The first Lu–Hf zircon isotope data for gabbro–diorite–tonalite associations of the Urals

Abstract

The Lu–Hf isotope systematics of zircon from the gabbro–plagiogranite association (gabbro, diorite, tonalite, and plagiogranite), which is one of the most typical associations of igneous rocks in the Urals, was studied for the first time. The isotope study yielded a unified age limit of 433 Ma, which corresponds to the time of formation of this rock association. The younger “rejuvenated” ages characterize superimposed thermal impact events, induced by the volcanic arc activity, as well as collisional and postcollisional processes. Here, the initial ¹⁷⁶Hf/¹⁷⁷Hf(t) ratio in the studied zircon from gabbro and plagiogranite corresponds in fact to a highly LILE-depleted (DM) mantle.