Rare-earth minerals yttrian zirconolite and allanite-(Ce) and associated minerals from Koberg mine, Bergslagen, Sweden

Abstract

A study of mine dump material from Koberg, Bergslagen, Sweden has revealed a varied mineral assemblage, including Zr-, REE-, Th- and U-bearing minerals associated with the sulphide ore deposit. Detailed descriptions and microprobe analyses are presented of the rare earth minerals yttrian zirconolite and allanite-(Ce), and the zirconium oxide baddeleyite. Yttrian zirconolite is patchily zoned in the actinide elements Th and U, and the low analytical totals suggest the presence of several weight per cent of H2O. The implications of these features with respect to synthetic zirconolite in SYNROC and to radioactive waste management are briefly discussed. Chemical zoning of individual REE in yttrian zirconolite is described and the REE distribution compared with those of zirconolites from other localities. Allanite-(Ce) is generally unzoned, but contains REE-rich rims which are considered to be sub-micron intergrowths of allanite plus a bastnäisite-type mineral phase. The MgO content of allanite-(Ce) is unusually high and appears to be a characteristic feature of allanite from other cerium and mineral occurrences of Central Sweden. The rare earth minerals at Koberg are interpretated as having been formed as a result of localized remobilization of elements including Ti and Zr with H2O- and CO2-rich fluids.

The Mess That Is "Allanite"

“…Method 6: 12.5(O) and all Fe 3+ at M1, all Fe 2+ at M3 Zakrzewski et al (1992) used this method as a basis of calculation of the formulae of dissakisite-(Ce) samples from the Koberg mine, Bergslagen district, Sweden. Although Fe 2+ has been shown to avoid the M1 site (Dollase 1971, Bonazzi & Menchetti 1995, Fe 3+ actually prefers the M3 site over the M1 site (hence the species epidote).…”

“…In the absence of A1-site vacancies, the normalized sum should be 1. Data sources are: Campbell & Ethier (1984), Carcangiu et al (1997), Chesner & Ettlinger (1989), Finger et al (1998), Gieré (1986), Peterson & MacFarlane (1993), Pan & Fleet (1990), Treloar & Charnley (1987), Wood & Ricketts (2000), Zakrzewski et al (1992), and unpublished data of the author for granitic pegmatites from the Grenville Province, Canada.…”

“…Without a formal definition of "allanite", much less of allanite-(Ce), it is difficult to accurately name lanthanon-bearing species of the epidote group; indeed, errors in nomenclature are bound to be occasionally made. The following is a review of the current status of "allanite", vestigators, who associate the term "allanite" with Lnbearing or Ln-dominant epidote: Zakrzewski et al (1992) originally called the dissakisite-(Ce) from Bergslagen, Sweden "allanite-(Ce)". Third, the formula contents of "allanite" are commonly grouped, rather than assigned to individual sites (or even not grouped at all).…”

ALLANITE-(Ce) FROM THE EOCENE CASTO GRANITE, IDAHO: RESPONSE TO HYDROTHERMAL ALTERATION

“…This fact indicates that replacement of allanite by monazite is a reversible process, and as equation (3) would indicate, which phase will be stable is a function of phosphate, calcium, iron, aluminum, silica and hydrogen ion activities. Moreover, allanite of purely hydrothermal origin has been reported from a wide variety of geological environments (Söhnge 1945, Watson & Snyman 1975, Exley 1980, Campbell & Ethier 1984, Gieré 1986, Pan & Fleet 1990, Zakrzewski et al 1992, Kerr & Samson 1998, indicating that the components of allanite can be completely mobilized in aqueous solutions under the appropriate conditions.…”

Mg-Al yttrian zirconolite in a partially melted sapphirine granulite, Vestfold Hills, East Antarctica

“…The Vestfold Hills phase plots well inside the perrierite field as determined by Ito (1967), with average A and B+ C-site cation radii of 0.108 and 0.062 nm respectively, and is therefore considered to be perrierite rather than chevkinite. (Purtscheller and Tessardi, 1985;Platt et al, 1987;Zakrzewski et al, 1992;Gier6 and Williams, 1992), is responsible for 58-63% of the total REE+Y content of the Vestfold Hills zirconolite.…”