Zircon and whole-rock Zr/Hf ratios as markers of the evolution of granitic magmas: Examples from the Teplice caldera (Czech Republic/Germany)
| Authors | |
|---|---|
| Year of publication | 2017 |
| Type | Article in Periodical |
| Magazine / Source | Mineralogy and Petrology |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1007/s00710-017-0509-z |
| Keywords | Zr/Hf value; Zircon; Teplice caldera; Rhyolite; Rare-metal granite; Cinovec deposit |
| Description | Hafnium contents and Zr/Hf ratios were studied in zircons and their parent rocks from three magmatic suites associated with the Teplice caldera, Eastern Erzgebirge: rhyolite and dacite from the peraluminous Schonfeld Unit, relatively younger A-type Teplice rhyolite, and post-caldera A-type biotite and zinnwaldite granite and greisen. New data suggest that zircon crystallizing from a geochemically less evolved volatile- and water-poor melt is, compared to the host rock, relatively Hf-depleted, while zircon crystallizing from an evolved volatile- and water-rich melt has a Zr/Hf value approximately identical to that of the parental melt. Zr/Hf values in zircon did not change substantially either during greisenization, or during low-temperature alteration after metamictization. Zr/Hf values in the whole rock may serve as a sensitive indicator of magmatic fractionation of evolved granitic melts, as they are only negligibly influenced by the following hydrothermal processes. Zr/Hf values in individual cogenetic zircon grains are scattered but their general evolution trend in the rock series is consistent with the evolution of the whole-rock Zr/Hf values. |
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