Petrogenesis of Diamonds in Ureilites
Abstract
Currently
there are twenty some specimens of ureilite meteorites which have crashed into
Earth. These meteorites are particular because of their lack of low temperature
minerals and the diamonds that can be found in some of them. The origins of
these diamonds are under great scrutiny since the 1960's. Three major hypotheses
have come to the forefront of this debate. Vdovykin (1963) who stated that they
were the result of asteroids colliding into one another in space submitted first
hypothesis. John Berkley, who feels that it is completely up to the petrogenesis
of the ureilite parent body magma that created these diamonds bearing ureilite,
submitted the second hypothesis in the 1980. Finally, the hypothesis mostly
supported by Goodrich (2002). She believes that the diamonds that are present in
ureilite are the direct cause of shock impacts when the meteorites crashed into
earth. While these are three of a host of hypotheses, these have come to the
forefront because of the evidence that they have been able to provide. Currently
there are twenty some specimens of ureilite meteorites which have crashed into
Earth. These meteorites are particular because of their lack of low temperature
minerals and the diamonds that can be found in some of them. The origins of
these diamonds are under great scrutiny since the 1960's. Three major hypotheses
have come to the forefront of this debate. Vdovykin (1963) who stated that they
were the result of asteroids colliding into one another in space submitted first
hypothesis. John Berkley, who feels that it is completely up to the petrogenesis
of the ureilite parent body magma that created these diamonds bearing ureilite,
submitted the second hypothesis in the 1980. Finally, the hypothesis mostly
supported by Goodrich (2002). She believes that the diamonds that are present in
ureilite are the direct cause of shock impacts when the meteorites crashed into
earth. While these are three of a host of hypotheses, these have come to the
forefront because of the evidence that they have been able to provide.
 |
Berkley, (1980) Example of the Parent Body Magma's pressure and temperature and Composition at different levels
|
|
Composition
–I:
High in FeO/MgO <80 mol%
of Forsterite
–II:
Intermediate in FeO/MgO 80 – 90 mol% of Forsterite
–III:
Low FeO/MgO <90 mol% Forsterite
|
|
 |
 |
 |
| Weakly shocked Euhedral graphite crystal, no diamonds were present. | SEI of diamonds surrounded by graphite. | Enhanced SEI of diamonds surrounded by graphite. |
|
Images from Goodrich Et al (2002) |
||
References
Aoki, Y., Nakamuta, T., 2001. Catalytic High Pressure Formation of Diamond in Ureilites. 64th Annual Meteoritical Society Meeting.
Berkly, J., Taylor, G., Keil, K., Harlow, G., Prinz, M., 1980. The Nature and Origin of Ureilites. Geochimica et Cosmocimica Acta, Vol. 44 No. 10, 1579-97.
Bischoff, A., Grund, T., Goodrich, C.A., Shock Induced Origin of Diamonds in Ureilites. Lunar and Planetary Science, XXX, Abstract# 1100, Lunar and Planetary Institute, Huston (CD-ROM).
Clayton, R., Mayeda, T., 1988. Formation of Ureilites by Nebular Processes, Geochimica et Cosmocimica Acta, Vol. 52 No. 5, 1313-8.
Fisenko, A., Semjonova, L., 2001. Estimation of Shock Pressure for Ureilites from the Contents AR and XE in Diamonds. Lunar and Planetary Science, XXXII, Abstract# 1678, Lunar and Planetary Institute, Huston (CD-ROM).
Ikeeda, Y., Kita, N., Morishita, Y., Shimonda, H., Togashi, S., 3003. Timing of Basaltic Volcanism in Ureilites Parentbody Inferred from the 26Al Ages in Plagioclase Bearing Clasts in DAG-319 Polymict Ureilite. Lunar and Planetary Science, XXXIV, Abstract# 1557, Lunar and Planetary Institute, Huston (CD-ROM).
Vdovykin, G., 1970. Ureilites, Space and Science Reviews, Vol. 10 No. 4, 483-510.
Weir, D., 2003 Dar al Gani 868: Ureilite, olivine pigeonite group. <http://www.geocities.com/dgweir/DAG868.HTM>
Weir, D., 2003 Kenna: Ureilite, olivine pigeonite group. <http://www.geocities.com/dgweir/KENNA.HTM>