西北地质2024，Vol.57Issue(6)：25-43,19.DOI:10.12401/j.nwg.2024098
中国西天山古生代岩浆岩时空架构、源区特征及构造背景
Spatial and Temporal Framework,Evolution of Magma Sources,and Tectonic Settings of Paleozoic Magmatic Rocks in West Tianshan,China
摘要
Abstract
The Central Asian Orogenic Belt(CAOB)is Earth's largest and most representative accretionary belt and records the most extensive growth and reworking of the continental crust.Accompanying the closure of the giant Paleo-Asian Ocean and the amalgamation of tectonic blocks in the CAOB regime,with different origins and evolutionary histories,voluminous magmatic rocks were formed.This study focuses on Paleozoic magmat-ic rocks exposed in West Tianshan and systemically summarizes the spatiotemporal frameworks,genetic types,evolution of their magma sources in space and time,and tectonic settings of these rocks.Paleozoic magmatic rocks in West Tianshan were mainly formed at three stages,i.e.,Early Cambrian to Middle Devonian(～479 to～388 Ma),Late Devonian to Early Carboniferous(～375 to～372 Ma),and Late Carboniferous to Middle Per-mian(～322 to～263 Ma).Magmatic rocks formed at the first and second stages are mainly of calc-alkaline I-type granite and intermediate and mafic rocks with"arc-like"geochemical fingerprints,with a few rocks bear-ing"adakite-like"features;a few A-type granites are also found.By contrast,Late Carboniferous to Middle Per-mian magmatic rocks show a diversity in rock types,including calc-alkaline I-type,adakite-like,and A-type fel-sic rocks,with a few locally exposed S-type granites;OIB-like mafic rocks formed in this period,such as gab-bros and basalts,occur locally.In combination with other geological evidence,this study proposes that Early Cambrian to early Middle Devonian and Late Devonian to Early Carboniferous magmatic activities took place in convergent continental margin settings,which were associated with the subduction of branches of the Paleo-Asian Ocean.Besides,both magmatic migration and secular changes in geochemical proxies indicate the transi-tion from advancing low-angle to retreating high-angle subduction.The final closure of oceanic basins plausibly occurred in the Late Carboniferous.Following the closure of the South Tianshan Ocean,a"hard"collision with the arriving Tarim Craton occurred;by contrast,in the north,the northern margin of the Yili-Central Tianshan Block amalgamated with an immature/nascent island arc.In terms of continental evolution,based on Hf isotopic datasets,this study identifies alternating occurrences of growth and reworking.During subduction stages,re-treating subduction(slab rollback)played a predominant role,resulting in large-scale replacement of ancient,pre-accretionary materials by new-formed,syn-accretionary materials.Therefore,Yili and Central Tianshan blocks,can be viewed as ancient microcontinents that were significantly rejuvenated during accretionary processes.In the post-collisional stage,large-scale underplating of mantle-derived magmas represents another phase of conti-nental growth.During the Paleozoic,West Tianshan and adjacent regions were characterized dominantly by con-tinental growth.关键词
中亚造山带/西天山/古生代/岩浆岩/地壳生长Key words
Central Asian Orogenic Belt/West Tianshan/Paleozoic/magmatic rock/continental crustal growth分类
天文与地球科学引用本文复制引用
黄河,王涛,童英,张建军,王朝阳..中国西天山古生代岩浆岩时空架构、源区特征及构造背景[J].西北地质,2024,57(6):25-43,19.基金项目
中国地质调查局项目"中生代松辽盆地周缘复合造山带岩浆演化及成矿效应专题地质调查"(DD20230213),国家重点研发计划课题"增生造山带典型地区三维岩石圈物质架构的示踪方法"(2019YFA0708601)联合资助. （DD20230213）
