Primitive oxygen-isotope ratio recorded in magmatic zircon from the Mid-Atlantic Ridge
MetadataShow full item record
The oxygen-isotope composition of the Earth's upper mantle is an important reference for understanding mantle and crust geochemical cycles. Olivine is the most commonly used mineral for determining the influence of crustal processes on the oxygen-isotope ratio (d18O) of primitive rocks, however it is an uncommon mineral in continental crust and readily alters at or near Earth's surface. Here we report the first measurements of oxygen-isotope ratios in zircon from oceanic crust exposed at a mid-ocean ridge. Measurements of d18O and trace elements were made by ion microprobe on zircon in polished rock chips of gabbro and veins in serpentinized peridotite drilled from the Mid-Atlantic Ridge. The zircon grains contain both oscillatory and sector growth zoning, features characteristic of magmatic zircon. Values of d18O (zircon) = 5.3 ± 0.8‰ (2 st. dev., n = 68) for the population are consistent with the interpretation that these grains are igneous in origin and formed in high-temperature isotopic equilibrium with mantle oxygen. The d18O values demonstrate that zircon in oceanic crust preserves primitive d18O in spite of sub-solidus alteration of the whole rock. The fact that the primitive d18O (zircon) values fall in a narrow range (5.3 ± 0.8‰) strengthens the use of oxygen isotopes in zircon as a tracer to identify processes of exchange in a wide range of modern and ancient crustal environments, including subducted oceanic crust (eclogite), and also in the oldest known pieces of Earth, >3900 million-year-old detrital zircon grains from Western Australia.
Showing items related by title, author, creator and subject.
Bouvier, L.; Costa, M.; Connelly, J.; Jensen, N.; Wielandt, D.; Storey, M.; Nemchin, Alexander; Whitehouse, M.; Snape, J.; Bellucci, J.; Moynier, F.; Agranier, A.; Gueguen, B.; Schönbächler, M.; Bizzarro, M. (2018)The formation of a primordial crust is a critical step in the evolution of terrestrial planets but the timing of this process is poorly understood. The mineral zircon is a powerful tool for constraining crust formation ...
Proterozoic crustal evolution of the Eucla basement, Australia: Implications for destruction of oceanic crust during emergence of NunaKirkland, Chris; Smithies, R.; Spaggiari, C.; Wingate, M.; Quentin de Gromard, R.; Clark, Christopher; Gardiner, Nicholas; Belousova, E. (2017)The crystalline basement beneath the Cretaceous to Cenozoic Bight and Eucla Basins, in Western Australia has received comparatively little attention even though it lies on the eastern margin of one of the most mineral ...
The burning heart - The Proterozoic geology and geological evolution of the west Musgrave Region, central AustraliaHoward, H.; Smithies, R.; Kirkland, Chris; Kelsey, D.; Aitken, A.; Wingate, M.; Quentin de Gromard, R.; Spaggiari, C.; Maier, W. (2015)The Musgrave Province is one of the most geodynamically significant of Australia's Proterozoic orogenic belts, lying at the intersection of the continent's three cratonic elements - the West, North and South Australian ...