HR: 1340h
AN: V53C-1576    [Abstracts]
TI: Dyke Nucleation And Earlier Growth From Pressurized Magma Chambers:Insights From Analogue Models
AU: Merle, O
EM: merle@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, 5 rue Kessler, Clermont-Ferrand, 63038 France
AU: * Ca¤¢n-Tapia, E
EM: ecanon@cicese.mx
AF: CICESE, Dept de Geologia, P.O. Box 434843 san Diego, California, San Diego, Ca 434843 United States
AB: Nucleation and dyke growth from magma chambers are important, yet poorly understood aspects of magma transport in the lithosphere. To tackle this issue, we conducted qualitative experiments using gelatin and silicone to simulate, respectively, country rock and magma. In our experiments the pressurization of the magma-filled reservoir was the main responsible for dyke formation rather than the density difference between magma and country rock. Our results show that an overpressurized magma chamber leads to simultaneous nucleation of dykes in different parts of the reservoir, especially at places with large angular irregularities where local perturbation of elastic stress occurs. Early propagation of the leading-edge of a dyke results in arc-shape tabular intrusions that are controlled by the stresses surrounding the overpressurized magma chamber. The overall process of earlier dyke formation reveals three stages: 1) very rapid increase of the fracture length at constant width, 2) arrest of the intrusion front and 3) thickening of the intrusion. These stages suggest that dyke propagation to the surface occurs through several steps separated by the time needed for the renewal of magma pressure in the reservoir. In consequence, our experiments suggest that overpressurization of a magma chamber is a necessary condition that must be met to explain why is that some magmas can reach the surface even when the reservoir is located in a region close to the neutral buoyancy, but that the distribution of such overpressure is a dynamic variable that requires further examination.
DE: 8178 Tectonics and magmatism
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8445 Experimental volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005