Neogene exhumation of the Variscan Szeghalom Dome, Pannonian Basin, E. Hungary

Abstract

AbstractThe Pannonian Basin consists of several deep sub‐basins separated by uplifted basement highs. One of the largest and deepest sub‐basins is the Békés Basin in SE Hungary which is surrounded to the north by several crystalline domes. Of these, the Szeghalom Dome is the best known petrologically, and has been used for studying the Neogene exhumation history of the area.On the basis of metabasite bulk chemistry, the Szeghalom Dome can be subdivided into four distinct zones, the borders of which correspond closely to geophysical anomalies. The four zones exhibit different pre‐Variscan and Variscan pressure–temperature–time (P–T–t) histories. In zone I, high‐pressure relics (600°C, > 12 kbar) occur. Peak‐metamorphic conditions of the main Barrovian overprint were c. 700°C and 6 kbar, and amphibole K/Ar ages scatter around 260 Ma. Zone II shows similar characteristics, with the formation of anatectic granite at peak conditions. K/Ar ages are as low as 220 Ma. Zones III and IV show similar evolution to each other with high‐grade Barrovian relics (700°C), peak metamorphism at 570°C and amphibole ages of 300 Ma.Throughout the dome, fingerprints of a three‐fold Neogene tectonic evolution can be observed. An early detachment fault formed quartz–feldspar–mylonite in zone IV, while chloritic breccia developed at the border of zones II and III. Following the thermal subsidence phase of the basin evolution, the area was dominated geodynamically by the reactivation of older strike‐slip fault systems. These movements were responsible for the horizontal transport of the crystalline blocks at both the southern and northern flanks of the dome. Copyright © 2000 John Wiley & Sons, Ltd.