Abstract:
Formation of the oceanic crust at mid-ocean ridges is a fundamental component of
plate tectonics. A majority of the crust at many ridges is composed of plutonic rocks
that form by crystallization of mantle-derived magmas within the crust. Recent
application of U/Pb dating to samples from in-situ oceanic crust has begun to
provide exciting new insight into the timing, duration and distribution of
magmatism during formation of the plutonic crust1-4. Previous studies have focused
on samples from slow-spreading ridges, however, the time scales and processes of
crustal growth are expected to vary with plate spreading rate. Here we present the
first high-precision dates from plutonic crust formed at the fast-spreading East
Pacific Rise (EPR). Individual zircon minerals yielded dates from 1.420–1.271
million years ago, with uncertainties of ± 0.006–0.081 million years. Within
individual samples, zircons record a range of dates of up to ~0.124 million years,
consistent with protracted crystallization or assimilation of older zircons from
adjacent rocks. The variability in dates is comparable to data from the Vema
lithospheric section on the Mid-Atlantic Ridge (MAR)3, suggesting that time scales
of magmatic processes in the lower crust may be similar at slow- and fast-spreading
ridges.
Description:
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Geoscience 5 (2012): 275-278, doi:10.1038/ngeo1378.
