There's a number of data reported for the exsolution of different mineral phases from high temperature and high pressure garnets (including pyroxenes, rutile, apatite, spinel and others). Presence of corundum in orogenic peridotite assemblages is commonly attributed to UHT conditions. The point is what the hypothetical exsolution of Crn from Grt can tell us about. So I would be grateful for any personal suggestions or advises of already existing information from studies of natural and experimental objects.
Dear Prof. Menzies,
Thank you for your constructive reply. Indeed, we have a nice example of Cr-poor retrograded orogenic peridotites with a Sr maximum in the trace element patterns that allow suggesting Pl-rich residues/cumulates as a protolith. And there's a number of studies where corundum is mentioned in the paragenesis. Currently I'm more curious about findings of corundum no as a separate phase but as inclusions and exsolution structures in garnet, since I have not found such examples so far.
But in general, of course, there should be similar considerations.
Regards,
Sergei
Corundum exsolution from mantle minerals is rare. However, exsolved Crn was described in clinopyroxene and kyanite. As for garnet host, Crn was found to compose oriented inclusions in garnet from UHP metamorphic rocks. [Please, see paper in JMG of Hwang et al., 2015 "Origin of rutile needles in star garnet and implications for interpretation of inclusion textures in ultrahigh-pressure metamorphic rocks". ]
When considering corundum as a product of garnet decomposition, firstly the information about the composition of precursor garnet can be taken.
Taisia, thanks a lot for the information, I was sure you could help with that. Just to make it clear, could you please provide me with the mentioned references on the Crn-in-Px and Crn-in-Ky exsolution?
Thank you again in advance.
As for Crn-in-Cpx, you may know paper in RGG of Qi et al., 1997 "Detailed petrology and geochemistry of a rare corundum eclogite xenolith from Obnazhennaya pipe (Yakutia)".
Crn-in-Ky: Bobrievich et al., 1959. THE DIAMOND DEPOSITS OF YAKUTIA. (1st Edition, in English).
Corundum exsolution is also known in rutile as I remember. For instance, paper in IGR of Sobolev&Yefimova, 2000 "Composition and Petrogenesis of Ti-Oxides Associated with Diamonds".
These references are just examples, especially when considering Crn-in-Cpx and Crn-in-Rt.
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