李家草泊铁矿黑云变粒岩LA-ICP-MS锆石U-Pb年代学研究
LA-ICP-MS Zircon U-Pb Geochronological Study of Biotite Leptynite from the Lijiacaobo Iron Deposit

本研究采用激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)技术，对山东省莱西市李家草泊铁矿矿体夹层中的黑云变粒岩开展锆石U-Pb年代学研究。分析结果表明：锆石核部年龄呈2346~2925 Ma连续概率密度分布，其中峰值年龄为2679 Ma，与新太古代TTG岩浆活动期高度吻合，揭示初始矿源形成于板块碰撞背景下的火山–沉积环境；锆石边部变质增生域记录了~1853 Ma变质年龄，与华北克拉通古元古代造山事件(1.95~1.80 Ga)具显著耦合性，指示变质热液对铁矿的二次富集作用。综合区域地质演化与已有成矿数据，揭示李家草泊铁矿成矿过程具有多期演化的的特征：矿源层初始沉积形成于新太古代早期(~2750 Ma)，经新太古代中期变质富集作用形成矿体，最终在古元古代~1.85 Ga经历区域变质–热液改造，促使铁质进一步活化富集。这一发现不仅完善了胶北地体铁矿成矿年代谱系，更为华北克拉通早前寒武纪构造–成矿演化研究提供了关键年代学约束。
This study employs the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) technique to conduct zircon U-Pb geochronological research on the biotite granulite intercalated within the iron ore body of the Lijiacaobo Iron Deposit in Laixi City, Shandong Province. The analysis results indicate that the zircon core ages exhibit a continuous probability density distribution ranging from 2346 to 2925 Ma, with a peak age of 2679 Ma, which highly coincides with the Neoarchean TTG magmatic activity period, revealing that the initial ore source formed in a volcanic-sedimentary environment under a plate collision setting. The zircon rim metamorphic overgrowth domains record a metamorphic age of ~1853 Ma, showing significant coupling with the Paleoproterozoic orogenic event (1.95~1.80 Ga) of the North China Craton, indicating the secondary enrichment of iron ore by metamorphic hydrothermal processes. Based on comprehensive regional geological evolution and existing metallogenic data, it is revealed that the mineralization process of the LijiaCaobo iron deposit exhibits multi-stage evolution characteristics: the initial deposition of the source bed occurred in the early Neoarchean (~2750 Ma), the ore body was formed through metamorphic enrichment during the middle Neoarchean, and finally, it underwent regional metamorphism-hydrothermal alteration around ~1.85 Ga in the Paleoproterozoic, which further activated and enriched the iron content. This discovery not only refines the metallogenic chronology of the iron deposits in the Jiaobei Terrane, but also provides crucial chronological constraints for the study of the tectonic-metallogenic evolution of the North China Craton during the Early Precambrian.