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2010 Annual Science Report

University of Hawaii, Manoa Reporting  |  SEP 2009 – AUG 2010

D/H Measurements in Samples From Mantle Hotspots

Project Summary

The origin of Earth’s water is an open question. We are trying to constrain the origin of Earth’s water by measuring the D/H ratios of glass inclusions inside olivine grains from lavas erupted at the Hawaiian and Icelandic hot spots. The hope is that these glass inclusions retain hydrogen from the deep mantle of the Earth, hydrogen that may preserve the original hydrogen isotopic composition of the Earth.

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

We are continuing to work on samples from the Hawaiian deep drill core. The first round of samples were not as pristine and we had hoped and most of the inclusions were partially recrystallized. Kim Binsted has been preparing a second set of samples from different layers in the core that appear to be better suited for D/H measurements. We will make the next round of measurements in a few weeks.

Thor Thordarson provided us with a suite of samples from Iceland. There were processed by a team of NAI Co-Is and Post Docs over the summer of 2010. Thor then sent a graduate student from his lab to Hawaii to characterize the samples in detail and to carry out ion probe measurements. The samples again were not ideal (we only learn this once we have characterized them). These samples were all partially degassed, as indicated by bubbles in the melt inclusions. We made some D/H measurements of these melt inclusions in September, 2010, but the results were disappointing. We will continue to work on the data from those measurements, and we will try to get better samples, now that we know what can go wrong.

Electron Backscatter Image of Melt Inclusions

(a) Skridufell. Olivine with multiple Cr-spinel inclusions and a larger, crystalline melt inclusion. (b) Háleyjabunga. Inclusion with multiple vesicle-like void spaces. (c) Hrólfsvík. Crystalline texture in inclusion. Note the crystals growing into the large void space and the crack in the host crystal running N-S across the image.