LATE CAMBRIAN (~490 MA) ARC VOLCANIC ROCKS OF THE NORTH TIANSHAN OF KYRGYZSTAN: AGE CONSTRAINTS FROM U–Pb ZIRCON DATING

Abstract

In the present contribution, we aim to determine the age of the oldest arc-related volcanic units in the North Tianshan of Kyrgyzstan (NTS) to better understand the early evolution of subduction systems in the western part of the Central Asian Orogenic Belt. We conducted zircon U–Pb dating (LA–ICP–MS) on andesitic tuffs from the Sultansary and Tashtambektor formations, which were previously believed to be of early Cambrian and middle Cambrian to early Ordovician age, respectively. Our results reveal age estimates of 491 ± 3 and 487 ± 3 Ma for these formations, indicating that both units are late Cambrian in age. The volcanic rocks belong to a major magmatic arc with a heterogeneous basement that evolved in the NTS during the late Cambrian and early Ordovician.