THE NEOPROTEROZOIC AND EARLY PALEOZOIC GEOLOGICAL HISTORY OF THE URAL-KAZAKHSTAN MARGIN OF THE PALEOASIAN OCEAN USING NEW ISOTOPIC AND GEOCHRONOLOGICAL DATA OBTAINED FOR THE POLAR URAL REGION

Abstract

The presence of pre-Paleozoic ophiolites in the Polar Ural region has been a matter of debate for a long time. In order to solve this problem rock samples were collected from the Enganepe Ridge and the Kharbei metamorphic rock complex to carry out their isotope and geochemical study. The U-Pb method was used to study the zircons from the plagiogranites of the ophiolite rocks from the Enganepe Ridge and from the granite and granite gneiss samples collected from the Kharbei complex. The Enganepe plagiogranite samples showed the concordant age values of 670 +- 5 million years. The data obtained for the Kharbei metamorphosed volcanic and sedimentary rocks suggest that some of them had accumulated in pre-Vendian time (about 640 Ma) and were metamorphozed at 460+- 10 million years. These data suggest the same scenario for the evolution of the Paleoasian ocean, including its Ural margin, and the margins of the Paleoatlantic Ocean.