Zircon in the multiphase Turginsky massif with amazonite granites (Eastern Transbaikalia) and its petrogenetic significance

A.A. Ivanova, l. F. Syritso, E. V. Badanina, A. M. Sagitova

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 6. P. 1-21

https://doi.org/10.30695/zrmo/2018.1476.00

Language: Russian

Abstract

Zircon from granitoids of the multiphase Turginsky massif in the Eastern Transbaikalia shows a wide variety of morphological features and composition of trace elements. This granitoid massif of the Kukulbey complex has the spatial association with rocks of the Shakhtama monzonitoid complex; their ages are about 133 and 158 Ma, respectively. A decrease of the hafnium content together with increase of the Th+U and Y+REE amounts, within the trend of their contents increasing in absolute values, has been checked in composition of zircon of different granitoid phases of the Kukulbey complex, finalizing formation of the Li-F-bearing granites. This process of the trace elements accumulation in rocks of the main phase of the Turginsky massif — Li-biotite granites — was accompanied by a significant rise of their crystallization temperature, relatively to the earlier phase. The indicative features of zircon in these granites are the intensive development of a specific twinning (up to 30% of all grains) and presence of contrasting growth zones, confirming the idea of increasing crystallization temperatures and alkalinity of the melt. These features of zircon, together with geochemical composition of rocks, indicate the belonging of the Turginsky massif amazonite granites to the alkalized type of Li-F-bearing granites with a mixed geochemical specialization: on the one hand, Li, Ta, Nb, which are typical for the ore-bearing Orlovksky massif, and, on the other hand: Z, REE, Th, U — more typical for subalkaline granites.

Key words: zircon, rare-metal Li-F-bearing granite, morphology, geochemistry, crystallization temperature, petrogenesis, Eastern Transbaikalia.