GEOCHEMISTRY AND TECTONIC IMPLICATIONS OF KARAMAILI OPHIOLITE IN EAST JUNGGAR OF XINJIANG

The Karamaili ophiolite complex in East Junggar of Xinjiang province was composed of metamorphic peridotite,gabbro,diabase and basic lava.LA-ICP-MS zircon U-Pb dating of gabbro from the Karamaili ophiolite revealed an isotopic age of 329.9 Ma±1.6 Ma,indicated that the Karamaili ophiolite occurred in the Visean of Early Carboniferous.The basic lava and gabbro in Karamaili ophiolite fragment showed flat patterns in chondrite-normalized REE diagram and primitive mantle-normalized trace elements diagram with low LILE abundance and no characteristics of IAT and OIB.These geochemical characteristics were similar to MORB and different from IAT and OIB,indicating that the ophiolite may be formed in middle ocean ridge.Combination of field geological feature of Karamaili region,with petrogeochemistry and high-precision geochronology,it was concluded that Karamaili ocean basin opened in early stage of Devonian and closed in the Serpukhovian during late Carboniferous.