PDF Publication Title:
Text from PDF Page: 257
REE Mineralogy and Resources Chapter 279 221 The fractionation between Ce and other REE is commonly recognized in a weathering profile and numerous studies reported positive Ce anomalies in weathered granitic rocks (eg, Banfield and Eggleton, 1989; Huang et al., 1989; Mongelli, 1993). The positive Ce anomaly results from immobilization as CeO2 by oxidizing from Ce3+ to Ce4+ near the surface because CeO2 is hardly soluble compared with other REE3+ at 25°C under atmospheric pres- sure (Brookins, 1988). Sanematsu and Watanabe (2016) proposed that the weathering profile can be simply divided into a REE-leached zone of the upper part of the profile and a REE-accumulation zone in the lower part of the profile unless the contact zone fluctuates dramatically (Fig. 43). REEs, except for Ce, are scavenged from the leached zone, and they are immobilized by incorporating into secondary minerals or by adsorbing onto weathering products in the accumulation zone during weathering. This migration and fractionation of REEs lead to the negative Ce anomaly in the accumulation zone including ion-adsorption ores (eg, Bao and Zhao, 2008; Chi et al., 2005; Sanematsu et al., 2013; Sanematsu and Watanabe, 2016; Wu et al., 1990; Fig. 44). Aggregates of fine-grained CeO2 commonly occur with feldspars, clays, and Mn oxides in weathered granite, particularly in the REE-leached zone. The significant Ce enrichment in Mn oxides is most likely to result from adsorption and oxidization from Ce3+ to Ce4+ by d-MnO2 (De Carlo et al., 1998; Ohta and Kawabe, 2001). FIG. 43 Schematic model of the genesis of ion-adsorption type REE ore bodies developed on granites (Sanematsu and Watanabe, 2016). Graphs show the typical examples of chondrite- normalized REE patterns of the REE-leached zone, REE-accumulation zone (ion-adsorption ores), and parent granite.PDF Image | HANDBOOK ON THE PHYSICS AND CHEMISTRY OF RARE EARTHS
PDF Search Title:
HANDBOOK ON THE PHYSICS AND CHEMISTRY OF RARE EARTHSOriginal File Name Searched:
Chemistry-Rare-Earths-49.pdfDIY PDF Search: Google It | Yahoo | Bing
Sulfur Deposition on Carbon Nanofibers using Supercritical CO2 Sulfur Deposition on Carbon Nanofibers using Supercritical CO2. Gamma sulfur also known as mother of pearl sulfur and nacreous sulfur... More Info
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |