摘要
鄂尔多斯盆地北部东胜地区砂岩型铀矿主要产在侏罗系直罗组地层中。直罗组地层可分为上、下两段 :下段又分为上、下两个亚段 ,其中下亚段主要为容矿的灰色砂岩 ;上亚段主要为灰绿色砂岩、泥岩 ;上段为杂色的中细砂岩、泥岩。笔者通过对直罗组砂岩的镜下观察研究 ,在垂向上确立了岩石的后生蚀变分带 :直罗组下段下亚段为灰色 灰白色砂岩 (含矿段 )的绿化 (Ⅰ ) (主要为长石的绿帘石化 ) +碳酸盐化带 ;上亚段为灰绿色砂岩的绿化 (Ⅱ ) (主要为黑云母绿泥石化 ,也有长石绿泥石化和绿帘石化 ) +粘土化 +碳酸盐化带 ;直罗组上段杂色细砂岩的褐铁矿化 +粘土化 +碳酸盐化带。主要的后生蚀变作用发生在灰绿色的砂岩中。砂岩呈现灰绿色的原因主要在于含较多绿色黑云母 ,而非绿泥石 ,其本质原因在于矿物中Fe2 +含量较高。砂岩层中的后生蚀变现象与铀成矿作用关系密切。
Sandstone-type uranium depotits located in Dongsheng area,northern Ordos basin,occur in Zhiluo Formation,Middle Jurassic.The Zhiluo Formation is divided into two members.The lower member is further divided into two submembers.The lower submember is dominantly composed of grey sandstone being the ore-hosting horizon;the upper submember consists of grey-green sandstone and mudstone,The upper member of Zhiluo Formation is made of mottled medium-fine grained sandstone and mudstone.Through the microscopic observation and study on sandstones of Zhiluo Formation,authors have established a vertical zonation of epigenetic alteration(from the top to the bottom):the limonitization+clayization+carbonation in the mottled fine-grained sandstone of the upper member of Zhiluo Formation;the green alteration(Ⅱ)(mainly the chloritization of biotite,as well as the chloritization and epidotization of feldspar)+clayization+carbonation in the grey-green sandstone of the upper submember of the lower member of Zhiluo Formation;and the green alteration(Ⅰ)(mainly the epidotization of feldspar)+carbonation in grey,grey-white sandstone of the lower submember.The epigenetic alteration basically occurs in grey-green sandstone.The sandstone shows grey-green color because it contains much green biotite(not chlorite).The epigenetic alteration in sandstone layer is closely associated with the uranium ore-formation.
出处
《铀矿地质》
CAS
CSCD
2004年第3期136-140,共5页
Uranium Geology
基金
核工业地质总局生产科研项目 (地GJ0 0 0 1
地D0 2 0 9)资助
关键词
鄂尔多斯盆地
砂岩型铀矿床
直罗组
蚀变分带
灰绿色砂岩
Ordos basin
sandstone-type uranium deposit
Zhiluo Formation
alteration zoning
grey-green sandstone
