摘要
龙宝山碱性杂岩体位于华北克拉通鲁西地区东南缘,是新发现的龙宝山稀土矿的赋矿岩体,但其岩石成因和稀土富集机制仍没有得到很好的解释。本文对该碱性杂岩体中的正长斑岩、石英正长斑岩、含角闪正长斑岩的岩石地球化学特征进行了系统的研究,旨在限定该岩体的成因机制,揭示稀土元素的富集机制。研究结果显示,龙宝山碱性杂岩体形成于早白垩世(130~128 Ma),所分析样品具有较高的SiO_(2)、Na_(2)O、K_(2)O和Al_(2)O_(3)含量以及较低的MgO、FeO和CaO含量,属于准铝质岩、过碱性岩、高钾钙碱性岩和钾玄岩。样品都表现出富集的Sr-Nd同位素特征,富集大离子亲石元素(large-ion lithophile element,LILE)和轻稀土元素(light rare earth element,LREE),亏损Nb、Ta和Ti重稀土元素(heavy rare earth element,HREE),且具较高的Nb/Y、Th/Yb、La/Sm和较低的Ba/Th值,这些均指示俯冲沉积物熔体交代了地幔源区并为源区提供了稀土元素的初始富集。在岩浆演化早期,角闪石和黑云母的分离结晶促进了稀土元素的进一步富集。钠长石交代是热液作用的结果,岩浆晚期的热液交代作用导致了稀土元素的富集成矿。因此,龙宝山碱性杂岩体起源于富集岩石圈地幔的部分熔融,俯冲海洋沉积物再循环诱发的稀土元素(rare earth elements,REE)初始富集对龙宝山碱性岩型稀土矿床的形成具有重要制约,岩浆热液作用过程是稀土元素富集成矿的关键过程。
The Longbaoshan alkaline complex,located in the southeastern Luxi Terrane of the North China Craton,hosts a newly discovered REE deposit.However,the petrogenesis of the complex and the mechanisms of rare earth element(REE)enrichment remain poorly understood.This study presents a systematic investigation of the whole-rock geochemistry of the syenite porphyry,quartz syenite porphyry,and amphibole-bearing syenite porphyry within the complex,aiming to elucidate its petrogenesis and reveal the REE enrichment mechanisms.The results indicate that the Longbaoshan alkaline complex formed in the Early Cretaceous(130128 Ma).It is characterized by high SiO_(2),Na_(2)O+K_(2)O,and Al_(2)O_(3)contents,but low MgO,FeO,and CaO,displaying metaluminous to peralkaline and belongs to the high-K calc-alkaline to shoshonitic series.All samples exhibit enriched Sr-Nd isotopic compositions and are enriched in large-ion lithophile element(LILE)and light rare earth element(LREE),but are depleted in high field strength element(HFSE;e.g.,Nb,Ta,Ti)and heavy rare earth element(HREE).They also feature low Ba/Th and high Nb/Y,Th/Yb,and La/Sm ratios.These geochemical characteristics suggest that the mantle source was metasomatized by melts derived from subducted sediments,which provided the initial REE enrichment.During early magmatic evolution,fractional crystallization of hornblende and biotite promoted further enrichment of REE.The albitization results from hydrothermal processes,and late magmatic-hydrothermal metasomatism resulted in ore-forming REE enrichment.Therefore,the Longbaoshan alkaline complex originated from the partial melting of enriched lithospheric mantle.Initial REE enrichment by metasomatic subduction-related melts was crucial for mineralization,while subsequent magmatic-hydrothermal processes were key to further enrichment and ore formation.
作者
刘传朋
马钊
安茂国
支成龙
杨泽宇
吴鸣谦
尚振
陈怀鑫
韩宗瑞
姜腾飞
高文白
LIU Chuanpeng;MA Zhao;AN Maoguo;ZHI Chenglong;YANG Zeyu;WU Mingqian;SHANG Zhen;CHEN Huaixin;HAN Zongrui;JIANG Tengfei;GAO Wenbai(Shandong Provincial Lunan Geology and Exploration Institute(Shandong Provincial Bureau of Geology and Mineral Resources No.2 Geological Brigade),Jining 272100,China;Rare Mineral Exploration and Comprehensive Utilization Engineering Research Center of Shandong Province,Jining 272100,China;Shandong Provincial No.3 Exploration Institute of Geology and Mineral Resources,Yantai 264004,China;State key Laboratory of Geological Processes and Mineral Resources/School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;School of the Environment,University of Windsor,Windsor N9B 3P4,Canada)
出处
《地学前缘》
北大核心
2026年第2期265-289,共25页
Earth Science Frontiers
基金
山东省鲁南地质工程勘察院(山东省地质矿产勘查开发局第二地质大队)及三稀矿产勘查与综合利用山东省工程研究中心开放基金项目(LNY202206,LNY202301,LNY202302)。
