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摘要
Five lamprophyre dikes (L-1-L-5) intruded Abu Rusheid rocks (cataclastics and monzogranite) in the South Eastern Desert of Egypt along shear zones with NNW-SSE and E-W. The two sets of dikes differ in age, mineralization, and geochemical aspect. The NNW-SSE trending dikes (L-1 and L-2) are polymineralized and dislocate the E-W (L-3, L-4, and L-5) trending dikes. These dikes underwent multistage of hydrothermal processes (ferrugination, fluoritization, kaolinitization, and calcification). They are characterized by common box works (physical trap) filled by incoming mineralization, and their feldspars and micas are relatively altered to clay minerals (chemical trap). From the mineralogical point of view, the cataclastic rocks are rich in base metals (pyrite, sphalerite, molybdenite, chalcopyrite, and galena), radioactive minerals (thorite, uranophane, kasolite, uranothorite), and accessories phases (zircon, xenotime, cassiterite, molybdenite, copper, columbite, and fluorite). L-1 and L-2 lamprophyre dikes contain U minerals (uranophane, kasolite, autunite, and torbernite), Mn-franklinite, woodruffite, xenotime, fluorite, silver, copper, and scheelite. L-3 contains Zn and U minerals, whereas L-4 and L-5 contain Zn minerals only. The source magma producing lamprophyre dikes (L-1 to L-4) are peralkaline to alkaline, whereas L-5 lamprophyres are mainly calc-alkaline in character; they were generated from the mantle and had formed in a post-collision tectonic setting with extensive Ti-rich metasomatism. The average I REE pound content in (L-1 and L-2) lamprophyres is 8006 ppm. REE patterns display clear concave upward pattern of W-type tetrad effect in the REE pattern accompanied by enrichment of the HREE over the LREE and marked negative Eu anomaly due to secondary mobilization of REEs.
- 出版日期2015-11
