Proterozoic Rocks

Metamorphic units-  Several types of metamorphic rocks are found in the range, including quartzo-feldspathic gneiss (figure 3), amphibolitic gneiss, and heavily foliated rocks of granitic, and dioritic origin.  These metamorphics are strongly banded on both cm and meter scale.    The likely protolith of these units is the Union Hills and Alder Groups, which are a series of volcanic (both basaltic and andesitic) and volcanic clastic rocks found in the Transition Zone.

Foliated tonalitic and granodioritc plutons- Foliated intrusive rocks are also found to the north and south of the metamorphics. Though these plutons can contain compositional banding and intense foliation, they are distinguished by their mineralogy and grain size (which is generally coarser than the metamorphics).  These bodies appear to have intruded either during or between foliation forming events as tabular sheets that are elongate along the strike of the S1 foliation.
 
 
 

Figure 3.  Photograph of quartzo-feldspathic gneiss in the southern White Tank Mtns. The gneiss is banded on the cm scale with amphibolitic gneiss.  A Proterozoic pegmatite vein  (right center of view) has locally disrupted and complexly folded the gneiss.
 

Introduction Page
 

Geologic Map

Bedrock Geology Project
         Abstract
         Overview
         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