摘要
加不斯钽铌稀有金属矿是位于大兴安岭稀有金属成矿带西南部的一处大型钽矿床,伴生有Nb、Li、Rb、Cs矿化。本文通过系统的岩相学、岩石地球化学及铌钽矿LA-ICP-MS U-Pb年代学工作,对矿床成岩成矿机制进行了研究。加不斯成矿花岗岩主要为黄玉锂白云母碱长花岗岩和锂白云母钠长花岗岩,富硅、铝和碱,贫铁和镁,尤其贫钛和磷,属过铝质高钾钙碱性系列;相对富集Rb、Th、Nd、Zr,亏损Ba、Nb、Sr、P,强烈亏损Ti;稀土元素总量较低,平均47.97×10^(-6),具有强烈负Eu异常和显著的M型“四分组”效应;成矿花岗岩的Zr/Hf=2.58~3.47,Nb/Ta=0.3~0.39,表明成矿岩体经历了强烈的分异作用,属高分异花岗岩。矿区矿石矿物主要为细晶石、铌钽锰矿和锂白云母,铷(铯)主要以类质同象赋存于锂白云母和铌钽矿物中。矿区不含矿的黑云母(角闪)花岗岩中锆石的^(206)Pb/^(238)U加权平均年龄为144.0±1.0 Ma(2σ,n=16,MSWD=1.3),反映了围岩那仁乌拉岩体的成岩年龄。成矿的黄玉锂白云母碱长花岗岩矿石中岩浆成因铌钽矿物的^(206)Pb/^(238)U加权平均年龄为120.7±0.2 Ma(2σ,n=17,MSWD=6),代表了铌钽矿的成矿年龄,也代表了成矿岩体的成岩年龄为早白垩世晚期,成岩成矿与蒙古-鄂霍茨克洋中侏罗世闭合后的岩石圈伸展有关。笔者认为,加不斯钽铌稀有金属矿床是高分异演化的花岗岩熔体和富Li、F等挥发分流体共同作用和制约的结果,成矿可以划分为两个阶段,第一阶段为岩浆原始结晶阶段,以Ta、Nb矿化为主,第二阶段为热液流体的自交代阶段,以Li、Rb、Cs矿化为主。围绕着那仁乌拉岩体,仍然具有找到同类型稀有金属矿床的潜力。
The Jiabusi Ta-Nb rare metal deposit,accompanied by Li-Rb-Cs mineralization,is a medium-sized Ta-deposit located in the southwest of the Daxinganling rare metal metallogenic belt.In this paper,through systematic petrographic,rock geochemical,and LA-ICP-MS U-Pb chronological analyses,the diagenesis and metallogenic mechanisms of the deposit and its ore-forming granite were studied.The lithology of the ore-forming granite in the Jiabusi deposit consists mainly of topaz-lithium muscovite-alkali feldspar granite and lithium muscovite-albite granite.Whole-rock geochemical data show that the granites are rich in Si,Al,and alkalis,but depleted in Fe,Mg,Ca,Ti,and P,belonging to the peraluminous high-K calc-alkaline series.Their trace elements are enriched in Rb,Th,Nd,and Zr,and depleted in Ba,Nb,Sr,and P,with strong Ti depletion.Rare earth element(REE)data show very low total REE contents(average 47.97×10^(-6)),strong negative Eu anomalies,and significant M-type tetrad effect.Ratios of Zr/Hf(2.58~3.47)and Nb/Ta(0.3~0.39)indicate the rocks are highly fractionated granites.Ore minerals in Jiabusi deposit include microlite,manganotantalite,and Li-muscovite,with Rb and Cs are mainly hosted in Li-mica and Ta-Nb minerals.This paper reports U-Pb dating results from different granites in the deposit using the LA-ICP-MS method.The zircon U-Pb age of the ore-barren biotite(hornblende)granite is 144.0±1.0 Ma(2σ,n=16,MSWD=1.3),which represents the crystallization age of the surrounding Narenwula pluton.The weighted mean ^(206)Pb/^(238)U age of magmatic Ta-Nb minerals in the mineralized alkali feldspar granite is 120.7±0.2 Ma(2σ,n=17,MSWD=6).These results indicate that mineralization and crystallization age of the Jiabusi ore-forming granite occurred during the late Early Cretaceous,related to lithospheric extension following the Middle Jurassic closure of the Mongolian-Okhotsk Ocean.We propose that the formation of the Jabusi deposit can be divided into two stages:a primary magmatic crystallization stage,which is dominated by Ta and Nb mineralization,followed by a hydrothermal autometasomatism stage,which is dominated by Li,Rb,and Cs mineralization.The area around the Narenwula intrusive body foundation retains potential for discovering further rare metal deposits of the same type.
作者
丁建华
张勇
叶会寿
余金杰
付雪瑞
吴胜华
张彤
DING Jianhua;ZHANG Yong;YE Huishou;YU Jinjie;FU Xuerui;WU Shenghua;ZHANG Tong(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China;State Key Laboratory of Deep Earth and Mineral Exploration,Beijing 100094,China;China University of Geosciences,Beijing 100083,China;Inner Mongolia Institute of Geological Survey,Hohhot,Inner Mongolia 010020,China)
出处
《地质学报》
北大核心
2026年第1期145-167,共23页
Acta Geologica Sinica
基金
国家科技基础调查专项项目(编号2022FY101705)
中国地质调查项目(编号DD20230305)联合资助的成果。
关键词
高分异花岗岩
稀有金属
铌钽矿物U-Pb年龄
加不斯
大兴安岭
highly fractionated granite
rare metal
U-Pb dating of niobium-tantalum mineral
Jiabusi
Da Hinggan Mountains
