地质学报2025，Vol.99Issue(5)：1606-1631,26.DOI:10.19762/j.cnki.dizhixuebao.2024131
南岭骑田岭岩体岩浆演化序列与成因
Magma evolution sequence and genesis of the Qitianling pluton in Nanling Range
摘要
Abstract
Qitianling pluton is one of the most intensively researched plutons in the Nanling area.Despite this,its formation age,genetic types,and magmatic evolution process remain subjects of debate.This paper,based on detailed field investigations and U-Pb zircon dating by LA-ICP-MS,applies the theory of homologous magma evolution to divide Qitianling pluton into six lithofacies(mapping)units from early to late stages:Fine-to medium-grained porphyritic hornblende biotite monzogranite and granodiorite(ηγJ3a);medium-grained multi-porphyritic hornblende biotite monzogranite(ηγJ3b);medium-grained porphyritic(hornblende)biotite(syenogranite)monzogranite(ηγJ3c);coarse-to medium-grained porphyritic biotite(monzogranite)syenogranite(ζγJ3d);medium-to fine-grained oligoporphyritic biotite(monzogranite)syenogranite(ζγJ3e);and fine-to medium-grained biotite(monzogranite)syenogranite(ζγJ3f).U-Pb dating reveals that these units formed between 163 and 153 Ma,corresponding to the early Yanshanian of the Late Jurassic period.Geochemical analysis shows a gradual increase in SiO2 and K2 O content,a slight increase in Na2O,and a slight decrease in A12O3.MnO,TiO2,FeO*,MgO,CaO,and P2O5 all decrease gradually.The REE distribution patterns exhibit a right-inclined pattern,with decreasing δEu and deepening negative Eu anomalies.Trace element analysis reveals enrichment in Rb,Th,U,and Nd and depletion in Ba,Sr,Nb,and Ti.The Rb/Sr and Sm/Nd ratios gradually increase,while the Nb/Ta and Zr/Hf ratios decrease,indicating progressive magma differentiation and evolution.Our findings suggest that the late-stage Qitianling granite(ζγJ3e,ζγJ3f)formed through 40％～60％fractional crystallization of the early magma(ηγJ3a).Zircon saturation temperatures range from 604 to 821℃,with an average of 760.6℃.Combined with other data,we classify the Qitianling pluton as A2-type granite.Hf isotope analysis reveals εHf(t)values for the six lithofacies units ranging from-4.5 to-10.6,-4.9 to-8.9,-5.2 to-7.3,-5.1 to-9.4,-4.6 to-10.2,and-2.7 to-8.7,respectively.This indicates that the Qitianling pluton is primarily derived from the melting of metamorphic crustal rocks,with minor contributions from newly formed mantle material.The Hf isotope model ages for the second stage of the pluton cluster between 1658 and 1322 Ma,confirming that the source rocks separated from the mantle reservoir during the Mesoproterozoic.Therefore,the Qitianling pluton formed in an intracontinental extensional environment associated with the subduction of the Pacific plate.关键词
锆石U-Pb年龄/地球化学/Hf同位素/花岗岩成因/骑田岭/南岭Key words
zircon U-Pb age/geochemistry/Hf isotope/granite origin/Qitianling/Nanling area引用本文复制引用
夏杰,张遵遵,卢友月,李剑锋,付建明,陈希清,周念峰..南岭骑田岭岩体岩浆演化序列与成因[J].地质学报,2025,99(5):1606-1631,26.基金项目
本文为国家自然科学基金项目(编号U2344207)、中国地质调查局花岗岩成岩成矿研究中心开放基金课题(编号PMGR2020009,PMGR202108)和中国地质调查局地调项目(编号DD20243425,DD20230030,DD20230050)联合资助的成果. （编号U2344207）
