Fenite halos of geological-geochemical features of Proskurivka and Chernigivka’s alkaline-ultramafic massifs of Ukrainian shield

Abstract

Geological, petrographic and, mainly, geochemical features of two massifs of Ukrainian Shield’s alkaline-ultramafic formation – Proskurivka alkaline (PM) and typical carbonatite Chernigivka (ChCM) are reviewed. Both of them belong to two different structural-morphological types (ChCM – linear, PM – central) and differ by rock complex (carbonatites absence in PM). Petrographic and geochemical features of two massifs fenite halos that differ by form and various compositions of host rocks have been investigated. It was found out that the fenitization process in both research cases, except on some similar features, lead to geochemically different final products formation – fenites. Moreover, the last ones differ significantly by their geochemical features from massifs of alkaline rocks. It allows to assume that fenitization process was initiated by the so-called “forward wave” fluids, which outrun the introduction of alkaline rocks properly. In this case geochemical difference between PM and ChCM fenites is evidence of significant distinction in corresponding fenitization fluids composition and potentially contains the information to be estimated.