanic rocks belonging to the Paleoproterozoic Skellefte Group. The mine sequence ranges in composition from rhyolite to basaltic andesite and includes abundant volcaniclastic and lesser coherent rocks. This sequence is interpreted to have been deposited in a deep marine environment. The volcaniclastic rocks include rhyolite hyaloclastites, subaqueous mass flow units of juvenile felsic pyroclastic debris and mass flow units of mafic fire fountain debris. The main ore lens is located at the contact of felsic and basaltic andesitic volcaniclastic rocks. This "ore horizon" can be traced laterally through the mine area and is a major exploration guide to ore. A synvolcanic felsic sill, comagmatic with some of the felsic footwall volcaniclastic rocks, was emplaced in the proximal footwall slightly after formation of the massive sulfide lenses. The mine sequence was then intruded by andesite and rhyolite sills and mafic dykes after ore formation and alteration. The ores are interpreted to have formed at or slightly below the sea floor, above the proximal part of the footwall rhyolite volcano. The ore-host rhyolite volcano overlies a shallow marine andesite-dacite shield volcano, and the proximal facies of the rhyolite volcano interfingers with medial facies of an adjacent andesite volcano.

Subject headings

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Keyword

Malmgeologi

Ore Geology

Publication and Content Type

vet (subject category)

kon (subject category)