A photo of a Cretaceous dyke intruding into Appalachian-deformed sedimentary rocks deposited in the lower Paleozoic: Earth history from 110 to almost 500 million years ago.

But #kyanite records more of the story: it's part of xenoliths brought to the surface by these dykes that document Grenville crust (1.1 billion years old) at depth.

See: Trzcienski: Kyanite-garnet-bearing Cambrian rocks and Grenville granulites from the Ayer's Cliff, Quebec... Geology (1989)
#MinCup25 #Quebec #Appalachians