Basic characteristics of the Karamay ophiolitic mélange, Xinjiang, and its zircon SHRIMP dating

Abstract：The newly discovered Karamay ophiolitic mélange distributed along the NW edge of the Junggar basin has a complete sequence of ophiolite and accretionary complex. From the basin edge toward the mountains, ultramafic rocks, mafic, pillow lavas and abyssal radiolarian cherts generally show a zonal distribution. The ultramafic rocks are unconformably overlain by volcanic molasse. The ages given by zircon SHRIMP dating of altered gabbro samples taken from the Baijiantan segment of the Karamay ophiolite mélange cluster at 414.4±8.6 and 332±14 Ma. This discovery provides important evidence for studying the ages of formation and elimination of the Central Asian ocean basin and also an important clue ｔｏ the determination of the nature of the basement of the Junggar basin.