Geochronology and tectonics of the Tien-Shan Mountains in the Athashy and Aktyuz areas, Kyrgyzstan

(1)在阿特巴什地区局部榴辉岩组（Choloktor组）构造上覆的砾岩层中发现了新发现的蓝透榴辉岩碎屑，该组榴辉岩在蓝透片岩向榴辉岩相（> - 15kb, 500-560℃）过渡的条件下结晶。砾岩中的榴辉岩经历了两次高压型变质作用。变形形成。榴辉岩（> - 15 kb, 490-590℃）和变质作用由蓝闪片岩相向绿闪角闪岩相渐变。这些结果表明，天山南部古生代榴辉岩的形成至少经历了两次构造和变质事件。(2)在Makbal地区滑石-石榴石-绿泥石类片岩和石英岩中新发现了榴辉石。说明榴辉岩块体的基质变质岩受到超高压变质作用。(3) Neldy组和Makbal组榴辉岩的变质条件分别为> ~ 12kb， 480 ~ 570℃和> ~ 15kb, 540 ~ 620℃。两种榴辉岩分别经历了绿帘石角闪岩相和蓝闪片岩相的渐进变质作用。(4)用COME U-Pb法测定了滑石-石榴石-绿绿片岩中分离出的独居石的年龄为480 Ma，测定了石榴石卟绿母岩中独居石的年龄，与分离出的独居石年龄一致，480 Ma为Makbal地区UHF变质作用的年龄。黑云母片岩和角闪岩的K-Ar年龄分别为769 Ma和881 Ma，比UHP变质作用年龄更老。(4)在榴辉岩变质作用（15 ~ 25 kb, 600 ~ 710℃）之前，阿克图兹地区榴辉岩经历了角闪岩-麻粒岩相变质作用（4 ~ 10 kb, 560 ~ 660℃），表明其变质作用发生在俯冲事件的开始阶段。

(1)The clasts of glaucophane eclogites were newly found from a conglomerate bed tectonically overlying on the regional eclogite formation (Choloktor Formation) in the Atbashy area The eclogites in the Choloktor Formation ware crystallized thorn the conditions of the glaucophane schist fides to the eclogite facies (>15kb, 500-560℃). The eclogites from the conglomerate have experienced two events of high pressure type metamorphism, ie. metamorphismform to form. eclogite (>15 kb, 490-590℃) and metamorphism from the glaucophane schist facies to the epidote amphibolite fades. These suggest that there are at least two tectonic and metamorphic events of eclogite formation in the Paleozoic Southern Tien-Shan .(2) Coesites have been newly described from talc-garnet-chloritoid schists and quartzites in the Makbal area. This suggests that the matrix metamorphic rocks of the eclogite blocks are suffered UHP metamorphism.(3) The metamorphic conditions of the eclogites form the Neldy Formation and Makbal Formation are >12 kb, 480-570℃ and >15 kb, 540-620℃, respectively. Both eclogites were suffered prograde metamorphism of the epidote amphibolite facies and the glaucophane schist facies, respectively.(4) Monazite separated from the talc-garnet-chloritoid schists were dated by COME U-Pb method, and the ages of the monazite are 480 Ma The ages of the monazites in garnet porphyroblasts were also measured and the ages are the same as those of separated monazites, 480 Ma is the age of the UHF metamorphism in the Makbal area. The K-Ar ages of biotite schists and amphibolites are 769 Ma and 881 Ma, respectively and they are older than the age of the UHP metamorphism.(4) Eclogites in the Aktyuz area experienced the amphibolite to granulite facies metamorphism (4-10 kb, 560-660℃) before the eclogite metamorphism (15-25 kb, 600-710℃), suggesting a metamorphism of inception of subduction event.