本文選題：富鈾地層 + 沉積成巖作用��； 參考：《南京大學(xué)》2017年碩士論文

【摘要】：修水碳硅泥巖型鈾礦是我國(guó)南方碳硅泥巖型鈾礦的重要組成部分。前人認(rèn)為修水地區(qū)的碳硅泥巖型鈾礦是在沉積成巖過(guò)程中鈾預(yù)富集的基礎(chǔ)上,又經(jīng)歷了熱液作用或者淋積作用而富集成礦。在修水地區(qū),碳硅泥巖型鈾礦的賦礦地層也是富鈾地層,說(shuō)明沉積環(huán)境影響著碳硅泥巖型鈾礦的分布。但是,前人對(duì)于賦礦地層的研究主要集中于大尺度的沉積相方面,對(duì)于具體的沉積環(huán)境及其與鈾富集的關(guān)系研究很少。本研究對(duì)修水地區(qū)下寒武統(tǒng)王音鋪組至觀音堂組下部富鈾地層鉆孔樣品(U含量為9.37～202PPm)進(jìn)行了細(xì)致的顯微觀察和分析,揭示這些鉆孔樣品顯示明顯的沉積成巖特征,未發(fā)現(xiàn)明顯熱液疊加/淋積作用現(xiàn)象,表明本區(qū)下寒武統(tǒng)地層只經(jīng)歷了沉積成巖作用,而沒(méi)有經(jīng)歷過(guò)明顯的熱液作用或者淋積作用。在此基礎(chǔ)上,進(jìn)一步分析了修水地區(qū)下寒武統(tǒng)地層中U含量與沉積環(huán)境因素(沉積盆地中的生物生產(chǎn)力、底層水體的氧化還原狀態(tài)、及盆地與廣海間的流通性)之間的關(guān)系。研究結(jié)果顯示:修水地區(qū)下寒武統(tǒng)王音鋪組和觀音堂組下部地層大部分樣品中的U含量與TOC含量呈正相關(guān);王音鋪組上部U含量最高(202ppm)的樣品沉積時(shí)的初級(jí)生物生產(chǎn)力也最高,經(jīng)掃描電鏡觀察和電子探針?lè)治?發(fā)現(xiàn)其中有機(jī)質(zhì)中包裹著瀝青鈾礦,兩者關(guān)系密切,U與有機(jī)質(zhì)很可能是一起沉積-成巖富集的;U含量最高的樣品中的綠泥石中,八面體位置有空缺,六次配位ⅥAl的數(shù)量明顯大于四次配位ⅣAl,顯示為沉積成巖階段的綠泥石;U含量最高的樣品中也沒(méi)有發(fā)現(xiàn)典型的熱液成因或者淋積成因的礦物;修水下寒武統(tǒng)地層源區(qū)的化學(xué)風(fēng)化程度很高,說(shuō)明古氣候是溫暖濕潤(rùn)的;在缺氧硫化的強(qiáng)還原沉積環(huán)境下沉積的王音鋪組地層的U含量明顯高于在缺氧非硫化環(huán)境下沉積的觀音堂組下部地層中的U含量,而且在強(qiáng)還原硫化環(huán)境下,沉積時(shí)盆地處于開(kāi)放流通性程度較高時(shí)期的樣品,其U含量明顯高于盆地處于開(kāi)放程度較低時(shí)期的樣品。綜合這些觀察和分析得出,早寒武世王音鋪組上部地層沉積時(shí),高生物生產(chǎn)力所形成的有機(jī)質(zhì)降解時(shí)大量耗氧,導(dǎo)致底層水沉積環(huán)境處于強(qiáng)還原硫化狀態(tài),同時(shí),沉積盆地處于適當(dāng)?shù)拈_(kāi)放程度,U在強(qiáng)還原硫化環(huán)境下形成的沉積物中達(dá)到較高的程度富集乃至礦化的水平。
[Abstract]:Xiushui Carbon-Si-mudstone uranium deposit is an important part of Carbon-Si-mudstone type uranium deposit in southern China. It is believed that the Carbon-Si-mudstone type uranium deposits in Xiushui area were enriched by hydrothermal or leaching processes on the basis of uranium preenrichment during sedimentary diagenesis. In Xiushui area, the ore-bearing strata of carbon-silicon-mudstone type uranium deposits are also uranium-rich strata, indicating that the sedimentary environment affects the distribution of carbon-silicon-mudstone type uranium deposits. However, previous researches on ore-bearing strata are mainly focused on large-scale sedimentary facies, but few on the specific sedimentary environment and its relationship with uranium enrichment. In this study, detailed microscopic observation and analysis of the uranium rich formation samples from the lower part of the Lower Cambrian Wangyinpu formation to the Guanyintang formation in Xiushui area were carried out. The results showed that these borehole samples showed obvious sedimentary diagenetic characteristics. There is no obvious hydrothermal superposition / leaching phenomenon which indicates that the Lower Cambrian strata in this area have only experienced sedimentary diagenesis but have not experienced obvious hydrothermal action or leaching. On this basis, the relationship between U content in Lower Cambrian strata and sedimentary environmental factors (biological productivity in sedimentary basin, redox state of bottom water body, and circulation between basin and Guang Hai) in Xiushui area is further analyzed. The results show that the U content in most samples of lower Cambrian Wangyinpu formation and Guanyintang formation in Xiushui area is positively correlated with TOC content, and the primary biological productivity of samples with the highest U content in the upper part of Wangyinpu formation is the highest. By scanning electron microscopy and electron microprobe analysis, it was found that the organic matter is covered with asphaltene uranium ore, and the relationship between the U and the organic matter is probably the chlorite in the sample with the highest content of U in the sedimentary diagenetic enrichment. There is a vacancy in octahedral position, and the quantity of VI Al in six times coordination is obviously larger than that in fourth coordination 鈪，

本文編號(hào)：2035413