Magmatic fluids and skarn mineralization: the Burdigalian As-W skarn at Karezas (Edough Massif, NE Algeria)

摘要

The tungsten mineralization at Karezas resulted from the overprinting of a first generation of reducing, barren skarn, by a series of hydrothermal fluids with a strong magmatic fingerprint, leading to the formation of the fluorite-scheelite-loellingite-Li-micas association typical of the second generation of "greisenised" skarn. The former skarn probably resulted from high-temperature fluid-rock interactions at the end of the tec-tonothermal event responsible of the emplacement of the Edough metamorphic core complex. The latter skarn is likely related to the shallow-level emplacement of a highly specialised granite cupola and the unmixing a Li-F-As-W-rich magmatic fluid. This fluid, in turn, underwent a complex history of phase separation and mixing with metamorphic-derived fluids enriched in CH_4 and N_2, eventually leading to the deposition of scheelite.