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Wakefieldite‐(Nd), a New Neodymium Vanadate Mineral in the Arase Stratiform Ferromanganese Deposit, Kochi Prefecture, Japan
Author(s) -
Moriyama Takeru,
Miyawaki Ritsuro,
Yokoyama Kazumi,
Matsubara Satoshi,
Hirano Hideo,
Murakami Hiroyasu,
Watanabe Yasushi
Publication year - 2011
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2010.00151.x
Subject(s) - ferromanganese , mineral , tetragonal crystal system , hematite , mineralogy , geology , materials science , crystallography , metallurgy , chemistry , manganese , crystal structure
Wakefieldite‐(Nd), NdVO 4 , is a new mineral found from the Arase stratiform ferromanganese deposit in Kochi Prefecture, Shikoku Island, Japan. It is the Nd‐dominant analogue of wakefieldite‐(Y) and wakefieldite‐(Ce). The ferromanganese ore specimen mainly consists of hematite and caryopilite, and wakefieldite‐(Nd) is typically enclosed in caryopilite. Wakefieldite‐(Nd) is tetragonal, I 4 1 / amd , a = 7.338(16) Å, c = 6.509(19) Å, V = 350.5(18) Å 3 , Z = 4. The four strongest lines in the X‐ray diffraction pattern [ d (Å), I / I 0 , hkl ] using a Gandolfi camera are (3.67, 100, 200); (2.74, 51, 112); (4.84, 27, 101) and (1.89, 25, 312). Chemical composition of wakefieldite‐(Nd) are V 2 O 3 35.25, As 2 O 3 0.93, SiO 2 0.14, MnO 1.45, Fe 2 O 3 0.41, Y 2 O 3 2.87, La 2 O 3 7.61, Ce 2 O 3 7.37, Pr 2 O 3 6.04, Nd 2 O 3 26.79, Sm 2 O 3 4.41, Eu 2 O 3 1.36, Gd 2 O 3 3.41, Tb 2 O 3 0.22, Dy 2 O 3 1.41, Er 2 O 3 0.10, total 99.77 wt.%. The empirical formula is (Nd 0.403 La 0.118 Ce 0.114 Pr 0.093 Y 0.064 Sm 0.064 Mn 0.052 Gd 0.048 Eu 0.020 Dy 0.019 Fe 0.013 Tb 0.003 Er 0.001 ) 1.012 (V 0.981 As 0.020 Si 0.006 ) 1.007 O 4 on the basis of O = 4. The calculated density is 4.782 g/cm 3 . Microtexture and co‐existing relationship between wakefieldite‐(Nd) and caryopilite suggest that recrystallization and dehydration of Fe‐ and Mn‐oxyhydroxide led to the generation of hematite, caryopilite, rhodochrosite and wakefieldite‐(Nd) by the metamorphism during the accretion of the host unit of the Arase deposit. Chondrite‐normalized REE pattern of the host ferromanganese ore, which is regarded as oceanic metalliferous sediment in origin, shows negative Ce anomaly. Chemical composition of wakefieldite‐(Nd) reflects Ce‐depleted bulk composition of REE‐enriched ferromanganese ore.