甘肃南祁连—北山铌钽铷等稀有金属成矿地质特征与成矿规律的研究

发布时间：2018-05-16 20:11

  本文选题：稀有金属 + 地质特征　； 参考：《兰州大学》2016年博士论文

【摘要】：祁连山和北山地区分属古特提斯和古亚洲大洋构造域,在其构造演化过程中形成了中国北方及中亚地区重要的岩浆-成矿带而备受地质学家的关注。近年来,甘肃省地质调查院在祁连、北山等地区的地质调查和研究工作显示了以上地区具有形成大型、特大型稀有金属矿的地质条件,通过深入研究,有望取得找矿突破。本文以南祁连余石山铌钽矿、北山国宝山铷矿为研究对象,在系统收集前人研究成果的基础上,通过野外地质调查、室内研究和测试分析等工作,基于现代成矿理论、岩石学和矿物学、地球化学和同位素年代学等,对以上两处稀有金属的成矿地质背景、年代学、物质来源、成矿规律等方面进行了研究。取得了如下成果和认识:1.通过野外地质调查,详细研究了余石山铌钽矿和国宝山铷矿的区域地质、矿化类型、岩石学、矿物学、矿石学等特征。确定了余石山铌钽矿主要赋存于变粒岩中,国宝山铷矿主要赋存于含天河石花岗岩、花岗伟晶岩中。2.对余石山变粒岩、国宝山花岗岩类开展了锆石U-Pb同位素定年研究。余石山变粒岩中锆石有岩浆成因和变质成因两类,岩浆锆石206Pb/238U年龄值在810±6Ma~854±7Ma之间,谐和年龄为829.4±2.7Ma,代表了岩浆侵入的时代;变质成因锆石206Pb/238U年龄值在768±8Ma~809±7Ma之间,谐和年龄为795±5.4Ma;代表了岩浆期后的热事件。国宝山地区花岗片麻岩成岩年龄为1853±16Ma;(含天河石)二长花岗岩、花岗伟晶岩成岩年龄分别为427±8Ma、406±5Ma,揭示了岩浆从花岗岩浆演化到花岗伟晶岩持续时间达21Ma。3.运用岩石地球化学方法,对余石山变粒岩进行了原岩恢复。结果显示原岩为正长岩,富硅、碱,贫钙、镁,高Rb、Th、Nb、Ta、Zr、Hf、Ga、Y,低Sr、Ba、Cr、Ni,以及明显的负Eu异常和高的Ga/Al值(3~11)的特征,类似于A型花岗岩,形成于伸展的构造背景,可能与Rodinia超大陆的裂解有关。国宝山花岗岩类属于过铝质高钾钙碱性花岗岩,具有A型花岗岩的特征,稀土元素显示弱的“四分组效应”,指示了岩浆高度分异演化的特征,源于富含白云母的变质泥岩类在正常地壳(约30km)深度下部分熔融。结合大地构造背景,国宝山花岗片麻岩指示了古元古代晚期国宝山地区伸展构造背景下的一次岩浆活动,岩浆经历了高度的演化;(含天河石)二长花岗岩和花岗伟晶岩形成于南天山洋盆的碰撞闭合后地壳伸展的构造环境下,揭示了南天山洋于427 Ma之前闭合。4.电子探针结果显示,余石山变粒岩中Nb和Ta主要赋存于金红石、独居石中,金红石和独居石地球化学特征表现为热液变质成因;国宝山铷矿Rb主要赋存于天河石中。5.余石山地区Nb、Ta的富集主要由金红石引起,其富集机制也受控于金红石的形成过程,变粒岩原岩(正长岩)在829.4Ma形成后,受795Ma左右发生的热事件影响,与富H2O、F-等挥发分及K的岩浆期后热液流体发生交代作用,随着交代作用的进行,磷灰石、萤石等富F矿物的形成导致金红石的生成,Nb、Ta伴随金红石的生成沉淀,聚集成矿。6.国宝山花岗岩源区中的白云母是成矿物质Rb的主要来源,富含白云母的源岩脱水部分熔融产生高F、富Rb岩浆,岩浆的高度演化促使Rb进一步富集,主要富集机制是F的络合作用,Rb与F络合迁移至岩浆演化末期,最终随温度降低络合物发生水解,F与Ca2+形成萤石,Rb进入长石形成矿化的含天河石花岗岩。7.余石山地区变粒岩及与其呈断层接触的大理岩是区域上寻找铌钽矿的主要标志;国宝山地区钠长石化花岗岩、含天河石花岗岩(伟晶岩)是寻找铷矿的主要线索。
[Abstract]:The Qilian Mountains and the Beishan area belong to the Gut Tis and the paleo Asian oceanic domains. In the course of its tectonic evolution, the important magma metallogenic belt in northern and Central Asia has been formed and the geologists have attracted much attention. In recent years, the geological survey and research work of Gansu Geological Survey Institute in Qilian, Beishan and other areas showed the above area The geological conditions for the formation of large and large rare metal ores are expected to make a breakthrough in prospecting. This paper is based on the field geological survey, indoor research and test analysis on the basis of the systematic collection of previous research results, based on the modern study and the modern research results. Metallogenic theory, petrology and mineralogy, geochemistry and isotopic chronology have studied the metallogenic geological background, chronology, material source and metallogenic regularity of the two rare metals above. The following achievements and understanding are obtained: 1. the area of the Yu Shi Shan NB tantalum and rubidium in Baoshan is studied in detail through field geological investigation. The characteristics of geology, mineralization type, petrology, mineralogy, ore and so on. It is determined that the Yu Shi Shan niobium and tantalite ore mainly occurs in the granulite. The rubidium mine of the national treasure mountain is mainly located in the Tianhe stone granite. In the granitic pegmatite,.2. has carried out the zircon U-Pb isotopic study of the zircon, and the zircon in the granulite of the Yu stone mountain. There are two types of magma genesis and metamorphism, the 206Pb/238U age of magmatic zircon is between 810 + 6Ma~854 + 7Ma, and the harmonic age is 829.4 + 2.7Ma, representing the age of magma invasion; the 206Pb/238U age of the metamorphic zircons is between 768 + 8Ma~809 + 7Ma, and the harmonic age is 795 + 5.4Ma; it represents the heat event after the magma period. The age of gneiss rock formation is 1853 + 16Ma, (including Tianhe stone) two long granite, and the age of granite pegmatite diagenesis is 427 + 8Ma and 406 + 5Ma respectively. It reveals that the magma evolved from granitic pulp to granite pegmatite for 21Ma.3. using rock geochemistry method, and resumed the original rock of Yu Shi Shan granulite. The result showed that the original rock was syenite. The characteristics of rich silicon, alkali, poor calcium, magnesium, high Rb, Th, Nb, Ta, Zr, Hf, Ga, Y, low Sr, Ba, Cr, Ni, and obvious characteristics of negative anomalies and high values, formed in extensional tectonic setting, which may be related to the fragmentation of supercontinent. The rare earth element shows the weak "four grouping effect" indicating the characteristics of the magma height differentiation and evolution, which originated from the partial melting of metamorphic mudstones rich in Muscovite in the normal crust (about 30km). Combined with the tectonic setting, guomoshan granite gneiss indicates the extensional tectonic setting in the late proproterozoic Guobao mountain area. One magma activity, magma experienced a high degree of evolution, and (including Tianhe stone) two granites and granite pegmatite formed in the tectonic setting of the crust extension after the collision and closure of the South Tianshan ocean basin. The results of the closed.4. electron probe before the South Tianshan ocean in the southern Tianshan ocean revealed that Nb and Ta in the granulite of the Yu Shi Shan were mainly in rutile and solitary. In the stone, the geochemical characteristics of Jin Hongshi and monazite are characterized by hydrothermal metamorphism, and the Rb of the rubidium mine of the national treasure mountain is mainly located in the Nb in the.5. Yu Shi Shan area in Tianhe stone, and the enrichment of Ta is mainly caused by the formation of Jin Hongshi, and the metamorphic lithofacies (syenite), after the formation of 829.4Ma, is caused by the heat around 795Ma. The event is influenced by the metasomatism of the rich H2O, F- and K's post magmatic hydrothermal fluids. With the metasomatism, the formation of F minerals such as apatite and fluorite lead to the formation of rutile. Nb, Ta is accompanied by the formation and precipitation of rutile, and the Muscovite in the source area of the metallogenic.6. national treasure mountain granite is the main source of the mineral Rb. The source rocks of the source rock rich in Muscovite produce high F and rich Rb magma, and the high evolution of the magma leads to the further enrichment of Rb. The main enrichment mechanism is the complexation of F. Rb and F complex migrate to the end of the magma evolution, and the hydrolysis of the complex is reduced with the temperature, F and Ca2+ form the fluorite, and Rb enters the feldspar to form a mineralized containing Tianhe stone. The granulite in the.7. Yu Shi Shan area and the marble that contact with its faults are the main signs to find niobium and tantalite in the region, and the natriuretic granite and the Tianhe stone granite (pegmatite) are the main clues for the search for rubidium ore.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.2
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本文编号：1898236