Big Branch Gneiss

Big Branch Gneiss
State Texas
Name Big Branch Gneiss
Geologic age preCambrian (Proterozoic)
Lithologic constituents
Major
Metamorphic > GneissGneissic quartz diorite, fine- to medium-grained, gray, heavily contaminated with partly digested remnants of Packsaddle Schist. Locally near Red Mountain, potassium metasomatism produced a quartz monzonite-augen gneiss rich in pink microcline phenocrysts.
Comments intrudes Valley Springs Gneiss and Packsaddle Schist. Present in northeast Gillespe and northwest Blanco Counties. felsic gneiss, gneissic quartz-diorite, mafic gneiss, quartzmonzonite-augen gneiss, hornblende schist, graphite schist
References

Barnes, V.E., 1946, Texas Univ. Bureau of Economic Geology Pub. 4301, p. 56-57.

Bureau of Economic Geology, 1981, Llano sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000.

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 Blanco - Gillespie - Llano