西北地质2026，Vol.59Issue(3)：121-142,22.DOI:10.12401/j.nwg.2025097
北山造山带南部早古生代歪咀山岩体的年代学、地球化学特征及地质意义
Geochronology,Geochemistry and Geological Significance of the Early Paleozoic Waizuishan Pluton in the Southern Beishan Orogenic Belt
摘要
Abstract
The Beishan Orogenic Belt,situated in the central segment of the southern margin of the Central Asian Orogenic Belt(CAOB),has undergone prolonged,multi-stage subduction and accretion.It represents a key region for reconstructing the tectonic evolution of the southern CAOB margin and the closure of the Paleo-Asian Ocean.The Early Paleozoic was a significant crustal evolution period for the Beishan Orogenic Belt,char-acterized by frequent magmatic activity.Previous studies primarily focused on the central-western part of the belt,reporting a magmatic flare-up at 450-420 Ma.This study presents systematic geochronological and geo-chemical investigations of the Waizuishan pluton,located on the southeastern edge of the Shuangyingshan-Hua-niushan tectonic unit within the Beishan Orogenic Belt.The Waizuishan pluton mainly comprises quartz diorite(and granodiorite.Zircon U-Pb dating yielded crystallization ages of(427.1±3.4)Ma and(418.6±2.8)Ma.The rocks belong to the metaluminous series(A/CNK＜1),exhibiting calc-alkaline and magnesian affinities.They possess low total rare earth element(ΣREE)contents,are enriched in light rare earth elements(LREEs),and show weak negative Eu anomalies(δEu=0.72-0.86).Geochemically,they are enriched in large-ion lithophile el-ements(LILEs:e.g.,Rb,Th,U,K,Pb)and depleted in high-field-strength elements(HFSEs:e.g.,Nb,Ta,P,Zr,Ti).Zircon εHf(t)values range from-2.0 to 0.6,corresponding to Hf crustal model ages(TDMC)of 1.53-1.36 Ga.The geochemical signatures indicate that the Waizuishan pluton is an I-type granite formed within a subduction-related continental margin igneous arc.It was derived predominantly from the remelting of Mesoproterozoic crustal material with minor contributions from mantle-derived components.Nearly contemporaneous magma-tism occurred within all four tectonic units of the Beishan Orogenic Belt.Zircon Hf model ages from Paleozoic igneous rocks(500-350 Ma)exhibit prominent peaks at 1.5-1.4 Ga and 0.8-1.0 Ga,correlating with Mesopro-terozoic(～1.4 Ga)and Neoproterozoic(～0.9 Ga)tectonothermal events.This suggests that the various tecton-ic units of the Beishan Orogenic Belt likely share a common source region.Comparisons with the Yili Block and Central Tianshan Block indicate that these three terranes show stronger affinities with the Baltica and Laurentia cratons,whereas they lack affinity with the Tarim Craton,as represented by the Dunhuang Block.关键词
北山造山带/早古生代/歪咀山岩体/年代学/地球化学Key words
Beishan Orogenic Belt/Early Paleozoic/Waizuishan pluton/geochronology/geochemistry分类
天文与地球科学引用本文复制引用
董美玲,滕超,杨欣杰,王必任,曹军,陈喜庆,邵杰,张晓飞,李树才..北山造山带南部早古生代歪咀山岩体的年代学、地球化学特征及地质意义[J].西北地质,2026,59(3):121-142,22.基金项目
中国地质调查局项目(GC20231205-3、DD20221814、DD20160010)联合资助. （GC20231205-3、DD20221814、DD20160010）
