THE POLYCHRONOUS NATURE OF ZIRCONS IN GABBROIDS OF THE URAL PLATINUM BELT AND THE ISSUE OF THE PRECAMBRIAN IN THE TAGIL SYNCLINORIUM

Abstract

Application of high-precision analytical methods for the investigation of isotope parameters of single zircon crystals has significantly enhanced the potential of zircon geochronology. The issue of the Precambrian in the Tagil Synclinorium zone is related to problematic Proterozoic datings obtained by the laser ablation method at Granada University (Spain) for some zircon grains extracted from the Chernyi Istochnik gabbro massif of the Ural Platinum Belt. The age of the predominant zircon variety was estimated at 422 ± 11 Ma. However, some datings obtained for the classic Late Ordovician–Silurian magmatism created a paradoxical situation that requires not only more reliable substantiation of ancient datings, but also the assessment of their geological significance with consideration of the large body of information pertaining to the TSZ origin.