Abstract Weathering of the Merensky reef was enhanced under laboratory conditions by Fe- and S-oxidizing bacteria: Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans. These bacteria preferentially colonized pyrrhotite and pyrite, versus pentlandite and chalcopyrite (all of which were common within the rock substrate), promoting weathering. Weathering of base metal sulfides resulted in the precipitation of Fe oxides, Fe phosphate, and elemental sulfur as secondary minerals. Fe pyroxene weathered readily under acidic conditions and resulted in mineral dissolution, while other silicates (orthopyroxene and plagio-clase) precipitated Fe phosphate spherules or coatings on their surface. The deterioration of the platinum group metal (PGM) matrix (base metal sulfides and silicates) and the occurrence of a platinum grain associated with platinum nanoparticles observed in the biotic thin sections demonstrate that biogeochemical acid weathering is an important step in the active release of intact PGM grains. A platinum grain embedded in secondary Fe oxides/phosphate that had settled by gravity within the weathering solution demonstrates that secondary minerals that formed during weathering of PGM-hosting minerals also represent targets in PGM exploration by trapping and potentially slowing PGM migration. Dispersion halos surrounding or occurring downstream from PGM occurrences will likely produce two physical target classes—i.e., grains and colloids—under surficial weathering conditions.

中文翻译：

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梅伦斯基礁的实验室细菌风化及其对铂族矿物迁移的影响

摘要 在实验室条件下，Fe-和 S-氧化细菌增强了 Merensky 礁的风化：Acidithiobacillus ferrooxidans、Acidithiobacillus thiooxidans 和 Leptospirillum ferrooxidans。这些细菌优先寄居在磁黄铁矿和黄铁矿上，而不是镍黄铁矿和黄铜矿（所有这些都在岩石基质中很常见），从而促进风化。贱金属硫化物的风化导致作为次生矿物的铁氧化物、磷酸铁和元素硫沉淀。Fe 辉石在酸性条件下容易风化并导致矿物溶解，而其他硅酸盐（斜辉石和斜长石）在其表面沉淀出磷酸铁球或涂层。在生物薄片中观察到的铂族金属（PGM）基质（贱金属硫化物和硅酸盐）的劣化和与铂纳米颗粒相关的铂颗粒的出现表明，生物地球化学酸风化是完整的主动释放的重要步骤。 PGM 谷物。嵌入在风化溶液中通过重力沉降的次生铁氧化物/磷酸盐中的铂颗粒表明，在 PGM 宿主矿物的风化过程中形成的次生矿物也代表了 PGM 勘探的目标，因为它可以捕获并可能减缓 PGM 迁移。在表面风化条件下，PGM 矿点周围或下游出现的弥散晕可能会产生两种物理目标类别，即颗粒和胶体。