Sources of Continental Crust: Neodymium Isotope Evidence from the Sierra Nevada and Peninsular Ranges

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Science  08 Aug 1980:
Vol. 209, Issue 4457, pp. 684-687
DOI: 10.1126/science.209.4457.684


Granitic rocks from batholiths of the Sierra Nevada and Peninsular Ranges exhibit initial 143Nd/144Nd ratios that vary over a large range and correlate with 87Sr/86Sr ratios. The data suggest that the batholiths represent mixtures of materials derived from (i) chemically depleted mantle identical to the source of island arcs and (ii) old continental crust, probably sediments or metasediments with a provenance age of1.6 x 109 years. These conclusions are consistent with a model for continental growth whereby new crustal additions are repeatedly extracted from the same limited volume of the upper mantle, which has consequently become depleted in elements that are enriched in the crust. There is little evidence that hydrothermally altered, subducted oceanic crust is a primary source of the magmas.