Abstract
Volodichev et al. (Volodichev et al., 2021) reported on the first finding of omphacite (23%–25% Jd) inclusions in 2.68 Ga metamorphic zircons from Gridino eclogites and presented it as evidence for Archean eclogite-facies metamorphism in the Belomorian Mobile Belt. We believe that the Archean age of the garnets referred to by the above authors was estimated incorrectly. Our interpretation is that omphacite origin is related to Archean high-pressure granulite-facies metamorphism.
Highlights
One of the major problems in the study of Belomorian mobile belt (BMB) eclogites is determining the timing of their formation
Available geochronological data on BMB eclogites are interpreted in various ways
The dominant point of view of the Paleoproterozoic age of BMB eclogites is based on the results of a set of independent isotopic-geochemical dating methods, such as the local U–Pb method for heterogeneous zircons with magmatic cores and eclogite rims, as well as the Lu–Hf and Sm–Nd methods for rock-forming minerals of eclogite paragenesis
Summary
HCl solutions for one hour at 80 C results in the loss of 30% to 40% of lead. The discordance of the analyzed samples to is have assumed have by been by the discordance of the analyzed samples is assumed beento caused thecaused disturbance of the of. U–Pb system of the garnets during the preliminary the ofdisturbance the U–Pb system the garnets during the preliminary treatment of thetreatment mineral. 3 at theFurthermore, garnets werethe dissolved a mixture of in HFa mixture and HNO at ~200
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