The Miocene Paine Granite in the Torres del Paine Intrusive Complex,
southern Chile, is an extraordinary example of an upper crustal mafic
and granitic intrusion. The granite intruded as a series of three
sheets, each one underplating the previous sheet along the top of the
basal Paine Mafic Complex. High-precision U/Pb geochronology on single
zircons using isotope dilution-thermal ionization mass spectrometry
yields distinct ages of 12.59 +/- 0.02 Ma and 12.50 +/- 0.02 Ma,
respectively, for the first and last sheet of the laccolith. This age
relationship is consistent with field observations. The zircon ages
define a time frame of 90 +/- 40 k.y. for the emplacement of a
>2000-m-thick granite laccollith. These precise U-Pb zircon ages permit
identification of the pulses in a 20 k.y. range. The data obtained for
the Paine Granite fill the gap between 100 k.y. and 100-1000 yr pulses
described in the literature for crustal magma chambers.