Intrusions of ultramafic bodies into the lower density continental crust are documented for a large variety of tectonic settings spanning continental shields, rift systems, collision orogens and magmatic arcs. The intriguing point is that these intrusive bodies have a density higher by 300-500 kg m −3 than host rocks. Resolving this paradox requires an understanding of the emplacement mechanism. We have employed finite differences and marker-in-cell techniques to carry out a 2D modeling study of intrusion of partly crystallized ultramafic magma from sublithospheric depth to the crust through a pre-existing magmatic channel. By systematically varying the model parameters we document variations in intrusion dynamics and geometry that range from funnel-and finger-shaped bodies (pipes, dikes) to deep seated balloon-shaped intrusions and flattened shallow magmatic sills. Emplacement of ultramafic bodies in the crust lasts from a few kyr to several hundreds kyr depending mainly on the viscosity of the intruding, partly crystallized magma. The positive buoyancy of the sublithospheric magma compared to the overriding, colder mantle lithosphere drives intrusion while the crustal rheology controls the final location and the shape of the ultramafic body. Relatively cold elasto-plastic crust (T Moho = 400 • C) promotes a strong upward propagation of magma due to the significant decrease of plastic strength of the crust with decreasing confining pressure. Emplacement in this case is controlled by crustal faulting and subsequent block displacements. Warmer crust (T Moho = 600 • C) triggers lateral spreading of magma above the Moho, with emplacement being accommodated by coeval viscous deformation of the lower crust and fault tectonics in the upper crust. Strong effects of magma emplacement on surface topography are also documented. Emplacement of high-density, ultramafic magma into low-density rocks is a stable mechanism for a wide range of model parameters that match geological settings in which partially molten mafic-ultramafic rocks are generated below the lithosphere. We expect this process to be particularly active beneath subduction-related magmatic arcs where huge volumes of partially molten rocks produced from hydrous cold plume activity accumulate below the overriding lithosphere.

Taras V. Gerya

Jean-Pierre Burg

Physics of The Earth and Planetary Interiors

《地球物理学》和《行星内部》于 1968 年推出，旨在满足行星物理学、大地测量学和地球物理学领域对国际期刊的需求，现已发展成为所有地球物理学家的重要阅读材料。它是唯一完全致力于行星内部物理和化学过程的期刊。原创研究论文、评论文章、短通讯和书评均定期发表；该杂志不时发布特刊，专门刊登编辑认为读者会特别感兴趣的专题讨论会和大会的会议记录。

"Physics of the Earth and Planetary Interiors" was launched in 1968 to meet the demand for an international journal in the fields of planetary physics, geodesy, and geophysics. It has since developed into an essential reading material for all geophysicists and is the only journal fully dedicated to the physical and chemical processes of planetary interiors. The journal regularly publishes original research papers, review articles, short communications, and book reviews, and occasionally releases special issues featuring conference proceedings and discussions on topics of particular interest to readers.

《Physics of the Earth and Planetary Interiors》创刊于1968年，旨在满足行星物理学、大地测量学和地球物理学领域对国际期刊的需求。该期刊现已成为所有地球物理学家的重要阅读材料，是唯一专注于行星内部物理和化学过程的期刊。期刊定期发表原创研究论文、评论文章、短通讯和书评，并不时发布特刊，专门刊登编辑认为读者会特别感兴趣的专题讨论会和大会的会议记录。

Category	Quartile
地球科学	3
地球科学, 地球化学与地球物理	3

Intrusion of ultramafic magmatic bodies into the continental crust: Numerical simulation

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Journal Info

Category	Quartile
GEOCHEMISTRY & GEOPHYSICS	2