西北地质2024，Vol.57Issue(6)：44-57,14.DOI:10.12401/j.nwg.2024074
北山造山带尖山子新元古代早期似斑状花岗岩年代学、地球化学特征及地质意义
Age,Geochemistry and Geological Significance of an Early Neoproterozoic Porphyritic Granite in the Jianshanzi Area of the Beishan Orogenic Belt
摘要
Abstract
The geochronological and geochemical data of an early Neoproterozoic porphyritic granite in the Jianshanzi Area of the Beishan Orogenic Belt has been present.Combined with published geochemical data of contemporaneous granitic rocks,their magma sources and the tectonic affinity between the Precambrian base-ment in the southern Beishan and Tarim Cration are discussed.Two samples from the porphyritic granite have zircon U-Pb ages of(901±5)Ma and(935±3)Ma,respectively,indicating that it was formed during the early Neoproterozoic.Samples from the porphyritic granite contain K-feldspar phenocrysts with high SiO2 contents(70.41%～76.05%)and peraluminous characteristics(A/CNK=1.01～1.21),and exhibit similar chondrite-nor-malized REE patterns with LREE-enrichment and pronounced negative Eu anomalies(δEu=0.30～0.46),and show positive Rb,Th,U and K anomalies,negative Ba,Nb,Ta,Sr,P and Ti anomalies in the primitive mantle-normalized trace-element diagram,and have evolved zircon εHf(t)values of-5.0 to-1.4 and two-stage Hf mod-el ages of 2.08～1.61 Ga.All these geochemical characteristics suggest that the porphyritic granite is a typical crustal-derived granite,indicating an older crustal reworking event.Together with the reported data,the Precam-brian basement of the southern Beishan experienced both Mesoproterozoic crustal growth and early Neoprotero-zoic crustal reworking events with the zircon εHf(t)values of granitic rocks plotting within the crustal evolution trend defined by 2.1～1.3 Ga crustal material,indicating the absence of an Archean basement in the southern Beishan,and therefore it may not have tectonic affinity with the Tarim craton with an Archean crystalline base-ment.关键词
新元古代/花岗质岩石/地壳再造/北山造山带Key words
Neoproterozoic/granitic rocks/crustal reworking/Beishan Orogenic Belt分类
天文与地球科学引用本文复制引用
王必任,滕超,白相东,关成尧,袁四化,张晓飞,杨欣杰..北山造山带尖山子新元古代早期似斑状花岗岩年代学、地球化学特征及地质意义[J].西北地质,2024,57(6):44-57,14.基金项目
廊坊市科学技术研究与发展计划自筹经费项目"三河市段甲岭-邦均断裂断层泥石英微形貌及其年代学研究"(2021013165),中央高校基本科研业务费专项自主申报项目"北山微地块前寒武纪地层对比及其对构造亲缘性的制约"(ZY20215119)联合资助. （2021013165）
