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

Abstract

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. In the southern metamorphic envelope, distinct populations of apatite can be recognized within individual samples based on their rare earth element (REE) and actinide contents. One population of apatite (Ap1) yields a relatively imprecise U-Pb age of 340 ± 31 Ma. This population comprises apatite grains with very similar trace element compositions to apatite in the northern amphibolite samples, which suggests they crystallized under similar metamorphic conditions to their northern counterparts. A second apatite population (Ap2) yields an age of c. 328 ± 22 Ma, which is interpreted as neocrystalline apatite that formed during a late-Variscan (hydrothermal?) process involving (P, F, Ca, REE)-rich fluid migration. The youngest generation of apatite (Ap3) yields a U-Pb age of 260 ± 8 Ma and may have resulted from thermal resetting associated with the regional emplacement of Permian A-type granites. The proposed tectonic model assumes that rapid uplift (and cooling) of the Tatra block initiated at ca. 345 Ma, contemporaneous with anatexis. Subsequent fluid migration, possibly facilitated by extension related to the opening of Paleo-Tethys, affected only the southern part of the Tatra block.

Two-Stage Late Jurassic to Early Cretaceous Hydrothermal Activity in the Sakar Unit of Southeastern Bulgaria

“…155 Ma Rb-Sr ages as being related to regional metamorphism and thrusting during orogenesis. The ages presented here are coeval with other regional events, such as those documented further west in the Rhodope Massif [58,59], to the north in the Carpathians [60][61][62], and to the east in Turkey and Iran [63], and they are likely connected to the Cimmerian Orogeny [4]. The Cimmerian Orogeny is mostly documented from Central Asia, where oceanic island arcs were subducted beneath Asia prior to the arrival of India and the of the Neo-Tethys basin [4].…”

“…InŞengör [4,64], the Cimmerian Orogeny was defined by the continent-continent collision of a Gondwana-derived continental ribbon on to Laurasia. However, more recent work indicates a series of Cimmerian tectonic events [62,[65][66][67][68][69]. The Cimmerian Orogeny is succeeded by the Alpine Orogeny, which stretches further to the west, and includes the Pyrenees, Alps, Carpathians, Balkanides, Pontides, Zagros, and ultimately, the Himalayas, as the bulk of Africa and India collided with Europe and Asia, respectively.…”

Acta Geologica Polonica

“…That fact could reflect the contribution of variable (but prevailingly crustal) sources in the episodes of partial melting and granitoid incremental intrusion. Granitoids from the Sudety Mountains represent much younger magmatic pulses (320-295 Ma; Mazur et al 2007), however, they share the same similar geotectonic interpretation as late-collisional to post-collisional plutons, which is also the case with the High Tatra granitoid (Gawęda et al 2016;Gawęda et al 2018).…”

“…The composite granitoid intrusion has recently been interpreted as having been formed by the repeated magma influx into an active shear zone over a c. 30 Ma period (Gawęda et al 2016). That long lasting granitoid magmatism was a result of the multistep subduction of oceanic crust and the collision of the Proto-Carpathian terrane with a volcanic arc and finally with Laurussia, finalized with post-orogenic uplift (2 mm/y) and fast cooling (70°C/myr) at c. 345-340 Ma (Gawęda et al 2018). Traditionally, the older granitoids (370-355 Ma; Burda et al 2011;Gawęda et al 2016) were called the common Tatra type, while the younger granitoids (350-340 Ma; Burda et al 2013;Gawęda et al, 2016), predominating in the eastern part of the massif, were called the High Tatra type (Text-fig.…”

“…3f) might result from both felsic -mafic magma mixing (Hibbard 1991;Słaby et al 2007) and sub-isothermal decompression during intrusion resulting in changes in water content (Nekvasil 1991;Eklund and Shebanov 1999) or both processes acting. The last possibility is strongly advocated by a documentation of the rapid uplift at 345-340 Ma, synchronous with the last stages of the magmatic activity in the Tatra Mountains (Gawęda et al 2018). Quartzplagioclase-titanite ocelli and biotite-rimmed quartz ocelli are attributed to magma mixing during crystal nucleation, e.g.…”