Chemical, radiometric, and mineralogic trend surfaces within the Enchanted Rock batholith, Llano and Gillespie counties, Texas
Ragland, Paul C.
Doctor of Philosophy
The quantitative areal distribution of chemical, radiometric, and mineralogic variates within the Enchanted Rock batholith is examined statistically by means of least squares. The resultant partial trend surfaces and deviation maps indicate that the rocks are progressively more basic from the center of the batholith outward. The core of the batholith, however, deviates in composition from the regional trend. Alternative explanations are offered for the crystallization of the batholith and formation of the core. Hypotheses are also proposed to explain the following observations: (1) the heterogeneous distribution of thorium and uranium within the outer zones of the batholith, (2) different systematic chemical trends within the surrounding wall-rocks, and (3) the NW-SE trends and anomalies on the deviation maps. Trend surface analysis of least squares is demonstrated to be applicable to the petrogenesis of a single pluton such as the Enchanted Rock batholith.