Micrometer sized stromatolitic structures called Frutexites are features observed in samples from the deep subsurface, and hot-spring environments. These structures are comprised of fine laminations, columnar morphology, and commonly consist of iron oxides, manganese oxides, and/or carbonates. Although a biological origin is commonly invoked, few reports have shown direct evidence of their association with microbial activity. Here, we report for the first time the occurrence of subsurface manganese-dominated Frutexites preserved within carbonate veins in ultramafic rocks. To determine the biogenicity of these putative biosignatures, we analyzed their chemical and isotopic composition using Raman spectroscopy and secondary ion mass spectroscopy (SIMS). These structures were found to contain macromolecular carbon signal and have a depleted ¹³C/¹²C carbon isotopic composition of – 35.4 ± 0.50‰ relative to the entombing carbonate matrix. These observations are consistent with a biological origin for the observed Frutexites structures.

在深地下和温泉环境中的样品中观察到的特征是称为Frutexite的微米级叠层岩结构。这些结构由精细的叠层，柱状形态组成，并且通常由氧化铁，氧化锰和/或碳酸盐组成。尽管通常引用生物学起源，但很少有报道显示它们与微生物活性相关的直接证据。在这里，我们首次报告了以地下锰为主的Frutexites的发生保留在超镁铁质岩石的碳酸盐岩脉内。为了确定这些推定生物特征的生物成因，我们使用拉曼光谱和二次离子质谱（SIMS）分析了它们的化学和同位素组成。发现这些结构包含大分子碳信号，相对于包裹碳酸盐基质，其耗尽的¹³ C / ¹² C碳同位素组成为– 35.4±0.50‰。这些观察结果与所观察到的Frutexite结构的生物学起源是一致的。