New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

Abstract

Stress-dependent nonlinear upper mantle rheology has a firm base in rock mechanical tests, where this nonlinearity results from dislocation creep of minerals. In the last few decades there has been some attention to nonlinear, power-law, materials for application in scaled analogue experiments for tectonic processes. However, studies describing the rheology of analogue materials with the same nonlinear dependency on stress as observed for lithospheric mantle materials at relevant stress levels, are still lacking.In this study we have developed and rheologically tested materials based on combinations of silicone polymers and plasticine, with the aim of obtaining a material that can serve as a laboratory analogue to the power-law rheology of olivine aggregates at lithospheric mantle conditions. From our steadystate creep tests we find that it is possible to obtain such a power-law material, with effective viscosities over relevant model stress ranges We apply the developed material to a process where localized deformation of the lithosphere can be expected: slab break-off. We study this process using analogue models, where we apply the new nonlinear material to the lithospheric mantle domains, while we use Newtonian glucose to represent the low viscous asthenosphere. Now that we properly manage power-law behavior in our analogue lithosphere materials, we are able to model localized lithospheric tearing.

Rheological and kinematic conditions for forced subduction initiation at continental passive margins

“…The slope for the brittle stress is 294.3 Pa/cm representing ~58 MPa/km in nature which is close to Byerlee's law. To simulate ductile behavior, we use silicone putties with different densities and viscosities (Table 3.1), which approximate flow by creep (Broerse et al, 2019). The strength of the ductile layers is calculated for a simple power law flow law linking stress and strain rate (chapter 2, equation 2.20).…”