Geochronology of high-pressure rocks on Sifnos (Cyclades, Greece)

✍ Scribed by Rainer Altherr; Manfred Schliestedt; Martin Okrusch; Eberhard Seidel; Hans Kreuzer; Wilhelm Harre; Heinz Lenz; Immo Wendt; Günther A. Wagner

• Book ID: 104747072
• Publisher: Springer
• Year: 1979
• Tongue: English
• Weight: 983 KB
• Volume: 70
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00375354

✦ Synopsis

Polymetamorphic rocks of Sifnos (Greece) have been investigated by Rb-Sr, K -Ar, and fission track methods. Critical mineral assemblages from the northern and southernmost parts of Sifnos include jadeite + quartz + 3 T phengite, and omphacite + gar-net+ 3 T phengite, whereas the central part is characterized by the assemblage albite+chlorite+epidote + 2M1 phengite. K-Ar and Rb-Sr dates on phengites (predominantly 373 of the best preserved high PIT metamorphic rocks from northern Sifnos gave concordant ages around 42 m.y., indicating a Late Lutetian age for the high PIT metamorphism. Phengites (2M1 +37) of less preserved high PIT assemblages yielded K-Ar dates between 48 and 41 m.y. but generally lower Rb -Sr dates. The higher K -Ar dates are interpreted as being elevated by excess argon. K-Ar and Rb-Sr ages on 2Mr phengites from central Sifnos vary between 24 and 21 m.y. These ages date a second, greenschist-facies metamorphism which overprinted the earlier high-pressure metamorphic rocks.