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Mechanisms for the generation of HREE mineralization in carbonatites: Evidence from Huanglongpu, China.The Hunaglongpu carbonatites, Qinling Mountains, China, are exceptional as they form both an economic Mo resource, and are enriched in the HREE compared to typical carbonatites, giving a metal profile that may closely match projected future demand. The carbonatites at the level currently exposed appear to be transitional between magmatic and hydrothermal processes. The multistage dykes and veins are cored by quartz which hosts a fluid inclusion assemblage with a high proportion of sulphate daughter or trapped minerals, and later stage, cross-cutting veins are rich in barite-celestine. The REE mineral paragenesis evolves from monazite, through apatite and bastnäsite to Ca-REE fluorcabonates, with an increase in HREE enrichment at every stage. Radio-isotope ratios are typical of enriched mantle sources and sulphur stable isotopes are consistent with magmatic S sources. However, Mg stable isotopes are consistent with a component of recycled subducted marine carbonate in the source region, The HREE enrichment is a function of both unusual mantle source for the primary magmas and REE mobility and concentration during post-magmatic modification in a sulphate-rich hydrothermal system. Aqueous sulphate is a none specific ligand for the REE, and this coupled with crystal fraction lead to HREE enrichment during subsolidus alteration.
Porphyry Cu(Mo) deposits of the Urals: insights from molybdenite trace element geochemistryThe first data on EMPA and LA-ICPMS study of molybdenite from four porphyry deposits of the South and Middle Urals (Tomino, Mikheevskoe and Benkala porphyry Cu and Talitsa porphyry Mo deposits) are presented. It is shown that most trace elements form mineral inclusions within molybdenite in all the deposits studied; only Re and W are most likely to be incorporated into the molybdenite lattice. Porphyry Cu deposits (Tomino and Mikheevskoe) formed within oceanic arc settings are featured by high contents of Re (mostly over 400 ppm) and low contents of W (<10 ppm) in molybdenite; porphyry Cu deposits from Andean-type geotectonic environment (Benkala) are featured by lower Re content (hundreds ppm) and high contents of W (tens ppm) in molybdenite. Molybdenite from porphyry deposits from collisional setting (Talitsa) has low content of Re and elevated W contents (tens ppm). It is demonstrated that trace element geochemistry of molybdenite is a useful tool to define the source of metal components and the geotectonic environment for porphyry Cu(Mo) deposits.