(June 9, 2025 at 6:43 pm)Paleophyte Wrote:(June 9, 2025 at 6:15 pm)SubtleVirtue Wrote: how do you date those minerals in the rocks that were erupted?
That depends a little on the exact minerals. For a silica-rich rock I'd look for zircons, titanite, monazite, or other uranium-rich minerals to date by U-Pb and/or potassium-rich minerals (K-feldspar, biotite, hornblende) to date by Ar-Ar and/or Rb-Sr. For a silica-poor rock you have a more limited selection. There are still a few minerals (apatite, baddeleyite, titanite, rutile, and possibly even zircon) that you might be able to get an age from but the selection is more limited and you have to be a little more selective. If you have strong metamorphic overprint that may have reset the ages on your minerals you may need to pass on the trickier silica-poor volcanics in favour of the more robust minerals in the silica-rich rocks.
U-Pb for example; how do you know how much U is in the zircons by dating?
-------
