Cogenetic origin of mafic and felsic enclaves in the Tarnița Complex, Ditrău Alkaline Massif (Eastern Carpathians, Romania): Insights from structural, textural, and geochemical features

Abstract

Enclaves in plutonic and volcanic rocks serve as pivotal indicators of magmatic processes and magma dynamics, offering valuable insights into the evolution of igneous systems. This study investigates the structural, textural, and geochemical characteristics of mafic and felsic enclaves in the Triassic, continental rift-related Ditrău Alkaline Massif (Eastern Carpathians, Romania), aiming to elucidate their origin and relationship with the host rock which belongs to the Tarnița Complex. Overlapping whole-rock geochemical as well as amphibole and plagioclase compositions strongly suggest the cognate origin of the different lithologies. The mafic enclaves are characterised by sharp contacts and fine-grained igneous textures, implying rapid crystallisation along the margins of the magma batches. Side-wall cumulates were fragmented, transported and dispersed in the partially solidified host magma by convective currents. Felsic enclaves represent fragments of previously crystallised felsic roof cumulates and felsic rock fragments as well as loosely packed crystal mush fragments. The study emphasises the dynamic nature of the studied magma reservoir in the Ditrău Alkaline Massif, where convective magma flow and injections of replenishing magma batches played a crucial role in the formation and distribution of the enclaves.