On the Morphology and Geochemistry of Hydrothermal Crypto- and Microcrystalline Zircon Aggregates in a Peralkaline Granite

Singular crypto- and microcrystalline hydrothermal zircon aggregates occur in peralkaline granites from the Corupá Pluton of “A-type” syenites Graciosa Province, Southern Brazil, are herein characterized for their morphological, textural geochemical (major, minor trace elements, Lu-Hf isotopes) properties. The were found to present a variety habits, such as dendritic, oolitic, botryoidal spherulitic, they associated with typical minerals (alkali-feldspars, quartz, fluorite, epidote-group minerals, phyllosilicates Fe oxides) micro-fractures small miarolitic cavities host rock. They precipitated directly fluid and, compared magmatic crystals host, contain relatively high abundances “non-formula” elements (e.g., Fe, Al, Ca) HFSEs (High-Field-Strength Elements), particularly L- MREEs (Light Medium Rare Earth features most zircon, well Th/U ratios, whereas isotopic signatures be similar. formation epidote-groups was probably due interaction between an orthomagmatic, F-bearing, aqueous transporting host-rock and/or external meteoritic country rocks. preservation amorphous-like Zr-silicate compound crypto-to-microcrystalline varieties is arguably related inefficient flux elemental diffusion low-temperature oxidizing environment.