Origin of phlogopite and potassic richterite bearing peridotite xenoliths from South Africa

✍ Scribed by Ken-ichiro Aoki

• Publisher: Springer
• Year: 1975
• Tongue: English
• Weight: 742 KB
• Volume: 53
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00372601

✦ Synopsis

Peridotite xenoliths containing primary phlogopite with or without potassic richterites as major constituent (up to 12 vol. %) are rarely found in kimberlite from the Bultfontein Floors. Chemically, these rocks are similar in compositions with those of the granular type garnet peridotite xenoliths from South Africa and Lesotho, except for an abnormally high content of K20 in the former.

Phlogopite and potassic richterite are thought to have the following genesis: garnet peridotites at a depth from 170 to 100 km suffered local introduction of a potash-rich fluid, and garnet and enstatite reacted with this fluid to form phlogopite and diopside. Potassic richterite may have been produced by the reaction between diopside and fluid at the same time as crystallization of phlogopite at depths shallower than 120 kin.