Supporting Information to Härtel et al. (2022),, Geochemistry, Geophysics, Geosystems (Multi-band Raman analysis)
Four zircon Raman bands were previously calibrated to give consistent estimates of the accumulated self-irradiation α-dose in unannealed volcanic samples. Partial annealing of radiation damage produces inconsistent values because the relative annealing sensitivities of the different bands differ from their relative accumulation rates. The damage estimate based on the external rotation band (DER) is the most sensitive and that based on the internal bending mode, ν2(SiO4) (D2), is the least sensitive to annealing. The D2/DER-ratio thus provides an estimate of the extent of annealing that a zircon sample has experienced. Further, it characterizes its Raman age and thermal history but also its state of radiation damage during its geologic history—and therefore—the manner in which this state influences other thermochronologic methods. Meaningful interpretation of the thermal signal and of the zircon Raman age requires that the spectra are free of measurement artifacts. The major artifacts result from micrometer-scale gradients of the damage densities within a zircon grain due to uranium and thorium zoning. The sampled volume may span different densities, producing overlapping spectra, causing apparent peak broadening, overestimated damage densities, and zircon Raman ages. The D3/D2-ratio calculated from the ν3(SiO4) and ν2(SiO4) bands, most and least affected by the overlap, is an efficient indicator of a meaningless signal. It reveals overlap in annealed and unannealed samples, because the ν2(SiO4) and ν3(SiO4) bands have similar responses to annealing. Multi-band Raman maps can be converted to damage-ratio maps for screening zircon mounts and for selecting suitable spots for thermochronologic investigations.
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Supplemental Material to "Multi-band Raman analysis of radiation damage in zircon for thermochronology: Partial annealing and mixed signals" Supplement Texts S1, S2, and S3 Figures S1, S2, S3, and S4 Tables T1 and T2
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Supplemental material to "Multi-band Raman analysis of radiation damage in zircon for thermochronology: Partial annealing and mixed signals" (Technische Universität Bergakademie Freiberg, 2021)This supporting information contains the sample informations on the Myanmar data used in the main text, and the backgrounds of the modeling approach used for the inset in Figure 5.