The marine‐continental transition of the early proterozoic Skellefte‐Arvidsjaur volcanic arc in the Bure area, Northern Sweden

Abstract

It is generally assumed that c. 1.9 Ga ago the northern part of the Fennoscandian (Baltic) Shield comprised a continental margin along which plate tectonism and subduction took place. The main division of the region is a marine domain towards the south and a continental domain towards the north. At Bure in northern Sweden, the marine‐continental transition is exposed and the lithologies and palaeotectonic environment of this area are investigated in the present paper. The results show that the former lithostratigraphic division has to be modified and a reconstruction of the geological development is necessary. The Bure supracrustal sequence shows a successive change from a marine schist‐greywacke‐basaltic environment in the stratigraphically lowest part (Stalo Formation) to a continental volcanic environment in the upper part (Bure Formation). The continental volcanic rocks are intermediate‐felsic and mildly alkaline. Minor intercalations of similar volcanic rocks occur within the marine sequence. The youngest event in the Bure area is the deposition of the Loito Formation which consists of a red conglomerate‐sandstone lying on top of the Bure and Stalo volcanic rocks. The chemical character and lithological associations infer that the Bure Formation volcanic rocks were deposited in an extensional environment and may constitute the late stage member of the calc‐alkaline volcanism that occurs further east, the Arvidsjaur Porphyries. Continental bimodal and slightly alkaline volcanic rocks occur north and northwest of the Bure area and would, together with the continental Bure volcanic rocks, form a separate group, here collectively referred to as the Arjeplog Porphyries.

Perdahl, J.‐A. & Einarsson, Ö., 1994: The marine‐continental transition of the Early Proterozoic Skellefte‐Arvidsjaur volcanic arc in the Bure area, northern Sweden. GFF, Vol. 116 (Pt. 3, September), pp. 133–138. Stockholm. ISSN 1103–5897.

Keywords:

• Proterozoic
• marine‐continental transition
• volcanic arc
• mafic
• intermediate‐felsic volcanism
• chemistry
• Skellefte‐Arvidsjaur
• Norrbotten
• Sweden