How did quartz vein get into the gabbro-diorite?

Oct 12, 2021
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I recently visited the cliffs on the northeastern side of Isle au Haut in Maine and discovered gabbro-diorite rocks with, what looked like, veins of quartz (from 1/2" - 2" wide) running through them. I'm curious about how did the quartz vein happen? diorite with quartz.jpg
 

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