Oxygen-isotope evidence for recycled crust in the sources of mid-ocean-ridge basalts

Article Abstract:

Mid-ocean-ridge basalts (MORBs) are geochemical varied, occurring in several physical settings. They are thought to form by partial melting of a globally extensive reservoir of ultramafic rocks. The variations may reflect recycling of subducted crustal materials into the source reservoir. Certain ratios of MORBs are linked to aspects of their incompatible-element chemistry.

Basalt, Mid-ocean ridges

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Oxygen isotope evidence against bulk recycled sediment in the mantle sources of Pitcairn Island lavas

Article Abstract:

A study of oxygen isotopes suggests that sediment does not survive subduction zone conditions. An oxygen isotope equilibrium exists between olivine phenocrysts and plagioclase as revealed by the studies of phenocrysts from basalts from Pitcairn Island, in the Southeast Pacific Ocean. Possible causes for the differences in the results of the study and analysis of Pitcairn seamount glasses are discussed.

Analysis, History, Oxygen, Oxygen isotopes, Sediments (Geology), Pitcairn

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Oxygen isotope evidence for slab-derived fluids in the sub-arc mantle

Article Abstract:

Silicate glass inclusions are derived from a source rich in material from the subducted oceanic crust, according to oxygen isotope data from inclusions taken from mantle olivine samples in an island-arc location. The trace element contents of the phonolitic glasses have a number of distinctive features, including enrichments in Rb and B in relation to mid-ocean-ridge basalts. There is no observational reason for dismissing the existence of highly depleted, extensively metasomatized peridotites in the sub-arc mantle.

Chemical oceanography, Submarine geology, Marine geology

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