摘要
栾川县水磨沟稀土矿床位于华北克拉通南缘,为一新发现以轻稀土为主的高品位稀土矿。稀土矿体呈不规则脉状展布于古元古代末期龙王䃥碱性花岗岩体中的北西-北西西向构造带内,赋矿围岩为富含稀土的中粗粒钠铁闪石正长花岗岩。本文对其开展了显微矿物学、稀土元素地球化学和氟碳铈矿U-Th-Pb年代学研究,并探讨其成矿作用过程。矿物学研究显示,稀土矿石矿物主要为氟碳铈矿、氟碳钙铈矿、褐帘石和铈硅磷灰石,发育明显的交代结构,指示后期热液活动对稀土元素的富集成矿起着重要的作用。稀土元素地球化学特征显示矿石强烈富集轻稀土,轻重稀土分馏较强,稀土配分曲线呈具中等Eu负异常的右倾斜模式,与围岩龙王䃥碱性花岗岩稀土元素地球化学特征总体较为相似,指示其与龙王䃥碱性花岗岩体的亲缘性。氟碳铈矿激光剥蚀电感耦合等离子体质谱法(laser ablation inductively coupled plasma mass spectrometer, LA-ICP-MS)U-Th-Pb测年获得主体Th-Pb加权平均年龄为(381.4±6.5)Ma,表明其主要形成时代属晚泥盆世早期。稀土成矿作用过程如下:古元古代末期,区域龙王䃥碱型花岗质岩浆在高度结晶分异过程中稀土元素进行了初步富集;泥盆纪时,受构造挤压作用碱性花岗岩体中稀土元素发生活化,并沿构造破碎带迁移富集沉淀成矿,为水磨沟稀土矿的主成矿期;中生代时,碱性花岗岩体及稀土矿体局部发生构造热事件,部分稀土元素再次活化迁移,沿原来矿体位置局部发生了改造富集。
The Shuimogo REE deposit in Luanchuan County,Henan Province,is a newly discovered,high-grade deposit on the southern margin of the North China Craton,dominated by light rare earth elements(LREEs).REE ore bodies occur as irregular veins within a NW-to WWN-trending structural zone of the Late Paleoproterozoic Longwangzhuang alkaline granite and are hosted by medium-to coarse-grained sodic-ferro-amphibole syenitic granite,which itself has high REE content.This study investigates the metallogenic age and processes through detailed mineralogy,rare earth element geochemistry,and bastn site U-Th-Pb geochronology by LA-ICP-MS.Mineralogical analysis shows that the main REE minerals are bastn site,parisite,allanite,and ellestadite.The presence of obvious metasomatic textures indicates that late-stage hydrothermal activity played a critical role in REE enrichment and mineralization.Geochemically,the ore is strongly enriched in LREEs,shows a high degree of LREE-HREE fractionation,and exhibits a right-sloping REE distribution pattern with a moderate negative Eu anomaly.These patterns are generally similar to the geochemical signature of the Longwangzhuang alkaline granites,implying a genetic affinity.Bastn site U-Th-Pb dating yielded a weighted average age of(381.4±6.5)Ma,indicating that the main mineralization phase occurred during the early Late Devonian.The REE mineralization process of Shuimogou REE deposit involved three key stages:(1)Initial REEs enrichment occurred during the Late Paleoproterozoic,accompanied by extensive fractional crystallization of the Longwangzhuang alkaline granitic magma.(2)During the Devonian as main mineralization stage,REEs within the alkaline granite were mobilized by tectonic compression,migrated along fault zones,and accumulated to form ore bodies.(3)In the Mesozoic,tectonic-thermal events remobilized some REEs,leading to local modification and further enrichment of pre-existing ore bodies.
作者
杜保峰
李山坡
吴鸣谦
张荣臻
陈俊魁
王莉
李珊珊
邱昆峰
DU Baofeng;LI Shanpo;WU Mingqian;ZHANG Rongzhen;CHEN Junkui;WANG Li;LI Shanshan;QIU Kunfeng(Frontiers Science Center for Deep-time Digital Earth,State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Henan Key Laboratory of Metal Mineral Mineralization Geological Processes and Resource Utilization,Henan Academy of Geology,Zhengzhou 450016,China;Lang Fang Natural Resources Comprehensive Survey Center,China Geological Survey,Tianjin 300301,China)
出处
《地学前缘》
北大核心
2026年第2期247-264,共18页
Earth Science Frontiers
基金
河南省科技攻关项目(242102320363)
河南省财政地质勘查项目(豫财招标采购-2020-165-3,豫财招标采购-2024-424-12)
河南省地质研究院基本科研业务费项目(2024-903-XM04,2025-901-XM09)。
关键词
水磨沟稀土矿
氟碳铈矿定年
泥盆纪
成矿作用
华北克拉通南缘
Shuimogo REE deposit
bastn site U-Th-Pb dating
Devonian
mineralization process
south margin of the North China craton
