The Age of Monazite from the Ichet’yu Occurrence, Middle Timan (CHIME and LA–ICP–MS Methods)

Abstract

Abstract—A study of the morphology, composition, and age (by the CHIME and LA–ICP–MS methods) of monazite from the Ichet’yu occurrence, located in Middle Timan, revealed some principal differences in the typomorphic features and genesis of its two varieties. The common yellow monazite from this occurrence is monazite-(Ce), in which the content of La is higher than that of Nd. The time of its crystallization (recrystallization) is estimated by the CHIME method as 518 ± 40 Ma. Kularite (a grayish-brown globular variety of monazite, in which Nd is higher than La) was dated at 978 ± 31 Ma. The age of some kularite grains is 520 ± 27 Ma, which may be interpreted as the date of a hydrothermal event that resulted in the simultaneous recrystallization of both monazite and kularite. However, these two monazite varieties were formed in two completely different sources and were combined in the mineral parasteresis of the Ichet’yu occurrence. The CHIME age of monazite from the Ichet’yu occurrence that belongs to two intervals (500–600 and 960–1000 Ma) is consistent with the age determined in the same monazite grains using the LA–ICP–MS technique.