Abstract

The study of trap intrusions with a large-scale occurrence of native iron allowed us to identify general features in their composition and origin. Intrusive bodies are weakly differentiated and have similar structure and mineralogical, petrochemical and geochemical composition. Two associations of rock-forming minerals were found in all studied bodies: early deep-seated (pre-chamber) and intra-chamber. Native iron forms nodular segregations, with a subordinate amount of cohenite, troilite and magnetite–wüstite. Metallic iron can accumulate Ni, Co, Au, and PGE. Their content in metal increases by hundreds or even thousands of times compared to host silicate rock. The formation of native iron is based on the fluid-magmatic interaction between magma and reducing components of the fluid, mainly of methane–hydrogen composition. As a result, an initially homogeneous basalt liquid is dispersed into silicate and metallic components. In the course of transportation, finely dispersed iron phases form droplet-liquid segregations with a monomolecular gas layer on their surface, thus preventing enlargement of metallic droplets. In the hypabyssal chamber, magma, including metallic spherules, is degassed, and droplets are merged to form nodular segregations of native iron.

中文翻译：

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西伯利亚陷阱中的天然铁

摘要

对大量存在的天然铁的陷阱侵入的研究使我们能够确定其成分和起源的一般特征。侵入体分化较弱，具有相似的结构和矿物学、石油化学和地球化学成分。在所有研究的天体中都发现了两种造岩矿物组合：早期深层（前室）和室内。天然铁形成球状偏析，其中含有少量的硬铁矿、硫铁矿和磁铁矿-方铁矿。金属铁可以积累Ni、Co、Au和PGE。与硅酸盐岩石相比，它们的金属含量增加数百甚至数千倍。天然铁的形成基于岩浆与流体还原成分（主要是甲烷-氢成分）之间的流体-岩浆相互作用。因此，最初均匀的玄武岩液体分散成硅酸盐和金属成分。在运输过程中，细分散的铁相形成液滴-液体偏析，其表面形成单分子气体层，从而防止金属液滴的扩大。在浅成岩室中，包括金属球粒在内的岩浆被脱气，液滴合并形成天然铁的结节状偏析。