ORIGIN AND EVOLUTION OF GRANITES IN THE SANTA CATALINA CORE COMPLEX, ARIZONA

The Santa Catalina Mountains, SE Arizona, was one of the first-described metamorphic core complexes. Despite its status as a type example, relatively little is known about precise ages and origins of the intrusive rocks which make up most of the crystalline core. U-Pb and Hf isotopic data by laser from zircons and whole-rock Nd isotopic results were obtained for 12 granitoids ranging from 1440 to 26 Ma. Results confirm that the 1.44 Ga Oracle Granite extends through the Catalina Range as variably mylonitic granite and banded gneiss. Laramide intrusions (67-72 Ma) display initial ε_Nd values -5 to -8, and ε_Hf from -6.5 to -9. Magmatic ages for the prominent white granite sills of the Wilderness suite are 45 to 57 Ma, in agreement with Terrien et al (in review), and these granites have initial ε_Nd values -8 to -10.5, and ε_Hf from -7 to -13. Lastly, the undeformed Catalina Granite has an age of 26 Ma, with initial ε_Nd and ε_Hf of -6 and -8, respectively. Our Nd results agree with limited results from Farmer and DePaolo (1983). Although the Catalina Granite seems to have a significant juvenile component based on Nd and Hf, most of the Laramide and Wilderness intrusions contain Nd and Hf compositions lying close to the evolution of 1.44 Ga Oracle Granites. This is confirmed by the U-Pb data, which show both 1.7 and 1.4 Ga zircon cores in these samples, with 1.4 Ga as the dominant core age. In order to become the dominant source of most of the 72-45 Ma magmas, the Oracle pluton must not only extend across the whole Catalina region, but also have abundant deep-seated equivalents to provide magma sources.