Chevkinite-group minerals from Russia and Mongolia: new compositional data from metasomatites and ore deposits

Abstract

Electron-microprobe analyses of Russian and Mongolian chevkinite-group minerals from little-known host lithologies, including various metasomatic rocks, quartzolites and an apatite deposit, are presented. The mineral species analysed include chevkinite-(Ce), perrierite-(Ce), polyakovite-(Ce) and Sr- and Zr-rich perrierite-(Ce). Compositional variation in the Sr-rich members of the group is broadly represented by the exchange vector (Fe + Mn + Al + REE) ↔ (Ca + Sr + Ti + Zr). Despite the varied parageneses, the chevkinite-(Ce) compositions are similar to previously published data. Many crystals have strong internal compositional variations, partly produced during primary crystallization and partly during low-temperature hydrothermal alteration.

Hydrothermal alteration of a chevkinite-group mineral to a bastnäsite-(Ce)-ilmenite- columbite-(Fe) assemblage: interaction with a F-, CO2-rich fluid

“…2b, are presented in Table 1, and supplemented in Supplementary Table 1a by five analyses from Macdonald et al (2012). The phase has been classified as chevkinite-(Ce) using the empirical discriminant of Macdonald et al (2009) (Fig.…”

The chevkinite group: underestimated accessory phases from a wide range of parageneses

“…In Figure 3b, chevkinite-(Ce) mantles ilmenite, presumably in a reaction relationship. Figure 3a also depicts a reaction relationship, this time of chevkinite-(Ce) to allanite-(Ce) (see more details in Macdonald et al 2012).…”

The occurrence and composition of chevkinite-(Ce) and perrierite-(Ce) in tholeiitic intrusive rocks and lunar mare basalt

“…The line of discrimination has been modified slightly in subsequent compilations Macdonald et al 2009Macdonald et al , 2012 but has been found to be valid. In c/p from mafic samples, FeO* ranges from ~6.5 to 10.5 wt% and CaO from 3.4 to 7.4 wt%.…”

“…Both chevkinite-(Ce) and perrierite-(Ce) are found in a wide range of rock types (Macdonald and Belkin 2002 and references therein), including intrusive and volcanic igneous rocks Troll et al 2003;Jiang 2006;Vlach and Gualda 2007;Carlier and Lorand 2008;Prol-Ledesma et al 2012;Macdonald et al 2013), metasomatized or hydrothermal rocks such as fenites and ore deposits (Macdonald et al 2012), and metamorphic rocks including granulite facies gneisses ) and metacarbonates ). Chevkinite-(Ce) occurs mainly in syenites, alkaline to peralkaline granites and rhyolites, and fenites whereas perrierite-(Ce) is more common in metaluminous felsic igneous rocks.…”

“…The discriminant was based on an extensive investigation of the compositional variations of the two minerals (Macdonald and Belkin 2002) and has been supported by subsequent studies Macdonald et al 2009Macdonald et al , 2012Macdonald et al , 2013) that found that perrierite-(Ce) has less FeO* and Ce 2 O 3 and more CaO, Al 2 O 3 , and ZrO 2 than chevkinite-(Ce). These compilations lacked analyses of chevkinite group minerals from true mafic igneous rocks, the only analyses from mafic rocks being those reported by Azambre et al (1987) of either chevkinite-(Ce) or perrierite-(Ce).…”