Eclogites occur in three districts of the northern and southern parts of Tien-Shan. Three eclogites collected from the Aktyuz, Makbal and Atbashy districts were analyzed; the P-T paths of three eclogites were estimated by analyzing compositional growth zoning and retrograde reaction of garnet and omphacite. Aktyuz and Makbal eclogites have not preserved the prograde path. An Aktyuz eclogite that underwent a quartz eclogite facies metamorphism (about T = 600"C, P = 12 kbar) has recorded three stages of retrograde metamorphism. Four stages of retrograde metamorphism were recognized in a Makbal eclogite; the garnet-omphacite geothermometer gave about T = 560°C at 20 kbar as the highest metamorphic condition. Garnet from a garnetchloritoid-talc schist of the Makbal district includes quartz pseudomorphs after coesite; some units evidently underwent a low-temperature part of coesite eclogite facies metamorphism. Prograde and retrograde paths were recognized in an Atbashy eclogite; five stages of metamorphic reaction were observed in the Atbashy sample. The prograde path from stage I to stage I11 has been recorded in garnet and omphacite in which quartz pseudomorphs after coesite are included. The peak metamorphism of stage I11 took place at about 660°C at 25 kbar. The stages IV and V are retrograde. UHP eclogite facies metamorphism took place twice in Kyrghyzstan. The Aktyuz and Atbashy eclogites gave Rb-Sr mineral-isochron ages of about 750 Ma and 270 Ma, respectively. The K-Ar age of paragonite from the Makbal eclogite is about 480 Ma.
We report 52 new K-Ar age determinations of volcanic rocks from the Society Islands in French Polynesia. The newly obtained ages range from 0.51 to 4.61 Ma, which are consistent with previously reported ones. The magnetostratigraphy based on 45 data sets combining K-Ar ages and paleomagnetic polarity agrees with the geomagnetic polarity time scale at the 2σ level, except for a few age data. Assuming the absolute motion of the Pacific plate, paleopositions of the dated rocks are estimated from the K-Ar ages, showing a narrow distribution in the western part of the easternmost volcano of the active hotspot region. This suggests that a hotspot of a few tens of kilometers in diameter might have been fixed nearly at the eastern margin of the presently active region in the Society archipelago and that the volcanism of each island might have persisted for about 1 myr.
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