Tertiary intrusive rocks, undivided

Tertiary intrusive rocks, undivided
State Texas
Name Tertiary intrusive rocks, undivided
Geologic age Tertiary
Lithologic constituents
Major
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).
References

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.

NGMDB product
Counties Brewster - Culberson - Jeff Davis - Presidio