Paleomagnetism and age relations of the rocks in the main sulphide ore belt in central Finland

Abstract

Paleomagnetic data on the Main Sulphide Ore Belt in Finland are coherent but differ clearly from those obtained on the Archean basement area immediately north of it. The coherent magnetization in the Belt could have been caused by (i) axial uplift, (ii) a plate suture along the Belt or (iii) a short-time igneous pulse. The last interpretation is accepted since it agrees with the radiometric age data. Thus the paleomagnetic measurements in the area date the same thermal events as do the radiometric U-Pb age determinations, and the shape of the APW curve is thereby verified. A paleomagnetic pole determined for dykes intersecting the Archean basement block lies off the accepted APW curve which possibly need to be corrected. The magmatic pulse between 1880— 1840 Ma may have been associated with a plate collision or with a deep fluid convection producing the sulphide ore precipitation within the Belt.