What controls sill formation: an overview from analogue models

Abstract

This data publication includes movies and figures of twenty-six analogue models which are used to investigate what controls sill emplacement, defining a hierarchy among a selection of the proposed factors: compressive stresses, interface strength between layers, rigidity contrast between layers, density layering, ratio of layer thickness, magma flow rate and driving buoyancy pressure (Sili et al., 2019).


Crust layering is simulated by pig-skin gelatin layers and magma intrusions is simulated by colored water. The experimental set-up is composed of a 40.5 X 29 X 40 cm3 clear-Perspex tank where a mobile wall applies a deviatoric compressive stress (C, in Table 1) to the solid gelatin (Figure 1). In each experiment is imposed two layers with different density and rigidity, separated by a weak or strong interface, excluding two experiments characterized by homogeneous gelatin (experiment 4 and 12). Three different rigidity contrast (1, 1.3, 1.8) between the two layers are imposed, defined as the ratio between the Young’s moduli of the upper (Eu) and lower (El) layer. By using NaCl and gelatin concentration, two layers with same rigidity but different densities are obtained, investigating the influence of the density contrasts on sill emplacement. The effects of the ratio between layer thicknesses (i.e. the ratio between upper and lower layer thickness: Thu/Thl) was simulated by changing only the thickness of the upper layer; while magma flow rate are studied changing the flow rate of peristaltic pump.


Water density was increased by adding NaCl to analyze the effect of changing driving buoyancy pressure (Pm) that depends on the density difference between host rock and magma (Δρ), gravitational acceleration (g) and intrusion length (H). In the table different colors indicate the experiment result: black = dike; red = sill and blue = sheet. The here provided material includes time-lapse movies showing intrusion propagation of the twenty-six models with a velocity of 5 times higher compared to the real time (1 second in the movie is 25 real seconds). These visualizations are side (XZ or YZ plane in Figure 1) and/or top views (XY plane in Figure 1).

Authors

• Sili, Giulia;Universitá degli studi "Roma TRE", Rome, Italy
• Urbani, Stefano;Universitá degli studi "Roma TRE", Rome, Italy
• Acocella, Valerio;Universitá degli studi "Roma TRE", Rome, Italy

Contact

• Sili Giulia (Student) ; Universitá degli studi "Roma TRE", Rome, Italy;

Contributors

Laboratory of Experimental Tectonics (University of Roma TRE, Italy); Sili Giulia

Keywords

buoyancy pressure, intrusion, magmatic process, EPOS, multi-scale laboratories, analogue models of geologic processes, analogue modelling results, Density, Fracture toughness, Yield stress, Young modulus, dike, sill, earth interior setting > crust setting > continental-crustal setting > upper continental crustal setting, Gelatine > Pig skin, Water, Generic camera, Glass/Plexiglas box > Glass/Plexiglas box (cm scale), magmatic process > intrusion, Density, Fracture toughness, Gelatine > Pig skin, Generic camera, Glass/Plexiglas box > Glass/Plexiglas box (cm scale), Water, Yield stress, Young modulus, dike, earth interior setting > crust setting > continental-crustal setting > upper continental crustal setting, magmatic process > intrusion, sill