地质与勘探2024，Vol.60Issue(6)：1168-1182,15.DOI:10.12134/j.dzykt.2024.06.007
湘东北幕阜山西北部黑(二)云母二长花岗岩锆石U-Pb年龄、地球化学特征及其地质意义
Zircon U-Pb Ages,Geochemical Characteristics and Geological Significance of Biotite Monzogranite and Two-Mica Monzogranite in the Northwestern Mufushan of Northeast Hunan Province
摘要
Abstract
In the Mufushan region of northeastern Hunan Province,a significant discovery has been made in recent years,with the unearthing of several large-scale rare metal deposits,particularly those of the granitic pegmatite-type,rich in lithium(Li),niobium(Nb),tantalum(Ta),and beryllium(Be).These deposits exhibit a pronounced metallogenic association with the two-mica monzogranite and associated pegmatite formations.This study delves deeper into the petrogenesis and metallogenic potential of these monzogranites by employing LA-ICP-MS zircon U-Pb dating and whole-rock geochemical analyses on samples collected from the northwestern part of the Mufushan massif.The analysis results show that these monzogranites in this area are rich in silicon(w(SiO2)=71.99％～76.23％)and aluminum(w(Al2O3)=13.37％～14.86％),belonging to weak-to-strong peraluminous(A/CNK=1.08～1.14),medium-to-high K(w(K2O)=2.89％～5.27％,σ=1.67～2.38),calc-alkaline S-type(S-I type)granites,suggesting a crustal origin and a possible role of crustal melting in their formation.The zircon U-Pb weighted average ages of the two samples were determined to be 137.5±1.2 Ma and 134.7±1.6 Ma,respectively,indicating that they were formed in the Early Cretaceous.This temporal framework is crucial for understanding the tectonic and magmatic evolution of the region.These leucogranites in the northwestern part of the Mufushan massif are highly differentiated granites of typical crust-derived origin.They exhibit a relative enrichment in elements such as rubidium(Rb),thorium(Th),uranium(U),lanthanum(La),and cerium(Ce),which are typically associated with the presence of accessory minerals that can host these elements.Conversely,they show relative depletion in elements like barium(Ba),niobium(Nb),strontium(Sr),and ytterbium(Yb),which could be indicative of fractionation processes during their petrogenesis.A noteworthy observation is the significant positive lithium anomalies in these granites,with concentrations ranging from 39.6×10-6 to 97.8×10-6.This,coupled with their chondrite-normalized rare earth element(REE)patterns that display a clear light rare earth element(LREE)enrichment(LREE/HREE=8.16～22.53)and a right-leaning feature,is characteristic of highly evolved,fractionated granites.Integrated the results of this study with previous research,it is inferred that the leucogranite-hosting magmas may have originated from the partial melting of clay-poor Lengjiaxi Group sediments or coeval metamorphic sandstone.The tectonic setting of this magma generation is likely to have been during a critical transition period from collisional extrusion to a tensile regime,reflecting the dynamic nature of the Earth's crust during the Early Cretaceous in this region.This study thus contributes to a more nuanced understanding of the complex interplay between magmatism,tectonics,and the potential for economically significant mineral deposits in the Mufushan area.关键词
年代学/地球化学/二长花岗岩/稀有金属成矿/幕阜山/湘东北Key words
chronology/geochemistry/monzogranite/rare metal mineralization/Mufushan/northeast Hunan Province分类
天文与地球科学引用本文复制引用
陈旭,文春华,曹创华,黄乐清,李彬,曾广乾..湘东北幕阜山西北部黑(二)云母二长花岗岩锆石U-Pb年龄、地球化学特征及其地质意义[J].地质与勘探,2024,60(6):1168-1182,15.基金项目
中国博士后科学基金项目(编号:2022M713508)、国家重点研发项目专题(编号:2023YFC2906405)、湖南省自然科学部门联合基金项目(编号:2023JJ60164、2023JJ60166)、湖南省自然资源厅科技计划项目(编号:湘自资科20230102DZ)和湖南省地质院科研项目(编号:HNGSTP202318)联合资助. （编号:2022M713508）
