Plutonic And Metamorphic Rocks

Radium and radon in ground water in the Chickies Quartzite, southeastern Pennsylvania

“…Frequency of water-bearing zones decreases with depth, ard no zones are reported at depths greater than 400 ft below land surface, although data are limited b^low 400 ft. This analysis supports the model of a shallow, local flow system in the Chickies Quartzite similar to other geologic units in the Piedmont (Trainer, 1988). The data do not preclude groundwater flow at depths greater than 400 ft. …”

Hydrogeologic framework and hydrologic budget components of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

“…The latter conditions may be important in the study area because of the existing tectonic stress that would tend to decrease fracture openings. Previous studies of well yields in crystalline rocks indicate networks of open joints are found principally within 300 to 500 ft of the surface and decline lognormally with increasing depth (Trainer, 1988). Trainer also reported that K h values for crystalline rocks range from 3 × 10 -6 to 0.3 ft/d.…”

“…K h values for fractured metamorphic and igneous rocks can be five orders of magnitude larger than for unfractured rock (about 0.001 to -1 ft/d). Joints within crystalline rock are of limited lateral extent but are numerous enough to increase permeability locally, and such fractures are commonly tighter and less abundant with increasing depth owing to the state of stress in the earth's crust (Trainer, 1988). The latter conditions may be important in the study area because of the existing tectonic stress that would tend to decrease fracture openings.…”

Analysis of the results of hydraulic-fracture stimulation of two crystalline bedrock boreholes, Grand Portage, Minnesota

“…Shallow bedrock formations usually are extensively fractured and weathered even where boreholes in such rocks are not very productive. Furthermore, near-surface ground water has low dissolved mineral content and vertical stress associated with the overburden is small, so fractures do not seal with mineralization (Trainer, 1987). In addition, packer spacings used in water-well stimulations tend to be greater than 10 ft or involve the entire open borehole below a single packer.…”

“…Fractured crystalline basement rocks provide an important source of drinking water for many regions in North America (Trainer, 1987). There is also great interest in predicting the movement of contaminants accidentally introduced into aquifers in fractured crystalline rock (Vernon and others, 1993).…”