REE geochemical characteristics of apatite, sphene and zircon from alkaline rocks
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The accessory minerals apatite and sphene are the main carriers of REE in alkaline rocks. Their chondrite-normalized REE patterns decline sharply to the right as those of the host rocks. In the patterns an obvious negative Eu anomaly and a positive Ce anomaly can be seen in apatite and sphene, respectively. Zircon from alkaline rocks is different in REE pattern, i. e., a nearly symmetric “V” -shaped pattern with a maximum negative Eu anomaly. Compared with the equivalents from granites, apatite, sphene and zircon from alkaline rocks are all characterized by higher (La/Yb)n ratio and less Eu depletion. As to the relative contents of REE in minerals, apatite, sphene and zircon are enriched in LREE, MREE and HREE respectively, depending on their crystallochemical properties.
KeywordsHost Rock Alkaline Rock Nepheline Syenite Enrichment Ratio LREE Enrichment
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