阿拉善地块东部早前寒武纪变质基底性质及归属  

The property and tectonic affinity of the Early Precambrian metamorphic basements in the eastern Alxa block

作　　者：牛鹏飞 曲军峰[1] 张进[1] 张北航[1] 赵衡[1] NIU Peng-fei;QU Jun-feng;ZHANG Jin;ZHANG Bei-hang;ZHAO Heng(Key Laboratory of Deep-Earth Dynamics,Ministry of Natural Resources of Geology,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质科学院地质研究所,自然资源部深地动力学重点实验室,北京100037

出　　处：《岩石矿物学杂志》2022年第2期446-466,共21页Acta Petrologica et Mineralogica

基　　金：中国地质科学院地质研究所基本科研业务专项(J2104);国家自然科学基金(41972224);中国地质调查局地质调查项目(DD2019004)。

摘　　要：阿拉善地块是一个被造山带和断裂带围限的前寒武纪微陆块,其早前寒武纪变质基底的性质和归属一直存在争议。本文根据笔者最近在阿拉善地块东部地区获取的研究资料,结合阿拉善地块近年来的研究进展,对阿拉善地块东部早前寒武纪变质基底的性质和归属进行了讨论,认为阿拉善地块东部地区出露的2.64 Ga的斜长角闪岩和~2.5 Ga的TTG片麻岩,明确指示阿拉善地块东部也存在新太古代变质基底。这些新太古代变质岩石的锆石Hf同位素模式年龄主要集中在3.38~2.88 Ga之间,与阿拉善地块东部的叠布斯格岩群和巴彦乌拉山岩群中古元古代锆石的Hf模式年龄(3.4~2.6 Ga)一致,表明阿拉善地块东部经历了古太古代晚期—新太古代早期的陆壳生长事件和~2.5 Ga的岩浆-变质事件。此外,阿拉善地块东部的早前寒武纪变质基底还记录了2.3~2.0 Ga的岩浆事件和~1.95 Ga、~1.85 Ga的岩浆-变质事件,与阿拉善地块西部和华北克拉通变质基底具有相似的地壳演化历史。对比分析锆石年代学数据和Hf同位素组成的结果表明,阿拉善地块东部早前寒武纪变质基底所记录的古元古代中晚期岩浆-变质事件与孔兹岩带极为相似,指示阿拉善地块很有可能在古元古代时期作为孔兹岩带的西延部分卷入到了这一古元古代造山带中。The Alxa block is a Precambrian microcontinent bounded by orogenic belts and fault zones,and its property and tectonic affinity have always been controversial.Based on the recent research data obtained by the author in the eastern Alxa block and combined with the research progress of Alxa block in recent years,it is considered that the 2.64 Ga amphibolite and~2.5 Ga TTG gneiss exposed in the eastern Alxa block,and clearly indicates that Neoarchean metamorphic basement also exists in the eastern Alxa block.The zircon Hf isotopic data of these Neoarchean metamorphic rocks show that the model ages mainly range from 3.38 Ga to 2.88 Ga,which are consistent with the Hf model ages(3.4~2.6 Ga)of the Paleoproterozoic zircons from the Diebusige Complex and Bayanwulashan Complex in the eastern Alxa block.The above data indicate that the eastern Alxa block has experienced crustal growth from the Late Paleoarchean to Early Neoarchean and magmatic-metamorphic event of the~2.5 Ga.In addition,the magmatic event of 2.3~2.0 Ga and magmatic-metamorphic events of~1.95 Ga and~1.85 Ga were also recorded in the Early Precambrian basements of the eastern Alxa block,similar to that of the western Alxa block and the North China Craton.Based on the similarities in the zircon chronology data and Hf isotopic compositions of the Early Precambrian basements from the Alxa block and the Khondalite belt,we proposed that the Alxa block has a similar crustal evolutionary history with the Khondalite belt,and was probably involved in the Khondalite belt as its western extension in the Paleoproterozoic.

关 键 词：阿拉善地块东部 新太古代岩石 古元古代 构造归属 

分 类 号：P534.1[天文地球—古生物学与地层学] P542.4[天文地球—地质学]