Fibrous dolomite widely formed in Neoproterozoic marine sedimentary environments, but apparently disappeared in the Phanerozoic. Here, fibrous dolomite is recognised in a Miocene methane seep limestone (Marmorito, Italy) by synchrotron X-ray diffraction, length slow crystal optics and primary zonation under cathodoluminescence, which is unexpected. Low δ¹³C values and their negative correlation with MgCO₃ contents indicate a formation driven by highly alkaline pore waters and catalysis of dissolved sulphide generated by sulphate-driven anaerobic oxidation of methane. Cementing cavities of reefal carbonate, Neoproterozoic fibrous dolomite might have formed under sulphate-reducing conditions like Quaternary reef microbialites. Since the cavities of Neoproterozoic reefs were restricted microenvironments, the formation of fibrous dolomite was possibly favoured by catalysis similar to its Miocene seep counterpart. Our findings reinforce the concept of penecontemporaneous dolomite formation by sulphide catalysis and contribute to our understanding of the environmental conditions of the Neoproterozoic.

纤维白云岩广泛形成于新元古代海洋沉积环境中，但在显生宙明显消失。在这里，通过同步加速器 X 射线衍射、长度慢晶体光学和阴极发光下的初级分带，在中新世甲烷渗透石灰岩（意大利马莫里托）中识别出纤维状白云石，这是出乎意料的。低 δ ¹³ C 值及其与 MgCO _{3的负相关性}含量表明由高碱性孔隙水和硫酸盐驱动的甲烷厌氧氧化产生的溶解硫化物的催化驱动形成。珊瑚礁碳酸盐、新元古代纤维状白云岩的胶结洞可能是在硫酸盐还原条件下形成的，如第四纪珊瑚礁微生物岩。由于新元古代珊瑚礁的空腔是有限的微环境，纤维状白云石的形成可能受到类似于中新世渗透对应物的催化作用的促进。我们的发现强化了硫化物催化形成准同生白云石的概念，并有助于我们了解新元古代的环境条件。