内蒙古克什克腾旗红山子铀钼矿床成矿作用研究

发布时间：2018-06-12 15:44

本文选题：成矿流体 + 成矿作用　；参考：《核工业北京地质研究院》2015年博士论文

【摘要】：位于华北陆块北缘的沽源—红山子铀多金属成矿带是我国重要的中生代火山岩型铀多金属成矿带,红山子铀钼矿床为该成矿带上典型的火山岩型铀矿床之一。本论文通过系统研究矿床地质、岩浆作用、铀成矿特征、控矿因素和成矿流体性质,剖析了该矿床的成矿流体来源、铀的迁移及富集机制,运用热点铀成矿理论揭示了该矿床的深源成矿机理,探讨了该矿床的铀成矿作用,并构建了成矿模式。⑴研究区岩浆岩均属于钙碱性系列岩石,均具有相对富集轻稀土元素,δEu负异常和δCe正异常的特征。其中辉绿岩具有相对富集Nb、Ta和Ti等高场强元素而贫Rb、U和Th等大离子亲石元素的特点,其它岩浆岩均具有相对富集Rb、U和Th等大离子亲石元素而贫Nb、Ta和Ti等高场强元素的特点。岩浆岩的锆石SHRIMP U-Pb同位素地质年代学研究显示,安山质角砾凝灰岩形成年龄为277.1.9±4.7Ma,花岗闪长岩形成年龄为268±3Ma,粗面岩形成年龄为159±4Ma,流纹斑岩形成年龄为160.6±2.9Ma,正长斑岩形成年龄为160.2±1.9Ma,花岗岩形成年龄为132.9±1.4Ma,辉绿岩形成年龄为134.2±2.7Ma。微量元素和Sr-Nd同位素指示花岗斑岩、粗面岩、流纹斑岩、花岗闪长岩和正长斑岩具有来自于下地壳或壳幔混合源区的特点,黑云母花岗岩和辉绿岩具有来源于地幔源区的特点,岩浆活动具有从富集地幔EM1组分向亏损地幔组分方向转变的特征,本区岩浆岩是在华北克拉通岩石圈拆沉的大地构造背景下形成的。⑵研究区发育的围岩蚀变主要有钠长石化、萤石化、赤铁矿化、绿泥石化、钾化和硅化,铀矿化与以钠长石化为主的碱性热液蚀变关系密切,钍矿化与酸性萤石化蚀变关系密切,钼矿化与硅化关系密切。围岩蚀变具有明显的水平分带性,以天台永—河盛源断裂为中心对称发育硅化、赤铁矿和绿泥石化,矿化蚀变钠长石化具有叠加在赤铁矿化之上的特点。碱性矿化蚀变与新发现的酸性矿化蚀变在空间上构成了酸碱蚀变分带,即东北部发育碱性矿化蚀变,西南部发育酸性矿化蚀变。⑶铀矿体主要产出于火山盆地内,矿体形态受控于火山断陷盆地的盆缘断裂F1和F2及火山颈构造。切穿盆地基底的天台永—河盛源断裂为该矿床的一级控矿构造,盆缘断裂F1和F2及火山颈构造为二级控矿构造。铀矿化主要位于盆缘断裂上盘的构造破碎粗面岩内,流纹斑岩体与火山颈颈壁的内接触带也发育有铀矿化,铀主要沥青铀矿形式存在。钼矿化主要位于流纹斑岩和花岗岩内,钼以辉钼矿形式存在,钼矿化具有叠加到铀矿化之上的特点。钍矿化位于萤石化石英脉中,钍以方钍石和钍石形式存在。⑷在前人的研究基础之上,根据铀钍和钼矿化特征发现铀钍矿化和钼矿化在时代上具有明显晚于火山活动期粗面岩和流纹斑岩的特点,矿化时代限定为早白垩世。铀钍矿化与钼矿化时代上相近,铀钍矿化稍早,而钼矿化稍晚。二者的成矿作用与火山活动期岩浆岩在时间上相对独立,空间上存在矿化继承叠置于火山活动期岩浆岩之上的特点。⑸研究区的矿化、围岩蚀变和流体包裹体特征指示铀成矿流体为相对高温的富F、Na、U、Th的还原性深源流体。U应是以UCl3+、UF3+或无机杂化配合物的形式在还原性流体中存在并迁移。富铀的深源成矿流体进入成矿有利部位时,由于温度、压力、Eh、pH和氧逸度等条件突变,气相组分逸出,流体中的UCl3+、UF3+或含U的无机杂化配体发生快速分解,U4+在溶液中达到过饱和而生成溶胶发生聚沉,残余液体逸出,同时产生了多元素矿物沉淀和蚀变交代。
[Abstract]:The Guyuan red mountain uranium polymetallic metallogenic belt, located in the northern margin of the North China block, is an important Mesozoic volcanic uranium polymetallic metallogenic belt in China. The red mountain uranium molybdenum deposit is one of the typical volcanic type uranium deposits in this metallogenic belt. This paper studies ore geology, magmatism, uranium metallogenic characteristics, ore controlling factors and ore-forming fluids through systematic study. The metallogenic fluid source of the deposit, the migration and enrichment mechanism of uranium are analyzed, the deep source metallogenic mechanism of the deposit is revealed by the hot spot uranium metallogenic theory, the uranium mineralization of the deposit is discussed, and the metallogenic model is constructed. (1) the magmatic rocks in the study area belong to the calc alkaline series of rocks, all of which have relatively rich light rare earth elements, Delta Eu The characteristics of negative anomalies and positive Delta Ce anomalies are characterized by the characteristics of relatively high field and strong elements such as Nb, Ta and Ti, poor Rb, U and Th and other large ionic stone elements, and the other magmatic rocks are characterized by relative enrichment of Rb, U and Th and other large ionic stone elements, and the characteristics of poor Nb, Ta and other high field elements. The aging study shows that the age of the Anshan breccia tuff is 277.1.9 + 4.7Ma, the formation age of granodiorite is 268 + 3Ma, the age of the coarse rock formation is 159 + 4Ma, the age of the RIS porphyry is 160.6 + 2.9Ma, the age of the syenite is 160.2 + 1.9Ma, the age of the granite is 132.9 + 1.4Ma, and the age of the diabase is 134.2 +. 2.7Ma. trace elements and Sr-Nd isotopes indicate granite porphyry, rough rock, rhyolite porphyry, granodiorite and syenite derived from the lower crust or crust mantle mixed source area. The biotite granite and diabase are derived from the mantle source region, and the magmatism has the direction from the enriched mantle EM1 component to the depleted mantle component. The magmatic rocks in this area are formed in the tectonic setting of the North China Craton lithosphere deformation. (2) the surrounding rock alteration developed in the study area mainly consists of sodium feldspar, fluorfossilization, hematite mineralization, green mud fossilization, potassium and silicification, uranium mineralization is closely related to alkaline hydrothermal alteration mainly with sodium feldspar, thorium mineralization and acidic fluorite The relationship between alteration and alteration is close, and the relationship between molybdenum mineralization and silicification is close. The alteration of surrounding rock has obvious horizontal zoning, with the centralization of silicification, hematite and green mud fossilization, and the mineralization alteration sodium feldspar with the characteristics of superimposed on the hematite mineralization. In space, the acid and alkali alteration zone is formed, that is, the northeastern development of alkaline mineralization alteration and the acidic mineralization and alteration in the southwest. 3. The uranium orebodies are mainly produced in the volcanic basin, and the ore bodies are controlled by the basin margin fracture F1 and F2 and the volcano structure of the volcanic fault basin. The F1 and F2 and the volcanic necks of the basin are two grade ore controlling structures. The uranium mineralization is mainly located in the tectonic fractured rough rocks of the upper edge of the basin margin, and the inner contact zone of the pluton and the neck wall of the volcano also has uranium mineralization, and the main uranium bituminous uranium exists. Molybdenum is in the form of molybdenite, and molybdenum mineralization is superimposed on uranium mineralization. Thorium is located in the quartz vein of fluorite fossils. Thorium exists in the form of thorium and thorium in the form of thorium and thorium. 4. On the basis of previous studies, it was found that uranium and thorium mineralization and molybdenum mineralization were evidently later than those of volcanic active facies on the basis of the characteristics of uranium and thorium and molybdenum mineralization. The mineralization age is limited to the early Cretaceous. The mineralization age is limited to the early Cretaceous. The uranium and thorium mineralization is similar to the molybdenum mineralization age. The uranium and thorium mineralization is earlier, and the molybdenum mineralization is slightly late. The mineralization of the two is relatively independent of the volcanic active magmatic rocks, and the mineralization inherits the characteristics of the magmatic rocks in the volcanic activity period. Mineralization, wall rock alteration and fluid inclusions indicate that the uranium ore-forming fluid is a relatively high temperature rich F, Na, U, Th reductive deep source fluid.U should exist and migrate in the form of UCl3+, UF3+ or inorganic hybrid complex in the reductive fluid. When the deep source ore-forming fluid of uranium rich enters the favorable position of the mineralization, it is due to temperature, pressure, Eh, pH, and oxygen. UCl3+, UF3+ or U containing inorganic hybrid ligands in the fluid are decomposed rapidly, and U4+ is supersaturated in the solution, resulting in the formation of the sols, the residual liquid escapes, and the multi element mineral precipitation and alteration are produced.
【学位授予单位】：核工业北京地质研究院
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P619.14;P618.65

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