A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics

RESOURCESFor significant resources to exist then geologicalfractionation processes will need to have improved onthe inherent crustal abundance. Two commongeochernical processes, hydrothermal activity anddifferentiation by magmatic recystallization, howevertend - for the lanthanides - to oppose each other.Minerals enriched in the lanthanide elementsnevertheless are known[1] and have created lanthaniderich deposits although only a few major commerciallysignificant sources are recognized[2].majormoderateLanthanidesMineral Resources(by tonnage)BastnastteMonaziteLopariteion-adsorptionMinerals containing lanthanides can becategorized, according to total Ln content, as having,• very low Ln concentrations, a group with manycommon rock-forming minerals, or• minor amounts of these elements, not asessential constituents, with ≈200 mineralsknown to have a Ln content of > 0.01 %., orminorpotentialXenotimeApatitesEudialyteBrannerite• major, usually essential - that is structure determining - Ln contents. (Recent listings[3]describe >70 discrete minerals under this heading.)The Ln-elements are the major, structure-determining, elements in some magma-derivedminerals. In one unusual type of deposit the concentration of the Ln-elements has been especiallyenhanced. Carbonatite magmas form when mantle rocks melt deep in the earth's crust with largeamounts of carbon dioxide present. This magma type occasionally rises to the surface to producealkaline igneous rocks. If fluoride enters during the ascent specific Ln-fluoride carbonate minerals,e.g. Bastnasite, are formed.Currently the two major sources in the world for the lanthanides are two bastnasitedeposits, one at Mountain Pass, California, U.S.A., the other at Bayun-obo, Inner Mongolia,China. The U.S.A. mine is devoted solely to the Ln's whereas the chinese deposit is minedprimarily for iron ore.[1] The Not-So-Rare Earths, G.KMuecke and P.Möller, Sci.Amer., 1988, 258(l), 72[2] Rare Earths, Enter the Dragon, M.O'Driscoll, Industrial Minerals, 1988(11), 21[3] Crystal Structures of Rare-Earth Minerals, R. Miyawaki and I. Nakai, Rare Earths (publ. Jpn. Rare EarthSoc.), 1987, 11, 1 : Mineralogy of the Rare Earth Elements, A.M.Clark, in Rare Earth Element Geochemistry,ed. P. Henderson, publ. Elsevier, 1984, 133