岩石矿物学杂志2025，Vol.44Issue(6)：1381-1408,28.DOI:10.20086/j.cnki.yskw.2025.4206
华北克拉通西南缘陇山杂岩新太古代晚期TTG岩石成因及其地质意义
The petrogenesis and geological significance of Late Neoarchean TTG in the Longshan Complex,southwestern margin of the North China Craton
摘要
Abstract
This study presents a comprehensive analysis of Late Neoarchean TTG(tonalite-trondhjemite-granodior-ite)within the Longshan Complex,situated at the southwestern margin of the North China Craton(NCC),providing critical constraints on the tectonic evolution of this region.These TTG,located in the Guanshan area of the Long-shan Complex,were dated using zircon U-Pb isotopic analysis,yielding crystallization ages of 2 535～2 485 Ma(2 503±39 Ma,2 535±39 Ma).The zircon εHf(t)values of the TTG are predominantly positive,and show two-stage Hf model ages ranging mainly from 3.1 Ga to 2.8 Ga.These data suggest that the TTG originated from partial melting of ancient crustal material with contributions from depleted mantle-derived components.Notably,one sample(23LS28)displays uniformly positive εHf(t)values,with some zircons closely approximating the isotopic composi-tion of the coeval depleted mantle.The two-stage model ages for this sample fall within 2.8～2.5 Ga,indicating derivation from partial melting of juvenile crustal material.The TTG exhibit high SiO2,Na2O,and low K2O.Most samples are characterized by flat heavy rare earth element(HREE)patterns,moderately elevated Y and Yb con-centrations,low Sr/Y and(La/Yb)N ratios,and minor to negligible Eu anomalies(δEu=0.70～0.96).These characteristics suggest that the TTG were generated by partial melting of source rocks under low-to medium-pres-sure(LP-MP)conditions,with amphibole,plagioclase,and minor garnet as the residual phases.However,one sam-ple(22LS30)exhibits distinct geochemical features,including lower Y and Yb concentrations,higher Sr/Y and(La/Yb)N ratios,and a pronounced positive Eu anomaly(δEu=2.47).These attributes indicate a deeper melting environment,corresponding to high-pressure(HP)conditions,with garnet,amphibole,and rutile as the dominant residual phases.The high Mg#,Cr,and Ni contents observed in all TTG are consistent with geochemical signatures associated with melts derived from the subducted oceanic crust.According to the chronology,isotope geochemistry and petrogeochemistry,these Late Neoarchean TTG belong to the NCC,and may have been in a subduction-related setting at this time.With the increase of subduction depth,the subduction fluid/melt continuously reacts with the mantle wedge,and the mantle interaction continues to strengthen.In addition,this study obtained metamorphic ages of 1 871±26 Ma and 459～335 Ma.The former age is consistent with the metamorphic events dated at 1.97～1.80 Ga in the NCC,while the latter aligns with the Paleozoic metamorphic events in the North Qinling Orogenic Belt.It is concluded that the TTG subsequently experienced metamorphism during Late Paleoproterozoic thermo-tectonic event and were eventually incorporated into the Longshan Complex during the Paleozoic orogenic event.关键词
华北克拉通/陇山杂岩/新太古代晚期/TTGKey words
North China Craton/Longshan Complex/Late Neoarchean/TTG(tonalite-trondhjemite-granodiorite)分类
天文与地球科学引用本文复制引用
张艺一,卢俊生,李玉婷,孔旭,刘刚,封强,栗娟娟,段增印..华北克拉通西南缘陇山杂岩新太古代晚期TTG岩石成因及其地质意义[J].岩石矿物学杂志,2025,44(6):1381-1408,28.基金项目
国家自然科学基金项目(41890834,41872195) （41890834,41872195）
科技部大陆动力学国家重点实验室专项资金 National Natural Science Foundation of China(41890832,41872195) （41890832,41872195）
MOST Special Fund from State Key Laboratory of Continental Evolution and Early Life,Northwest University （）
