Geology and mineralogy of the Ashram Zone carbonatite, Eldor Complex, Québec

摘要: Abstract The Ashram Zone, which is host to the Rare Earth Element (REE) Deposit, occurs within Eldor Carbonatite Complex, Quebec, Canada. complex located Paleoproterozoic New Quebec Orogen (Labrador Trough), and has been subjected greenschist metamorphism folding during Hudsonian Orogeny at 1.75 Ga. To date, consanguineous undersaturated alkaline rocks have not recognized or adjacent complex. It evident that bulk compositions of rocks, essentially magnesiocarbonatites ferrocarbonatites, do represent those liquid compositions, as many are breccias later hydrothermal activity. Zone dominated by diverse textural varieties carbonatite include: fluorite-rich schlieren carbonatites; coarse-to-medium grained granular fine grained, commonly mosaic-textured, quartz-bearing colloform carbonatites. Compositional data provided for minerals present in major rock-forming Ca-Mg-Fe carbonates, fluorite, quartz. carbonates range their compositional evolution from rare dolomite through ferrodolomite magnesian siderite siderite. principal REE-bearing Deposit monazite-(Ce) monazite-(Nd), with lesser amounts bastnaesite-(Ce) bastnaesite-(Nd). minor accessory mineral suite characterized presence apatite, phlogopite, xenotime, Sc- sn-bearing Nb-Ti-minerals (niobian rutile, nioboaeschynite, samarskite), barite, sphalerite, several uncommon, but here relatively abundant, Ba- Ba-Be (bafertisite, magbasite, barylite, betrandite, sanbornite, cebaite), yangzhumingite, cassiterite, galena, pyrite, magnetite potassium feldspar. Pyrochlore absent Nb-Ti oxide assemblage similar found NYF-pegmatites associated F-rich, A-type granitoids. mineralogy compared other carbonatites silicate unique, especially respect abundance fluorite monazite (commonly Nd-enrichment), Ba-Be-enrichment, NYF-type (especially Y-Nb-aeschynite, phlogopite-potassium feldspar quartz-rich residua granitoid characteristics, paucity magnetite, pyrochlore, Sr-bearing carbonates. considered be a late-magmatic-to-hydrothermal F-REE magnesio-to-ferrocarbonatite derived yet unknown antecedents.