Late Silurian Age of Intrusive Rocks of the Bestobe Gold Deposit (Northern Kazakhstan)

For the Stepnyak complex granitoids, which includes the Bestobe quartz vein gold deposit (Northern Kazakhstan), a Late Silurian crystallization age has been established. U‒Pb (SIMS) geochronological studies were conducted on rocks from the Western and Central intrusions, as well as small bodies in the Dal’nyaya zone. Quartz diorites, quartz gabbros, granite porphyries, and porphyry diorites were estimated to be 425‒420 million years old. These dates are significantly younger than the known Middle-Late Ordovician crystallization age of the Stepnyak complex in the Aksu, Stepnyak, and Zholymbet deposits. It has therefore been suggested that the Stepnyak complex formed heterochronously and that the emplacement of similar intrusive massifs occurred in a pulsating manner over a period of approximately 20 million years.