Genesis of carbonate aggregates in lamprophyres from the northeastern Transdanubian Central Range, Hungary: Magmatic or hydrothermal origin?

摘要

Carbonate aggregates in Late Cretaceous lamprophyre dikes of the northeastern Transdanubian Central Range (TCR) in Northwest Hungary have been classified into three genetic groups. Type-I dolomite + calcite +- magnesite aggregates have petrograph-ic and geochemical features similar to ocelli described by other workers. Fluid inclusions in Type-I aggregates homogenize between 77 and 204 deg C and are of hydrothermal origin. Type-II aggregates are characterized by a polygonal shape and are mostly dolomite. Based on their shape and primary fluid inclusions which homogenize between 95 and 172 deg C, these carbonate aggregates are interpreted to fill vugs produced by the dissolution of olivine phenocrysts. Type-in carbonate aggregates show an irregular to polygonal shape and distinct compositional zonation and contain secondary aqueous fluid inclusions. Homogenization temperatures of fluid inclusions are below 104 deg C, and zonation patterns suggest partial recrystallization. These carbonate aggregates are most likely xenoliths and xenocrysts from the wall rocks of the lamprophyre melt conduits.