scholarly journals Major oxide analyses, CIPW norms, modes, and bulk specific gravities of plutonic rocks from the Mariposa 1 degree by 2 degrees sheet, central Sierra Nevada, California

1984 ◽  
Author(s):  
P.C. Bateman ◽  
F.C. Dodge ◽  
P.E. Bruggman
Keyword(s):  
Sierra Nevada ◽  
Major Oxide ◽  
Plutonic Rocks

A petrologic and Rb–Sr isotopic study of intrusive rocks near Fairbanks, Alaska

1985 ◽  
Vol 22 (9) ◽  
pp. 1314-1321 ◽  
Author(s):  
Joel D. Blum
Keyword(s):  
Trace Element ◽  
Shallow Depth ◽  
Early Paleozoic ◽  
Uplift Rate ◽  
Isotopic Study ◽  
Crustal Rocks ◽  
Late Proterozoic ◽  
Intrusive Rocks ◽  
Major Oxide ◽  
Plutonic Rocks

Epizonal granodiorite and granite plutons intrude the northwestern portion of the Yukon Crystalline Terrane near Fairbanks, Alaska. Mineralogic, major-oxide, and trace-element studies indicate that the plutons represent a comagmatic fractionation suite. A Rb–Sr whole-rock isochron for one pluton yields an age of 90.9 ± 0.9 Ma, in agreement with previous K–Ar dating of biotite and hornblende and an initial 87Sr/86Sr ratio of 0.71238 ± 0.00014. The elevated initial 87Sr/86Sr ratio suggests that the plutons may have had a different source from that of the belt of subduction-related, mid-Cretaceous plutonic rocks found farther to the southeast in the Yukon Crystalline Terrane. In contrast, they appear to have been formed at least in part by anatectic melting of Late Proterozoic or early Paleozoic crustal rocks. Comparison of aplite dike compositions with the synthetic granite system, estimates of average uplift rate, and K–Ar cooling ages of surrounding schists all indicate that the magmas that formed the plutons near Fairbanks intruded much higher into the crust after anatectic melting and crystallized at a relatively shallow depth of 3–5 km.

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