Today: I offer some photos I took in Boulder Canyon, Colorado, in June. These are all igneous rocks exposed in the Precambrian 'basement' rocks, brought to the surface by the Laramide Orogeny.

Directions: Drive to Boulder; go west up the main canyon into the Rocky Mountain Front Range.

Location map:


Granite pegmatite:


Contact! Granite pegmatite meets granodiorite:


Contact! Granite dike cutting across granodiorite (with one small mafic xenolith):


Contact! Mafic xenoliths afloat in granodiorite:


Put the previous two pictures together, and what do you get? My favorite outcrop of the whole excursion... Contact contact! A granite dike cutting across mafic-xenolith-bearing granodiorite. This would be a good practice photo for introductory level students to establish relative ages of the three different rocks shown:


Contact! More prosaic, but high-contrast... Granite meets basalt:


Epidote vein (Without any good reason, I love the color of epidote):


My Prius parked on the side of Boulder Canyon Drive:

Labels: basalt, colorado, granite, primary structures, prius, travel, xenoliths