Инд. авторы:	Kiseeva E.S., Yaxley G.M., Stepanov A.S., Tkalčić H., Litasov K.D., Kamenetsky V.S.
Заглавие:	Metapyroxenite in the mantle transition zone revealed from majorite inclusions in diamonds
Библ. ссылка:	Kiseeva E.S., Yaxley G.M., Stepanov A.S., Tkalčić H., Litasov K.D., Kamenetsky V.S. Metapyroxenite in the mantle transition zone revealed from majorite inclusions in diamonds // Geology. - 2013. - Vol.41. - Iss. 8. - P.883-886. - ISSN 0091-7613. - EISSN 1943-2682.
Внешние системы:	DOI: 10.1130/G34311.1; SCOPUS: 2-s2.0-84888808772; WoS: 000323274600017;
Реферат:	eng: The transition zone of the Earth's mantle (the depth interval between two major seismic discontinuities at 410 km and 660 km) is critical to understanding our planet's evolution. Some diamonds are thought to have originated in the transition zone and the inclusions found in them are the only samples of material directly extracted from this depth range. By comparing natural majorite garnet inclusions in diamonds with the compositions of experimentally crystallized majorite garnets, we determine two major compositional trends, the pure metabasitic (or eclogitic) trend and the combined metaperidotitic and metapyroxenitic trend, that are strongly correlated with their preferred substitution mechanisms during majorite formation. Based on these trends, we demonstrate that the majority of the reported majorite inclusions in natural diamonds formed neither in a pure metabasite nor in a metaperidotite lithology, but in fact crystallized from a wide range of compositions intermediate between conventional basaltic and peridotitic, referred to here as metapyroxenitic. Given the dominance of metapyroxenite-type majorite diamond inclusions and their inferred syngenetic origin, we argue that a significant fraction of metapyroxenite rock is present within Earth's transition zone and is important in the diamond-forming process. This is in agreement with recent self-consistent seismological and/or mineral physics studies that support models of a lithologically heterogeneous transition zone. From trace element and carbon isotope features, we infer a crustal origin for these rocks. © 2013 Geological Society of America.
Ключевые слова:	transition zone; trace element; pyroxenite; peridotite; metabasite; mantle structure; majorite; lithology; inclusion; diamond; carbon isotope; basalt; Diamond deposits; Seismology; Lithology; Isotopes; Garnets; Diamonds; Transition zones; Substitution mechanisms; Seismic discontinuities; Natural diamonds; Mantle transition zone; Inclusions in diamond; Diamond inclusions; Carbon isotopes;
Издано:	2013
Физ. характеристика:	с.883-886