Samples from 39 dikes and 11 other intrusive bodies of the Monument dike swarm in central Oregon were analyzed by instrumental neutron activation analysis. All but two of the dikes have distinctive trace element compositions that clearly identify them as possible sources for the basalt flows at the Picture Gorge type section and equivalent or stratigraphically lower flows elsewhere in the region. The correlations are supported by paleomagnetic polarity measurements and by major element analyses of nine of the samples.

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