Effectiveness of Geologic Characterization Techniques, Climax Granitic Stock, Nevada Test Site

Abstract

Several different techniques were used to characterize the structural geology of the quartz monzonite unit of the Climax Stock. This study examined major geologic structural features and yielded detailed data on over 1,500 fractures. The data were used to identify joint sets, faults and shear zones as well as to statistically analyze joint frequencies and spacings. Eight joint sets, three major shear sets, and a fault zone were studied. The results of previous geologic characterization work performed by many other investigators were compared with the results of our studies. These data provided the basis for evaluating how effective various techniques were in describing the structural geology of the Climax Stock. The specific techniques that were evaluated included the use of unoriented diiamond drilled core, mappoing of only major fractures within the drifts, detailed mapping using modified scan-line techniques, data reduction techniques to account for orientation biases, and surface trench mapping. The results of this study identified several issues for consideration during characterization studies. Firstly, geologic structural features that are often assumed to be uniform and continuous were shown to change characteristics within very short distances. Secondly, we demonstrated that when applied properly to an adequate data set, orientation bias correctionmore » techniques were effective in identifying all fracture sets. Thirdly, we demonstrate that unless three nearly equal length orthogonal surfaces are mapped, interpretations of spacing or of joint prevalence can be misleading. Finally, we demonstrate the usefulness of mapping only isolated and limited sized areas in detail with more general or reconnaissance mapping of the entire facility to tie the detailed map sections together and to identify major features. 10 refs., 23 figs., 2 tabs.« less