【摘要】 通过对柴北缘马北地区古近系下干柴沟组下段(E31)岩芯的观测分析,挑选出3个样品,进行了碎屑锆石U-Pb年代学研究.发现碎屑锆石U-Pb年龄区间明显可以划分为早古生代和晚古生代-早中生代2个主年龄区间以及古、中、新元古代3个次级年龄区间.主年龄区间分别为380-480和200-320 Ma,峰值年龄分别为432和249 Ma;次级年龄区间分别为2000-2500、1400-1800、800-1000 Ma,峰值年龄不明显. 5个年龄区间分别代表了柴北缘造山带5次不同的构造事件:古元古代岩浆事件;中元古代非造山岩浆活动;新元古代Rodinia超大陆汇聚事件;古生代柴达木板块的俯冲-碰撞-折返过程;晚古生代-早中生代构造热事件.碎屑锆石年龄特征及对比结果证明了马北地区古近纪以来的沉积物源主要来自于嗷唠山和吐尔根达坂山,水动力条件稳定,沉积物源具有很好的继承性.更多还原

【Abstract】 Through an observation and analysis of the main drilling cores of the lower Xiaganchaigou formation（E₃¹） in the northern Mahai area, northern margin of Qaidam Basin, three samples were selected and their detrital zircon U-Pb chronology was studied. The results showed that the zircon U-Pb age spectra could be divided into two main age ranges of late Paleozoic-early Mesozoic and early Paleozoic, as well as three secondary ages of late Proterozoic, middle Proterozoic and early Proterozoic. The main age ranges were 200-320, 380-480 Ma, the peak age was 249 and 432 Ma respectively, the secondary age ranges were 800-1000, 1400-1800, 2000-2500 Ma, and the peak age was not obvious. Combined with the previous research results, our findings suggested that the five age ranges represented five different tectonic events of the northern part of Qaidam Basin marginal orogenic belt: Paleoproterozoic magmatic events, Mesoproterozoic non-orogenic magmatic activity, Neoproterozoic Rodinia Super Continental Convergence event, Paleozoic Qaidam block subduction-collision-exhumation process, and Late Paleozoic-early Mesozoic heat events. The age distribution of the clastic zircon also reflected that the source direction of the Paleogene sedimentary period in the northern area of Mahai mainly came from the Ao-Lao Mountain and Turgendaban Mountain and the hydrodynamic condition was stable and had good inheritance.更多还原