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A moissanite cell apparatus for optical in situ observation of crystallizing melts at high temperature

Federica Schiavi, Nicolas Walte, Alexander Konschak and Hans Keppler
A moissanite cell apparatus for optical in situ observation of crystallizing melts at high temperature
American Mineralogist (July 2010) 95 (7): 1069-1079

Abstract

An experimental apparatus is described that allows for optical in situ observation of samples at 1 bar and temperatures up to 1250 degrees C for durations up to several days. The apparatus resembles a Bassett-type externally heated diamond cell, where the diamond anvils are replaced by cylinders of synthetic moissanite (SiC). The sample is placed inside a gasket of glassy carbon between the two moissanite windows. The moissanite cell allows for the direct and continuous observation of the sample with an optical resolution in the range of a few micrometers. Partially molten systems can be investigated during cooling-heating cycles within a single experimental run. Texture evolution can be observed continuously through time. The technique also allows for direct measurements of crystal growth and dissolution rates at defined cooling and heating rates. The method was tested by observing the crystallization of KNO (sub 3) -LiNO (sub 3) and NaCl-KCl salt melts as well as of a basaltic-trachyandesitic melt. Dendrite formation, static grain growth, and dissolution were observed in the salt melts. During textural coarsening (static grain growth) of rock salt in the presence of melt, grain coalescence was observed. Both nitrate and rock salt grains growing in contact with melt generally showed curved boundaries and roundish shapes, rather than facets. In one experiment, the final texture did not contain any traces of the previous textural evolution anymore. In a basaltic trachyandesite at temperatures near the liquidus several phenomena, in particular the interactions between crystals, magmatic flow and bubbles during nucleation, growth and dissolution of crystals, and crystal-clusters were observed simultaneously. Crystal growth rates and dissolution rates were also measured.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 95
Serial Issue: 7
Title: A moissanite cell apparatus for optical in situ observation of crystallizing melts at high temperature
Affiliation: Universitaet Bayreuth, Bayerisches Geoinstitut, Bayreuth, Federal Republic of Germany
Pages: 1069-1079
Published: 201007
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 57
Accession Number: 2010-068200
Categories: General mineralogyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201037
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