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The Discovery of Phlogopite Exsolution Lamellae in Garnets of Eclogite Inclusions, Liaoning Province
Author(s) -
Xiuzhong Zhou
Publication year - 1997
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.1997.tb00343.x
Subject(s) - phlogopite , eclogite , kimberlite , geology , pyroxene , geochemistry , acicular , mineral , olivine , pseudomorph , rutile , inclusion (mineral) , mineralogy , mantle (geology) , quartz , materials science , subduction , paleontology , metallurgy , microstructure , tectonics
In No. 50 kimberlite pipe of Fuxian County, Liaoning Province, an eclogite inclusion (nodule), which is extremely rare in kimberlites, was discovered and phlogopite exsolution lamellae were found in garnets of the inclusion. Microscopic, TEM and energy spectral observations and studies confirmed that these lamellae are phlogopite. They are colourless and acicular in section, generally 0.5–5 μ m in width and 10–100 μ m in length. Nevertheless, fine lamellae, 0.05–0.1 μ m wide and 1–2 μ m long, are also well developed. Along [111] of the garnet, three sets of phlogopite lamellae show oriented arrangement approximately at angles of 60° −70°, indicating that these lamellae might be the product of exsolution from garnet as a result of pressure–release when eclogite ascended from the relatively deep level to the relatively shallow level of the mantle. Tiny acicular exsolution minerals (or inclusions) are commonly found in garnet and pyroxene in eclogite inclusions of kimberlites all over the world and it has been reported that the identified exsolution minerals include pyroxene and rutile. This is the first time that phlogopite exsolution lamillae were found in eclogite inclusions in the world.