I don't have the answer to this...I'm actually posting this to get help from my geoscience blogging colleagues. Lab Lemming and/or Thermochronic, in particular, might have some good leads for me.
This is a question that I've been pondering this evening as I write up this last chapter on some detrital zircon data. We are looking at sedimentary rocks that were deposited in the Late Cretaceous (spanning from ~85 to 70 million years ago). The source area for this basin was an active continental arc. There's a boatload of volcanic and volcaniclastic grains in the sandstones and we are finding zircons that are only slightly older than the suspected depositional age. Furthermore, we are finding populations of nearly concurrent zircons as we go up through the stratigraphy. That is, the next younger formation includes a population of zircons younger than the depositional age of the formation below it. This is a pattern that is being found in other arc-sourced detrital records as well.
One issue is that the biostratigraphic control is poor and we don't have any ashes for absolute dating. The detritals are actually helping constrain the timing of deposition.
This made me wonder ... just how quickly can a zircon go from crystallization in an arc pluton to being a grain of sediment? Or, put another way, what is the age of the Earth's youngest exhumed pluton? This seems like one of those things that other geologists probably know off the top of their head. Along those lines, how common is it for zircons that crystallize at depth to be transported to the surface via volcanism?
Any references, resources, papers, etc. appreciated.
UPDATE: Ron found a paper discussing a ~1 million year-old exhumed pluton in Japan (see full citation in comments below). This is the winner so far.
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