现代地质2023，Vol.37Issue(6)：1580-1596,17.DOI:10.19657/j.geoscience.1000-8527.2023.063
阿拉善北大山地区花岗斑岩岩石成因及构造启示:元素地球化学、锆石U-Pb年代学及Hf同位素约束
Petrogenesis and Tectonic Implications of Granite Porphyry in the Beidashan Area,Alxa Block:Constraints from Geochemistry,Zircon U-Pb Geochronology and Hf Isotopes
摘要
Abstract
The Beidashan Complex is located in the Beidashan area of the Alxa block,and represents an Early Precambrian metamorphic basement.These magmatic-metamorphic events are of great significance for studying the tectonic evolution and tectonic affinity of the Early Precambrian Alxa block.Here,we studied the petrogra-phy,geochemistry,zircon geochronology and Hf isotopes of the Cijingzi granite porphyry in the Beidashan area.The geochemical data shows that Cijingzi granite porphyry is characterized by high SiO2(73.85％-75.41％),A12O3(13.40％-14.19％)and K2O(3.83％-4.80％),and low Na2O(2.10％-3.31％)and Fe2O3T(0.93％-1.33％).The rocks have obvious negative Eu anomalies(δEu=0.15-0.29),with obvious enrichment of light rare earth elements(LREE)and depletion in heavy rare earth elements(HREE)in the chondrite-normalized REE patterns.It is also depleted in Nb,Ta,Ti and other high field strength elements(HFSEs)in the primitive mantle-normalized trace element patterns,similar to highly fractional I-type granite.LA-ICP-MS zircon U-Pb dating of the Cijingzi granite porphyry yielded an emplacement age of 2,035.6±8.4 Ma.The Cijingzi granite porphyry has εHf(t)=0.48-7.04 and Hf model age=2,627-2,222 Ma,indica-ting that the characteristics of the mixing of crust-derived magmas with mantle-derived ones.Combined with the previous studies,the magmatic event at Ca.2.0 Ga in the Alxa block exhibits the bimodal volcanic assemblage,and the felsic rocks are mostly of A-type,which were formed in an extensional environment.Zircon ages and Hf isotope compositions shows that the Alxa block and the Khondalite belt of the North China Craton have clear affinity in the Paleoproterozoic.关键词
华北克拉通/阿拉善地块/北大山地区/古元古代/锆石/岩浆事件Key words
North China Craton/Alxa block/Beidashan area/Paleoproterozoic/zircon/magmatic event分类
天文与地球科学引用本文复制引用
苏惠,曾认宇,甘德斌,严杰..阿拉善北大山地区花岗斑岩岩石成因及构造启示:元素地球化学、锆石U-Pb年代学及Hf同位素约束[J].现代地质,2023,37(6):1580-1596,17.基金项目
国家自然科学基金项目(41902075,42030809,42002095,42162013,42262017) （41902075,42030809,42002095,42162013,42262017）
核资源与环境国家重点实验室开放基金项目(2020NRE13) （2020NRE13）
有色金属成矿预测与地质环境监测教育部重点实验室(中南大学)开放基金资助项目(2022YSJS10) （中南大学）
国家留学基金委访问学者项目(202008360018) （202008360018）
江西省自然科学基金项目(20232BAB213061). （20232BAB213061）
