Position of the Anai Formation in the Proterozoic Section of the Baikal Salient of the Siberian Platform Basement

Abstract

The paper presents the first U-Pb (LA-ICP-MS) dating results for detrital zircons from the quartzsericite-chlorite schist of the Anai formation within the Baikal salient of the Siberian platform basement. During the study the detrital zircons showed a major age peak at 1.86 Ga, which indicates that the rocks of the Anai formation were accumulated after the development of magmatic rocks of the South Siberian post-collisional magmatic belt with an age of 1.88‒1.84 Ga. This fact makes it possible to reconsider a point of view on the belonging of the Anai formation to the section of the Paleoproterozoic Sarma group whose rocks were intruded by granitoids of the South Siberian magmatic belt. It is shown that the rocks of the Anai formation can be considered as age and facial equivalents of the Proterozoic sediments of the Purpol formation of the Patom zone. Taking into account the Anai formation sediments intruded by sills and dikes of the Neoproterozoic (~720 Ma) dolerites, it can be concluded that the rocks of this formation were presumably accumulated in the Early Neoproterozoic time.