【作者】 李雪；

【导师】 王可勇；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2023， 博士

【摘要】 稀有金属Nb和Ta因其独特的物理和化学性质,被广泛的应用在钢铁工业、超导材料工业、电子工业、原子能、航天航空以及医疗等诸多领域,在国际关键矿产资源中具有重要的战略地位。近年来,区域地质调查和研究工作显示大兴安岭一些地区具有Nb、Ta等稀有金属成矿的地质条件。本文在对已有区域地质矿产资料进行预研究的基础上,选取大兴安岭地区扎鲁特旗巴尔哲、鄂温克族自治旗头道桥典型铌（钽）矿床,以及鄂伦春自治旗克一河地区的托河林场、乌鲁康沟和吉源林场铌（钽）矿点为研究对象,开展详细的野外地质调研、样品采集、成矿地质特征、成岩成矿年代学、岩石矿物地球化学以及同位素地球化学等多方面的研究,查明了区内典型矿床（点）的火成岩侵位时代、岩浆源区和岩石成因与铌钽成矿的关系,并在此基础上探讨了区域构造演化与矿床（点）成因,进而建立研究区铌（钽）稀有金属成矿模式。巴尔哲是典型的碱性花岗岩型铌钽矿床,分为东、西两个矿体,东矿体具有明显的垂直矿化分带,是巴尔哲铌钽矿床的主矿体,成矿主要与其中部的钠铁闪石钠长石花岗岩和顶部的钠长石花岗岩相关;西矿体矿石工业品位不如东矿体,成矿主要与钠铁闪石花岗岩、含钠铁闪石花岗岩有关;两个矿体的矿石矿物种类大体相同,主要为铌铁矿、铌锰矿、铌钇矿、铈-铌钙矿、复稀金矿和铌-易解石等,这些铌钽矿石矿物大多呈浸染状分布在岩浆早期结晶的矿物颗粒之间。头道桥是碱性火山岩型铌（钽）矿床,矿化主要出现在碱性流纹岩中,铌钽矿石矿物主要是铌铁矿,其次是含铌磁铁矿和含铌钛铁矿。克一河地区的托河林场、乌鲁康沟和吉源林场均为碱性火山岩型铌（钽）矿点,除乌鲁康沟矿点铌（钽）成矿主要出现在碱性流纹质熔结凝灰岩中,其余两处铌（钽）成矿均与碱性流纹岩密切相关。托河林场铌钽矿石矿物为含铌钛铁矿和含铌锆石;吉源林场矿点以铌金红石和铌铁矿为主,还有少量的褐钇铌矿和铌钇矿;乌鲁康沟矿点主要是含铌钛铁矿,还有少量的含铌锆石、褐钇铌矿、黑稀金矿以及微量的黄钇钽矿、铌钇矿、铌铁矿和钽铁矿。这些火山岩中的（含）铌（钽）矿石矿物主要呈星散浸染状镶嵌在石英等主要造岩矿物颗粒边缘或分布在长英质基质中。LA-ICP-MS锆石U-Pb年代学结果显示,巴尔哲东、西矿体各存在两期成矿作用:巴尔哲东（DBEZ1）、西矿体（XBEZ1,XBEZ2）岩浆锆石U-Pb年龄（122.4±2.6 Ma、132.6±3.3 Ma和130.3±3.5 Ma）分别代表巴尔哲东、西矿体高演化花岗质岩浆结晶的时代,该年龄为铌钽稀有金属成矿的峰期年龄;热液锆石UPb年龄（115.4±1.8 Ma、123.5±1.7 Ma和122.2±0.87 Ma）则分别代表了巴尔哲东、西矿体高演化花岗质岩浆晚期流体-熔体相互作用的时代。另外,研究区火山岩岩浆锆石U-Pb年龄显示,与其有关的铌（钽）成矿作用主要分为两期:早白垩世早期是头道桥（132.1±1.3 Ma）和乌鲁康沟（142.5±1.2 Ma）满克头鄂博组火山岩及其铌（钽）成矿形成的时代,而托河林场（109.3±1.2 Ma）和吉源林场（104.5±0.65 Ma）白音高老组火山岩年龄则代表了另一期铌（钽）成矿作用发生于早白垩世晚期。巴尔哲、头道桥、以及克一河地区与铌（钽）成矿有关的花岗岩和火山岩以富Si、ALK、Fe,贫Mg、Ca为特征,全岩地球化学组成（高的10000*Ga/Al和Zr+Nb+Ce+Y值）显示其具有典型的A型花岗质岩石的性质。巴尔哲、头道桥、托河林场和吉源林场锆石Lu-Hf和乌鲁康沟全岩Sr-Nd同位素示踪,以及巴尔哲钠铁闪石电子探针成分研究,指示早白垩世时期大兴安岭地区受到了古太平洋板块后撤回卷俯冲作用,岩石圈发生伸展减薄,从而引发了软流圈地幔物质上涌加热新元古代-古生代新增生的富钾中基性下地壳并使其部分熔融,形成了巴尔哲碱性花岗岩和头道桥-克一河地区碱性火山岩。巴尔哲、头道桥、以及克一河地区矿化岩体均具有富Rb、Nb、Ta、Zr和Hf等不相容元素,而贫P、Ti、Ca、Mg、Ba和Sr等元素的特征。同时,它们具有较高的Rb/Sr比值、显著的Eu负异常和M型稀土四分组效应(TE_1,3>1.10),表明形成这些岩石的岩浆都经历了较高程度的分离结晶作用。在花岗质岩浆分异演化过程中,F和H₂O等挥发分可以通过降低熔体的粘度和固相线温度使岩浆发生高度分异演化作用,同时还可以增加熔体中的非桥氧数,进而增大Nb-Ta元素的溶解度,使其在残余熔体中的不断富集并最终达到矿化。矿化岩体中大部分的铌钽矿石矿物以浸染状分布在早期的造岩矿物之间,且具有相似地球化学性质的Nb-Ta、Zr-Hf、HREE-Y等元素表现出明显的线性相关关系。因此,本文提出巴尔哲、头道桥、以及克一河地区Nb-Ta元素成矿主要受控于岩浆晚期高度的分离结晶作用,热液流体作用仅对巴尔哲花岗岩型铌钽成矿产生叠加影响。另外,显著富碱、稀有稀土元素和挥发分等物质特性的岩浆源区是研究区Nb-Ta成矿的另一个关键因素。成矿区内的褶皱和次生断裂构造的发育,也为区内含矿岩浆的上升运移和分异演化提供了有利的成矿环境。本文基于巴尔哲、头道桥和克一河地区岩浆源区性质与岩浆演化作用的研究,首次提出研究区铌（钽）矿的形成主要受岩浆高度分离结晶作用（和热液交代作用）与富稀有、稀土元素等岩浆源区的双重控制,同时利用矿物分析手段查明了铌（钽）矿物主要以浸染状赋存在早期矿物颗粒之间或边缘。以上认识对区域上Nb-Ta等稀有金属矿产勘查工作以及进一步的开发利用具有重要的指导意义。更多还原

【Abstract】 The rare metals Nb and Ta are widely used in various fields such as steel industry,superconducting material industry,electronics industry,atomic energy,aerospace and medical treatment because of their unique physical and chemical properties,and have an important strategic position in the international key mineral resources.In recent years,regional geological survey and research work show that some areas in the Great Xing’an Range have geological conditions for the mineralization of rare metals such as Nb and Ta.On the basis of pre-study of existing regional geological and mineral data,the paper selectes the Baerzhe of Jarud Banner,the Toudaoqiao of Ewenki Autonomous Banner typical Nb（Ta）deposits,and the Tuohelinchang,Wulukanggou and Jiyuanlinchang in Keyihe area of Oroqen Autonomous Banner Nb（Ta）ore occurrences as the research objects.Through detailed field geological investigation,sample collection,metallogenic geological characteristics,diagenetic and metallogenic chronology,rock,mineral and isotope geochemistry,the relationship between igneous emplacement age,magma source and petrogenesis and niobium-tantalum mineralization of typical deposits（occurrences）in the area has been identified.Based on this,the regional tectonic evolution and genesis of deposits（occurrences）have been discussed and the metallogenic model of Nb（Ta）rare metals in the study area is established.Baerzhe is a typical alkaline granitic-type Nb-Ta deposit,which is divided into east and west ore bodies.The east ore body has obvious vertical mineralization zoning,which is the main ore body of the Baerzhe Nb-Ta deposit.The mineralization is mainly related to the arfvedsonite-albite granite in the middle and the albite granite at the top.The industrial grade of the west ore body is not as good as that of the east ore body,and the mineralization is mainly related to the arfvedsonite granite and the arfvedsonitebearing granite.The ore mineral types of the two ore bodies are roughly the same,composed of columbite,manganocolumbite,samarskite,fersmite-（Ce）,polycrase and nioboaeschynite,most of these Nb-Ta ore minerals are disseminated among the mineral particles crystallized in the early stage of magma.The mineralization of Toudaoqiao alkaline volcanic-type Nb（Ta）deposit mainly occurs in alkaline rhyolite.The ore minerals are mainly columbite,followed by niobium-bearing magnetite and niobiumbearing ilmenite.The Tuohelinchang,Wulukanggou and Jiyuanlinchang in Keyihe area are all alkaline volcanic-type Nb（Ta）ore occurrences.Except that the Nb（Ta）mineralization in the Wulukanggou ore occurrence mainly occurs in the alkaline ignimbrite,the other two Nb（Ta）mineralizations are closely related to alkaline rhyolite.The Nb（Ta）ore minerals in Tuohelinchang are composed of niobium-bearing ilmenite and niobium-bearing zircon;Jiyuanlinchang are composed of mainly niobium-rutile and columbite,as well as a small amount of fergusonite and samarskite;Wulukanggou are composed of mainly niobium-bearing ilmenite,with a small amount of niobiumbearing zircon,fergusonite,euxenite,and trace amounts of formanite,samarskite,columbite and tantalite.The Nb（Ta）ore minerals in these volcanic rocks are mainly scattered in the edge of the main rock-forming mineral particles such as quartz or distributed in the felsic matrix.The results of LA-ICP-MS zircon U-Pb geochronology show that there are two stages of mineralization in the eastern and western ore bodies of Baerzhe: the magmatic zircon U-Pb ages（122.4 ± 2.6 Ma,132.6 ± 3.3 Ma and 130.3 ± 3.5 Ma）of the eastern（DBEZ1）and western（XBEZ1,XBEZ2）ore bodies of Baerzhe represent the crystallization age of highly evolved granitic magma in the eastern and western ore bodies of Baerzhe,respectively,which is the peak age of Nb-Ta rare metals mineralization.The hydrothermal zircon U-Pb ages（115.4 ± 1.8 Ma,123.5 ± 1.7 Ma and 122.2 ± 0.87 Ma）,which represent the age of fluid-melt interaction in the late stage of highly evolved granitic magma in the eastern and western ore bodies of Baerzhe,respectively.In addition,the zircon U-Pb age of the volcanic rocks in the study area shows that the related Nb（Ta）mineralization is mainly divided into two periods: the early Early Cretaceous is the age of the volcanic rocks of the Manketouebo Formation and their Nb（Ta）mineralization of the Toudaoqiao（132.1 ± 1.3 Ma）and Wulukanggou（142.5 ± 1.2 Ma）,while the age of the volcanic rocks of the Baiyingaolao Formation in Tuohelinchang（109.3 ± 1.2 Ma）and Jiyuanlinchang（104.5 ± 0.65 Ma）represents another period of Nb（Ta）mineralization occurred in the late Early Cretaceous.The granites and volcanic rocks related to Nb（Ta）mineralization in Baerzhe,Toudaoqiao,and Keyihe areas are characterized by rich Si,ALK,Fe and poor Mg,Ca.The geochemical composition of the whole rock（high 10000*Ga/Al and Zr+Nb+Ce+Y values）shows that it has typical A-type granitic rock properties.The tracings of zircon Lu-Hf isotopes of Baerzhe,Toudaoqiao,Tuohelinchang and Jiyuanlinchang,and whole-rock Sr-Nd isotopes of Wulukanggou,as well as the study of the electron probe composition of Baerzhe arfvedsonite,indicate that the Great Xing’an Range area was subjected to the retro-subduction of the ancient Pacific plate during the early Cretaceous period,and the lithosphere was stretched and thinned,which triggered the upwelling of the asthenosphere mantle material to heat the Neoproterozoic-Paleozoic newly generated potassium-rich intermediate-basic lower crust partially melted and formed the Baerzhe alkaline granite and the Toudaoqiao-Keyihe area alkaline volcanic rock.The mineralized rocks in Baerzhe,Toudaoqiao and Keyihe areas are rich in incompatible elements such as Rb,Nb,Ta,Zr and Hf,and poor in elements such as P,Ti,Ca,Mg,Ba and Sr.At the same time,they have high Rb/Sr ratios,significant negative Eu anomalies and M-type rare earth tetrad effect(TE_1,3>1.10),indicating that the magmas forming these rocks have undergone a high degree of fractional crystallization.In the process of differentiation and evolution of granitic magma,volatiles such as F and H₂O can make the magma highly differentiated and evolved by reducing the viscosity and solidus temperature of the melt.At the same time,they can also increase the number of non-bridging oxygen（NBO）in the melt,thereby increasing the solubility of Nb-Ta elements,so that they are continuously enriched in the residual melt and eventually mineralized.Most of the niobium-tantalum ore minerals in the mineralized rock mass are disseminated between the early rock-forming minerals,and the elements such as Nb-Ta,Zr-Hf and HREE-Y with similar geochemical properties show obvious linear correlation.Therefore,this paper proposes that the Nb-Ta element mineralization in Baerzhe,Toudaoqiao,and Keyihe areas is mainly controlled by the high degree of fractional crystallization in the late magmatic stage,and the hydrothermal fluid only has a superimposed effect on the Nb-Ta mineralization of the Baerzhe granite type.In addition,the magma source with significant rich in alkali,rare earth elements and volatiles is also another key factor in the Nb-Ta mineralization in the study area.The development of folds and secondary faults in the ore-forming area also provides a favorable metallogenic environment for the upward migration and differentiation evolution of ore-bearing magma in the area.Based on the study of the nature of magmatic source and magmatic evolution in Baerzhe,Toudaoqiao and Keyihe areas,this paper proposes for the first time that the formation of Nb（Ta）ore in the study area is mainly double controlled by the highly fractional crystallization（and hydrothermal metasomatism）of magma and the magmatic source rich in rare and rare earth elements.At the same time,it is found that niobium（tantalum）minerals are mainly in the form of disseminated occurrence between or at the edges of early mineral particles by means of mineral analysis.The above understanding has important guiding significance for the exploration and further development and utilization of rare metal minerals such as Nb-Ta in the region.更多还原