Paleonet: oldest Earth igneous rocks

JAMES STJOHN stjohn.2 at osu.edu
Mon Mar 12 23:42:45 GMT 2007


Alex,

I doubt you'll get a precise answer.  There are lots of "granite"-looking things in the Paleoproterozoic and Archean, but they've have been metamorphosed to some degree, and are still given igneous names (e.g., "lineated granite").  Or, they'll have foliation on a scale coarser than hand samples or coarser even than roadcut scale.

You probably already know the dates of the "oldest ______" on your list (4.03 Ga Acasta Gneiss, 4.404 Ga Jack Hills zircons, 4.55 Ga lunaites & Martian rocks & asteroid belt rocks & possible Mercury rocks, 4.57 Ga CAIs in Allende Meteorite, 4.59 Ga presolar SiC grains, etc.).

Best,

James St. John

stjohn.2 at osu.edu

http://newark.osu.edu/professional/osu/faculty/jstjohn/










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