|Name||Tertiary intrusive rocks, undivided|
Igneous > Plutonic > Granitic > Granite (Laccolith)
|Comments||McKinney Hills laccolith intrusion is augite-hornblende granite or microgranite with variable amounts of iron-rich olivine that in some samples forms as much as 5 percent of the rock. At Roy's Peak the intrusion is about 950 ft thick. Most abundant type of rock is fayalite microgranite (Maxwell and others, 1967, p. 186-188).|
Henry, C.D. and McDowell, F.W., 1986, Geochronology of magmatism in the Tertiary volcanic field, Trans-Pecos, Texas, in Price, J.G. and others, eds., Igneous geology of Trans-Pecos, Texas: The University of Texas at Austin, Bureau of Economic Geology Guidebook 23, p. 99-122.
Maxwell, R.A., Lonsdale, J.T., Hazzard, R.T., and Wilson, J.A., 1967, Geology of Big Bend National Park, Brewster County, Texas: The University of Texas Bureau of Economic Geology Publication 6711, 320 p.
Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000.
|Counties||Brewster - Culberson - Jeff Davis - Presidio|