Variscan post-collisional cooling and uplift of the Tatra Mountains crystalline block constrained by integrated zircon, apatite and titanite LA-(MC)-ICP-MS U-Pb dating and rare earth element analyses

摘要

LA-ICP-MS U-Pb dating of apatite, titanite and zircon from the metamorphic cover of the Western Tatra granite was undertaken to constrain the timing of metamorphic events related to the final stages of Variscan orogenesis and subsequent post-orogenic exhumation. Zircon was found only in one sample from the northern metamorphic envelope. U-Pb ages from the outermost rims of zircons define a concordia age of 346 +/- 6 Ma, while the inner rims yield a concordia age of 385 +/- 8 Ma. Apatite from three samples from the northern metamorphic envelope yield U-Pb ages of 351.8 +/- 4.4 Ma, 346.7 +/- 5.9 Ma and 342.6 +/- 7.1 Ma. Titanite from an amphibolite from the southern metamorphic envelope yields a U-Pb age of 345.3 +/- 4.5 Ma. The age of c. 345 Ma is interpreted to represent the climax of metamorphism and the onset of simultaneous exhumation of the entire Tatra Mountains massif, and is recorded mainly in the northern part of the metamorphic cover.