准噶尔盆地中部钻井岩心凝灰质砂岩锆石U-Pb年龄及其地质意义

Zircon U-Pb dating for the tuffaceous sandstone from drilling well of central Junggar Basin and its geological implications

对准噶尔盆地中央凹陷内部钻井岩心凝灰质细砂岩样品进行岩石学及LA-ICP-MS锆石U-Pb测年,探讨研究区的地层沉积时代及基底构造属性。结果表明:(1)碎屑锆石的年龄分布范围为(270±2)Ma^(568±3)Ma,具有多峰的分布特征,表明其碎屑物质来源较为复杂。岩浆锆石样品最小年龄为270 Ma,代表该样品的沉积时代为中二叠世。(2)研究还获得(568±3)Ma新元古代和(1 790±14)Ma的古元古代锆石年龄,这可为准噶尔盆地存在前寒武纪古老结晶基底提供依据。同时研究还获得晚古生代363~401Ma,300~358 Ma,270~299 Ma的年龄纪录,反映准噶尔盆地基底经历了多阶段复杂陆壳演化过程。

This paper discussed ages of deposition of strata and property of basement, using petrological obser- vation and LA-ICP-MS zircon U-Pb dating for the fine tuffaceous sandstone from drilling well in central Junggar Basin. Two results and its implications are documented as follow. ①The dated ages of detrital zircon rang from （ 270 ±2） Ma to （568 ± 3 ） Ma, and show features of multi-peaks, indicating complex provenance. The youn- gest dated ages of magmatic zircon are 270 Ma and 272 Ma respectively, suggesting the depositional period is middle Permian.②One Neoproterozoic （568 ± 3 ） Ma and one Paleoproterozoic （ 1790 ± 14） Ma age are ob- tained, which might provide evidences for presence of Precambrian crystalline basement of Junggar Basin. Fi- nally, the ages record Late Paleozoic, 363 to 401 Ma, 300 to 358 Ma, and 270 to 299 Ma reflect complex and multi-stages tectonic evolutions of basement of Junggar Basin.