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Unconventional Resources of Rare Elements:

The Bearing of Source and Process on the Genesis of Residual Deposits

Table of Contents

Project Objectives

1. To quantify the favorable factors for the enrichment of rare earth elements, In, Ga, and W in residual deposits associated with weathered granitoid rock suites, especially those predicted to have high heavy-rare-earth-elements
2. To establish the behavior of the rare elements during weathering of various igneous rock suites
3. To develop methods and models that can be used in the evaluation of the domestic potential for rare earth elements, Ga, Sn, and W and other metals in residual deposits.

Relevance and Impact

There is considerable controversy regarding rare earth elements-Ga-In-Sn-W in residual deposits. For
example (Wu et al. 1996, Sanematsu et al. 2011, Bao and Zhao 2007, Mentani et al. 2010,
Long et al. 2010):

• source granites have been described as unspecialized, I-type, A-type, highly evolved topaz-bearing, tin-bearing, calc-alkaline, alkaline, peraluminous, and as ilmenite and magnetite-bearing;
• the weathering process and products have been described as deep lateritic leaching resulting in weathered crusts, kaolins, soils, laterites, and/or bauxites and
• the specific mineralogy has been described variously as rare earth elements adsorption on clays, as rare earth elements-carbonate, and rare earth elements in secondary phosphate.

Field Work; Stragtegy and Approach

Field work for this project will include surface sampling of granite, weathered granite, and
soil profiles in the southeastern United States, with the aim of providing a common geologic and geochemical
database for the four constituent task efforts (e.g, Foley, 2012, Bern et al., 2011, Hubbard et al., 2006, Ayuso et al., 2009). Weathering profiles will be studied at complementary field
sites (1) Robertson River batholith, Irish Creek pluton, Virginia, a peraluminous, low-P, A-type
granite of the Blue Ridge province, and 2) a to-be-determined cordierite-almandinebiotite
granite pluton of the Eastern Piedmont province, for example, the Clouds Creek, South Carolina,
or the Stumpy Point, North Carolina, pluton.
Based on a positive outcome of the 1 year's work, the proposed plan is to drill a cored
profile for detailed study at a selected site. The project will utilize state-of-the-art SEM, EMPA, XRD, LA-icpms,
TIMS, total-digest methods for analytical geochemistry, remote sensing techniques, and soil
sampling and characterization methods.
The synthesis of data will be used to develop process-based models for the genesis of rare earth element
ion adsorption clay deposits that incorporate detailed economic geology, igneous petrology,
mineralogical pathways, chemical mass balance, geochemical modeling and remote sensing
components.

• Field work at Virginia sites and submittal of samples from new and legacy sample collections and datasets, plan drilling work;
• Initiate laboratory studies;
• Selection of second site, pending availability of core from Sample Libraries;
• Compilation and analysis of currently available datasets;
• Potential meetings:
  1. Geological Society of America meeting, Charlotte, NC, Nov 2013; paper on the potential for rare earth element ion adsorption clay deposits in the southeastern US.
  2. Joint meeting of the Geological Society of China and the Geological Society of America, Chengdu, China, 17–19 JUNE 2013 (paper/potential field trip to South China deposits).

Soil science activities will incorporate site-specific and regional soil and solute sampling,
characterization and geochemistry with the goal of modeling the role of climate and
weathering mechanisms in the formation of soils enriched in sorbed rare earth elements. FY13 (1) Field
work at VA sites and submittal of samples from new and legacy sample collections and
datasets, (2) Initiate laboratory studies; (3) Compilation and analysis of currently available
datasets; (5) Potential meetings: GSA Denver 2013/Soil conference.