Carbonate veins of different texture and their role in reconstructing fracture cementation (Ófalu, Goldgrund Valley)

Abstract

The amphibolite member of the Ófalu Formation is exposed by an outcrop in the Goldgrund Valley, near Ófalu
(Mecsek Hills, South Hungary) and is cut through by carbonate veins composed of several generations of carbonates and
quartz. The main aim of the present study is to confirm the phase-sequence and to reconstruct the precipitation
mechanisms of the vein minerals. Optical microscopic observations were carried out alongside cathodo-luminescent and
scanning electron microscopic studies to enable careful interpretation of internal vein textures. Another goal was to
delineate the physico-chemical circumstances of vein material precipitation through fluid inclusion data.
With these it became possible to define six calcite phases, one dolomite phase and one quartz phase from which
parent solutions flew advectively through fracture systems or percolated through former mineral phases of the veins. The
investigation also sheds light on the possible role of hydrofracturing at the time of certain fluid flow events. Based on the
fluid inclusion studies the parent solutions were of a low temperature and low in salinity fluids.