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Geochemical and mineralogical characteristics of REE in granite-derived regolith: a model for the Southeast United States

August 27, 2015
Rare earth element (REE) ion-adsorption clay deposits are of global economic importance because they currently supply a significant portion of the world’s annual production of both light (LREE) and heavy REE (HREE). There is considerable ambiguity regarding the origin of
this deposit type: The main criteria include the presence of large, generally granitic, igneous suites; long periods of intense weathering with little subsequent erosion; and evidence for mobility of REE within the regolith. Granitic rocks of the southeastern United States have been
subjected to a long history of chemical weathering, comparable to that of South China, an area which contains many REE clay deposits. Detailed comparisons of weathered bedrock-soil profiles for large masses of granitic rocks as exemplified by the Stewartsville, Striped
Rock, and Liberty Hill plutons, USA, indicate that REE are mobile within many regolith profiles and locally can attain grades comparable to mined deposits of South China. Primary accessory mineralogy, modal content, and element redistribution as a result of weathering are
identified as distinguishing factors in mobility-related enrichment of REE in the regolith profiles. Only limited geochemical separation of REE was observed within profiles, which suggests the importance of source rock composition and mineralogy in the initial distribution of
extractable REE in the regolith. Retention of extractable HREE was favored over LREE, Th and U within most of the studied profiles.

Citation Information

Publication Year 2015
Title Geochemical and mineralogical characteristics of REE in granite-derived regolith: a model for the Southeast United States
DOI
Authors Nora K. Foley, Carleton R. Bern, Robert A. Ayuso, Bernard E. Hubbard, Anjana K. Shah
Publication Type Conference Paper
Publication Subtype Conference Paper
Series Title
Series Number
Index ID 70141188
Record Source USGS Publications Warehouse
USGS Organization Eastern Mineral and Environmental Resources Science Center