Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Via Campi, 103, 41125, Modena, Italy.
University of Liège, Department of Geology, Allée du six Août, 14, Sart Tilman, B-4000, Liège, Belgium.
Nat Commun. 2018 Nov 28;9(1):5049. doi: 10.1038/s41467-018-07385-6.
Thermodynamic modeling has recently suggested that condensed carbonaceous matter should be the dominant product of abiotic organic synthesis during serpentinization, although it has not yet been described in natural serpentinites. Here we report evidence for three distinct types of abiotic condensed carbonaceous matter in paragenetic equilibrium with low-temperature mineralogical assemblages hosted by magma-impregnated, mantle-derived, serpentinites of the Ligurian Tethyan ophiolite. The first type coats hydroandraditic garnets in bastitized pyroxenes and bears mainly aliphatic chains. The second type forms small aggregates (2 µm) associated with the alteration rims of spinel and plagioclase. The third type appears as large aggregates (100-200 µm), bearing aromatic carbon and short aliphatic chains associated with saponite and hematite assemblage after plagioclase. These assemblages result from successive alteration at decreasing temperature and increasing oxygen fugacity. They affect a hybrid mafic-ultramafic paragenesis commonly occurring in the lower oceanic crust, pointing to ubiquity of the highlighted process during serpentinization.
热力学模型最近表明，在蛇纹石化过程中，凝聚态含碳物质应该是生物成因有机合成的主要产物，尽管在天然蛇纹岩中尚未描述。在这里，我们报告了与熔体注入的地幔衍生蛇纹岩共生的低温矿物组合处于平衡状态的三种不同类型的非生物凝聚态含碳物质的证据。第一种类型覆盖在变质辉石中的水钙铝榴石上，主要含有脂肪链。第二种类型形成与尖晶石和斜长石蚀变边相关的小聚集体（2 µm）。第三种类型以大聚集体（100-200 µm）的形式出现，与蛇纹石和赤铁矿组合有关，在斜长石之后形成，含有芳香族碳和短脂肪链。这些组合是在温度降低和氧逸度增加的连续蚀变过程中形成的。它们影响普遍存在于下部海洋地壳中的混合镁铁质-超镁铁质共生组合，表明在蛇纹石化过程中强调的过程普遍存在。
