The Arizona Geological Survey has just made available a paper on lateritic rare earth element (REE) deposits around the world. There is some potential for these deposits in the southeastern U.S.
The following is from the paper introduction.
Most current research and exploration efforts for REE deposits are focused on primary hard rock
deposits. These include REE mineralization associated with carbonatites, peralkaline igneous complexes, granites, pegmatites and migmatites.
Primary minerals in primary deposits may include bastnäsite, monazite, xenotime, eudialyte, allanite, zircon, apatite, and a variety of more uncommon minerals. Extraction and concentration of REE minerals and metallurgical processing to remove and separate the various REE can be difficult and expensive, and the beneficiation for each deposit may be unique.
In contrast to primary deposits, laterites, those soils formed during intense weathering of bedrock under tropical or sub-tropical (i.e., hot and humid) conditions, are important sources of viable economic mineral deposits. Lateritic weathering results in the breakdown of primary rocks and minerals, and concentration of metals such as aluminum, iron, manganese, nickel, gold, phosphorous, and niobium. Many occurrences of rocks containing these elements had minerals that were difficult or costly to mine or process to obtain these elements; e.g. nickel in olivine and aluminum in mica, clay, and feldspar. Laterization changes the mineralogy and hence how these elements are situated in relation to the bonding of these minerals. Metallurgical methods, mostly developed during the last 50 years, allow economic recovery of these elements from lateritic minerals.
Cocker, M.D., 2014, Lateritic, supergene rare earth element (REE) deposits, in, Conway, F.M., ed., Proceedings of the 48th Annual Forum on the Geology of Industrial Minerals, Phoenix, Arizona, April 30 – May 4, 2012. Arizona Geological Survey Special Paper #9, Chapter 4, p. 1-18.
The paper has some interesting cross-sections showing how these deposits were formed.
The paper may be downloaded for free: