http://www.cnr.it/ontology/cnr/individuo/prodotto/ID29454
Site preference and local geometry of Sc in garnets: I. Multifarious mechanisms in the pyrope-grossular join. (Articolo in rivista)
- Type
- Label
- Site preference and local geometry of Sc in garnets: I. Multifarious mechanisms in the pyrope-grossular join. (Articolo in rivista) (literal)
- Anno
- 2006-01-01T00:00:00+01:00 (literal)
- Alternative label
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- Oberti R.; Quartieri S.; Dalconi M.C.; Boscherini F.; Iezzi G.; Boiocchi M.; Eeckhout S. (literal)
- Pagina inizio
- Pagina fine
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
- Rivista
- Note
- ISI Web of Science (WOS) (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
- ROBERTA OBERTI,1 SIMONA QUARTIERI,2,* MARIA CHIARA DALCONI,2, FEDERICO BOSCHERINI,3
GIANLUCA IEZZI,4 MASSIMO BOIOCCHI,5 AND SIGRID GRIET EECKHOUT6
1CNR, Istituto di Geoscienze e Georisorse, Università di Pavia, via Ferrata 1, I-27100 Pavia, Italy
2Dipartimento di Scienze della Terra,Università di Messina, Salita Sperone 31, I-98166 Messina S. Agata, Italy
3Dipartimento di Fisica and CNISM, Università di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna, Italy
4Dipartimento di Scienze della Terra, Università di Chieti, via dei Vestini 30, I-66013 Chieti Scalo, Italy
5Centro Grandi Strumenti, Università di Pavia, via Bassi 21, I-27100 Pavia, Italy
6European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP 220, F-38043 Grenoble Cedex, France (literal)
- Titolo
- Site preference and local geometry of Sc in garnets: I. Multifarious mechanisms in the pyrope-grossular join. (literal)
- Abstract
- We applied different independent techniques (electron microprobe analysis, structure reÞ nement,
and X-ray absorption spectroscopy) to unravel the possible mechanisms of Sc incorporation in the
pyrope-grossular join. Samples were synthesized at elevated pressure and temperature by adding 5
wt% of Sc2O3 to selected nominal compositions (pyrope, pyrope60grossular40, pyrope20grossular80,
and grossular). In this way, the site of incorporation was not pre-determined, and only depends on the
availability of a mechanism for local charge-balance. The EXAFS spectra of the two end-members
could be analyzed by a multi-shell Þ t procedure, whereas the chemical heterogeneity of the Sc-doped
solid-solution terms prevented this approach. However, the available information allows detection of
different mechanisms of incorporation, which are active as a function of the bulk composition. In pyrope,
Sc mainly enters the dodecahedral X site, and the local charge balance is achieved by incorporation of
Mg at the adjacent tetrahedral Z site. Local charge-balance requirements suggest that a Z site occupied
by Mg bridges two X sites occupied by Sc. When the entrance of Ca provides relaxation of the averaged
structure, Sc may enter all the three available cation sites via the coupled heterovalent exchange
XSc1
ZSc1
XMg.1
ZSi.1 and the homovalent exchange YSc1
YAl.1. In the samples of this work, there is an
apparent limit in the Sc incorporation at the Y site, which is in contrast to the favored mechanism of
incorporation in Sc-doped andradites. This limit can be explained in terms of relative dimensions of
the structural sites when Al is the dominant Y cation. These results must be taken into account when
evaluating trace-element behavior in garnets for geochemical purposes. In particular, they explain why
DSc can be treated together with DREE in models based on the elastic strain theory in garnets close to
the pyrope composition, but deviate from the parabolic Þ t in grossular-rich garnets. (literal)
- Prodotto di
- Autore CNR
- Insieme di parole chiave
Incoming links:
- Autore CNR di
- Prodotto
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#rivistaDi
- Insieme di parole chiave di
