下庄铀矿田方解石的谱学特征研究  

SPECTROGRAPHIC CHARACTERISTICS OF CALCITE FORMED AT DIFFERENT MINERALIZATION STAGES IN XIAZHUANG URANIUM ORE FIELD

作　　者：张展适[1] 华仁民[1] 季峻峰[1] 蔡元峰[1] 

机构地区：[1]南京大学地球科学系成矿作用研究国家重点实验室

出　　处：《矿物学报》2005年第1期33-38,共6页Acta Mineralogica Sinica

基　　金：国家重点基础研究发展规划项目(编号:1999CB403209);国家自然科学基金重点项目(批准号:40132010);国家自然科学基金项目(批准号:40472147)

摘　　要：下庄铀矿田是我国最大的花岗岩型铀矿田,其中的沥青铀矿方解石型矿化类型是近年来新发现的一种富矿类型。系统采集了该矿田中不同成矿期、不同颜色的方解石样品,进行了粉晶X射线衍射、电子顺磁共振波谱及反射光谱学研究。电子顺磁共振波谱揭示成矿期方解石中普遍含有Fe3+和Mn2+色心离子,而成矿期后和远矿样品中则一般只含有单独的Fe3+或者Mn2+色心离子,说明矿田中唯一的工业矿石矿物沥青铀矿可能是在氧化还原过渡环境下沉淀的,强氧化和强还原环境均不利于矿石的沉淀。反射光谱学研究揭示不同成矿期方解石的光谱学特征不同,反映了它们在特征元素、含水性等方面均存在差异,成矿期方解石以890nm和400nm两个波长处Fe3+氧化物的吸收为特征,而成矿期后的方解石则分别在1922nm和1400nm呈现明显的水的吸收。利用反射光谱测定可以定量计算矿物在不同光波波段的吸收性强弱,并得到色度值。研究表明红度较灰度和亮度能更好地定量表示本区方解石的颜色,这也许是由于研究区的方解石大多呈现不同程度的红色和白色所致。The Xiazhuang uranium ore field is the biggest granitic-type uranium ore field in China,and the pitchblende-calcite mineralization type is a new type of high-grade ores. Calcites of different mineralization stages and various colours were sampled based on the field work. Crystal powder X-Ray diffraction,electron paramagnetic resonance and reflectance spectroscopic analyses were profermed in this study. The results included: 1)EPR results showed that the calcites formed during the mineralization stage consist of both Fe^(3+)and Mn^(2+), while the calcites formed after the mineralization stage consist only of Fe^(3+)or Mn^(2+). It might be inferred that pitchblende,the exclusive ore mineral in the Xiazhuang uranium ore field, was precipitated in a redox environment; whereas oxidation or reduction environment did not favor the precipitation of pitchblende; 2)The calcites formed in different mineralization stages displayed different reflectance spectroscopic characteristics in minor elements and aquosity, the calcites formed during the mineralization stage had an absorbility of Fe^(3+)at 890 nm and 400 nm wavelengths, respectively, the calcites formed later than the mineralization stage had an absorbility of H_(2)O and OH at 1922 nm and 1400 nm, respectively; 3) Reflectance could be used as a proxy of the (mineral's) colour in VIS wavelength. In our case redness was more suitable to be used as the proxy for the colour of calcite than grayness and brightness.

关 键 词：方解石 XRD EPR 反射光谱 下庄铀矿田 富矿类型 

分 类 号：P619.14[天文地球—矿床学] P578.61[天文地球—地质学]