My previous reply appears to have disappeared into the ether without
returning to me at least. As I said, this occurrence is remarkable and
reminds me of combustion metamorphic rocks of SE Utah, the Monterey Fm. of
Calif, and the Mottled Zone of Israel. The "Fe-rich wollastonite" may be
ferrobustamite, which could exsolve wo on cooling from very high T. S and
O isotopic studies are indicated. The minerals that are coarse enough
should be analyzed with EMPA.
>I am writing a manuscript on new textural, mineralogical and chemical results
>on volcanic ash and aerosols: SEM and FE SEM examinations. All data are from
>the recent activity of Popocatepetl volcano, Mexico. One part is dedicated to
>the occurrence of Fe-rich wollastonite, hercynite and buchites (glasses
>origin of contact metamorphism [CM]) as a population of fragments of the
>volcanic ash. The wollastonite is not homogeneous, it shows Fe-rich and
>parts which are intergrown. Some grains show vesiculation-like textures.
>Does anybody know SEM studies of similar wollastonites etc.? Also the buchites
>are highly heterogeneous.
>The main question is: Are these fragments products of ongoing CM underneath
>Popocatepetl, or are they fragments of an old aureol. Popocatepetl is situated
>on a ca. 3 km thick sequence of lime/dolostones/evaporites etc. of Cretaceous
>Buchites show wild compositions, they are rich in S, Cl and P. Anhydrite and
>inheritated zircons are enbedded in this glassy/devitrified matrix.
>Ideas, references and coauthorship for essential contributions are welcome.
>Thanks and best wishes
>Johannes H. Obenholzner, PhD
>email: [log in to unmask]