微陆块属性厘定的依据——以中亚造山带南缘中段为例  

Criteria for defining the nature of microcontinents——A case study from the middle segment of the southern margin of the Central Asian Orogenic Belt

作　　者：王振义 张进[1] 吴春娇 赵衡[1] 张北航[1] 张义平[3] WANG Zhenyi;ZHANG Jin;WU Chunjiao;ZHAO Heng;ZHANG Beihang;ZHANG Yiping(Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037;Hohhot General Survey of Natural Resources Centre,China Geological Survey,Hohhot,010010;Chinese Academy of Geological Sciences,Beijing,100037)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质调查局呼和浩特自然资源综合调查中心,呼和浩特010010 [3]中国地质科学院,北京100037

出　　处：《地质论评》2024年第3期945-959,共15页Geological Review

基　　金：国家自然科学基金资助项目(编号:U2344215);中国地质科学院基本科研业务费专项(编号:JKYZD202309);中国地质调查局项目(编号:DD20221649)的成果。

摘　　要：造山带中残存有许多前寒武纪地质体,其中一些被当作前寒武纪基底用于探讨所在微陆块的大地构造属性。由于微陆块属性对于造山带结构和演化具有重要意义,以及所讨论的前寒武纪地质体蕴含地球早期历史演化信息,对微陆块属性的厘定成为造山带研究的重点和难点问题之一。笔者等以中亚造山带南缘中段的微陆块为例,总结梳理了微陆块厘定的相关依据:岩石组合和变质变形特征,碎屑锆石谱峰显示的源区时代特征,地质事件序列,前寒武纪地壳演化信息,继承锆石、捕获锆石和古生代侵入体同位素显示的深源地壳信息,以及地球物理等方面的特征。由于不同学者采用的厘定依据不同,对微陆块属性认识争论不断,即使相同依据也有一定的差异,从而影响对造山带结构和演化的认识。基于以上原因,笔者等认为前寒武纪基底的亲缘性探讨不仅要注重岩石组合和形成时代,还要在精细野外解剖和高精度年代学工作基础上,注意其变质—变形特征、接触关系、源区时代特征、岩石成因和构造环境、地壳增生信息和深源地壳信息等的综合对比分析,以得到较全面依据,探讨其构造属性。当获得一组前寒武纪地质体信息时,可先进行同构造单元内对比,再与其他构造单元对比。当特征相异时则需进行构造单元拆分或考虑构造就位的可能(包括但不限于推覆体、走滑外来体、俯冲刮削的构造岩片);当特征相似时,可能指示了相同微陆块的裂解或破坏或者不同的微陆块共同经历了相似的前寒武纪演化历程。Many Precambrian geological units remained in the orogenic belt;some of them were considered as the Precambrian basements for discussing the tectonic affinities of the microcontinents they belonged to.Because the nature of the microcontinents is of great significance to the architecture and evolution of the orogenic belt,and the Precambrian geological units discussed contain information about the early evolution history of Earth,the definition of the nature of the microcontinent has become one of the key and difficult issues in the study of the orogenic belt.This study takes the microcontinents of the middle segment of the southern Central Asian Orogenic Belt as an example to summarize and sort out the criteria for defining the nature of microcontinents:rock assemblages,metamorphism and deformation,the age feature of provenance revealed by detrital zircon spectra,geological event sequences,the Precambrian crustal evolution characteristic indicated by Hf or Nd isotopes,deep crust information denoted by inherited zircons or zircon xenocrysts and the isotopic composition of Paleozoic igneous rocks,and geophysical characteristics.The different criteria for defining the nature of microcontinents,even the same criterion,lead to huge controversies over it,which affects the understanding of the tectonics and evolution of orogenic belts.Based on the above reasons,this paper suggests that the discussion on the affinity of the Precambrian basement should not only focus on the rock assemblages and formation age but also pay attention to the comprehensive comparative analysis of its metamorphism and deformation characteristics,contact relationships,provenance age characteristics,rock genesis and tectonic setting,crustal accretion information,and deep crustal information on the basis of elaborate field anatomy and high-resolution geochronology,so as to obtain more comprehensive criteria and explore its tectonic affinity.When a series of information of Precambrian geological units are obtained,they can be compared with the same

关 键 词：微陆块 大地构造属性 前寒武纪 北山造山带 中亚造山带 

分 类 号：P548[天文地球—构造地质学]