Coupled Sr-O isotope variations as an indicator of source heterogeneity for the Northern peninsular ranges batholith |
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Authors: | R I Hill L T Silver H P Taylor Jr |
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Institution: | (1) Division of Geological and Planetary Sciences, California Institute of Technology, 91125 Pasadena, CA., USA;(2) Research School of Earth Sciences, Australian National University, Po Box 4, 2601 Canberra, Australia |
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Abstract: | Primary
18O values for tonalitic rocks from the San Jacinto Intrusive Complex range from +9.0 to +10.6; initial87Sr/86Sr for the same samples varies from 0.7058 to 0.7076. Rocks with low
18O tend to have higher initial87Sr/86Sr. The majority of samples have a limited range of
18O values (+10.0–+10.4) that is anticorrelated with colour index; this variation is compatible with crystallization of rocks with varying mineral abundances from an homogeneous (for oxygen) reservoir. More mafic rocks show a large range of
18O values, reflecting original variations in source material compositions. The combined Sr-O isotope data demonstrate that three or more distinct components were involved in the genesis of these rocks; these three components are also seen in batholithic rocks from the Mojave Block and Sierra Nevada to the north. These data are interpreted as indicating a 0–35% (oxygen atom basis) contribution to the San Jacinto rocks from an old continental lithosphere source.Division Contribution No. 4064 |
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