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The initial ratio of strontium-87 to strontium-86 rises systematically from 0.70395 to 0.70662 over the upper 10 percent of the Kiglapait layered intrusion. This ratio is strongly correlated with potassium and rubidium. Contamination, exchange, and magma mixing fail to account for the increase, which is ascribed to the imperfect retention of radiogenic strontium-87 in feldspar-like structural units of the melt inherited from the magma source. These accidents in chemical discrimination persist most readily in anhydrous melts.
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S. A. Morse (1983) studied this question.
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