Fluorapatite from Anemzi alkaline syenite hosts a wealth of solid organic inclusions, mainly of aliphatic (2,935–2,845 cm−1) and aromatic hydrocarbon compositions (3,100–3,000 cm−1), as well as traces of bituminous matter showing a low degree of ordering. The tiny inclusions built from oxides of titanium (rutile and anatase) are the only mineral phases found in host crystals. The two‐phase, liquid–gas fluid inclusions are composed of aliphatic and aromatic functional groups, revealing bands in the region 1,600–1,200 cm−1. A slightly chemically varied composition and blue, homogenous cathodoluminescence colours, activated mainly by Ce3+, as well as a small volume of mineral inclusions in apatite, indicate that its crystallization, as influenced by hydrocarbon‐ and carbonaceous matter‐bearing fluids, proceeded under stable environmental conditions. It is probable that these fluids were migrated within the adjacent carbonate rocks found in the vicinity of alkaline syenites, which could be the source of organic components entrapped by apatite. A numerous assemblage of organic inclusions is diagnostic feature for gem quality green apatite from Anemzi.
ores (Co arsenides, mainly skutterudite) and rock-forming minerals (among others, dolomite) by the solutions in the oxidation zone of the ore deposits. The heating of the Mgenriched erythrite up to 1000 °C leads to the crystallization of the water-free (Co,Mg) 3 (AsO 4) 2 phase.
Dumańska-Słowik, M., Budzyń, B., Heflik, W. and Sikorska, M. 2012. Stability relationships of REE-bearing phosphates in an alkali-rich system (nepheline syenite from the Mariupol Massif, SE Ukraine). Acta Geologica Polonica, 62 (2), 247-265.Primary REE-enriched fluorapatite and fluorbritholite-(Ce) in nepheline syenite from the Mariupol Massif (SE Ukraine), contain textural and chemical evidence of late-to post-magmatic metasomatic alteration. REE mobilization and replacement of the primary phases by fluid-mediated coupled dissolution-reprecipitation strongly depended on the distance between the altered minerals in the host rock. Fluorapatite and fluorbritholite-(Ce) forming individual pristine grains were partially replaced by the same phase with a new composition, resulting in the presence of patchy zoning in altered grains. The increased REE contents in altered fluorapatite rim domains are related to REE mobilization from the altered REE-depleted rim domains of the fluorbritholite-(Ce). The REEs were transported by a fluid with high F activity. The alteration of fluorapatite and fluorbritholite-(Ce) grains in contact resulted in the partial replacement of the primary phases by the same phase with a new composition, but also in the partial replacement of the fluorapatite by secondary monazite and fluorite. The REE mobilized from the fluorbritholite-(Ce) in the presence of a F-rich fluid in an alkali-rich system promoted formation of monazite as the new phosphate REE-host. The presence of secondary parisite in the altered domains of the fluorapatite and fluorbritholite-(Ce) indicates a CO 2 component in the fluid during metasomatic alteration.
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