ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract This study presents evidence to show that, in addition to preserving U−Pb isotope systematics, refractory zircons also preserve, at least in part, an inherited Sm−Nd isotope component. The zircons analyzed during this study were taken from the Strontian granitoid (NW Scotland). The inner intrusion of this composite pluton is known from a previous study to contain substantial U−Pb zircon inheritance, whereas the outer part has only minor inheritance. Zircons from the inner intrusion were found to have significantly lower εNd425 values than either their host rock, separated apatite or monazite. It is argued that this isotopic disequilibrium is due to the presence of an inherited Sm−Nd isotope component, rather than being due to a post-crystallization disturbance of the zircons. The preservation of inherted Sm−Nd isotopes within refractory zircons implies that they remain closed systems with respect to the diffusion of Sm and Nd (and presumably the other REE) to temperatures in excess of 700°C. The fact that zircons commonly have high Sm/Nd ratios, relative to sialic crustal material, means that the Nd isotopic evolution of inherited zircons will be very different to that of much of the continental crust.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00311198
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