Deciphering viscous flow of frictional melts with the mini-AMS method |
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| Affiliation: | 1. Department of Geology, Southern Illinois University, Carbondale, IL 62901-4324, USA;2. Department of Geosciences, National Taiwan University, Taipei 106, Taipei, Taiwan, ROC;3. Department of Earth Sciences, National Taiwan Normal University, Wenshan District, Taipei, Taiwan, ROC;4. School of Earth & Environment, University of Leeds, Leeds, UK;5. Department of Geosciences, University of Texas at Dallas, Richardson, TX 75080-3021, USA;1. ICT – Instituto de Ciências da Terra, Pólo da Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal;2. Tectonophysics, Institute of Geoscience, University of Mainz, 55128 Mainz, Germany;3. ICT - Instituto de Ciências da Terra, Pólo da Universidade do Porto / Departamento de Geociências, Ambiente e Ordenamento do Território, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal;4. School of Earth, Atmosphere and Environment, Monash University, 3800 Clayton, VIC, Australia;1. Institut für Geowissenschaften, Universität Frankfurt a.M., Altenhöferallee 1, D-60438, Frankfurt a.M., Germany;2. Institut für Neuroradiologie, Universität Frankfurt a.M., Theodor-Stern-Kai 7, 60596, Frankfurt a.M., Germany;1. Université de Cergy-Pontoise, Département Géosciences et Environnement, 95000 Cergy-Pontoise, France;2. Federal Office of Topography swisstopo, Wabern, Switzerland;1. School of Geosciences, University of Louisiana at Lafayette, Lafayette, LA 70504, USA;2. Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, USA;3. Biodiversity and Climate Research Centre and Senckenberg, Frankfurt am Main, Germany;4. Department of Geosciences, Goethe University Frankfurt, 60438 Frankfurt, Germany;5. Department of Geosciences, University of Wisconsin, Madison, WI 53706, USA;6. Institute of Mineralogy and Geochemistry, University of Lausanne, Lausanne, Switzerland;7. New Mexico Bureau of Geology and Mineral Resources, New Mexico, Institute of Mining and Technology, Socorro, NM, USA;1. Department of Geology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand;2. School of Geography, Environment, and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6012, New Zealand;3. GNS Science, PO Box 30-368, Lower Hutt, 5040, New Zealand;4. Department of Mathematics and Statistics, University of Otago, PO Box 56, Dunedin, 9054, New Zealand |
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| Abstract: | The anisotropy of magnetic susceptibility (AMS) is widely used to analyze magmatic flow in intrusive igneous bodies including plutons, sills and dikes. This method, owing its success to the rapid nature of measurements, provides a proxy for the orientation of markers with shape anisotropy that flow and align in a viscous medium. AMS specimens typically are 25 mm diameter right cylinders or 20 mm on-a-side cubes, representing a volume deemed statistically representative. Here, we present new AMS results, based on significantly smaller cubic specimens, which are 3.5 mm on a side, hence∼250 times volumetrically smaller than conventional specimens. We show that, in the case of frictional melts, which inherently have an extremely small grain size, this small volume is in most cases sufficient to characterize the pseudotachylyte fabric, particularly when magnetite is present. Further, we demonstrate that the mini-AMS method provides new opportunities to investigate the details of frictional melt flow in these coseismic miniature melt bodies. This new method offers significant potential to investigate frictional melt flow in pseudotachylyte veins including contributions to the lubrication of faults at shallow to moderate depths. |
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| Keywords: | Pseudotachylyte Anisotropy of magnetic susceptibility Fabric Frictional melt Fault Magma flow |
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