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通过对已有锆石U-Pb和Hf同位素数据进行综合分析,探讨了阿拉善地块早前寒武纪大陆地壳生长与再造的规律。数据表明,阿拉善地块内目前发现最古老锆石年龄约为3.6 Ga。3.0~3.6 Ga的碎屑锆石以及Hf模式年龄指示阿拉善地块存在中—古太古代地壳残片,其地壳生长可追溯至古太古代早期。与华北克拉通其他地区相似,阿拉善地块于新太古代2.7~2.9 Ga和2.5~2.6 Ga发育2次较为明显的地壳生长事件,前者在规模上可能大于后者。约2.5 Ga TTG构造—岩浆热事件作为华北克拉通化的标志事件,在阿拉善地块也同样存在,该期岩浆活动主体表现为对2.7~2.9 Ga新生地壳重熔再造,并可能存在更为古老地壳物质的混合,少部分为2.5~2.6 Ga新生地壳的即时再造。至古元古代时期,阿拉善地块发育2.30~2.35 Ga,2.15~2.17 Ga,2.00~2.10 Ga,1.95~1.98 Ga和1.90 Ga 5个阶段(幕式)构造—岩浆热事件,其物质来源以2.7~2.9Ga和2.5~2.6 Ga古老地壳再造为特征,也存在一些更为年轻的(约2.1 Ga)新生地壳物质。阿拉善地块在古元古代时期即存在太古宙地壳再造,也存在初生地壳生长。
Through the comprehensive analysis of the U-Pb and Hf isotope data of the existing zircons, the law of the crustal growth and remodeling in the Early Precambrian of Alxa Block was discussed. The data show that the oldest zircon currently found in the Alxa block is about 3.6 Ga. The detrital zircons of 3.0-3.6 Ga and Hf model ages indicate that the middle-and-middle Archean crustal fragments exist in the Alxa Block, and their crustal growth can be traced back to the early Paleo-Proterozoic. Similar to other parts of North China Craton, the Alxa Block developed two obvious crustal growth events in Neo-Archean 2.7 ~ 2.9 Ga and 2.5 ~ 2.6 Ga, the former may be larger in size than the latter. The 2.5 Ga TTG tectono-magmatic event, which is also a sign of the North China cratonization event, also exists in the Alxa Block. The magmatic activity of this period is characterized by reef melting of relicts of 2.7-2.9 Ga and may be more ancient The mix of crustal material is partly reconstructed in 2.5 ~ 2.6 Ga new crust. In the Paleoproterozoic, the Alxa block developed 2.30 ~ 2.35 Ga, 2.15 ~ 2.17 Ga, 2.00 ~ 2.10 Ga, 1.95 ~ 1.98 Ga and 1.90 Ga 5 stages (episodic) tectono-magmatic events with source of 2.7 ~ 2.9Ga and 2.5 ~ 2.6 Ga ancient crustal reefs are also characterized by some younger (about 2.1 Ga) crustal materials. The Alxa block existed in the Archean crustal rebuild in ancient Paleoproterozoic period, and there are also primary crustal growth.