光石沟花岗伟晶岩型铀矿床矿物学特征

发布时间：2018-05-07 07:53

本文选题：光石沟地区 + 伟晶岩型铀矿　；参考：《东华理工大学》2015年硕士论文

【摘要】：丹凤地区的光石沟铀矿床是我国典型的伟晶岩型铀矿床,该铀矿床地处北秦岭加里东褶皱带,夹持于蔡川断裂与商丹断裂构造之间。笔者在前人工作及光石沟伟晶岩型铀矿床区域地质特征、矿床地质特征分析的基础上,重点对该矿床中的晶质铀矿及与之紧密共生的锆石和黑云母开展了显微观察、扫描电镜和电子探针分析,进行了矿物学特征和化学成分测试等系统的矿物学工作,并据此初步分析了该区铀的迁移演化规律和铀沉淀富集机理。通过对光石沟铀矿床晶质铀矿、锆石和黑云母的镜下观察和电子探针分析,初步得到以下几点认识:(1)光石沟花岗伟晶岩型铀矿床中的铀主要以晶质铀矿的形式存在,部分以类质同像形式赋存于锆石和独居石中。晶质铀矿一般为立方体和八面体为主,晶体颗粒大(200μm左右);分布于石英、长石、黑云母等脉石矿物内部或粒间,与黑云母、锆石等共生关系密切。此外,常见绿泥石、黄铁矿和赤铁矿与晶质铀矿伴生,晶质铀矿常常被黄铁矿和绿泥石所包围,形成黄铁矿和绿泥石环边。(2)晶质铀矿主要成分为UO2、Th O2,其中UO2含量81.62%~89.40%,Th O2含量为1.39%~3.72%,多数样品含有不等量的Si O2、Y2O3、Pb O等。晶质铀矿的UO2④号伟晶岩脉含量高于②号伟晶岩脉,而小花岔矿体处则相对较低。此外,本次研究还发现,未发生后期热液活动、以单个晶体赋存石英、长石中晶质铀矿UO2含量最高,为86.75%~89.40%。(3)光石沟花岗伟晶岩型铀矿床中含矿伟晶岩脉和灰池子岩体中黑云母均具有富铁、钛的特征,灰池子黑云母二长花岗岩中黑云母属于富铁云母,含矿伟晶岩脉中黑云母均为铁叶云母;均具有较低的氧逸度;含矿伟晶岩中黑云母结晶温度高于灰池子岩体黑云母二长花岗岩中黑云母的结晶温度;说明伟晶岩不是由灰池子黑云母二长花岗岩分离结晶而来;(4)总体上,锆石成分变化较小,部分锆石具有明显的环带构造。根据上述结果,初步分析光石沟伟晶岩型铀矿中铀矿物成矿过程大致可以划分为两期:岩浆作用期、岩浆期后热液叠加改造期;主成矿期为岩浆作用期,铀矿物包括晶质铀矿、钍铀矿、铀石等;期后热液叠加改造期的晶质铀矿遭受挤压作用,然后岩浆晚期的自交代热液作用导致晶质铀矿发生破碎,使部分铀迁出。随后发生热液活动,使新形成的黄铁矿充填在晶质铀矿裂隙中,或包裹晶质铀矿(绿泥石、赤铁矿等)。最后,由于晶质铀矿等铀矿物近地表,发生表面氧化形成硅钙铀矿,呈脉状沿着岩石解理分布。因此,光石沟花岗伟晶岩铀矿是由原始岩浆的结晶分异作用、后期热液的叠加改造作用形成。
[Abstract]:The Guangshigou uranium deposit in Danfeng area is a typical pegmatite type uranium deposit in China. The uranium deposit is located in the Caledonian fold belt of the North Qinling Mountains between the Caichuan and Shangdan faults. Based on the previous work and the analysis of the regional geological characteristics and the geological characteristics of the Guangshigou pegmatite type uranium deposit, the authors have carried out microscopic observation of the crystalline uranium deposit and the zircon and biotite closely associated with the deposit. The mineralogical work of mineralogical characteristics and chemical composition testing system was carried out by scanning electron microscope and electron probe analysis. The migration and evolution law of uranium and the mechanism of uranium precipitation and enrichment in this area were preliminarily analyzed. Based on the microscopic observation and electron probe analysis of crystalline uranium deposits, zircon and biotite in the Guangshigou uranium deposit, it is preliminarily concluded that the uranium in the granitic pegmatite type uranium deposit in Guangshigou granitic pegmatite type uranium deposit is mainly in the form of crystalline uranium deposits. Some of them occur in the middle of zircon and monazite in the form of isomorphism. The crystalline uranium deposits are mainly cubic and octahedron with large crystal size of about 200 渭 m and are distributed in or between grains of gangue minerals such as quartz, feldspar and biotite, which are closely related to biotite and zircon. In addition, common chlorite, pyrite and hematite are associated with crystalline uranium deposits, which are often surrounded by pyrite and chlorite. The main composition of the pyrite and chlorite ring edge is UO _ 2 Th / O _ 2, in which the UO2 content is 81.62 ~ (89.40) and the Th _ 2 _ 2 content is 1.39 ~ 3.72%, and most samples contain different amounts of Sio _ 2o _ 2 Y _ 2O _ 3H _ 2O _ 3Pb _ O and so on. The content of UO24 pegmatite vein in crystalline uranium deposit is higher than that in No. 2 pegmatite vein, but it is relatively low at Xiaohuacha orebody. In addition, this study also found that there was no late hydrothermal activity and that quartz existed in a single crystal, and the UO2 content of uranite in feldspar was the highest. Both the pegmatite vein of the Guangshigou granitic pegmatite type uranium deposit and the biotite in the Huichizi rock mass have the characteristics of rich in iron and titanium. The biotite in the biotite monzonitic granite belongs to ferric mica rich in the ash chizi biotite monzonitic granite, and is rich in iron and mica in the granitic pegmatite type uranium deposit of Guangshigou granitic pegmatite type uranium deposit. The biotite in the pegmatite vein of ore-bearing pegmatite is iron leaf mica with low oxygen fugacity, and the crystallization temperature of biotite in pegmatite is higher than that in biotite monzogranite. The results show that pegmatite is not separated and crystallized from Liqizi biotite monzonitic granite. (4) in general, the change of zircon composition is relatively small, and some zircons have obvious zonal structure. Based on the above results, the metallogenic process of uranium ore in Guanshigou pegmatite type uranium deposit can be roughly divided into two periods: magmatism period, post-magmatic hydrothermal superposition period, main metallogenic period is magmatism period, and uranium ore material includes crystalline uranium deposit. Thorium uranium ore, uranium stone and so on, after the hydrothermal superposition transformation period, the crystalline uranium ore is squeezed, and then the late magma self-metasomatic hydrothermal process results in the breakup of the crystalline uranium deposit, which makes some uranium migrate out. Then hydrothermal activity occurs, which makes the newly formed pyrite fill in the fissure of the crystalline uranium ore or encapsulate the crystalline uranium deposit (chlorite, hematite, etc.) Finally, because the uraninite and other uranium deposits are near the surface of the earth, the surface oxidizes to form the calcium silicate uranium ore, which distributes along the rock cleavage in vein shape. Therefore, the granitic pegmatite uranium deposit in Guanshigou is formed by crystallization differentiation of primitive magma and superposition and transformation of hydrothermal solution.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.14

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