Determination of the crystallization age of the carbonatite massif and associated mineralization

What is it about?

We present the first results of a comprehensive isotope-geochemical study of dolomitic carbonatites of the Mal’dzhangarka massif located in the southeast of the Billyakh melange zone (southeastern periphery of the Anabar Shield). Zircon grains separated from core samples from a depth of 6–30 m have a three-phase structure. All of them were trapped from the host metamorphic rocks and mark the age of the main stage of high-gradient metamorphism in the region, 2027 ± 9 Ma. Pyrochlore containing 38–705 ppm U and 5–21 ppm radiogenic Pb, with weak metamictization of the crystal lattice and an undisturbed U–Pb system made it possible to estimate the concordant age of rare-metal mineralization in the massif, 167 ± 4 Ma, which is probably close to the crystallization age of the host carbonatites.

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Photo by pure julia on Unsplash

Photo by pure julia on Unsplash

Why is it important?

Based on the comprehensive isotope-geochemical studies of dolomitic carbonatites of the Mal’dzhangarka massif, we have first estimated the age of the massif and associated rare-metal mineralization represented by pyrochlore, 167 ± 4 Ma, while the upper age boundary of the formation of pyrite from superposed late carbonate–sulfide veinlets with the most homogeneous Re–Os system is estimated at 164 ± 2 Ma.The obtained age of carbonatite crystallization and associated mineralization differs significantly from the time of intrusion in the Maimecha–Kotui and Udzha provinces, but is close to the time of one of the stages of kimberlite–carbonatite magmatism on the eastern slope of the Anabar dome.

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