地球科学进展  2015, Vol.30 Issue (8): 878-890  DOI:10.11867/j.issn.1001-8166.2015.08.0878
阿拉善地块早前寒武纪大陆地壳的形成与演化
天津市地球物理勘探中心,天津 300170
Formation and Evolution of Early Precambrian Continental Crust in Alxa Block
Tianjin Geophysical Exploration Center, Tianjin 300170, China

摘要

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2.7~2.9 Ga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。关键词:早前寒武纪;地壳生长;地壳再造;锆石Hf同位素;阿拉善地块

Abstract

By the analysis of the published zircon U-Pb ages and Hf isotope data, this paper firstly presents a comprehensive review about the staggered growth and reworking of early Precambrian continental crust in Alxa Block. The results show that the ancient crustal remnants of Alxa Block was formed in Meso-Paleo Archean, which was recorded by 3.0~3.6 Ga detrital zircons and Hf model ages. The early crustal growth of Alxa Block could be traced back to early Paleo-archean. Currently, the oldest zircon U-Pb age is about 3.6 Ga. Analogous to the other places of North China Craton, the Alxa Block underwent two-stage crustal growth at 2.7~2.9 Ga and 2.5~2.6 Ga respectively, and the former might be wider. The ~2.5 Ga (TTG) tectono-magmatic event, which represents the North China continent’s cratonization, also existed in Alxa Block. The corresponding zircon Hf isotope data indicate that the TTGs were mainly derived by melting of 2.7~2.9 Ga juvenile crust, possibly by mixing with a certain ancient crust, and a small portion was produced by instant reworking of 2.5~2.6 Ga juvenile crust. Proceeding to Paleo-proterozoic, the Alxa Block underwent multi-stage tectono-magmatic events, approximately peaked at 2.30~2.35 Ga, 2.15~2.17 Ga, 2.00~2.10 Ga, 1.95~1.98 Ga and ~1.90 Ga. The continental crust was mainly formed by reworking of 2.7~2.9 Ga and 2.5~2.6 Ga juvenile crust, simultaneously by a fraction of ~2.1 Ga juvenile crust. In Paleo-proterozoic, not only the Archean crustal reworking but also the juvenile crustal growth existed in Alxa Block.
收稿日期:2015-04-10

基金资助

内蒙地勘基金项目“内蒙古自治区阿拉善左旗希力斯台呼都格地区蒙C-2010-1001 等航磁异常查证项目冶(编号:13-1-KC004)资助.

引用本文

[中文]
罗志波. 阿拉善地块早前寒武纪大陆地壳的形成与演化[J]. 地球科学进展, 2015, 30(8): 878-890.
[英文]
Luo Zhibo. Formation and Evolution of Early Precambrian Continental Crust in Alxa Block[J]. Advance in Earth Science, 2015, 30(8): 878-890.
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(b)据参考文献[33]修改)
Fig.2 Distribution diagram of the Hf model ages(a) and the plots of ε
Hf(t)与年龄相关图(b)(数据引自参考文献[21~23,25~27,29,30])
Fig.4 Distribution diagram of the 2.7~3.0 Ga Hf model ages(a) and the plots of corresponding ε
图1 阿拉善地块大地构造位置(a,b)及地质简图(c)((a),(c)据参考文献[32]修改
Fig.1 Tectonic framework and simplified geologic map of the Alxa Block ((a),(c) modified from reference [32], (b) modified from reference [33])
图2 阿拉善地块约2.5 Ga TTG锆石Hf模式年龄分布图(a)和ε
Hf(t) versus U-Pb ages(b) for ~2.5 Ga TTG in Alxa Block (date cited from reference [29])
图3 阿拉善地块古元古代岩浆锆石中2.7~3.0 Ga Hf模式年龄分布图(a)和ε
Hf(t) versus U-Pb ages(b) for palaeoproterozoic magmatic zircons in Alxa Block (date cited from references [21~23,25~27,29,30])
图4 阿拉善地块古元古代岩浆锆石中2.7~3.0 Ga Hf模式年龄分布图(a)和ε
Hf(t) versus U-Pb ages(b) for palaeoproterozoic magmatic zircons in Alxa Block (date cited from references[26,27,29])
Hf(t)与年龄相关图(b)(数据引自参考文献[29])
Fig.3 Distribution diagram of the 2.7~3.0 Ga Hf model ages(a) and the plots of corresponding ε
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