Zoning and sectoriality of the florencite and xenotime group minerals from quartz veins, the Subpolar Urals

Abstract

A detailed study of the florencite and xenotime assemblage from quartz veins of Au-REE occur rences in the Subpolar Urals allowed the REE fractionation and distribution of REE mixtures in the crystal structure to be characterized. In minerals of selective composition, isomorphic mixtures of LREE and HREE are divided into lanthanum La sg (La-Pr) and samarium Sm sg (Nd-Eu) subgroups in florencite and gadolin ium Gd sg (Gd-Dy) and ytterbium Yb sg (Ho-Lu) subgroups in xenotime. Concentrations of elements from these subgroups are inversely proportional to each other. Each florencite or xenotime crystal is characterized by several mineral varieties: xenotime (Y) and Gd bearing xenotime (Y), florencite (Sm), (Nd), and (Ce); they are selectively distributed by growth zones and pyramids of the crystal with formation of direct and inverse zoning. In both cases, cores of the crystals are enriched in HREE. The correlation between REEs, Y, and such trace elements as As, S, Ca, Sr, U, and Sc is established. REE deportment is considered in min erals formed as products of primary crystallization and hydrothermal redeposition. The REE fractionation is interpreted in terms of quantum mechanics.

Florencite-(Sm)—(Sm,Nd)Al3(PO4)2(OH)6: A new mineral species of the alunite-jarosite group from the subpolar urals

“…The crystals were constructed with the Shape 7.1 program at an X ray ratio of a : c = 1 : 2.32. This made it possible to refine the previous data (Repina and Yuzeeva, 2005;Repina, 2010) Similar to synthetic florencite (Sm) (Schwab et al, 1990) space group R3m; an X ray single crystal study was not performed. X ray crystallography.…”

“…The crystallization of florencite (Sm) in association with HREE minerals is possible from solu tions enriched in HREE and MREE. For example, at the Svodovy site, xenotime (Y) associated with floren cite contains up to 11-23 wt % Gd 2 O 3 and 7-8 wt % Dy 2 O 3 (Repina, 2010). Florencite (Sm) zones were probably formed as a result of REE fractionation and periodically oscillating oversaturation at the front of the growing crystals.…”

“…Florencites of complex composition are abundant in the Subpolar Urals ( Fig. 1), where they are found in altered rocks, quartz veins, and orebodies of the Au-REE ore fields (Mel'nikova et al, 2005;Repina and Yuzeeva, 2005;Repina, 2010). Florencites from carbonatite of the Eastern Sayan have been studied in detail (Somina and Bulakh, 1966).…”

“…Growth zones enriched in Sm were revealed in large florencite crystals (Repina, 2010). The detailed examination of such zones resulted in the identifica tion of florencite (Sm), an Sm dominant member of the florencite subgroup.…”

Gadolinium-dominant monazite and xenotime: Selective hydrothermal enrichment of middle REE during low-temperature alteration of uraninite, brannerite, and fluorapatite (the Zimná Voda REE-U-Au quartz vein, Western Carpathians, Slovakia)

“…The highest Gd 2 O 3 content in MGM described to date is most likely 13.5 wt% (accompanied by 14.3 wt% Sm 2 O 3 ) in monazite-(Sm) from its type locality of Annie Claim, Manitoba, Canada, where it occurs in a lepidolite-subtype granitic pegmatite(Massau et al 2002). The highest Gd 2 O 3 content in xenotime-(Y) noted to date is 25 wt% from the quartz vein of Au-REE mineralization in the Nether-Polar Urals, Russia(Repina 2010(Repina , 2011 and 12.6 wt% in gadolinite-(Y) from Alpine fissures in Glogstafelberg, Val Formazza, Italy(Demartin et al 1993).document the possible presence of other Gd-dominant minerals; unfortunately without suitable DOI: https://doi.org/10.2138/am-2022-8418. http://www.minsocam.org/ Always consult and cite the final, published document.…”