Petrologic origin of exsolution textures in mantle minerals

Evidence in pyroxenitic xenoliths from Yakutia kimberlites

Taisia Aleksandrovna Alifirova*, Lyudmila Nikolaevna Pokhilenko, Yuriy Ivanovich Ovchinnikov, Cara Lyhn Donnelly, Amy J V Riches, Lawrence August Taylor

*Corresponding author for this work

Research output: Contribution to journalReview article

19 Citations (Scopus)

Abstract

Exsolution lamellae in pyroxene and garnet porphyroblasts in pyroxenite xenoliths from the Mir, Udachnaya, and Obnazhennaya kimberlites (Siberian Craton) reveal a diverse suite of exsolved phases, including oxides (spinels, ilmenite, rutile, and chromite), pyroxene, and garnet. Textural characteristics suggest that exsolved phases progressively increased in volumetric proportions, and in some cases, the bulk xenoliths transformed from a lithology dominated by coarse grains (i.e. > 2 cm; megacrystalline) to a significantly finer-grained texture (i.e. < 1 cm).

These exsolved lamellae are the result of a complex and protracted sub solidus history following magmatic crystallization. Equilibrium pressure-temperature estimates place these xenoliths at low-to-moderate pressure-temperature conditions (690-910C and 2.0-4.5 GPa) in the lithospheric mantle at the time of entrainment in the kimberlite. However, reconstructed compositions of initial pyroxene and garnet crystals suggest that this suite of pyroxenites formed at considerably higher temperatures and pressures that, in some instances, may have approached the majorite stability field. Pyroxenites that do not contain primary garnet may have been derived from shallower depths.

Progressive exsolution in these pyroxenites is of importance inasmuch as such processes can permit localized changes in rheological properties and may also accommodate strain within portions of lithospheric mantle. Because most xenolith studies focus on peridotites and eclogites, the pyroxenite sample suite studied in this work represents an important contribution towards a greater understanding of the Siberian lithospheric mantle.

Original languageEnglish
Pages (from-to)1071-1092
Number of pages22
JournalInternational Geology Review
Volume54
Issue number9
DOIs
Publication statusPublished - 1 Jul 2012
Externally publishedYes

Keywords

  • exsolution lamellae
  • garnet
  • lherzolite
  • lithospheric mantle
  • pyroxenite
  • Yakutia

Fingerprint Dive into the research topics of 'Petrologic origin of exsolution textures in mantle minerals: Evidence in pyroxenitic xenoliths from Yakutia kimberlites'. Together they form a unique fingerprint.

Cite this