Abstract
Rb-Sr isotope systematics have been investigated of epidote, actinolite, albite and biotite concentrates from 4 spilite samples from the Precambrian basement directly W of lake Vanern in SW Sweden. The rocks belong to the Dalsland Supracrustal Group whose basal conglomerate was deposited on an erosion surface with a maximum age of c. 1,200 Ma. Epidote-WR and actinolite-WR tie lines in a Nicolaysen diagram give ages with an average of 990±10 (la) Ma, which is thought to represent the metamorphic culmination. Biotite-WR lines yield an average age of 900±15 (1σ) Ma, which indicates the time at which the rock complex cooled through the isotopic closure temperature of biotite, estimated at c. 250° C. The average cooling rate in this period was very low, 1–2° C/Ma. Initial Sr isotopic ratios of the 4 spilite samples vary from 0.7040 to 0.7080 and are thought to reflect interaction of mantle-derived basalts with seawater.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
