Timing of Deformation, Metamophism and Plutonism
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Timing of deformation and regional metamorphism is bracketed by protolith ages of the metamorphic rocks and undeformed plutonic rocks; timing is further defined by metamorphic ages. |
 Extensive U/Pb zircon dating of protoliths in the eastern uplift and minor dating in the western uplift yields ages of 1366-1232 Ma for the Valley Spring domain (VSD), 1274-1238 Ma for the Packsaddle domain (PSD), and 1326-1275 for the Coal Creek domain (CCD). Late granites range from 1126-1070 Ma; the oldest are syn-tectonic whereas the younger ones are post-tectonic. For more information, see Mosher (1998); Reese et al. (2000); Roback (1996); and Walker (1992). |
Published U/Pb metamorphic ages on zircon, rutile, titanite and monazite (above) and other unpublished data indicate that regional metamorphism occurred between ~1147 and 1115 Ma, with subsequent metamorphism related to intrusion of late granites. The CCD yields an older metamorphic age as well. For more information see Mosher (1998); Roback (1996 a & b), Rougvie et al. (1996) and Hoh (2000). |
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Histogram of published protolith ages. Regional deformation and metamorphism affected all protoliths of the CCD, PSD, and VSD; only the last phase of deformation affected the oldest of the late granites. Thus most regional deformation and metamorphism occurred between 1232 and 1119 Ma; metamorphic ages narrow this age range to ~1150 to 1120 Ma. (See Mosher, 1998). |
For more information, see Mosher (1998); Reese et al. (2000); Walker (1992)Roback (1996 a & b), Rougvie et al. (1996) and Hoh (2000).