Details
| Originalsprache | Englisch |
|---|---|
| Seiten (von - bis) | 369-381 |
| Seitenumfang | 13 |
| Fachzeitschrift | American mineralogist |
| Jahrgang | 95 |
| Ausgabenummer | 2-3 |
| Publikationsstatus | Veröffentlicht - 1 Feb. 2010 |
Abstract
Eleven compositions along the join Na(NaMg)Mg5Si 8O22(OH)2Na(NaCa)Mg5Si 8O22(OH)2 ("magnesiorichterite"- richterite) have been synthesized at T = 800-850 °C and PH2O = 0.35-0.5 GPa. The run products have been characterized by electron probe microanalysis (EPMA), synchrotron and conventional X-ray powder diffraction (XRPD), Fourier transformed infrared (FTIR) spectroscopy, and selected area electron diffraction (SAED-TEM). Nominally, the chemical variation along the join can be expressed as BMgxBCa-1xwith 0 ≤ x ≤ 1. A combination of EPMA and FTIR data in the OH-stretching region show that a complete solid solution is obtained under the conditions used. Nev-ertheless, a slight deviation from the nominal compositions involving a limited loss of Na at A and B sites, balanced by an increase of Ca at the B site, is present. Several indications of a displacive and coelastic P21/m → C2/m transformation induced by the Ca-Mg chemical substitution are observed. The phase transition occurs at B-site composition (Xc) close to B(Na1Mg0.7Ca0.3). C2/m samples with a Ca content of 0.34, 0.45, and 0.54 apfu show a significant strain tail related to local compositional inhomogeneities. This residual strain disappears as the amount of BCa significantly increases with respect to that of BMg. The transformation behavior observed here mirrors that of pyroxenes along the join diopside (CaMgSi2O6)-enstatite (Mg2Si 2O6). The cell parameters of amphiboles with CMg5, TSi8, and W(OH)2 and variable A- and B-site populations follow almost linear and continuous trends, indicative of small amounts of spontaneous strain accompanying these monoclinic phase transitions and the absence of significant miscibility gaps among different amphibole groups when quenched from higher temperatures of crystallization.
ASJC Scopus Sachgebiete
- Erdkunde und Planetologie (insg.)
- Geophysik
- Erdkunde und Planetologie (insg.)
- Geochemie und Petrologie
Zitieren
- Standard
- Harvard
- Apa
- Vancouver
- BibTex
- RIS
in: American mineralogist, Jahrgang 95, Nr. 2-3, 01.02.2010, S. 369-381.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Phase transition induced by solid solution
T2 - The BCa- BMg substitution in richteritic amphiboles
AU - Iezzi, Gianluca
AU - Ventura, Giancarlo Della
AU - Tribaudino, Mario
AU - Nemeth, Peter
AU - Margiolaki, Irene
AU - Cavallo, Andrea
AU - Gaillard, Fabrice
AU - Behrens, Harald
PY - 2010/2/1
Y1 - 2010/2/1
N2 - Eleven compositions along the join Na(NaMg)Mg5Si 8O22(OH)2Na(NaCa)Mg5Si 8O22(OH)2 ("magnesiorichterite"- richterite) have been synthesized at T = 800-850 °C and PH2O = 0.35-0.5 GPa. The run products have been characterized by electron probe microanalysis (EPMA), synchrotron and conventional X-ray powder diffraction (XRPD), Fourier transformed infrared (FTIR) spectroscopy, and selected area electron diffraction (SAED-TEM). Nominally, the chemical variation along the join can be expressed as BMgxBCa-1xwith 0 ≤ x ≤ 1. A combination of EPMA and FTIR data in the OH-stretching region show that a complete solid solution is obtained under the conditions used. Nev-ertheless, a slight deviation from the nominal compositions involving a limited loss of Na at A and B sites, balanced by an increase of Ca at the B site, is present. Several indications of a displacive and coelastic P21/m → C2/m transformation induced by the Ca-Mg chemical substitution are observed. The phase transition occurs at B-site composition (Xc) close to B(Na1Mg0.7Ca0.3). C2/m samples with a Ca content of 0.34, 0.45, and 0.54 apfu show a significant strain tail related to local compositional inhomogeneities. This residual strain disappears as the amount of BCa significantly increases with respect to that of BMg. The transformation behavior observed here mirrors that of pyroxenes along the join diopside (CaMgSi2O6)-enstatite (Mg2Si 2O6). The cell parameters of amphiboles with CMg5, TSi8, and W(OH)2 and variable A- and B-site populations follow almost linear and continuous trends, indicative of small amounts of spontaneous strain accompanying these monoclinic phase transitions and the absence of significant miscibility gaps among different amphibole groups when quenched from higher temperatures of crystallization.
AB - Eleven compositions along the join Na(NaMg)Mg5Si 8O22(OH)2Na(NaCa)Mg5Si 8O22(OH)2 ("magnesiorichterite"- richterite) have been synthesized at T = 800-850 °C and PH2O = 0.35-0.5 GPa. The run products have been characterized by electron probe microanalysis (EPMA), synchrotron and conventional X-ray powder diffraction (XRPD), Fourier transformed infrared (FTIR) spectroscopy, and selected area electron diffraction (SAED-TEM). Nominally, the chemical variation along the join can be expressed as BMgxBCa-1xwith 0 ≤ x ≤ 1. A combination of EPMA and FTIR data in the OH-stretching region show that a complete solid solution is obtained under the conditions used. Nev-ertheless, a slight deviation from the nominal compositions involving a limited loss of Na at A and B sites, balanced by an increase of Ca at the B site, is present. Several indications of a displacive and coelastic P21/m → C2/m transformation induced by the Ca-Mg chemical substitution are observed. The phase transition occurs at B-site composition (Xc) close to B(Na1Mg0.7Ca0.3). C2/m samples with a Ca content of 0.34, 0.45, and 0.54 apfu show a significant strain tail related to local compositional inhomogeneities. This residual strain disappears as the amount of BCa significantly increases with respect to that of BMg. The transformation behavior observed here mirrors that of pyroxenes along the join diopside (CaMgSi2O6)-enstatite (Mg2Si 2O6). The cell parameters of amphiboles with CMg5, TSi8, and W(OH)2 and variable A- and B-site populations follow almost linear and continuous trends, indicative of small amounts of spontaneous strain accompanying these monoclinic phase transitions and the absence of significant miscibility gaps among different amphibole groups when quenched from higher temperatures of crystallization.
KW - Cell parameters
KW - EPMA
KW - FTIR spectroscopy
KW - Phase transition
KW - SAED-TEM
KW - Synthetic amphiboles
KW - XRPD
UR - http://www.scopus.com/inward/record.url?scp=77950240800&partnerID=8YFLogxK
U2 - 10.2138/am.2010.3308
DO - 10.2138/am.2010.3308
M3 - Article
AN - SCOPUS:77950240800
VL - 95
SP - 369
EP - 381
JO - American mineralogist
JF - American mineralogist
SN - 0003-004X
IS - 2-3
ER -