| Popis: |
The Dongdagou area of Yamansu in the southeastern margin of Turpan-Hami basin, which is located to the north of the Kangguertag collision zone, is one of the representative areas to discuss whether there is a Precambrian basement problem in the Junggar Turpan-Hami massif. As a consequence, zircon LA-ICP-MS U-Pb dating has been carried out for the shallow metamorphic tuffaceous fine sandstone in the Yamansu formation of the Lower Carboniferous in this area. The results show that the ages of 30 clastic zircons range from 365 ±3 Ma to 2451 ±39 Ma, with multi-peak distribution characteristics. The ages of clastic zircons are mainly concentrated in 365~496 Ma, the main peak is 365~436Ma, the secondary peak is 440~496 Ma, and the ages of 8 clastic zircons are between 765~2451 Ma. The study shows that the formation age of the sedimentary rock is not the early Carboniferous but the late Middle Devonian. Based on the isotopic dating data of the two-cloud quartz schist in the Xiaohuangshan area in the northeast of the study area, it is considered that the lower limit of the formation period of this set of strata is not earlier than the Devonian. Combined with the age data of ancient zircons in diabase and fused tuff in the study area, and the comprehensive analysis of regional sedimentary characteristics, it is concluded that there may be Precambrian crystalline basement in the sediment source area-Junggar-Turpan-Hami block. |
