Deciphering the surface environment of the primitive Earth from nitrogen isotopes trapped in Archean sedimentary rocks-Investigation of its trapping forms in the rocks.

从太古宙沉积岩中捕获的氮同位素破译原始地球的表面环境——对其在岩石中捕获形式的调查。

• 批准号: 17340168
• 负责人: HASHIZUME Ko
• 金额: $ 8.26万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2005
• 资助国家: 日本
• 起止时间: 2005 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17340168/
• 关键词: Primitive Earth; Surface Environments; Nitrogen Isotopes; Sedimentary Rocks; Archean; Chert; Banded Iron Formations; 粘土鉱物; アンモニウム

In this study, search of the surface environments of the primitive earth was performed using the information of nitrogen isotopes obtained from Archean sedimentary rocks. Though the nitrogen isotopes trapped in the rock samples have potential of providing such information, it is not always clear how we may obtain and interprete the raw data. We studied 3.5 Ga old chert samples from western Australia (from Kitty's gap and Marble bar), and a 2.7-2.9 Ga old samples of the banded iron formation from Dhawar Craton of India. Volatile compounds (N_2, Ar, C and H_2O) were extracted from samples using a stepwise combustion method, and their elemental and/or isotopic compositions were analysed.We were able to specify or infer three trapping sites/forms of nitrogen by combining the information of different volitile compounds. In Kitty's gap chert, nitrogen concentrations were observed to be correlated well with those of radiogenic ^<40>Ar, suggesting that nitrogen is trapped in K-bearing clay minerals. The δ15N values showed a wide range between-4 to +10 permil, and were correlated with the ^<40>Ar/N ratio, suggesting existence of two different types of trapping sites among the clay minerals. In Marble bar chert, nitrogen with δ^<15>N values between +6.0 to +7.3 permil was observed, associated with carbon, suggesting that nitrogen in this sample is trapped in organic form. Furthur investigations imply that the N-bearing organic matter is protected by inorganic minerals. Among the BIF samples, N with δ^<15>N values around +10 permil was observed. There seem to exist two types of N-bearing C-associated host phases with different C/N ratios. Discrimination of the N isotopic components in different chemical forms among the Archean rocks may largly help us to decipher the isotopic evolution of nitrogen of the primitive biosphere.

在此螺柱中，使用从岩石中捕获的氮可以获得的氮可以获得e的氮可以获得并解释我们研究的3.5 ga旧cher，从而使用了岩石中的氮进行了。澳大利亚（来自Kitty的Gap和Marble Bar）来自印度Dhawar Craton的带状铁形成样品（N_2，AR，C和H_2O）是使用逐步燃烧方法从样品中提取的氮的形式结合了不同的自愿性，在猫咪的间隙chert中，氮收缩与k含k矿物质中的放射性 ^<40> PPP的相关性很好。 10渗透，并与 ^<40> ar/n的比例相关，表明粘土矿物质中有两个不同的捕获位点。使用碳在BIF样品中受到无机矿物的保护。 - 具有不同c/n比的含有C相关的宿主相。

项目成果

Biomarkers in Archaean banded iron formations from Pilbara and Dhawar Craton

皮尔巴拉和达瓦尔克拉通太古代带状铁地层中的生物标志物

• 发表时间: 2006
• 期刊: Geochimica et Cosmochimica Acta 18
• 作者: Pinti D.L.;Hashizume K.;Orberger B.;Gallien J.;Cloquet C.;Massault M.;Orberger B.
• 通讯作者: Orberger B.