3D Numerical Models for Along-axis Variations in Diking

Abstract:

For slow to intermediate spreading rate mid-ocean ridge (MOR) segments, magma supply decreases from center to tip if magma propagates from a central magma chamber to segment ends. Along-axis variation of magma supply implies changes in the amount of lithospheric extension accommodated by diking, which in turn are responsible for a variety of faulting styles, thermal structures and topography. Recent 2D numerical studies expressed the ratio between rate of dike injection and tectonic extension as a factor M and have successfully explained many characteristics of MOR tectonics. While they proved useful for understanding tectonics across axis, 3D models are still necessary for studying tectonic consequences of along-axis variations in diking. Here, we carry out 3D numerical experiments for such variations in diking by introducing the M factor formulation into SNAC, an updated Lagrangian explicit finite element code for modeling elasto-visco-plastic solid in 3D. We validate the M factor formulation implemented in SNAC through benchmarks against previous 2D models and will show 3D models under various scenarios for along-axis variation in M. We will also compare the 3D models with field observations and discuss implication for a formation mechanism of oceanic core complexes.