Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
Geology Don't get GSW? Talk to your librarian.
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Geology; April 2007; v. 35; no. 4; p. 339-342; DOI: 10.1130/G23092A.1
© 2007 Geological Society of America
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Malkovets, V.G.
Right arrow Articles by Wood, B.J.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Diamond, subcalcic garnet, and mantle metasomatism: Kimberlite sampling patterns define the link

V.G. Malkovets1, W.L. Griffin*,2, S.Y. O'Reilly2 and B.J. Wood2

1 Geochemical Evolution and Metallogeny of Continents, Australian Research Council National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia and Institute of Mineralogy and Petrography, Siberian Branch Russian Academy of Sciences, Novosibirsk 630090, Russia
2 Geochemical Evolution and Metallogeny of Continents, Australian Research Council National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia

A genetic relationship between diamond and subcalcic Cr-pyrope garnet, both being produced by a metasomatic process, can be inferred from the sampling patterns of kimberlites in the Daldyn-Alakit province, Yakutia, Russia. Pressure-temperature estimates for xenoliths and xenocrysts show a strong concentration of highly depleted rocks in a well-defined zone 140–190 km deep; diamond inclusions and diamond-bearing xenoliths show that most diamonds come from harzburgites within this layer. Xenocryst distribution curves indicate that diamondiferous kimberlites have sampled both garnet and chromite from the harzburgitic layer, but low-grade pipes have sampled only chromite. Diamond formation probably is due to the oxidation of methane-rich, silica-bearing fluids: Fe2O3 (in chromite) + CH4 -> C + H2O + FeO (in chromite), accompanied by another reaction: chromite ± olivine ± orthopyroxene + Si, Ca (in fluid) -> low-Ca, high-Cr garnet. The presence or absence of diamond in kimberlites thus reflects the distribution of metasomatized fluid conduits in a lithospheric mantle that originally consisted of highly refractory harzburgites containing neither garnet nor diamond.

Key Words: diamond genesis • subcalcic garnet • mantle harzburgite • mantle metasomatism • Archean mantle




This article has been cited by other articles:


Home page
 J PetrologyHome page
W. L. Griffin, S. Y. O'Reilly, J. C. Afonso, and G. C. Begg
The Composition and Evolution of Lithospheric Mantle: a Re-evaluation and its Tectonic Implications
J. Petrology, July 1, 2009; 50(7): 1185 - 1204.
[Abstract] [Full Text] [PDF]

Home page
 Geological MagazineHome page
S. PATRANABIS-DEB, J. SCHIEBER, and A. BASU
Almandine garnet phenocrysts in a ~ 1 Ga rhyolitic tuff from central India
Geological Magazine, January 1, 2009; 146(1): 133 - 143.
[Abstract] [Full Text] [PDF]

Home page
 Geological Society of America MemoirsHome page
W. B. Hamilton
Earth's first two billion years--The era of internally mobile crust
Geological Society of America Memoirs, January 1, 2007; 200(0): 233 - 296.
[Abstract] [Full Text] [PDF]


JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2009 by Geological Society of America