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GEOREF RECORD

Short-range order of cations in synthetic amphiboles along the richterite-pargasite join

Giancarlo Della Ventura, Frank C. Hawthorne, Jean-Louis Robert, Francois Delbove, Mark F. Welch and Mati Raudsepp
Short-range order of cations in synthetic amphiboles along the richterite-pargasite join
European Journal of Mineralogy (February 1999) 11 (1): 79-94

Abstract

Amphiboles along the richterite-pargasite join have been synthesized hydrothermally at 900 degrees C and 3 kbar, and were found with the exception of the end-member compositions to coexist with additional phases. These synthetic amphiboles are free of chain-multiplicity faults; they show very non-linear variations in cell parameters as a function of nominal composition. The IR spectra in the principal OH-stretching region can be resolved into eight bands. The spectrum of end-member richterite consists of two bands at 3734 and 3674 cm (super -1) due to the local configurations MgMgMg-OH- (super A) Na and MgMgMg-OH- (super A) [], respectively. The spectrum of end-member pargasite consists of six bands due to variations in NN (nearest-neighbour) and NNN (next-nearest neighbour) configurations around the OH anion. The MgMgMg-OH- (super A) Na band in pargasite is shifted to lower frequency (3705 cm (super -1) ) relative to the same band in richterite, as the latter is associated with an Si-O(7)-Si configuration rather than the Al-O(7)-Al configuration in pargasite. The amphibole compositions do not lie along the richterite-pargasite join, but extend from both end-members towards edenite, NaCa (sub 2) Mg (sub 5) Si (sub 7) AlO (sub 22) (OH) (sub 2) , with intermediate compositions being unstable.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 11
Serial Issue: 1
Title: Short-range order of cations in synthetic amphiboles along the richterite-pargasite join
Affiliation: Terza Universita di Roma, Dipartimento di Scienze Geologiche, Rome, Italy
Pages: 79-94
Published: 199902
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 48
Accession Number: 2007-031114
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 8 tables
Secondary Affiliation: Univesity of Manitoba, CAN, CanadaC.R.S.C.M.-C.N.R.S., FRA, FranceThe Natural History Museum, GBR, United KingdomUniversity of British Columbia, CAN, Canada
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200717
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