The White Tank Mountains lie 40 kilometers west of Phoenix Arizona (figure 1)  .   The range is within the basin and Range Physiographic province and they contain tertiary rocks and features commen in the basin and range.  The rangfe also contains Proterzooic metamorphic and igneous rocks that are closely related to the Arizona Transition Zone.
    In the Early Proterozoic, central Arizona lay along an active margin at the southeastern edge of the North America continent.  Continental crust was developed along this margin through magmatism, NW-SE directed compression and accretion.   These events are documented in the White Tank Mountains by the presence of syn-tectonic felsic and intermediate plutons, a penetrative NE-trending foliation, and the folding of this NE-trending foliation.
     The Tertiary-Cretaceous plutons found in the range were probably implaced as part of the widespread plutonism associated with the Larimide orogeny.  The range was brought up to the surface in mid-Tertiary time as part of the lower plate of a detachment fault system (figure 2).  This extension event is documented by a mid-Tertiary foliation, lineation and mylonites in the eastern part of the range and by exposure of the detachment fault itself on the western edge of the range.

 To better understand both the Proterozoic and Tertiary features, we mapped the range at 1:24000 scale.  We used TIMS (Thermal Infrared Multispectral Scanner) and NS001 (an airborne Landsat simulator) imagery to aid in the mapping process.  Hardcopy images were brought in field to help locate lithologic contacts.  Samples from the mapping area were used to obtain thermal spectra and thin section grain counts of the rock units.  This data was used to evaluate the effectiveness of the remote imagery in distinguishing mineralogical differences in the rocks.

Figure 1.  Map of Arizona showing the three geologic provinces, Proterozoic outcrops (in stipple), metamorphic core complexes (in black), and the location of the White Tank Mtns.  [From Alter  1994].


Figure 2.  A diagram showing the stages in the formation of the White Tank Mtn. metamorphic core complex [After Spencer and Reynolds, 1989 and Alter, 1994].   P-T indicators from mylonites in the eastern part of the range indicate that these rocks were 11-14km deep at the onset of extension.  With the shallow dip (~10 degrees) of the fault, this would indicate that the rocks in the range have been transported 40-50 km to the west and 10-15 kilometers up.  This movement would place the original location of the range under the Union Hills, north of Phoenix.



Introduction Page

Geologic Map

Bedrock Geology Project
Proterozoic rock units
Proterozoic Structures
Remote Sensing techniques
References and Acknowledgments

Geology and Web pages by Steven Wood and Stephen J. Reynolds, Dept. of Geology, Arizona State University, Tempe, AZ -- July 1998