Zircon from the Bishop Tuff (eastern California) was dated by the U-Pb isotope dilution thermal ionization mass spectrometry (ID-TIMS) method to evaluate time scales of magmatic evolution and applicability of the method to rocks younger than 1 Ma. The~206Pb/238U dates from 17 of 19 grains are equivalent with a weighted mean of 767.1 {\textpm} 0.9 ka that overlaps with the published~40Ar/39Ar sanidine age, requiring that most zircon crystallized immediately before eruption. Dates from two grains that are 6 and 12 k.y. older indicate minimum times that a small portion of the grains resided in the magma. These findings are consistent with chemical zoning patterns in zircon that suggest a relatively simple crystallization history, yet contrast with previous results of ion microprobe dating of zircon that show 50{\textendash}80 k.y. of magma residence. The weighted mean~207Pb/235U date is \~{}52 k.y. older than the~206Pb/238U date, a difference that is attributed to excess~207Pb from initial Pa/U disequilibrium. The results demonstrate that high-precision ID-TIMS geochronology can resolve magma chamber dynamics of \<1 Ma silicic eruptions at the millennial scale.
}, year = {2007}, journal = {Geology}, volume = {35}, pages = {1123-1126}, month = {12/2007}, url = {https://doi.org/10.1130/G24017A.1}, doi = {10.1130/G24017A.1}, language = {eng}, }