【摘要】：富有機質(zhì)沉積的定年研究在研究古環(huán)境、古氣候方面具有重大作用,而對于尋找石油以及與沉積有關(guān)的金屬礦床等更是具有指導(dǎo)意義。但是目前對于富有機質(zhì)沉積巖年齡的厘定多采用間接的方法,因而常常具有一定的不確定性。Re-Os同位素定年方法是一種可以直接厘定富有機質(zhì)沉積巖地層年齡的定年方法,但對于Re-Os同位素方法在富有機質(zhì)沉積巖中的應(yīng)用,目前還存在著一些技術(shù)上的問題。前人研究表明,富有機質(zhì)沉積巖中反映沉積年齡的Re和Os是賦存在有機質(zhì)中的,碎屑部分中的Re和Os的混入會影響所得到的Re-Os等時線的準確度和精度。目前最常用的方法是Cr O3-H2SO4溶樣法,該方法相比于HCl-HNO3溶樣的方法,能盡量避免碎屑物質(zhì)中Re和Os的溶出,但該方法具有Re流程空白高和環(huán)境污染嚴重等問題。因此,本文嘗試在富有機質(zhì)沉積巖Re-Os同位素定年分析中使用H2O2-HNO3溶樣來代替Cr O3-H2SO4溶樣。本研究利用國際油頁巖標(biāo)樣SGR-1b(USGS)為實驗研究對象,對HCl-HNO3溶樣、Cr O3-H2SO4溶樣和H2O2-HNO3溶樣三種溶樣方法進行了對比研究。研究表明,H2O2與HNO3的體積比約為5/1的H2O2-HNO3溶液,不僅能保證樣品和稀釋劑的Re、Os同位素達到同位素交換平衡而且盡可能的避免碎屑物質(zhì)中Re和Os的溶出。本方法相比于HCl-HNO3溶樣,能盡量避免碎屑物質(zhì)中Re和Os的溶出;而相比于Cr O3-H2SO4溶樣,該方法具有本底低、無污染的優(yōu)點。最后利用H2O2-HNO3溶樣方法對廣西金秀地區(qū)的泥巖樣品和廣東大寶山地區(qū)的炭質(zhì)頁巖樣品進行了Re-Os同位素定年分析,分別得到了404±5Ma(IOs=1.57±0.13,n=8,MSWD=50)和211±11Ma(IOs=0.67±0.09,n=5,MSWD=11.1)的等時線年齡,這一結(jié)果與HCl-HNO3溶樣得到的結(jié)果(412±11Ma,IOs=1.18±0.38,n=8,MSWD=311;223±18Ma,IOs=0.59±0.14,n=5,MSWD=63)在誤差范圍內(nèi)一致,但更為精確.
[Abstract]:The chronological study of organic deposits plays an important role in the study of paleoclimate and paleoclimate, and is of great significance in the search for oil and sedimentary-related metal deposits. However, at present, indirect methods are often used to determine the age of organic sedimentary rocks, so there is often certain uncertainty. Re-Os isotopic dating method is a direct dating method which can directly determine the formation age of organic sedimentary rocks. However, there are still some technical problems in the application of Re-Os isotopic method in organic sedimentary rocks. Previous studies have shown that Re and Os reflecting sedimentary age in organic sedimentary rocks are present in organic matter, and the mixing of Re and Os in clastic parts will affect the accuracy and accuracy of Re-Os isochron. At present, the most commonly used method is Cr O3-H2SO4 method. Compared with HCl-HNO3 method, this method can avoid the dissolution of Re and Os in clastic materials as far as possible, but this method has some problems, such as high blank of Re process and serious environmental pollution. Therefore, in this paper, H2O2-HNO3 dissolved samples are used instead of Cr O3-H2SO4 in Re-Os isotopic dating analysis of organic sedimentary rocks. In this study, the international oil shale standard sample SGR-1b (USGS) was used as the experimental research object, and three dissolution methods of HCl-HNO3, Cr O3-H2SO4 and H2O2-HNO3 were compared. The results show that the H2O2-HNO3 solution with a volume ratio of H2O2 to HNO3 of about 5 鈮，

本文編號：2480660