科研之友
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摘要
The present paper examines magmatic structures in the Jizera and Liberec granites of the Krkonose-Jizera Plutonic Bohemian Massif The magmatic structures are here interpreted to preserve direct field evidence for highly localized magma and other processes in crystal-rich mushes, and to capture the evolution of physical processes in an ancient granitic chamber. We propose that after chamber-wide mixing and hybridization, as suggested by recent petrological studies, magma flow became highly localized to weaker channel-like domains within the higher-strength crystal framework. schlieren formed at flow rims, and their formation presumably involved gravitational settling and velocity gradient flow coupled with interstitial melt escape. Local thermal or compositional convection may have resulted in the formation of schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in pressure. After the cessation or deceleration of channel flow, gravity-driven processes (settling of crystals and gravitational differentiation, development of downward dripping instabilities), accompanied by compaction, filter pressing melt segregation, dominated in the crystal mush within the flow channels. Subsequently, magmatic folds developed in layers and the magma chamber recorded complex, late magmatic strains at high magma crystallinities. Late-stage magma into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final We emphasize that the most favorable environments for the formation and preservation of magmatic structures, such as hosted in the Jizera and Liberec granites, are slowly cooling crystal-rich mushes. Therefore, where preserved in plutons, structures may lend strong support for a "mush model" of magmatic systems.
- 出版日期2007-8-1
