Carbonaceous matter in ~ 3.5 Ga hydrothermal vein deposits from the Dresser Formation, Western Australia, was analyzed using Fourier transform infrared (FTIR) microspectroscopy. Based on the spectroscopy, the carbonaceous matter was mainly composed of disordered aromatic structures, with minor aliphatic C–H functional groups. Spatially resolved analysis supports that the aliphatic C–H signatures are derived from kerogenous macro-molecule and not from free bitumen or other artificial sources. The intensity ratios of the asymmetric aliphatic CH₃ to the asymmetric aliphatic CH₂ (R_3/2 value) in the carbonaceous clots range from 0.22 to 0.51. Thermal alteration may increase or not change the R_3/2 value of organic matter, as suggested by previous experiments, but it is unlikely to be the cause of the substantially lower R_3/2 values when compared with those of primary organic matter. In particular, the low R_3/2 values (< ~ 0.4) suggest that the carbonaceous matter mainly contains aliphatic C–H bonds derived from bacterial cells. The carbonaceous clots may have been possibly produced by abiotic reaction such as Fischer-Tropsch-type (FTT) synthesis. However, the organic matter source only produced by the FTT synthesis is inconsistent with the R_3/2 values for the analyzed carbonaceous clots. The results obtained by combining these spectroscopic features of the carbonaceous clots together with the previously reported isotopic features may possibly suggest that both bacteria and archaea were colonized in the ~ 3.5 Ga Dresser hydrothermal system.

中文翻译：

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西澳大利亚州北极地区〜3.5 Ga海底热液矿床含碳物质的FTIR显微光谱

使用傅立叶变换红外（FTIR）显微技术分析了来自西澳大利亚德莱瑟组的〜3.5 Ga热液脉矿床中的碳质物质。根据光谱学，碳质物质主要由无序的芳族结构组成，具有少量的脂肪族CH官能团。空间分辨分析支持脂肪族C–H标记来自干酪根大分子，而不是来自游离沥青或其他人工来源。碳质凝块中的不对称脂肪族CH ₃与不对称脂肪族CH ₂的强度比（R _3/2值）为0.22〜0.51。热变化可能会增加或不会改变R _3/2如先前实验所暗示的，有机物的R _3/2值，但与主要有机物的R _3/2值相比，不太可能是R _3/2值显着降低的原因。特别是，低的R _3/2值（<〜0.4）表明碳质物质主要包含来源于细菌细胞的脂肪族CH键。碳凝块可能已经通过非生物反应如费托型（FTT）合成产生。但是，仅通过FTT合成产生的有机物来源与R _3/2不一致碳质凝块的分析值。将碳质凝块的这些光谱特征与先前报道的同位素特征结合在一起所获得的结果可能表明，细菌和古细菌都定居在〜3.5 Ga Dresser热液系统中。