Ulfanderssonite-(Ce), a new Cl-bearing REE silicate mineral species from the Malmkärra mine, Norberg, Sweden

Author(s)
Dan Holtstam, Ulf Hålenius, Uwe Kolitsch, Joakim Mansfeld
Abstract

Ulfanderssonite-(Ce) is a new mineral (IMA 2016-107) from the long-abandoned Malmkärra iron mine, one of the Bastnäs-type Fe-rare earth element (REE) deposits in the Bergslagen ore region, central Sweden. It is named for Ulf B. Andersson, a Swedish geologist and petrologist. In the type specimen, the mineral occurs with västmanlandite-(Ce), bastnäsite-(Ce), phlogopite, talc, magnetite, pyrite, fluorbritholite-(Ce) and scheelite. Ulfanderssonite-(Ce) forms pinkish, translucent subhedral grains, 100–300 mm, in aggregates up to 2 mm. Fracture is uneven, and there is an indistinct cleavage parallel (001). Mohs’ hardness is 5–6, D

calc = 4.97 g cm

3. Optically, ulfanderssonite-(Ce) is nonpleochroic, biaxial negative, with 2V

meas = 55° and n

calc = 1.82. The ideal composition is Ce

15CaMg

2(SiO

4)

10(SiO

3OH)(OH,F)

5Cl

3. Electron microprobe and LA-ICP-MS chemical analyses yielded (in wt%) La

2O

3 11.87, Ce

2O

3 30.98, Pr

2O

3 3.99, Nd

2O

3 17.14, Sm

2O

3 2.81, Eu

2O

3 0.18, Gd

2O

3 1.15, Dy

2O

3 0.30, Tb

2O

3 0.10, Y

2O

3 1.11, CaO 2.26, FeO 0.02, MgO 1.97, P

2O

5 0.08, SiO

2 19.13, H

2O

calc 1.07, F 1.09, Cl 2.89, O=(F, Cl) 1.10, sum 97.04. The five strongest powder X-ray diffraction lines are [I (%) d

obs (A ) (hkl)]: 100 2.948 (-421), 47 2.923 (204), 32 2.660 (-225), 26 3.524 (40-1), 25 1.7601 (6-23). Ulfanderssonite-(Ce) is monoclinic, Cm, with a = 14.1403(8), b = 10.7430(7), c = 15.498(1) A , b = 106.615(6)° and V = 2256.0 (2) A

3 for Z = 2. The crystal structure has been solved by direct methods and refined to R

1 = 2.97% for 5280 observed reflections. It consists of a regular alternation of two layers, designated A and B, along the c-axis: A (ca. 9 A thickness), with composition [(Ce

8Ca) MgSi

7O

22(OH,F)

4]

8þ, and B (ca. 6.5 A ), with composition [Ce

7MgSi

4O

21(OH,F)

2Cl

3]

8; the A layer is topologically and chemically closely related to cerite-(Ce). A FTIR spectrum shows strong absorption in the region 2850–3650 cm

1, related to the presence of O–H stretching bands. Ulfanderssonite-(Ce) is interpreted as a primary mineral at the deposit, along with the more common fluorbritholite-(Ce), formed by a magmatic-hydrothermal fluid with REE, Si, F and Cl ion complexes reacting with dolomite marble. The presence of ulfanderssonite-(Ce) is direct evidence of a Cl-rich mineral-forming aqueous solution, normally not reflected in the composition of skarn minerals in Bastnäs-type deposits.

Organisation(s)
Department of Mineralogy and Crystallography
External organisation(s)
Stockholm University, Swedish Research Council, Naturhistorisches Museum Wien (NHM), Swedish Museum of Natural History
Journal
European Journal of Mineralogy: an international journal of mineralogy, geochemistry and related sciences
Volume
29
Pages
1015-1026
No. of pages
12
ISSN
0935-1221
DOI
https://doi.org/10.1127/ejm/2017/0029-2670
Publication date
06-2017
Peer reviewed
Yes
Austrian Fields of Science 2012
104026 Spectroscopy, 105116 Mineralogy, 105113 Crystallography
Keywords
ASJC Scopus subject areas
Geochemistry and Petrology
Portal url
https://ucrisportal.univie.ac.at/en/publications/6f761836-9d1a-487a-9e4d-985ef27007dc