U-Pb and Ar-Ar dating of minerals from metamorphic and syn-orogenic sedimentary rocks as a key to understanding architecture and evolution of collisional orogens

点击翻译按钮获取中文摘要

The Variscan internides in central Europe are a collage of basement units, nappe relics, and syn-orogenic deposits that have varying origins and show a wide range in age and degree of metamor-phism and deformation. An outstanding example are continental crust rocks from the Erzgebirge and the Saxon Granulite Massif, which were deformed and metamorphosed in the Early Carboniferous un-der, respectively, ultrahigh-pressure (UHP) and ultrahigh-temperature (UHT) conditions. The initial near-isothermal exhumation of these rocks from mantle depths was very fast. Probably unique in the world, granulite emplacement in the upper crust caused a contact metamorphic aureole. High-grade metamorphism and major deformation had ended before granites with Late Viséan crystallization ages intruded. In contrast, the overlying Frankenberg Klippe and the contiguous Lusatian Block escaped this metamorphism. Locally-derived clastic sediments of the Hainichen Basin are coeval with meta-morphism and exhumation of the high-grade basement units, thus recording the history of exhumation, cooling, and erosion. Our primary aim is to investigate the exhumation and denudation history of the UHP/HP and UHT units in the eastern Variscan internides by using a combination of 40Ar/39Ar and U-Pb geochronology. Selected basement units will be targeted for correlation purposes in order to detect age discontinuities between them, to constrain recrystallization and exhumation ages, and for prove-nance and argon inheritance studies. In addition, by studying how the sediments of the Hainichen Ba-sin change over time in character and origin we will be able to establish exhumation rates, and the time of exposure and initial erosion of the UHP/HP and UHT units. Key words: continental collision orogeny, exhumation, syn-orogenic deposition, Ar-Ar and U-Pb geo-chronology, European Variscan Belt