The solidified remnants of mafic magmatic systems host the greatest concentrations of platinum-group metals in the Earth’s crust. Our understanding of precious-metal mineralization in these intrusive bodies is underpinned by a traditional view of magma chamber processes and crystal mush solidification. However, considerable uncertainty remains regarding the physical and temporal controls on concentrating these critical metals, despite their importance to modern society. We present high-precision ⁸⁷Sr/⁸⁶Sr analyses of plagioclase and clinopyroxene from within centimetre-thick precious-metal-enriched layers in the Palaeogene open-system Rum layered intrusion (northwest Scotland). Isotopic heterogeneity is present between plagioclase crystals, between clinopyroxene and plagioclase and within plagioclase crystals throughout the studied section. On the basis of these observations, we demonstrate that platinum-group element mineralization formed by repeated small-volume reactive melt percolation events. The preservation of strontium isotope heterogeneities at 10–100 µm length scales implies cooling of the melts that formed the precious-metal-rich layers occurred at rates greater than 1 °C per year, and cooling to diffusive closure within tens to hundreds of years. Our data highlight the importance of cyclic dissolution–recrystallization events within the crystal mush and raise the prospect that precious-metal-bearing mafic intrusions may form by repeated self-intrusion during cooling and solidification.

镁铁质岩浆系统的凝固残余物在地壳中含有最高浓度的铂族金属。我们对这些侵入体中的贵金属矿化的理解是基于岩浆腔室过程和晶体糊状物凝固的传统观点的基础。但是，尽管这些金属对现代社会很重要，但在集中和集中控制这些关键金属方面仍存在很大的不确定性。我们展示高精度⁸⁷ Sr / ⁸⁶在古生物开放系统朗姆酒分层入侵（苏格兰西北部）中，厘米厚的贵金属富集层中斜长石和斜生辉石的Sr分析。在整个研究部分，斜长石晶体之间，斜辉石和斜长石之间以及斜长石晶体内存在同位素异质性。基于这些观察，我们证明了铂族元素矿化是由反复的小体积反应性熔体渗流事件形成的。锶同位素异质性的长度尺度保持在10-100 µm，这意味着形成富贵金属层的熔体的冷却速度每年都超过1°C，并在数十至数百年内冷却至扩散封闭。