You may find the report of sector zoned zoisite by Enamai
in1970's in Mineralogical Abstracts if you have access to this.
        Sector zoning shows non-equilibrium crystallization. 

Shohei BANNO
Takano Higashi-Hiraki, Sakyo-ku, Kyoto ,606-8107 Japan
T &F :81-(0)75-722-7175

-----Original Message-----
From: No title defined [mailto:[log in to unmask]] On
Behalf Of Javier RodrĄ^uez Aller
Sent: Friday, December 14, 2001 12:17 AM
To: [log in to unmask]
Subject: sector-zoned zoisite in eclogite

Dear all,

I've read about chemical aspects of sector zoning in zoisite (variations
Fe3/Fe3+Al ratios: Deer, Howie & Zussman, 1986)... Going further, does
anybody have any opinion about the origin(s) of this rare feature?

I've found sector-zoned zoisite porphyroclasts in poorly deformed
Zoisite coexists with omphacite porphyroclasts and garnet, which is
arranged in honeycomb patterns (surrounding omphacite and zoisite

It seems therefore that eclogitization took place in this rock at nearly
static conditions, with low-range chemical diffusion... Is then zoisite
reflecting some chemical inhomogeneity in a pristine (now diappeared)
phase? ... I'm thinking about possible An-rich, (zoned?) igneous

PS:... Trace amounts of trivalent cations in the former phase can also
account for tiny rutile inclusions, arranged in preferred orientations
within zoisite clasts.


Javier Rodr®™guez
Dpto. Mineralog®™a y Petrolog®™a
Facultad de Ciencias, Univ. del Pa®™s Vasco
Apdo. Correos 644
E-48080 Bilbao, Spain

Tfn:  + 34 94 601 5456
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