柴北缘乌兰北部地区滩间山群碎屑锆石年代学、Hf同位素组成及其地质意义

柴北缘构造带位于柴达木地块与南祁连造山带之间,由于现存的中元古代沉积和岩浆活动的记录较为稀少,对于柴北缘及其邻区早期的构造演化及地壳生长等方面的研究相对薄弱。通过分析滩间山群中变质长石石英砂岩的碎屑锆石U-Pb年龄及Hf同位素组成,认为滩间山群碎屑沉积物主要来源于古老陆块——欧龙布鲁克陆块的剥蚀,古陆早期地壳生长有3.13～3.51Ga,2.21～2.47Ga和1.74～2.02Ga三个主要阶段,并且后期的地壳生长都受到了早期形成的古老陆壳重熔的影响,碎屑锆石的年龄还反映出中新元古代至少存在744～779Ma,967～1 169Ma,1 394～1 696Ma三期岩浆活动,可能分别代表了Columbia大陆的裂解,Rodinia大陆的聚合和裂解三次构造事件。

Detrital zircons chronology, Hf isotopes and its geological significance from Tanjianshan Group in the north Wulan terrane, north Qaidam

The Northern Qaidam belt lies between the Qaidam block and the southern Qilian orogenic belt. Due to the sparse records of mesoproterozoic sedimentary and magmatic activities, the research on the early tectonic evolution and crustal growth of the northern margin of Qaidam and its adjacent areas is relatively weak. Detrital zircons extracted from metamorphic feldspar-quartz sandstone of the Tanjianshan group collected in the north of Wulan terran were analyzed grain by using the U-Pb and Hf method. The results indicate their principal derivation from the Oulongbuluke block, and which have three crustal growth stages: 3.1-3.5 Ga, 2.2-2.5 Ga and 1.7-2.1 Ga,and the later crustal growth were influenced by the remelting of the ancient continental crust formed in the early period. The age of the detrital zircons also reflects the existence of 744-779 Ma, 967-1 169 Ma, and 1 394-1 696 Ma magmatic activities in the middle meo-neoproterozoic, which may represent three tectonic events, the initial fragmentation of the supercontinent Columbia, the convergence and the initial fragmentation of the supercontinent Rodinia, respectively.