Felsic alkaline igneous rocks include silica-undersaturated (e.g. phonolite, nepheline syenite), peralkaline silica-oversaturated (e.g. pantellerite, alkali granite) and critically saturated (trachyte, syenite) rocks. They are uncommon globally but have attracted a lot of attention from petrologists over the history of geology because their mineralogy and chemistry deviate markedly from those of the more common metaluminous granite-rhyolite clan. Alkaline rocks are typically strongly enriched in incompatible elements, a consequence of source chemistry and differentiation processes. These elements include the halogens F and Cl. Plutonic alkaline rocks are important sources for strategic metals, especially rare earth elements, Zr, Nb, Hf and Ta. Alkaline volcanoes located near populated regions pose significant hazards, for example Campi Flegrei, Italy; Tenerife, Spain; Changbaishan, China; and several volcanoes in East Africa. The origins, characteristics, behaviour and eruptibility of alkaline magmatic systems are therefore of critical interest.
The processes by which highly differentiated magma bodies evolve and either crystallize or erupt are of great topical interest to the petrology-volcanology community. The current paradigm is based on the concept of a trans-crustal magma system, consisting of pools of mobile, crystal-poor magma in a column dominated by static crystal-melt mush. Both magma and mush are overall more differentiated upwards. This model has largely been constructed through studies of metaluminous rhyolites and granites in calc-alkaline igneous suites. Alkaline rocks occur in different tectonic environments, have distinct chemistry, mineralogy, magma physical properties and phase relations, and hence the potential to shed a different light on dynamic processes within magma reservoirs and the evolution of differentiated magmas.
A key question is, do alkaline magmas exhibit truly different behaviour to the more common metaluminous systems, or do we simply get different insights into universal magmatic processes due to different chemistry and phase relations? With this in mind, we encourage submissions that consider any of the following subjects:
• Emphasis on magmatic processes;
• Physical modelling studies of magma dynamics;
• The role of volatile constituents, especially halogens F, Cl, Br and I, during magmatic differentiation;
• Experimental petrology investigations;
• Detailed descriptions and interpretations of individual geological examples;
• Comparisons between alkaline and metaluminous systems;
• Critical metals ore-forming-processes associated with magmatic differentiation in evolved alkaline systems;
• Although mantle melting, mafic alkaline magmatism and carbonatites are not the principal focus areas of the article collection, studies incorporating these topics are welcome insofar as they address the main issue of magmatic evolution producing alkaline felsic rocks.
Felsic alkaline igneous rocks include silica-undersaturated (e.g. phonolite, nepheline syenite), peralkaline silica-oversaturated (e.g. pantellerite, alkali granite) and critically saturated (trachyte, syenite) rocks. They are uncommon globally but have attracted a lot of attention from petrologists over the history of geology because their mineralogy and chemistry deviate markedly from those of the more common metaluminous granite-rhyolite clan. Alkaline rocks are typically strongly enriched in incompatible elements, a consequence of source chemistry and differentiation processes. These elements include the halogens F and Cl. Plutonic alkaline rocks are important sources for strategic metals, especially rare earth elements, Zr, Nb, Hf and Ta. Alkaline volcanoes located near populated regions pose significant hazards, for example Campi Flegrei, Italy; Tenerife, Spain; Changbaishan, China; and several volcanoes in East Africa. The origins, characteristics, behaviour and eruptibility of alkaline magmatic systems are therefore of critical interest.
The processes by which highly differentiated magma bodies evolve and either crystallize or erupt are of great topical interest to the petrology-volcanology community. The current paradigm is based on the concept of a trans-crustal magma system, consisting of pools of mobile, crystal-poor magma in a column dominated by static crystal-melt mush. Both magma and mush are overall more differentiated upwards. This model has largely been constructed through studies of metaluminous rhyolites and granites in calc-alkaline igneous suites. Alkaline rocks occur in different tectonic environments, have distinct chemistry, mineralogy, magma physical properties and phase relations, and hence the potential to shed a different light on dynamic processes within magma reservoirs and the evolution of differentiated magmas.
A key question is, do alkaline magmas exhibit truly different behaviour to the more common metaluminous systems, or do we simply get different insights into universal magmatic processes due to different chemistry and phase relations? With this in mind, we encourage submissions that consider any of the following subjects:
• Emphasis on magmatic processes;
• Physical modelling studies of magma dynamics;
• The role of volatile constituents, especially halogens F, Cl, Br and I, during magmatic differentiation;
• Experimental petrology investigations;
• Detailed descriptions and interpretations of individual geological examples;
• Comparisons between alkaline and metaluminous systems;
• Critical metals ore-forming-processes associated with magmatic differentiation in evolved alkaline systems;
• Although mantle melting, mafic alkaline magmatism and carbonatites are not the principal focus areas of the article collection, studies incorporating these topics are welcome insofar as they address the main issue of magmatic evolution producing alkaline felsic rocks.
