Regional implications of U-Pb zircon dating of two Proterozoic granites associated with molybdenite mineralized aplites in northern Sweden

Abstract

To contribute to the understanding of the timing of the molybdenite mineralizing events in the Proterozoic of Sweden, two granites associated with molybdenite enriched aplites at Allebuoda and Kåtaberget in northern Sweden have been dated by the U-Pb zircon method. The result is 1892±62 Ma for the Kåtaberget granite, and 1767±9 Ma for the Allebuoda granite. As the granitoids in the Svecofennian region generally fall into two major age groups, 1890-1860 Ma and 1800-1770 Ma respectively, this suggests that the Kåtaberget granite belongs to the older group and the Allebuoda granite to the younger group. Sulphur isotopic analyses suggest a larger admixture of sediments in the source material of the Allebuoda granite and aplite than in corresponding rocks at Kåtaberget. The results of this and previous studies suggest that the major Mo- and W-occurrences in the Precambrian of Sweden are associated with granites belonging to the 1800-1770 Ma group.

Key Words:

• Proterozoic
• granites
• Mo-mineralizations
• northern Sweden
• U-Pb zircon dating