PDF Publication Title:
Text from PDF Page: 281
REE Mineralogy and Resources Chapter 279 245 (Manheim and Gulbrandsen, 1979; Trappe, 1998). Some sedimentary phos- phorite deposits are biogenic and are derived mainly from excrement of sea- birds (guano: island deposits in Fig. 46). Most of the world’s guano deposits have been already mined out, and the current resource is much smaller than that of the other sedimentary phosphate deposits. Igneous apatite deposits are often associated with carbonatites and/or alkalic (silica deficient) intru- sions which generally occurred in Paleozoic age (Notholt, 1979). Igneous apa- tite rocks are mainly exploited in Russia, the Republic of South Africa, Brazil, Sweden, Finland, and Zimbabwe (Fig. 46). Commercial apatite ores vary in grade from over 37% P2O5 to less than 25% P2O5 (Van Kauwenbergh, 2010). Although present resources of apatite rock are large, the general high demand has over the years lead to a progressive depletion of high-grade ores and ores of good quality with few contaminants. The economic grade of a sizable igneous apatite deposit is now 4–5 wt.% P2O5 (Ihlen et al., 2014). The igneous ores are generally lower grade in terms of phosphate content compared to sedimentary ones, but give higher quality beneficiation products with low contents of unwanted impurities (eg, Cd, As, U, Th, Mg, and Al). Depending on their origin (igneous or sedimentary), apatite rocks have different mineralogical, textural, and chemical characteristics (Van Kauwenbergh, 2010). As mentioned earlier, one of the significant differences is the variety of apatite-group minerals occurring from each origin: francolite predominates in sedimentary apatite rocks, while fluorapatite predominates in igneous apatite rocks. Francolite is defined as apatite that contains significant CO2 with >1% fluorine (McConnell, 1938) and contains CO2 up to 7 wt.% (Van Kauwenbergh, 2010). On the other hand, the fluorapatite associated with igneous source rocks forms at the various stages such as primary magmatic and hydrothermal stages (eg, Ihlen et al., 2014). As mentioned earlier, apatite contains a variety of REE concentrations (several thousand ppm to several wt.%), due to substitution of REEs for Ca in the apatite structure. REE extraction from apatite rocks as by-product of phosphoric acid production would be economically efficient because of the high cost for development of new REE deposits. From this perspective, recently, several evaluations on REE resource potential of apatite rocks are published. For example, Ihlen et al. (2014) investigated the REE resource potential of various apatite deposits in Norway. REE contents in sedimentary phosphate rocks are several ppm at most and those in igneous apatite ores are up to 30% (Table 14), but size of deposits for the former is much larger than the latter. Thus, both types of the apatite deposits are well worth studying as new REE resources for the future. Table 16 shows the variation in chemical analyses of REE-rich apatite grains from some igneous phosphate deposits and prospects. These deposits are accompanied by carbonatite, nepheline syenite, and IOA deposits. It is notable that HREE-rich apatite occur in IOA deposits which are corresponding to “Kiruna-type” deposits. The origin of this deposit type hasPDF 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 |