Rb-Sr, U-Pb and Sm-Nd isotopic dates from Precambrian rocks of Finnmark.

• Main Authors: Lindahl, Ingvar, Krill, Allan G., Bergh, Steffen
• Format: Article in Journal/Newspaper
• Language: English
• Published: 1985
• Subjects: Alta; Kautokeino; Karasjok; Kvænangen; Finnmarksvidda; Raipas; Finnmark
• Online Access: https://hdl.handle.net/11250/2674245

Rb-Sr and Sm-Nd whole-rock dates, and Rb-Sr biotite dates are presented forpre-Caledonian rocks of Finnmarksvidda, the Alta-Kvænangen window. andSørvaranger. A Sm-Nd whole-rock date of 2085+-85 Ma was obtained from koma-tiites of the Karasjok Greenstone Belt. Granite of the Jer'gul Gneiss Complex,eroded by the basal unconformity of the Karasjok Greenstone Belt, yielded aRb-Sr whole-rock data of 2110 +- 105 Ma. These results suggest that theKarasjok Greenstone Belt is Early Proterozoic, and not Archean as earlier assumed. The Kautokeino Greenstone Belt and Raipas Group may have similarages, but dating attempts were not successful. Svecokarelian intrusions groupinto older intermediate rocks with intrusive ages about 1820 Ma, and youngergranitic rocks with ages of about 1650-1750 Ma. Biotite dates are mainlybetween 1486-1633 Ma, and presumably reflect the age of uplift and cooling. 36088