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6th Silicate Melt Workshop
Chemical Geology 174 Ž2001. 1–3 www.elsevier.comrlocaterchemgeo
Editorial
6th Silicate Melt Workshop
The Silicate Melt Workshops are the offspring of a French interdisciplinary program whose aim was to monitor and forecast the activity of volcanoes. This ambitious program, directed by Michel Treuil, and called PIRPSEV, was the result of a recommendation by an international scientific committee, which came together after the 1976 volcanic crisis of the Soufriere ` volcano on the island of Guadeloupe. PIRPSEV consisted of six working groups, one of which was concerned with the physico-chemical investigations of silicate melts and glasses. Amongst other things, this working group organized in Southern France, in the years 1981–1986, three meetings entitled Silicates Liquides. These were also attended by other European scientists interested in silicate melts and gave rise to special issues of the Bulletin de Mineralogie and Chemical Geology. ´ During the following decade the PIRPSEV program was discontinued and Earth Science oriented research on silicate melts and glasses in Europe changed drastically. Out of nowhere a very active institute sprang into being as the Bayerisches Geoinstitut at Bayreuth, while at the University of Hanover, the Institute of Mineralogy gradually also became an internationally recognized center for the study of silicate melt–gas interactions. At the same time French silicate melt research became concentrated in Paris and Orleans. We felt at that time that further ´ progress in these endeavors would benefit from meetings organized on a regular basis. Thus, a renewed meeting series, deliberately international in
scope, was initiated in Alsace in 1991 under the name International Silicate Melt Workshop. Much has changed since the first 1981 meeting. On certain problems great progress have been made, for example, the atomistic steps leading to viscous flow of silicate liquids as observed by NMR. The further application of this technique to study medium range order is one of the more recent developments. The experimental study of the solubility of water and carbon dioxide in silicate melts as functions of pressure and temperature and composition has seen seminal advances. The field has progressed, once and for all, beyond the stage of ideal mixing and regular solution models. The discovery of the first glimpses of medium ranged order in silicate melts and glasses has now relegated the once dominant completely random network work model to the museum shelf. The database concerning physical and thermodynamic characteristics of melts and glasses has improved enormously in quantity as well as quality. Most of current knowledge here on silicate liquids has been acquired during the last 20 years. Silicate Melt Workshop participants have obtained many of these data in their laboratories. Numerical simulation of silicate melts has now passed the stage where one noticed with a great sense of accomplishment that silicon atoms have four oxygen atoms as nearest neighbors. These numerical experiments have become very sophisticated and have begun to contribute significantly to our understanding of the equilibrium and transport properties of melts. A perusal
0009-2541r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 9 - 2 5 4 1 Ž 0 0 . 0 0 3 0 2 - 8
2
Editorial
of the Chemical Geology volumes containing reports of the Silicate Melt Workshops speaks for itself in this respect. There remains much to be done. The solubility of sulfur-containing gases has not yet received the attention it deserves. The rheology of suspensions, Žhere melts with crystals andror bubbles. remains a powerful challenge to general solutions of magma flow. Measurements of surface tension, and its consequences for the curvature of interfaces only recently received a re-awakened interest. Numerical simulation studies have become much more realistic, but it remains to see whether they will ever be sufficiently trustworthy to produce quantitative results. In any case, this will depend on the availability of better interatomic potentials. Moreover, Molecular Dynamics and Monte Carlo methods need to be applied to samples of several millions of particles in order to have a realistic picture of medium ranged order. Structural and compositional heterogeneity of silicate melts in the transition region has been the subject of much modeling and speculation. However, these models with their not directly measurable variables such as Afree volumeB, have not yet succeeded in predicting observable effects or explaining in sufficient detail the known characteristics of 3D network liquids. Hence, the true significance of the glass transition and the Kauzmann paradox remain shrouded in mystery. The inspiration of much silicate melt research is its link to the world of volcanology. To avoid the fate of research into dead languages, such as Latin, silicate melt research, in a geoscientific context, must also address problems in physical volcanology. Here we have great good fortune, because the new generation of numerical modellers of eruptive scenarios has an unbridled appetite for silicate melt property data of the highest quality. In fact, research into the strength and failure of silicate melts has helped to redefine the mechanistic basis of explosive volcanism in recent years. Historically the interaction between winegrowers and consumers has lead to the development of great wines. Thus, it is a part of our responsibility to present our observations in such a way that useful generalizations become obvious. Silicate liquids and water have in common that they are both liquids with an internal three-dimensional network structure and are the two most abun-
dant liquids on Earth. An inevitable consequence of this observation is that research on this type of liquid should be of very general interest. Those who study the general and principal properties of water understand the importance of their work quite well and very frequently publish their findings in the general science press. We happily remind the reader that the scientific principles to be gleaned from the study of silicate network liquids are as comparable in significance to those derived from water studies. The occurrence of the glass transition can be better observed in liquid silicates than in water or aqueous solutions. Hence, one should not forget to make more use of the general science periodicals for the publication of newly determined or discovered general physical or chemical properties. Such action will enhance the image of Earth Science liquid silicate research. The fact that physicists and physical chemists studying liquids rarely mention the properties of silicate liquids reveals a clear deficit that we must solve through communication. During the past 20 years the Silicate Melt Workshops have been quite effective in fostering cooperation between scientists among across formal disciplinary boundaries through their mutual curiosity for silicate melts. This has contributed materially to the evolution of this field. This new issue of Chemical Geology will be a new testimony to it. A perusal of the summary will underline the importance paid to water as a component of naturally occurring melts. Much of this work has been made within the framework of a TMR Research Network AIn Situ Hydrous MeltsB conceived and coordinated at CRSCM-CNRS Orleans. ´ In closing, two of the authors of this editorial ŽDBD, University of Munich and PR, Institut de Physique du Globe, Paris. take great pleasure in reminding the reader that this 6th Silicate Melt Workshop was dedicated to their long-time friend, colleague and co-organizer, Yan Bottinga ŽInstitut de Physique du Globe, Paris. in recognition of his benchmark contributions to the understanding of silicate melts. Held in the 18th century utopian Royal saltworks of Arc-et-Senans, constructed in the French Jura by Claude-Nicolas Ledoux, this meeting fitted very well with Yan’s well-known architectural interests. This most impressive and audacious ensemble of buildings contributed to the success of the meet-
Editorial
ing. The support received from Naturalia and Biologia, which we gratefully acknowledge, has helped us arrange the workshop in such a marvelous setting. Y. Bottinga Institut de Physique du Globe, 4 Place Jussieu, 75252 Paris Cedex 05, France E-mail address: [email protected] D.B. Dingwell Institut fur ¨ Mineralope, Petrologie und Geochemie, UniÕersitat ¨ Munchen, ¨ Theresienstr. 41, 80333 Munchen, Germany ¨ E-mail address: [email protected]
3
P. Richet Institut de Physique du Globe, 4 Place Jussieu, 75252 Paris Cedex 05, France E-mail address: [email protected]
Editorial
6th Silicate Melt Workshop
The Silicate Melt Workshops are the offspring of a French interdisciplinary program whose aim was to monitor and forecast the activity of volcanoes. This ambitious program, directed by Michel Treuil, and called PIRPSEV, was the result of a recommendation by an international scientific committee, which came together after the 1976 volcanic crisis of the Soufriere ` volcano on the island of Guadeloupe. PIRPSEV consisted of six working groups, one of which was concerned with the physico-chemical investigations of silicate melts and glasses. Amongst other things, this working group organized in Southern France, in the years 1981–1986, three meetings entitled Silicates Liquides. These were also attended by other European scientists interested in silicate melts and gave rise to special issues of the Bulletin de Mineralogie and Chemical Geology. ´ During the following decade the PIRPSEV program was discontinued and Earth Science oriented research on silicate melts and glasses in Europe changed drastically. Out of nowhere a very active institute sprang into being as the Bayerisches Geoinstitut at Bayreuth, while at the University of Hanover, the Institute of Mineralogy gradually also became an internationally recognized center for the study of silicate melt–gas interactions. At the same time French silicate melt research became concentrated in Paris and Orleans. We felt at that time that further ´ progress in these endeavors would benefit from meetings organized on a regular basis. Thus, a renewed meeting series, deliberately international in
scope, was initiated in Alsace in 1991 under the name International Silicate Melt Workshop. Much has changed since the first 1981 meeting. On certain problems great progress have been made, for example, the atomistic steps leading to viscous flow of silicate liquids as observed by NMR. The further application of this technique to study medium range order is one of the more recent developments. The experimental study of the solubility of water and carbon dioxide in silicate melts as functions of pressure and temperature and composition has seen seminal advances. The field has progressed, once and for all, beyond the stage of ideal mixing and regular solution models. The discovery of the first glimpses of medium ranged order in silicate melts and glasses has now relegated the once dominant completely random network work model to the museum shelf. The database concerning physical and thermodynamic characteristics of melts and glasses has improved enormously in quantity as well as quality. Most of current knowledge here on silicate liquids has been acquired during the last 20 years. Silicate Melt Workshop participants have obtained many of these data in their laboratories. Numerical simulation of silicate melts has now passed the stage where one noticed with a great sense of accomplishment that silicon atoms have four oxygen atoms as nearest neighbors. These numerical experiments have become very sophisticated and have begun to contribute significantly to our understanding of the equilibrium and transport properties of melts. A perusal
0009-2541r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 9 - 2 5 4 1 Ž 0 0 . 0 0 3 0 2 - 8
2
Editorial
of the Chemical Geology volumes containing reports of the Silicate Melt Workshops speaks for itself in this respect. There remains much to be done. The solubility of sulfur-containing gases has not yet received the attention it deserves. The rheology of suspensions, Žhere melts with crystals andror bubbles. remains a powerful challenge to general solutions of magma flow. Measurements of surface tension, and its consequences for the curvature of interfaces only recently received a re-awakened interest. Numerical simulation studies have become much more realistic, but it remains to see whether they will ever be sufficiently trustworthy to produce quantitative results. In any case, this will depend on the availability of better interatomic potentials. Moreover, Molecular Dynamics and Monte Carlo methods need to be applied to samples of several millions of particles in order to have a realistic picture of medium ranged order. Structural and compositional heterogeneity of silicate melts in the transition region has been the subject of much modeling and speculation. However, these models with their not directly measurable variables such as Afree volumeB, have not yet succeeded in predicting observable effects or explaining in sufficient detail the known characteristics of 3D network liquids. Hence, the true significance of the glass transition and the Kauzmann paradox remain shrouded in mystery. The inspiration of much silicate melt research is its link to the world of volcanology. To avoid the fate of research into dead languages, such as Latin, silicate melt research, in a geoscientific context, must also address problems in physical volcanology. Here we have great good fortune, because the new generation of numerical modellers of eruptive scenarios has an unbridled appetite for silicate melt property data of the highest quality. In fact, research into the strength and failure of silicate melts has helped to redefine the mechanistic basis of explosive volcanism in recent years. Historically the interaction between winegrowers and consumers has lead to the development of great wines. Thus, it is a part of our responsibility to present our observations in such a way that useful generalizations become obvious. Silicate liquids and water have in common that they are both liquids with an internal three-dimensional network structure and are the two most abun-
dant liquids on Earth. An inevitable consequence of this observation is that research on this type of liquid should be of very general interest. Those who study the general and principal properties of water understand the importance of their work quite well and very frequently publish their findings in the general science press. We happily remind the reader that the scientific principles to be gleaned from the study of silicate network liquids are as comparable in significance to those derived from water studies. The occurrence of the glass transition can be better observed in liquid silicates than in water or aqueous solutions. Hence, one should not forget to make more use of the general science periodicals for the publication of newly determined or discovered general physical or chemical properties. Such action will enhance the image of Earth Science liquid silicate research. The fact that physicists and physical chemists studying liquids rarely mention the properties of silicate liquids reveals a clear deficit that we must solve through communication. During the past 20 years the Silicate Melt Workshops have been quite effective in fostering cooperation between scientists among across formal disciplinary boundaries through their mutual curiosity for silicate melts. This has contributed materially to the evolution of this field. This new issue of Chemical Geology will be a new testimony to it. A perusal of the summary will underline the importance paid to water as a component of naturally occurring melts. Much of this work has been made within the framework of a TMR Research Network AIn Situ Hydrous MeltsB conceived and coordinated at CRSCM-CNRS Orleans. ´ In closing, two of the authors of this editorial ŽDBD, University of Munich and PR, Institut de Physique du Globe, Paris. take great pleasure in reminding the reader that this 6th Silicate Melt Workshop was dedicated to their long-time friend, colleague and co-organizer, Yan Bottinga ŽInstitut de Physique du Globe, Paris. in recognition of his benchmark contributions to the understanding of silicate melts. Held in the 18th century utopian Royal saltworks of Arc-et-Senans, constructed in the French Jura by Claude-Nicolas Ledoux, this meeting fitted very well with Yan’s well-known architectural interests. This most impressive and audacious ensemble of buildings contributed to the success of the meet-
Editorial
ing. The support received from Naturalia and Biologia, which we gratefully acknowledge, has helped us arrange the workshop in such a marvelous setting. Y. Bottinga Institut de Physique du Globe, 4 Place Jussieu, 75252 Paris Cedex 05, France E-mail address: [email protected] D.B. Dingwell Institut fur ¨ Mineralope, Petrologie und Geochemie, UniÕersitat ¨ Munchen, ¨ Theresienstr. 41, 80333 Munchen, Germany ¨ E-mail address: [email protected]
3
P. Richet Institut de Physique du Globe, 4 Place Jussieu, 75252 Paris Cedex 05, France E-mail address: [email protected]