Modelling of Igneous Intrusions Based on Emplacement Mechanisms

Abstract:

Geological 3D modelling has been widely used for the characterisation of rock distributions and structures in Earth’s subsurface. During the last decade, significant improvements have been made on 3D modelling of folds and faults with incorporation of geological knowledge into the modelling approach. In this contribution, we present a new method for the stochastic simulation of igneous intrusions that considers conceptual knowledge of emplacement mechanisms and the use of constraints from field observations.

The method is based on the Object-distance simulation method and has four main steps. The first step is the construction of an intrusion network, which represents the roof or floor contacts of the body. The intrusion network is simulated using a geological model of the area, anisotropies of the host rock, and field measurements. The second step consists in computing a custom distance field to build the coarse-scale geometry of the intrusion. The scalar field is then stochastically perturbed to generate realistic small-scale geometries. Finally, the model is conditioned to field observations.

The methodology was tested in one synthetic case that represents a sill emplaced into folded and faulted rocks of a sedimentary basin. The results show that the method accurately reproduces the geometry of intrusions observed in this type of system, such as steps, splitting of segments, and thickness changes. It also allows for testing of different scenarios to account for variability of host rock anisotropies. Further work will include tests of the methodology in natural cases studies.