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Measurements of Nd, Sr, and O isotopes were made on whole-rock Great Valley sandstones in order to determine the extent to which isotopes preserve the composition and weathering history of tectonically active sources. Previous work has shown that the Nd isotopic composition of sedimentary rocks provides an accurate record of the source and can be used to evaluate the effect of weathering and diagenesis on Sr-O isotope systematics. Variations in the whole-rock Nd, Sr, and O isotopic compositions are similar within and between petrofacies; this suggests that the isotopic composition is controlled by provenance. The Nd-Sr isotopic compositions are sensitive to the large west-east variation in crust formation ages of the igneous and metasedimentary components. The sandstones decrease from +7 to −5 in εNd and increase from 0.7045 to 0.7073 in 87Sr/86Sr with decreasing stratigraphic age. These values nearly encompass the range observed in the plutonic rocks and suggest that the Nd-Sr isotopic composition of the arc is preserved in the sandstones. In contrast, δ18O decreases from +19 to +9 with decreasing stratigraphic age; these values are significantly higher than δ18O values in the volcanic/plutonic arc source. Isotopic and petrographic variations are correlated; with increasing proportions of sedimentary and metasedimentary lithic fragments, values of εNd decrease, and values of 87Sr/86Sr and δ18O increase. The sedimentary and metasedimentary components decrease the whole-rock value by two to four εNd units and by one to 10‰, depending on the fraction and lithology of the recycled component. The metasedimentary component has a significantly lower Sr concentration than the igneous component and therefore has a smaller effect on the whole-rock 87Sr/86Sr value. Subtraction of the sedimentary-metasedimentary component from the whole-rock sandstone compositions yields igneous isotopic compositions that are directly comparable to the composition of the arc source. Calculated igneous compositions of the sandstones decrease in εNd from +7 to −5 with decreasing stratigraphic age and indicate that sediment sources were located at the eastward-migrating volcanic front. However, the calculated igneous components are +1 to +7‰ higher in δ18O than the igneous source. The high δ18O values are a measure of alteration of the source; increasing alteration in δ18O is correlated with increasing values of CIA. This suggests that high mechanical erosion rates of tectonically active sources do not preclude significant chemical weathering.

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