Alekseev, et al., report that this paper discusses the morphology, anatomy, and geochemistry of zircons from granitic rocks of post-orogenic intrusive series with Li–F granites in the Russian Far East. The multiphase Upper Urmi pluton in the Amur region and the Severny pluton in the Chukchi Peninsula have been chosen as reference objects. The directed variations of zircon morphology and geochemistry in the history of Pacific postorogenic granitic magmatism reflect decrease in depth of magma generation and crystallization temperature along with an increase in alkalinity, fluid saturation, and raremetal potential of granitic melts.
The authors conclude that:
1) Zircons contained in postorogenic intrusive series with Li–F granites in the Russian Far East are characterized by a wide range of crystallomorphological, anatomical, and chemical properties. Zircon from granitic complexes is a primary magmatic mineral that bears indications of hydrothermal influence. Zircon in monzonitoid and raremetal granitic complexes is formed during crystallization of the evolved melts or by means of transformation of zircon retained during partial melting of crustal sources.
2) Zircons from Late Cretaceous granitoids reveal systematic variations in morphology, internal structure, and chemical composition in series of consecutive intrusive complexes. The main tendency of morphological evolution is expressed as replacement of high temperature (900–800°C) zircon and hyacinth P5, P4, J5, and S20 morphotypes with low temperature (650–600°C) crystolite P1 and G1 morphotypes. This Th + U trend is accompanied by a decrease in dimensions and elongation of crystals. The main tendency in the evolution of zircon anatomy is characterized by complication of its internal structure: formation of rare-metal rims, secondary zones with imperfect structure, mineral inclusions, pores, and fractures. Zircons from monzogranite, Li–F granite, and ongonite contain identical relict cores indicating a common source of rare-metal magmas.
3) The main tendency in the geochemical evolution of zircon is progressive accumulation of Hf, U, Y, Th, Nb, Cs, Li, REE (Yb, Er, Dy), water, fluorine, and incompatible admixtures (Ca, Fe, Al, Sr, Ba, As). Zircons of raremetal granites reveal consecutive development of actinoid (U, Th) and xenotime (Y, REE, P) tendencies of geochemical evolution.
4) The established variations in the composition and properties of zircons reflect the evolution of Pacific post-orogenic magmatism directed toward a decrease in the depth of origination and crystallization temperature, as well as an increase in alkalinity, fluid saturation, and raremetal potential of granitic magmas. Cyrtolite is a transitional concentrator of ore elements and serves as a forecasting and prospecting guide of productive ore-magmatic systems.
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