The thick laterite developed over platinum group element (PGE)-bearing ultramafic rocks of the Owendale Alaskan-Uralian Complex in New South Wales, Australia, provides an ideal environment in which to address the question of whether Pt-Fe nuggets are formed during lateritization. This is an important issue to settle because Pt-Fe nuggets in alluvial placers and eluvial deposits associated with the Alaskan-Uralian complexes were the world’s major source of Pt prior to the commencement of Pt production from the Bushveld Complex and continue to produce a significant amount of Pt. Some of the Owendale laterites have high Pt but low Cu contents, while others have both high Pt and high Cu contents. Heavy mineral concentrates were prepared from about 1 kg of drill chips from both types of laterites. Only five of the 61 samples processed contained any platinum group minerals (PGMs) greater than 5 μm in size, even though many of the samples contained more than 1 g/t Pt. The largest PGM found was about 100 μm long, and the majority were <20 μm. The bulk of the PGMs recovered were zoned PGMs consisting of a core of isoferroplatinum mantled by tetraferroplatinum with an outer rim of tulameenite; many of these zoned PGMs are encased in hematite grains that often have high Pt contents and appear to be pseudomorphs after the PGMs. The textural evidence indicates that at least half of the primary PGMs in the ultramafic protoliths to the laterites were destroyed during weathering and that the liberated PGEs could have been available for the formation of PGM nuggets. However, despite the large amount of PGEs liberated during the destruction of the primary PGMs, no evidence was found for the neogenic growth of PGE nuggets. Rather, the Pt liberated during the destruction of the PGMs appears to have only traveled distances of micrometers to tens of centimeters to form Pt nanoparticles or Pt oxides or to be absorbed/adsorbed by the Fe oxide hosts.

中文翻译：

---

砂金矿块是在红土化过程中形成的吗？澳大利亚欧文代尔阿拉斯加-乌拉尔联合体的裁决是断然不！

澳大利亚新南威尔士州欧文代尔阿拉斯加-乌拉尔杂岩的含铂族元素 (PGE) 超镁铁岩上发育的厚红土岩为解决红土化过程中是否形成 Pt-Fe 矿块的问题提供了理想的环境。这是一个需要解决的重要问题，因为在 Bushveld 杂岩开始生产 Pt 之前，与阿拉斯加-乌拉尔杂岩相关的冲积砂矿和残积矿床中的 Pt-Fe 矿块是世界上 Pt 的主要来源，并且继续大量生产铂。一些 Owendale 红土具有高 Pt 但低 Cu 含量，而另一些则具有高 Pt 和高 Cu 含量。重矿物精矿由来自两种类型红土的约 1 kg 钻屑制备。在处理的 61 个样品中，只有 5 个样品含有尺寸大于 5 μm 的铂族矿物 (PGM)，尽管许多样品的铂含量超过 1 克/吨。发现的最大PGM长约100μm，大多数<20μm。回收的大部分铂族金属是分区铂族金属，由四铁铂覆盖的异铁铂核心和钛铁矿外缘组成；许多这些分区铂族金属被包裹在赤铁矿颗粒中，这些颗粒通常具有较高的 Pt 含量，并且在铂族金属之后似乎是假晶。结构证据表明，从超镁铁质原岩到红土中至少有一半的原生铂族金属在风化过程中被破坏，并且释放的铂族元素可能可用于形成铂族金属块。然而，尽管在初级铂族金属的破坏过程中释放出大量的铂族元素，但没有发现铂族元素块的新生生长的证据。相反，在 PGM 破坏过程中释放的 Pt 似乎仅移动了微米至数十厘米的距离，形成 Pt 纳米颗粒或 Pt 氧化物，或被 Fe 氧化物主体吸收/吸附。