Abstract: Metamorphic zircon is the most commonly used mineral to constrain the age and duration of metamorphic events for its host rocks. Metamorphic zircon can form through new growth or modification of inherited domains under different metamorphic conditions. New growth zircon occurs as new crystals or overgrowth rims around older inherited cores and shows no, weak, sector, fir-tree, or planar zoning, while the recrystallization and replacement generally obliterate the primary zoning of the preexisting zircon, resulting in no or weak zoning with some relict of the protolith oscillatory zoning. Primary mineral inclusions and their compositions are a powerful tool to constrain the formation P-T conditions of metamorphic zircons. Zircons formed under different metamorphic facies possess distinct trace element features because of the effect of the concurrent metamorphic minerals. The link between metamorphic zircon and P-T conditions can be established by rare earth element partitioning between coexisting zircon and garnet and the Ti-in-zircon thermometer. Recrystallized zircons can retain the pristine Hf—O isotope fingerprints, while the fluid-induced replacement zircons show disturbed O isotopes. The Hf isotope compositions of metamorphic growth zircon are dictated by the formation mechanism. Metamorphic growth zircon has δ18O values identical to or different from those of the protolith zircon, depending on whether the protolith has experienced hydrothermal alteration under high or low temperature conditions. An integrated study is crucial to constrain the genesis of metamorphic zircon and to provide a petrochronological tool for its host rock.
Publication Year: 2020
Publication Date: 2020-08-12
Language: en
Type: book-chapter
Indexed In: ['crossref']
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Cited By Count: 1
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