We report the formation of minerals from the tochilinite-valleriite group (TVG) during laboratory serpentinization experiments conducted at 300 and 328 °C. Minerals in the TVG are composed of a mixture of sulfide and hydroxide layers that can contain variable proportions of Fe, Mg, Cu, Ni, and other cations in both layers. Members of this group have been observed as accessory minerals in several serpentinites, and have also been observed in association with serpentine minerals in meteorites. To our knowledge, however, TVG minerals have not previously been identified as reaction products during laboratory simulation of serpentinization. The serpentinization experiments reacted olivine with artificial seawater containing 34S-labeled sulfate, with a small amount of solid FeS also added to the 300 °C experiment. In both experiments, the predominant reaction products were chrysotile serpentine, brucite, and magnetite. At 300 °C, these major products were accompanied by trace amounts of the Ni-bearing TVG member haapalaite, Ni,Fe-sulfide (likely pentlandite), and anhydrite. At 328 °C, valleriite occurs rather than haapalaite and the accompanying Ni,Fe-sulfide is proportionally more enriched in Ni. Reduction of sulfate by H2 produced during serpentinization evidently provided a source of reduced S that contributed to formation of the TVG minerals and Ni,Fe-sulfides. The results provide new constraints on the conditions that allow precipitation of tochilinite-valleriite group minerals in natural serpentinites.

中文翻译：

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橄榄石实验蛇纹石化过程中Tochilinite-Valleriite族混合层硫化物-氢氧化物矿物的形成

我们报告了在 300 和 328 °C 下进行的实验室蛇纹石化实验中形成了 Tochilinite-Vallerite Group (TVG) 矿物。TVG 中的矿物质由硫化物和氢氧化物层的混合物组成，两层中都含有不同比例的 Fe、Mg、Cu、Ni 和其他阳离子。该族的成员已在几种蛇纹岩中作为副矿物被观察到，并且还与陨石中的蛇纹石矿物一起被观察到。然而，据我们所知，TVG 矿物此前并未在实验室模拟蛇纹石化过程中被识别为反应产物。蛇纹石化实验将橄榄石与含有34S标记硫酸盐的人造海水反应，并在300℃实验中还添加了少量固体FeS。在这两个实验中，主要反应产物是温石棉蛇纹石、水镁石和磁铁矿。在 300 °C 时，这些主要产物伴随着微量的含 Ni TVG 成员哈帕拉石、Ni,Fe 硫化物（可能是镍黄铁矿）和硬石膏。在 328 °C 时，会出现六方铅矿而不是哈帕莱特石，并且伴随的 Ni,Fe 硫化物中 Ni 的含量按比例更高。蛇纹石化过程中产生的 H2 还原硫酸盐显然提供了还原 S 的来源，从而有助于 TVG 矿物和 Ni、Fe 硫化物的形成。研究结果为天然蛇纹石中托赤石-钒铅矿族矿物的沉淀条件提供了新的限制。