While Austin claims that orthopyroxenes should retain the most argon followed by hornblende an amphibole and finally plagioclase, he provides no references to support this claim. Therefore, IF hypothesis 1 was the only factor influencing the dates of Austin's samples, I would expect the hornblende-rich 'fraction' to provide an older date than the pyroxene- and feldspar-rich 'fractions.
From the online dating pdf discussions, we already know that hypothesis 2 is a likely explanation for Austin's old dates.
To evaluate hypothesis 3, we should look at the crystallization order of the phenocrysts as suggested by Bowen's Reaction Series.
The approximate log scale response of the obvious eye's rods and cones, superimposed on the visible member. These sensory organs respond to light in overlapping spectral bands, just as the ear's hair cells are tuned to respond to competitive bands of sound frequencies. The human eye sees a cumulative range of frequencies of light, aka, the visible spectrum. Like the ear, the eye has expanded cells rods and cones that detect light in broken but overlapping frequency bands. The visible spectrum extends from about THz deep red to THz deep seated [ 3 ].