Hi Shauket, check this article, might be of some help (??).
good luck,
hassina
Earth and Planetary Science Letters
Volume 216, Issue 4, 10 December 2003, Pages 591-601
doi:10.1016/S0012-821X(03)00551-X | How to Cite or Link Using DOI
Cited By in Scopus (57)
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Titanium solubility in coexisting garnet and clinopyroxene at very high pressure: the significance of exsolved rutile in garnet
R.Y. Zhanga, , , S.M. Zhaib, Y.W. Feic, J.G. Lioua
Purchase
a Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, USA
b College of Sciences, Department of Earth Sciences, Zhejiang University, Hangzhou, Zhejiang 310027, PR China
c Geophysical Laboratory of Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015, USA
Received 4 February 2003; revised 19 August 2003; Accepted 19 September 2003. Available online 19 November 2003.
Abstract
Exsolution microstructures including ilmeniteˇÓgarnet in clinopyroxene and rutile in garnet are common in clinopyroxenite and eclogite from the Sulu ultrahigh-pressure (UHP) terrane. In order to understand the phase relations and Ti solubility in both garnet and clinopyroxene in a natural TiO2-bearing system, several experiments at 5ˇV15 GPa, 1000ˇV1400˘XC were carried out using the multianvil high-pressure apparatus. The Hujianlin ilmenite-rich garnet clinopyroxenite showing exsolution microstructure was selected as starting material, because it closely approaches a composition lying in the TiO2ˇVCaOˇVMgOˇVFeOˇVAl2O3ˇVSiO2 system. Except for minor melt in one experiment at 1400˘XC and 5 GPa, other run products contain majoritic garnet+clinopyroxeneˇÓilmenite (or rutile) and exhibit neoblastic texture. With increasing pressure, Ti and Ca, Mg and Si contents of neoblastic garnet increase with decreasing Al. The principal coupled substitutions are Ca2+Ti4+ˇ÷2Al3+ and Si4+Mg2+ˇ÷2Al3+ responding to majorite component increase. Titanium solubility (0.8ˇV4.5 wt% as TiO2) in garnet and GrtTi/CpxTi ratio have a pronounced positive correlation with pressure between 5 and 15 GPa. On the other hand, the coexisting clinopyroxene contains low Ti (0.17ˇV0.53 wt% as TiO2), and shows no significant pressure effect. Rutile exsolution in garnet is coupled to that of pyroxene exsolution; both are exsolved from majoritic garnet on decompression. Therefore, the amount of such exsolved lamellae is a potential indicator of high-pressure metamorphism in exhumed rocks, whereas the TiO2 content of clinopyroxene coexisting with garnet is not sensitive to pressure change.
Keywords: high-P experiment; Ti solubility; rutile exsolution; majorite; garnet clinopyroxenite
Prof Hassina MOURI
Secretary General, Geological Society of Africa (GSAf) I http://www.geologicalsocietyofafrica.org/
Chair, Organising Committee CAG23- SA2011 I http://www.cag23.co.za
Department of Geology I University of Johannesburg I Auckland Park Campus I www.uj.ac.za
Tel: +27-11-559-4706 I Cell: 0820948079 I Fax: +27-11-559-4702
Email: [log in to unmask] I Skype: hassina.mouri
________________________________________
From: Metamorphic Studies Group [[log in to unmask]] on behalf of Shauket Baltybaev [[log in to unmask]]
Sent: 08 December 2011 08:56 PM
To: [log in to unmask]
Subject: Re: inclusions in garnet
Hassina and others, thanks a lot!
Yes, it's most probably rutile, next week I'll check its composition.
Let me concretize the question - I've never seen such rhomboidal location.
Is it decompressional structure, lamella or what?
Shauket
> Hi Shauket, I could not open the pictures properly, but could that not be Rutile?
> regards
> hassina
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