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Table 3. SHRIMP U-Pb isotopic ages of basement rocks in the field trip area.
Lithologic Unit
Sample
Number
Igneous
Crystallization
Age (Ma)
[± 2 sigma]
Metamorphic
Ages (Ma)
[± 2 sigma]
Inheritance
Ages (Ma)
[± 2 sigma]
low-silica charnockite (Yfqj) SNP-99-93 1050 ± 8 1018 ± 14
Old Rag magmatic suite (coarse-grained leucogranite) (Ygr) OR-97-35 1060 ± 5 1019 ± 15



979 ± 11


1059 ± 8* 1027 ± 9
garnetiferous syenogranite (Ygg) SNP-02-197 1064 ± 7 1028 ± 14 1135 ± 6
1099 ± 9
leucogranite gneiss (Ylgg) SNP-99-90 1078 ± 9 1028 ± 10



997 ± 19
foliated pyroxene granite (Yfpg) SNP-02-177 1117 ± 14 1043 ± 12 1175 ± 14
high-silica charnockite (Ycf) SNP-96-10 1159 ± 14 1052 ± 14
foliated megacrystic leucocratic granite (Ylg) SNP-02-189 1183 ± 11 1110 ± 38
1043 ± 16

* monazite ages indicated by italics; all other ages obtained from zircon.

U.S. Department of the Interior, U.S. Geological Survey
URL: https:// pubsdata.usgs.gov /pubs/circ/2004/1264/html/trip2/table3.html
For more information, contact Richard Tollo
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