A geochemical investigation of the Valley Spring gneiss and Packsaddle schist, Llano Uplift, Texas
Billings, Gale K
Rogers, John J. W.
Master of Arts
Samples of the Valley Spring gneiss and Packsaddle schist were taken along two profiles in northern and south-eastern Llano County, Texas. These samples were analyzed for the major oxides, thorium, and uranium. A comparison of the Valley Spring gneiss and Packsaddle schist analyses with analyses of other rock types indicated:. 1) the parent rock of the Valley Spring gneiss could have been granitic or arkosic material: 2) banded amphibolites of the Packsaddle schist were originally mafic tuffs mixed with calcareous sediments; and 3) the parent rocks of the non-banded amphibolites of the Packsaddle schist were iron-rich basaltic material, probably tholeiitic.