Al–Mg disorder in a gem-quality pargasite from Baffi n
The crystal structure of gem-quality pargasite from Soper River, near Kimmirut, Baffin Island, Nunavut, Canada, (K0.24Na0.73)0.97 (Ca1.86Na0.14)2.00 (Mg4.15Fe0.07Mn0.01Al0.71Ti0.06)5.00 (Si6.45Al1.55) O22 [(OH)1.25F0.63O2–0.12]2.00, a 9.8814(6), b 17.967(1), c 5.2927(4) Å, 105.263(5)°, V 906.5 Å3, C...
Main Authors: | , , , |
---|---|
Other Authors: | |
Format: | Text |
Language: | English |
Published: |
2001
|
Subjects: | |
Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.9235 http://www.geo.arizona.edu/xtal/group/pdf/cm39_1725.pdf |
id |
ftciteseerx:oai:CiteSeerX.psu:10.1.1.547.9235 |
---|---|
record_format |
openpolar |
spelling |
ftciteseerx:oai:CiteSeerX.psu:10.1.1.547.9235 2023-05-15T15:35:25+02:00 Al–Mg disorder in a gem-quality pargasite from Baffi n Kimberly T. Tait Frank C. Hawthorne Giancarlo Della Ventura The Pennsylvania State University CiteSeerX Archives 2001 application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.9235 http://www.geo.arizona.edu/xtal/group/pdf/cm39_1725.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.9235 http://www.geo.arizona.edu/xtal/group/pdf/cm39_1725.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://www.geo.arizona.edu/xtal/group/pdf/cm39_1725.pdf amphibole pargasite crystal-structure refinement electron-microprobe analysis Kimmirut Baffin Island Nunavut Canada. SOMMAIRE text 2001 ftciteseerx 2016-01-08T11:22:45Z The crystal structure of gem-quality pargasite from Soper River, near Kimmirut, Baffin Island, Nunavut, Canada, (K0.24Na0.73)0.97 (Ca1.86Na0.14)2.00 (Mg4.15Fe0.07Mn0.01Al0.71Ti0.06)5.00 (Si6.45Al1.55) O22 [(OH)1.25F0.63O2–0.12]2.00, a 9.8814(6), b 17.967(1), c 5.2927(4) Å, 105.263(5)°, V 906.5 Å3, C2/m, Z = 2, has been refined to an R index of 2.9 % using 1506 observed intensities measured with MoK X-radiation. The crystal used for collection of the X-ray intensity data was then analyzed with an electron microprobe. The amphibole composition is very close to that of end-member pargasite. There is significant disorder of Al over the M(2) [1.40 Mg + 0.54 Al + 0.06 Fe3+] and M(3) [0.81 Mg + 0.17 Al + 0.02 Fe2+] sites. Such disorder has been observed in Mg-rich pargasite from a high-pressure paragenesis in the western Alps. The infrared spectrum of this amphibole in the principal OH-stretching region shows a complex envelope that can be resolved into six bands by analogy with the spectra of synthetic (OH,F)-bearing pargasite in the literature. The relative intensities of the component bands are in accord with the observed OH:F ratio in this pargasite, and indicate complete short-range disorder of OH and F. The occurrence of Al–Mg disorder over M(2) and M(3) in the Soper River pargasite, from a lower-pressure environment, indicates that this disorder is a compositional feature of pargasite, rather than a result of crystallization or equilibration at high pressure and temperature. The pattern of electron density in the A cavity of the structure may be interpreted in terms of K and Na at the A(m) site and Na at the A(2) site. Moreover, the specific site-populations are conformable with the composition of this amphibole and the most favorable patterns of short- Text Baffin Island Baffin Kimmirut Nunavut Unknown Baffin Island Canada Kimmirut ENVELOPE(-69.870,-69.870,62.847,62.847) Nunavut Soper River ENVELOPE(-69.848,-69.848,62.901,62.901) |
institution |
Open Polar |
collection |
Unknown |
op_collection_id |
ftciteseerx |
language |
English |
topic |
amphibole pargasite crystal-structure refinement electron-microprobe analysis Kimmirut Baffin Island Nunavut Canada. SOMMAIRE |
spellingShingle |
amphibole pargasite crystal-structure refinement electron-microprobe analysis Kimmirut Baffin Island Nunavut Canada. SOMMAIRE Kimberly T. Tait Frank C. Hawthorne Giancarlo Della Ventura Al–Mg disorder in a gem-quality pargasite from Baffi n |
topic_facet |
amphibole pargasite crystal-structure refinement electron-microprobe analysis Kimmirut Baffin Island Nunavut Canada. SOMMAIRE |
description |
The crystal structure of gem-quality pargasite from Soper River, near Kimmirut, Baffin Island, Nunavut, Canada, (K0.24Na0.73)0.97 (Ca1.86Na0.14)2.00 (Mg4.15Fe0.07Mn0.01Al0.71Ti0.06)5.00 (Si6.45Al1.55) O22 [(OH)1.25F0.63O2–0.12]2.00, a 9.8814(6), b 17.967(1), c 5.2927(4) Å, 105.263(5)°, V 906.5 Å3, C2/m, Z = 2, has been refined to an R index of 2.9 % using 1506 observed intensities measured with MoK X-radiation. The crystal used for collection of the X-ray intensity data was then analyzed with an electron microprobe. The amphibole composition is very close to that of end-member pargasite. There is significant disorder of Al over the M(2) [1.40 Mg + 0.54 Al + 0.06 Fe3+] and M(3) [0.81 Mg + 0.17 Al + 0.02 Fe2+] sites. Such disorder has been observed in Mg-rich pargasite from a high-pressure paragenesis in the western Alps. The infrared spectrum of this amphibole in the principal OH-stretching region shows a complex envelope that can be resolved into six bands by analogy with the spectra of synthetic (OH,F)-bearing pargasite in the literature. The relative intensities of the component bands are in accord with the observed OH:F ratio in this pargasite, and indicate complete short-range disorder of OH and F. The occurrence of Al–Mg disorder over M(2) and M(3) in the Soper River pargasite, from a lower-pressure environment, indicates that this disorder is a compositional feature of pargasite, rather than a result of crystallization or equilibration at high pressure and temperature. The pattern of electron density in the A cavity of the structure may be interpreted in terms of K and Na at the A(m) site and Na at the A(2) site. Moreover, the specific site-populations are conformable with the composition of this amphibole and the most favorable patterns of short- |
author2 |
The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
Kimberly T. Tait Frank C. Hawthorne Giancarlo Della Ventura |
author_facet |
Kimberly T. Tait Frank C. Hawthorne Giancarlo Della Ventura |
author_sort |
Kimberly T. Tait |
title |
Al–Mg disorder in a gem-quality pargasite from Baffi n |
title_short |
Al–Mg disorder in a gem-quality pargasite from Baffi n |
title_full |
Al–Mg disorder in a gem-quality pargasite from Baffi n |
title_fullStr |
Al–Mg disorder in a gem-quality pargasite from Baffi n |
title_full_unstemmed |
Al–Mg disorder in a gem-quality pargasite from Baffi n |
title_sort |
al–mg disorder in a gem-quality pargasite from baffi n |
publishDate |
2001 |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.9235 http://www.geo.arizona.edu/xtal/group/pdf/cm39_1725.pdf |
long_lat |
ENVELOPE(-69.870,-69.870,62.847,62.847) ENVELOPE(-69.848,-69.848,62.901,62.901) |
geographic |
Baffin Island Canada Kimmirut Nunavut Soper River |
geographic_facet |
Baffin Island Canada Kimmirut Nunavut Soper River |
genre |
Baffin Island Baffin Kimmirut Nunavut |
genre_facet |
Baffin Island Baffin Kimmirut Nunavut |
op_source |
http://www.geo.arizona.edu/xtal/group/pdf/cm39_1725.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.9235 http://www.geo.arizona.edu/xtal/group/pdf/cm39_1725.pdf |
op_rights |
Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
_version_ |
1766365755028275200 |