Coronitic textures in the ferrogabbros of the Elet’ozero intrusive complex (Northern Karelia, Russia) as evidence for the existence of Fe-rich melt. 2. Origin of Fe-rich liquid

Аннотация

The study of coronitic textures in ferrogabbros and data on rhythmic layering of the Elet’ozero Massif supports the existence of a specific low-temperature Fe-rich liquid in nature. This liquid was formed during solidification of intrusion owing to the local multiple accumulation of Fe and Ti contents in a parental Fe-rich Fe–Ti basaltic melt. According to obtained data, this occurred on micro- and macroscale: 1) in the interglanular (intercumulus) space of the crystallization zone where intercumulus melt becomes rich in Fe and Ti owing to the crystallization of cumulus silicate minerals and is transformed into Fe-rich liquid, which concentrates residual components of an intergranular melt; 2) during formation of rhythmic layering when Fe-rich residual melt is accumulated before the upper part of the moving front of solidification; when Fe content reaches a certain limit, the melt is also transformed in a separate Fe-rich liquid, the interlayers of which form the upper (lowest temperature) members of rhythms. It was concluded that the emergence of a Fe-rich melt is related to its specific structure, which is formed when the Fe content reaches certain critical values in a liquid. Thus, this liquid is not a product of immiscible splitting of a melt, but represents a peculiar phenomenon. The preservation of primary textures and structures of the rocks is supposedly related to the lyophobic properties of surfaces, i.e., “repulsion” of nonwetting liquid by facets of cumulus crystals, especially plagioclase. Owing to this, the drops and even horizons of heavy Fe-rich liquid are retained in situ of their formation.