Hahns Peak, Hahns Peak Mining District (Columbine Mining District), Routt County, Colorado, USAi

Regional Level Types
Hahns Peak	Volcanic Peak (Extinct)
Hahns Peak Mining District (Columbine Mining District)	Mining District
Routt County	County
Colorado	State
USA	Country

Hahns Peak is somewhat of a geographic enigma and physiographers are unable to assign it to a specific mountain range. It seems geologically connected to the Elkhead Mountains to the west rather than the geologically complex Sierra Madre Range (part of the larger Park Range) to the east. The Elkheads are tied to Hahns Peak since both areas have abundant Miocene igneous rocks. Most of the rocks in the Elkhead Mountains are Upper Cretaceous to Tertiary sedimentary rocks crisscrossed by 7.6 to 11.5 Ma igneous rocks occurring as hypabyssal stocks (magma originates within the earth’s crust and starts toward the surface but ends up cooling before reaching the surface), sills (igneous rocks intruded parallel to the bedding), and dikes (igneous rocks intruded at an angle to the bedding). Intrusive rocks in the Elkhead Mountains are mostly alkaline (usually high in potassium and sodium) forms of such rocks as basalt and rhyodacite and their coarse-grain equivalents. Around Hahns Peak the igneous rocks are more felsic in nature, that is, the rocks are enriched in silicate minerals. At Hahns Peak itself the stock is composed of quartz latite, now partially hydrothermally altered to a porphyritic rhyolite. What this means is that the main unit at the center of Hahns Peak has a fine groundmass with large feldspar phenocrysts.