铀矿地质2025，Vol.41Issue(4)：617-636,20.DOI:10.3969/j.issn.1000-0658.2025.41.043
桂北摩天岭岩体舒家湾地区沥青铀矿原位微区年代学及其地质意义
In Situ Microchronology and Geological Significance of Pitchblende in Shujiawan Area of Motianling Pluton,Northern Guangxi
摘要
Abstract
Shujiawan area is located in the northern part of the Motianling pluton,characterized by numerous uranium mineralization occurrences,anomaly points,diverse ore-bearing fractures,and bears significant metallogenic potential.To precisely determine the uranium mineralization age in the study area,this study conducted chemical composition analysis,U-Pb isotopic dating,and rare earth element(REE)characterization of pitchblende using in-situ microanalysis techniques(EPMA,LA-ICP-MS)based on optical microscopy and scanning electron microscopy backscatter observations.Results show that the mass fraction of pitchblende is of UO2(87.56%average),CaO(1.21%),PbO(0.58%),and P2O5(0.78%).The 206Pb/238U weighted average age was determined as(54.5±1.5)Ma(MSWD=2.2,n=16),while the Tera-Wasserburg concordia diagram yielded a lower intercept age of(55.0±1.5)Ma(MSWD=2.2,n=16).Both ages are consistent within error limit,indicating a mineralization age of approximately 55 Ma.REE characteristics of pitchblendes reveal relatively low total REE contents with insignificant LREE-HREE fractionation,but distinct negative Eu anomalies.The chondrite-normalized REE pattern displays a V-shaped curve with slight LREE enrichment and relatively flat HREE distribution.The ΣREE contents,ThO2 and Y concentrations,and Eu anomalies collectively indicate a low-temperature hydrothermal origin with corresponding fluid characteristics.The obtained mineralization age corresponds to the 45-55 Ma lithospheric extension period in South China and mate with the critical uranium mineralization period(87-47 Ma)during Late Yanshanian to Early Himalayan brittle-ductile extensional tectonic activities in Motianling structural dome.This demonstrates that uranium mineralization in Shujiawan area was formed under a Cretaceous-Paleogene lithospheric extension and thinning geodynamic background,representing a product of late-stage uranium mineralization events in South China.关键词
LA-ICP-MS U-Pb同位素定年/沥青铀矿/成矿时代/舒家湾地区Key words
LA-ICP-MS U-Pb dating/pitchblende/metallogenic age/Shujiawan area分类
天文与地球科学引用本文复制引用
刘明,谭双,陈琪,范鹏飞,万建军,吴昆明,朱小兵,雷勇亮..桂北摩天岭岩体舒家湾地区沥青铀矿原位微区年代学及其地质意义[J].铀矿地质,2025,41(4):617-636,20.基金项目
中国核工业地质局地勘项目(编号:202223、202222) （编号:202223、202222）
核工业二三〇研究所自主研发/创新创效项目(编号:2022-02-09) （编号:2022-02-09）
江西省研究生创新基金(编号:YC2023-B208)联合资助. （编号:YC2023-B208）
