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Eclogites from the north eastern border of the Bel morian Mobile Belt (BMB) have not only been used for regional geodynamic reconstructions [1], but also as first direct evidence for plate tectonic processes in the Mesoarchean [2]. M.V. Mints and coworkers (2010) dated zircons from eclogites of the Salma area related to the so called Belomorian Meso-Neoar chean eclogite province and interpreted the age of 2.87 Ga obtained for some zircons as the age of meta morphism of the eclogite facies [2]. However, rocks of the Salma area undoubtedly underwent eclogite meta morphism with an age of ~1.9 Ga in the Paleoprotero zoic [2][3][4]; for this reason, there is a question of whether or not zircon datings of 2.87 Ga correspond to the age of Mesoarchean eclogite metamorphism [1, 2], or whether this is the age of the magmatic protolith (gabbro) of eclogites [3,4], or if it represents a low P metamorphic event. In this study we applied the LuHf garnet clinopyroxene geochronology, which are rock forming minerals of apo gabbro eclogites of the BMB. Consequently, the Lu-Hf datings of garnet provide unambiguous evidence for the age of meta morphism of the eclogite facies, provided that the blocking temperature was not exceeded (see discus sion below).We studied four eclogite samples from the Salma area (Samples 46 and 21) and Gridino (Samples 102 and 108), which were preliminarily dated using the U-Pb method by zircons providing evidence for the Svekofennian (~1.9 Ga) age of eclogites [3,4]. According to the specific geochemical characteristics, the studied grains or rims of zircons correspond to zir cons precisely of the eclogite facies [3,4]. Eclogitized gabbro (Samples 46 and 102) are the most abundant eclogite type in the BMB. These are homogeneous fine granular bimineral rocks mainly composed of omphacite partially replaced by decompression sym plectites of plagioclase and clinopyroxene with a very low portion of the jadeitic end member and numerous garnet porphyroblasts. Eclogitized ultrabasic rocks (Samples 21 and 108) form coarse granular garnetclinopyroxene bodies (with a thickness up to 20 cm) and aggregates in the central parts of metaultrabasite bodies transformed mainly into secondary tremo lite-actinolite schist (Sample 21) or amphibolite (Sample 108) along the perimeter.Mineral monofractions were sorted according to standard methods using heavy liquids at the Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, and finally manually separated under a binocular microscope. For each sample three garnet monofractions were independently analyzed (Table 1). Both whole rock powders and mineral sepa rates were dissolved using a selective digestion proce dure, aiming to dissolve the major silicate phases, while leaving behind refractory phases, such as rutile and zircon [5]. This approach circumvents a potential age bias due to zircon and other mineral inclusions [6] and frequently results in high precision Lu-Hf ages (e.g., [5,7,8]). These authors also provide detailed methodological sections, ...

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