Gel wax and Ultrasound Transmission Gel as upper and lower crustal rheology analogue

The laboratory modelling of upper and lower crustal rocks has been challenging in terms of rheological scaling for geologists. Upper and lower crusts have been considered as coulomb-brittle or elastic and viscous rheological material, respectively, by the analogue modeller in simulating several deformation related phenomena. However, in nature, they are not purely viscous or elastic, or plastic. Rather, they behave visco-elasto-plastically. This work introduces two new materials of complex visco-elastic and visco-elastoplastic rheology i) Gel wax and, ii) Ultrasound Transmission Gel (USTG). Gel wax is a commercial wax which is composed of mineral oil and hydrocarbon-based polymer. It is used for making transparent, long-lasting candles with melting temperatures of 70-80°C. On the other hand, USTG is a gel-like substance made mainly of Carbopol powder and water.

In this present work, we performed amplitude and frequency sweep tests in a rheometer for both the Gel wax and USTG to understand their complex rheology. The results suggest that Gel wax can be an appropriate analogue material to simulate upper crustal experiments. Similarly, visco-elastoplastic rheology of USTG is analogous to lower crustal rocks.

Considering these materials as crustal analogues, we conducted a few dike emplacement experiments following proper geometric, kinematic and dynamic scaling. The experimental results revealed remarkable 3D dike geometry as both the materials are transparent. Finally, we matched these patterns with a few exposed dikes observed in the field, which supports the applicability of Gel wax and USTG as crustal rock analogues.