Indentation of volcanic edifices by the ascending magma
Olivier Merle, Franck Donnadieu, 1999. "Indentation of volcanic edifices by the ascending magma", Salt, Shale and Igneous Diapirs in and around Europe, Bruno C. Vendeville, Yossi Mart, Jean-Louis Vigneresse
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The process by which magma ascends into and deforms a volcanic edifice is studied by analogue modelling. A control experiment is conducted with a wooden piston moving vertically into a sand cone. This reveals a well-defined fault pattern that makes it possible to draw the main compressive stress trajectory within the cone during the ascent of the piston. This makes it possible to show that the deformational process is that of indentation of the cone by the rigid piston. Experiments with an indenter that is viscous, as in nature, show that the motion of the viscous body is controlled by the first fault created in the cone. This fault serves as a structural guide, making the viscous body deviate from the vertical and resulting in deformation of the flank of the cone, which bulges out. Other major shear faults that were observed in the control experiment are then inhibited and do not form. This result emphasizes that the structural evolution of an indentation process within a brittle cone and at low rate depends on the rheology of the indenter.
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The ten articles in this book describe the mode of emplacement of various types of intrusions (salt diapirs, mud volcanoes and magmatic bodies) by means of theoretical reasoning, analogue and analytical modelling, interpretation of seismic and field data, and geodetic surveying. All the articles emphasize the role of regional tectonics in driving or controlling the emplacement of the intrusions. The selection of articles includes examples from Spain, Romania, onshore and offshore Italy, the Eastern Mediterranean, Israel and iran.
Better understanding of the mode of emplacement of these intrusions has applications in hydrocarbon exploration (e.g., where salt structures or mud diapirs are present) and in the mining industry (where mineralization is related to the emplacement of batholiths).