GEOCHEMISTRY, AGE, AND ORIGIN OF THE HOGBERGET GRANITE, WESTERN BERGSLAGEN, SWEDEN

An undeformed Palaeoproterozoic granite pluton, located at Hogberget, 10 km north of Kopparberg in western Bergslagen, has been investigated with respect to petrology, geochemistry, and geochronology. The geoch emistry indicates a leucocratic and peraluminous granite and a REE pat tern characterized by a large negative Eu-anomaly and a slight enrichm ent of the light REEs. Age determination by means of the U-Pb in zirco n method yielded 1750+/-10 Ma. The Hogberget granite is spatially and genetically related to the Wigstrom (Hogfors) tungsten skarn deposit a nd is comparable with other W-Mo related granites in western Bergslage n (e.g. Pingstaberg, Fjallberg, and Skalhojden), which traditionally a re considered to have an anatectic origin. The data presented in this paper give further support to genetical models favouring a Late- to po st-Svecofennian, granite-related origin for the W-Mo deposits in weste rn Bergslagen and are in strong conflict with theories favouring a rif t-related Early Svecofennian genesis for these ores. The recognition o f c. 1.75 Ga Late Svecofennian granites in western Bergslagen indicate s a large time interval between peak of regional metamorphism and gran ite formation, which makes a genetic relation between regional metamor phism and the Late Svecofennian granites in western Bergslagen uncerta in.