Source of Magma

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Science  02 Jan 2004:
Vol. 303, Issue 5654, pp. 12n
DOI: 10.1126/science.303.5654.12n

The decay of 187Re and 187Os can be used to trace the source and dynamic evolution of magmas from their origins in the mantle to their crystallization and cooling in the crust. Previous work relied principally on Re/Os ratios of the bulk rock. Gannoun et al. (p. 70) have now measured the Re/Os isotopic ratio in mineral and glass phases from mid-ocean ridge basalts. The different phases yield different ratios, such that some phases can be used to estimate when the minerals crystallized; other phases can be used to determine the source of the magma. Thus, bulk rock ratios might represent a mixed signal, whereas high-precision measurements of individual phases may yield a more complete history of magma dynamics and the evolution of the oceanic and continental crust.

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