This dataset compiles quantitative outputs from eight sandbox experiments conducted under different boundary conditions (differential extension, strong blocks, and a weak zone). It contains 3-D scanning–derived digital elevation models (DEMs) from the final stage of experiments simulating the V-shaped opening of the South China Sea. In addition, it includes particle image velocimetry (PIV) products at four extension states (25 mm, 50 mm, 75 mm, and 100 mm), together with the plotting codes used to generate the figures.
This data set includes the results of digital image correlation analysis applied to analogue modelling experiments (Table 1) on the effect of weakness during distributed crustal extension performed at the Helmholtz Laboratory for Tectonic Modelling (HelTec) of the GFZ German Research Centre for Geosciences in Potsdam. Ten generic analogue models made of a layer of Quartz sand (G12, Rosenau et al., 2018) including a weak silicone oil “seed” (PDMS G30M, Rudolf et al., 2016) to localize deformation have been extended on top of a basal foam block. A benchmark experiment (basal foam only) and a reference model (layer of sand without seed) are also reported. Detailed descriptions of the experiments can be found in Osagiede et al. (2021) to which this data set is supplement. The models have been monitored by means of digital image correlation (DIC) analysis (Adam et al., 2005). DIC analysis yields quantitative information about model surface deformation in 2D and 3D. The data presented here are visualized as finite strain and displacement maps as well as cumulative strain and displacement profiles.
This data set includes images and videos depicting the evolution of deformation and topography in 17 analogue experiments of passive margin development, to better understand the ongoing tec-tonics along the western margin of Afar, East Africa. The tectonic background that forms the basis for the experimental design is described in Zwaan et al. 2020a-d, and references therein. The ex-periments, in an enhanced gravity field in a large-capacity centrifuge, examined the influence of brittle layer thickness, strength contrast, syn-rift sedimentation and oblique extension on a brittle-viscous system with a strong and weak viscous domain.
All experiments were performed at the Tectonic Modelling Laboratory of the Istituto di Geoscience e Georisorse - Consiglio Nazionale delle Ricerche (CNR-IGG) and of the Earth Sciences Department of the University of Florence (CNR/UF). The brittle layer (sand) thickness ranged between 6 and 20 mm, the underlying viscous layer, split in a competent and weak domain (both viscous mixtures), was always 10 mm thick. Asymmetric extension was achieved by removing a 1.5 mm thick spacer at the side of the model at every time step, allowing the analogue materials to spread when en-hanced gravity was applied during a centrifuge run.
Differential stretching of the viscous material creates flexure and faulting in the overlying brittle layer. Total extension amounted to 10.5 mm over 7 intervals for Series 1 models that aimed at un-derstanding generic passive margin development in a generic orthogonal extension setting, where-as up to 16.5 mm of extension was applied for the additional Series 2 models aiming to reproduce the tectonic phases in Afar. In models involving sedimentation, sand was filled in at time steps 2, 4 and 6 (i.e. after 3, 6 and 9 mm of extension). Detailed descriptions of the experiments, monitoring techniques and tectonic interpretation of the model results are presented in Zwaan et al. (2020a).
The dataset includes movies of 29 analogue experiments performed to investigate the effects on dike propagation by the following imposed parameters: density ratio between host-rock and magma analogues, rigidity layering and density layering of the host medium, flow rate and topography. The purpose of the experiments is to define a hierarchy of all the parameters considered, by varying systematically each of them, comparing semi-quantitatively the variations on dike geometry and velocity.
Experimental setup
The experimental set-up consists of a 33 × 58 × 38.5 cm3 Plexiglas box and a peristaltic pump that injects water (magma analogue) into pig-skin gelatin (crustal analogue) alternatively from the bottom (Set 1) and the side of the box (Set 2).
The gelatin rheological properties are varied by mixing different concentrations of gelatin powder and NaCl. We refer to “rigidity layering” when the rigidity ratio (i.e. Young’s Modulus) between the upper and lower layer (Eu/El) is < or > 1, and to “density layering” when Eu/El ~ 1, but the two layers show different densities (i.e. the ratio between the density of the upper and lower layer, ρU/ρL). The experiments with topography are prepared by imposing a mold with gently inward dipping flanks (2.4° and 3.7°) on the opposite sides of the box separated by a 8 cm wide horizontal plain on the gelatin surface.
This configuration simulates the 2-D along-strike topography of the 2014 Bardarbunga intrusion (Iceland) and allows investigating the role of two opposite slopes on dike propagation. The topography profile dips parallel to the long side of the Plexiglas box (x axis in Figure 1 of Urbani et al. 2018). The flow rate has been changed between 0.079 and 0.435 ml/s. For the details about the model set-up, experimental results and interpretation refer to Urbani et al. (2018).
The time-lapse movies show the time evolution of the dike shape, in side and map view, of 29 out of 33 models presented in Urbani et al. (2018). It is recommended to open the films with the VLC media player. The time-lapse of each experiment is indicated in the bottom left corner.
A full list of files is given in “Experiments_Summary_2018-012.pdf” in which Set 1 (bottom injection) and Set 2 (lateral injection) experiments are indicated in red and blue color respectively. The same file also provides a summary of the boundary conditions imposed in each experiment. Tu and Tl indicate the thickness of the upper and lower layer respectively.