At the stage of magmatic crystallization, magmas of basic–ultrabasic intrusions of subduction origin and alkaline-ultrabasic intrusions have high oxygen fugacity, which prevents large-scale sulfide formation. Correspondingly, PGE in such intrusions are dispersed among cumulus minerals rather than accumulated in sulfides. It has been shown experimentally that the subsolidus interaction (P = 200 MPa, T = 950°C) of CO₂ with olivine, a typical cumulus mineral of basic–ultrabasic intrusions, leads to the oxidation of the fayalitic component and reduction of a fluid. At a low silica activity in the fluid, the content of CO in CO₂ reaches a maximum value of 14 mol %, which corresponds to fO₂ = QFM–2. With such a CO content, platinum from the capsule walls was dissolved in the fluid in the form of carbonyl and reprecipitated with spinel in olivine cracks. It has been experimentally established that the interaction of CO₂–H₂O fluid with pyrrhotite under the same P-T conditions is accompanied by the reduction of the fluid with a decrease in oxygen fugacity to QFM buffer. Analysis of the composition of fluid captured in an albite glass trap by micro-Raman scattering showed the formation of saturated (С₂Н₆ and СН₄) and unsaturated (with functional groups СН=СН and =СН₂) hydrocarbons, CO, H₂ and H₂S. The platinum of the capsule walls has buffered the sulfur fugacity at a low level of Pt–PtS buffer, resulting in the low content of sulfur species in the fluid and dissolution of Pt in carbonyl form. Crystallization of the isoferroplatinum from such a fluid was observed experimentally. Preliminary data indicate that the CO-bearing carbonic fluid extracts Cr from the Cr-spinel, which increases the range of the Cr/(Al + Cr) ratio with constant Fe³⁺/(Al + Cr) at the spinel surface. All established experimental effects of fluid interaction with cumulus minerals of the basic–ultrabasic intrusions have been found in nature. This supports the inferred important role of such interaction in the formation of the low-sulfide PGE deposits.

在岩浆结晶阶段，俯冲起源的基性-超基性侵入体和碱性-超基性侵入体的岩浆氧逸度高，阻碍了大规模硫化物的形成。相应地，这种侵入体中的 PGE 分散在积云矿物中，而不是在硫化物中积累。实验表明，CO ₂与橄榄石的亚固相线相互作用（P = 200 MPa，T = 950°C），橄榄石是一种典型的碱性-超基性侵入体的积云矿物，导致铁橄榄石组分的氧化和流体的还原. 在流体中二氧化硅活性较低的情况下，CO ₂中的 CO 含量达到最大值 14 mol %，对应于f O ₂= QFM–2。在这样的 CO 含量下，来自胶囊壁的铂以羰基的形式溶解在流体中，并与橄榄石裂缝中的尖晶石重新沉淀。实验表明，在相同的PT条件下，CO ₂ -H ₂ O 流体与磁黄铁矿的相互作用伴随着流体的减少，氧气逸度降低到 QFM 缓冲液。通过微拉曼散射对钠长石玻璃阱中捕获的流体成分的分析表明形成了饱和（С ₂ Н ₆和 СН ₄）和不饱和（具有官能团 СН=СН 和 =СН ₂）碳氢化合物、CO、H ₂和 H ₂S. 胶囊壁的铂在低水平的 Pt-PtS 缓冲液中缓冲了硫逸度，导致流体中硫物质的含量低，并且 Pt 以羰基形式溶解。通过实验观察到异铁铂从这种流体中结晶出来。初步数据表明，含 CO 的碳酸流体从 Cr 尖晶石中提取 Cr，这增加了尖晶石表面的 Cr/(Al + Cr) 比率范围，Fe ³⁺ /(Al + Cr)保持不变。流体与基本-超基本侵入体的积云矿物相互作用的所有已建立的实验效果都已在自然界中发现。这支持了这种相互作用在低硫化物 PGE 沉积物形成中所推断的重要作用。