Tschauner
O., Huang S., Greenberg E., Ma C., Rossman G., Shen A.H.
Bechtel H., Chen B., Zhang D., Dera P., Mewville M., Lanzirotti A.,
Kait K.
1Department
of Geoscience, University of Nevada Las Vegas, Las Vegas, Nevada 89154,
USA.
2
Center of Advanced Radiation Sources, University of Chicago, Illinois
60632,
USA.
3Division
of Geological and Planetary Sciences, California Institute of
Technology,
Pasadena, California 91125, USA.
4Gemological
Institute, China University of
Geosciences, Wuhan 430074, China
5Advanced
Light Source, Lawrence Berkeley
Laboratory, Berkeley, California 94720 USA.
6School
of Ocean and Earth Science and Technology, University of Hawai'i at
Mānoa,
Honolulu, HI 96822, USA.
7Royal
Ontario Museum, 100 Queen’s Park, Toronto, ON M5S 2C6, Canada.
Abstract
We
show that ice-VII
occurs as inclusions in natural diamond. As the residue of aqueous
fluid
present during growth of diamond, ice-VII crystallized upon obduction
of the
host diamonds and remained at pressures around 10 to 23 GPa, much
higher than any
previously known inclusion in diamonds. Ice-VII (now approved as a
mineral species
- IMA2017-029) appears to be common in diamonds and serves as a very
accurate
geobarometer. We report thirteen occurrences, nine of which correspond
to
encapsulation at or below 410 km depth, two at or below 660 km, and two
in the
range 130-180 km. These
inclusions bear
witness of water-saturated conditions near the 410 and 660 km
boundaries and
provide strong support for the presence of water-rich layers in these
regions.