Isotope U–Pb SHRIMP Dating of Eclogites from the Mugodzhar Range (Kazakhstan)

Dating of zircons from eclogites and amphibolite in metamorphic rocks of the Eastern Mugodzhar zone (terminal south of the Urals) is conducted. Of four eclogite samples, close (and the oldest ones of 520 ± 4 Ma) concordant age values are obtained in three samples, and these ages probably correspond to the age of the protolith. Concordant dates of 472 ± 3 and 379 ± 3 Ma correspond to the main stages of metamorphism in the East Mugodzhar Range: the former marks the time of high-pressure metamorphism, whereas the latter corresponds to the metamorphism of amphibolite facies. The presence of ancient and at the same time varied-age zircons (probably carrying rounding signatures) indicates the primary sedimentary nature of the amphibolites studied. The youngest zircons from eclogites of the Mugodzhar Range are of 282 ± 2 Ma in age, corresponding to the stage of collision. The obtained data show that the metamorphic complexes of the Mugodzhar Range are not units of Early Proterozoic or Riphean age (as was previously believed), but represent Lower–Middle Paleozoic complexes from the middle of the Earth’s crust. Thus, these metamorphic rocks belong to the deep part of an island-arc system that had been located in the eastern sector of the Urals, which later was drawn to the near-surface level when some regions of the Urals underwent uplift and erosion.