[S-IT17] Mass and energy transport in the crust and mantle: from properties to processes

[SIT17-09] Importance of deformation texture and anisotropic permeability in melt transport and large eruptions

*Boda Liu¹, Chao Qi², Ross N Mitchell¹, Cin-Ty Lee³, Chuan-Zhou Liu⁴ (1.Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, 2.Center for High Pressure Science and Technology Advanced Research, Beijing, China, 3.Department of Earth, Environmental & Planetary Sciences, Rice University, Houston, TX, USA, 4.Laoshan Laboratory, Qingdao, China)

Keywords:melt preferred orientation, permeability, mush, volcanic trigger

In a deforming partially molten rock, melt concentrates into a grain scale melt pocket aligned at a preferred orientation (melt preferred orientation, or MPO). Here, we modeled the MPO of experimentally deformed peridotites by simulating melt streaks arising from melt pockets of various shapes and 3D orientations. Observed MPO can then be incorporated into the simulation of melt flow through individual melt pockets, which allows us to estimate the permeability corresponding to the observed MPO.
We found that the permeability of vertically compressed peridotites increases with increasing compressive strain and a more elongated and thickened shape for melt pocket aligned at preferred orientation. For peridotites deformed under simple shear, the permeability exhibits an anisotropy of at least three. Such anisotropic permeability, coupled with the formation of melt rich bands and other melt channels, is believed to cause lateral melt focusing beneath midocean ridges. The same mechanism also accelerates rhyolite extraction and causes explosive eruptions.