摘要
中亚造山带内分布有众多的具有前寒武纪基底的微陆块,其构造起源一直是中亚造山带地质演化研究的核心问题之一。中国天山造山带呈东西向展布于中亚造山带的南部,发育伊犁和中天山两个古老微陆块。已有成果认为,伊犁地块和中天山地块可能存在古元古代地壳物质,其古老陆核主要形成于中元古代(ca.1.4~1.3Ga),并在新元古代早期(0.97~0.85Ga)发生强烈的地壳改造作用而固结形成统一的结晶基底。笔者最新的碎屑锆石研究表明,伊犁地块在1.8~1.7Ga和1.6~1.3Ga期间发生同时期的地壳生长和改造作用,此后主要以地壳改造为主(1.0~0.78Ga)。基于最近的岩浆研究认为中天山地块在中元古代(1.6~1.3Ga)经历了一期地壳生长事件,随后在新元古代早期开始以地壳的改造作用为主。在中-新元古代时期,伊犁和中天山地块可能都处于大陆地壳伸展环境(0.76~0.71Ga)。与塔里木克拉通及周缘其他主要古老块体的综合对比研究揭示,伊犁地块和中天山地块在前寒武纪时期具有相似的地壳演化过程,但不同于塔里木克拉通及其他古老块体。由此认为,伊犁地块和中天山地块与塔里木克拉通不具有亲缘性,其构造起源于相邻的哈萨克斯坦地块。
In the Central Asian Orogenic Belt（ CAOB）,there are many microcontinents with Precambrian basement. Tectonic affinities of these microcontinents are key issues for studying the geological evolution of this huge accretionary orogenic belt. The Yili Block and the Chinese Central Tianshan Block are two ancient continental segments within the east-westward Chinese Tianshan Orogenic Belt,which is located in the southern CAOB. Previous studies proposed that there could be Paleoproterozoic crustal materials in the Yili Block and the Chinese Central Tianshan Block whose united crystalline basements were formed in the early Neoproterozoic（ 0. 97-0. 85Ga） through the intensive crustal reworking of the ancient cores which were mainly formed in the Mesoproterozoic（ ca.1. 4-1. 3Ga）. Our new studies of detrital zircons indicate that the Yili Block had experienced two phases of synchronous crustal growth and reworking from 1. 8Ga to 1. 7Ga and from1. 6Ga to 1. 3 Ga,respectively,and then the continuous crustal reworking from 1. 0 Ga to 0. 78 Ga. Recent studies of magmatic rocks indicate thatthe Chinese Central Tianshan Block had experienced a crustal growth event in the Mesoproterozoic（ 1. 6-1. 3Ga） and then the extensive crustal reworking in the Neoproterozoic. In the Mid-Neoproterozoic（ 0. 76-0. 71 Ga）,these two blocks could be in an extensional setting of continental crust. Based on the comprehensive comparative study between the two blocks and the Tarim Craton and adjacent old blocks,we conclude that the Yili Block and the Chinese Central Tianshan Block have similar Precambrian crustal evolution processes,which are distinctly different tothose of the Tarim Craton and adjacent old blocks. This further suggests that these two blocks have no close tectonic affinity to the Tarim Craton,but have possible tectonic affinity to the adjacent Kazakhstan Block.
作者
龙晓平
黄宗莹
LONG Xiao-ping;HUANG Zong-ying(State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University,Xi＇an 710069, China;State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China)
出处
《矿物岩石地球化学通报》
CSCD
北大核心
2017年第5期771-785,共15页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家自然科学基金项目(41522202
41603028
41373034)
国家重点基础研究发展计划项目(2014CB440801)
关键词
伊犁地块
中天山地块
构造起源
中国天山造山带
中亚造山带
Yili Block
Chinese Central Tianshan Block
tectonic affinity
Chinese Tianshan Orogenic Belt
Central Asian Orogenic Belt
