Mineralogy of metamorphosed carbonatite of the Vesely occurrence, Northern Transbaikal region, Russia |
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Authors: | E I Lastochkin G S Ripp and A G Doroshkevich |
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Abstract: | Metamorphism of carbonatite is exemplified in the Vesely occurrence. According to available data, the age of the carbonatite
is 596 ± 3.5Ma, whereas metamorphism is dated at 550 ± 14 Ma. The rocks at the Vesely occurrence were metamorphosed under
conditions of greenschist facies (epidote-muscovite-chlorite subfacies) under elevated pressure. Microthermometry of fluid
inclusions in minerals indicates that the temperature of metamorphism is 377−450°C and the pressure estimated from phengite
geobarometer is 6−8 kbar. The low-grade metamorphism led to the partial recrystallization of carbonates and apatite with removal
of trace elements. This process resulted in a change of the oxygen isotopic composition of the studied minerals. Metamorphism
was accompanied by formation of talc, phengite, chlorite, quartz, tremolite-actinolite, and anthophyllite, which are not typical
of carbonatite. The data obtained show that the metamorphism exerted an effect on the mineralogical, isotopic, geochemical,
and technological properties of the carbonatite. The effect of metamorphism should be taken into account in determination
of the nature of ore mineralization and estimation of ore quality and perspective of the occurrence. |
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