First Age and Geochemical Data on Zircon from Riebeckite Granites of the Verkhnee Espe Rare Earth\u2013Rare Metal Deposit, East Kazakhstan

E V Levashova,S G Skublov,X.-H Li,Q.-L Li,T A Oitseva,V V Shatov,B A Dyachkov,N V Shatova

doi:10.1134/s0016702922010086

Abstract

This paper is dedicated to the isotope-geochemical study of zircon from riebeckite granites of the Verkhnee Espe rare earth-rare metal deposit and the specification of its U–Pb age. Zircon from the Verkhnee Espe massif is peculiar in the high content of non-formula elements (up to 43000 ppm REE, up to 22000 Y, and others) and demonstrates a clearly expressed heterogeneous structure. The central and rim zones of the zircon show a “magmatic” rare-earth element (REE) distribution. The intermediate zones are characterized by a flattening of the REE patterns and an anomalous enrichment in REE, Y, Nb, and Ca. This compositional feature of the zircon may be caused by impact of fluid-saturated granite melts enriched in incompatible trace elements. The δ18О values in the zircon are 5.83–7.16‰, which generally corresponds to zircon formed from granitoid melts. The age of zircon from the Verkhnee Espe rare earth–rare metal deposit is 283 ± 3 Ma, which indicates that there is no significant age gap between granite crystallization, on the one hand, and metasomatic processes and ore generation, on the other.

Highlights

During Р1–Т1 period of the Hercynian cycle, the East Kazakhstan region was spanned by intense granitoid magmatism formed in a post-collisional geodynamic setting, which is typical of the Central Asian Orogenic Belt (Dyachkov, 2015)
Obtained U–Pb zircon age of 283 ± 3 Ma for riebeckite granites is regarded as the age of the Verkhnee Espe massif and associated eponymous rare-earth– rare-metal deposit
Zircon from riebeckite granites of the Verkhnee Espe massif is characterized by the heterogeneous internal structure and composition

Summary

Introduction

During Р1–Т1 period of the Hercynian cycle, the East Kazakhstan region was spanned by intense granitoid magmatism formed in a post-collisional geodynamic setting, which is typical of the Central Asian Orogenic Belt (Dyachkov, 2015). The Verkhnee Espe granitoid massif is an important object of East Kazakhstan, because it is practically entirely occupied by a promising complex rare-earth–rare metal (REE, Zr, Nb, Ta) deposit. Numerous detailed studies have been carried out for the Verkhnee Espe massif. The composition of rock-forming and accessory minerals and geochemistry of apogranites and ore lodes of the Verkhnee Espe deposit were described in (Baisalova, 2018; Frolova, 2018). At the same time, such important and informative accessory mineral as zircon remains insufficiently studied

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