>Granulite facies garnets often show relatively high Ti contents in their
>cores and zonations to nearly Ti-free rims. Sometimes one can find
>finegrained rutile needles inside the garnets in strong orientation. Both
>features may be results of higher solubility of Ti in garnet at high
>pressures (or high temperatures?).
>I was searching for a reference dealing with Ti solubility in garnet, but
>did'nt find anything. Help!
Both Deer/Howie/Zussmann vol1a, Orthosilicates (starting p622) and MSA
Reviews in Mineralogy Vol 5 Orthosilicates chapter 2 have information about
Ti in garnet including experimental data. Descriptions of 'anomalously
elongate rutile needles' as exsolution lamellae in garnets of high pressure
origin are easy to find in the literature. These garnets certainly do not
belong the the titanian andradite types melanite (tetrahedral Fe3+ > Ti) or
schorlomite (tetrahedral Fe3+ < Ti) although they are often Ca-rich
(eclogite garnets often show > 30mol% Grossular). A charge balance with Na
at high pressure that is unstable with decompression could explain some