Rare-Metal Pegmatite Deposits of the Kalba Region, Eastern Kazakhstan: Age, Composition and Petrogenetic Implications

Sergey V Khromykh,Sergey Z Smirnov,Ekaterina N Sokolova,Boris A D’Yachkov,Tatiana A Oitseva,Alexey V Travin,Marina A Mizernaya,Alexander G Vladimirov,Pavel D Kotler,Oxana N Kuzmina,Bakytgul’ B Agaliyeva

doi:10.3390/min10111017

Sergey V Khromykh, Sergey Z Smirnov + Show 9 more

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https://doi.org/10.3390/min10111017

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Abstract

The paper presents new geological, mineralogical, and isotope geochronological data for rare-metal pegmatites in the Kalba granitic batholith (Eastern Kazakhstan). Mineralization is especially abundant in the Central-Kalba ore district, where pegmatite bodies occur at the top of large granite plutons and at intersections of deep faults. The pegmatites contain several successive mineral assemblages from barren quartz-microcline and quartz-microcline-albite to Li-Cs-Ta-Nb-Be-Sn-bearing cleavelandite-lepidolite-spodumene. Ar-Ar muscovite and lepidolite ages bracket the metallogenic event between 291 and 286 Ma. The pegmatite mineral deposits formed synchronously with the emplacement of the phase 1 Kalba granites during the evolution of hydrous silicate rare-metal magmas that are produced by the differentiation of granite magma at large sources with possible inputs of F and rare metals with fluids.

Highlights

Deposits of rare metals (Li, Rb, Cs, Be, Zr, Hf, Nb, Ta, Sn, Mo, and W) that are genetically and spatially related to magmatism are widespread in the Central Asian orogenic belt
More than 100 samples were collected from bedrock exposures from rare metal pegmatitic deposits
The geochronological data for pegmatites were compared with those for intrusions and dikes from the Kalba-Narym terrane in order to estimate the age of rare-metal mineralization in general (Figure 7)

Summary

Introduction

Deposits of rare metals (Li, Rb, Cs, Be, Zr, Hf, Nb, Ta, Sn, Mo, and W) that are genetically and spatially related to magmatism are widespread in the Central Asian orogenic belt. The metals (Li, Cs, Ta, Nb, Be, Sn) most often occur in pegmatites that are derived from granitoids of different compositions, in Asia as well as elsewhere worldwide [1,2,3,4,5,6,7,8,9,10]. The evolution of granitic magmas leading to rare-metal mineralization may be driven by different mechanisms, including effects from mantle sources, as in the case of Li-Cs-Ta pegmatites and coexisting Li-F granites in Central Asia [5,12,13]. The compositions and ages of coexisting rare-metal pegmatites and granites have important petrogenetic implications for the formation mechanisms of mineralization.

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