Granulite fades Nd-isotopic homogenization in the Lewisian complex of northwest Scotland
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Abstract
A published Sm–Nd whole-rock isochron of 2,920 ± 50 Myr, obtained from a wide range of lithologies in the Lewisian complex of north-west Scotland, was interpreted1 as the time of protolith formation. This date is ∼260 Myr older than estimates for the timing of high-grade metamorphism in the complex at ∼ 2,660 Myr2'3, and this period is considered to represent the duration of the Lewisian crustal accretion-differentiation superevent (CADS)4. Here we give new Sm-Nd data, obtained specifically from granulite facies tonalitic gneisses, that yield a date of 2,600 ±155 Myr. Although depleted-mantle model ages (tDM suggest >200 Myr of premetamorphic crustal residence, the regression date and its associated initial Nd-isotopic parameters demonstrate Nd-isotopic homogenization during the high-grade event, as well as the probability of general rare-earth-element (REE) mobility. Models for selective element depletion in the complex have previously assumed REE immobility since 2,920 Myr, but the data presented here suggest that a reappraisal of the depletion mechanism is required.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Granulite fades Nd-isotopic homogenization in the Lewisian complex of northwest Scotland |
| Series title | Nature |
| DOI | 10.1038/331705a0 |
| Volume | 331 |
| Issue | 6158 |
| Year Published | 1988 |
| Language | English |
| Publisher | Springer Nature |
| Description | 3 p. |
| First page | 705 |
| Last page | 707 |
| Country | Scotland |