(2020) The Ferrar Continental Flood Basalt: A ~1.6 Ma Long Duration Evidenced by High-Precision 40Ar/39Ar Ages
Ware B, Jourdan F, Chiaradia M & Nebel O
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06n: Room 2, Wednesday 24th June 23:33 - 23:36
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Are there rocks in the Ferrar province where both zircon U-Pb and plagioclase 40Ar/39Ar dates are obtained? If yes, how do they compare to each other?
Do you have a temperature estimate of the magma evolution? Can the K-Ar systems in plagioclase be closed to record ages before zircon saturation?
Enjoyed your presentation. If you have a 70%-30% mixture of compositionally different plagioclase grains, this should be readily determined by microprobe analyses of your bulk mineral separation - do you observe this? Have you considered a fractionation model for 40Ar relative to 39Ar to explain your climbing spectra? This is commonly observed in sanidine age spectra and it would predict 1-2 Ma age difference from initial heating steps to the final heating steps. This would not predict the differences between the samples, thus I agree you likely are seeing a spread in apparent ages of bulk samples. Lastly, Yuri's question is a good one. You show a model argon loss spectra for a 185 Ma plagioclase. Did you use a reasonable thermal history that would allow dissolution of older zircons, but only minor argon loss?
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