*2.3. Thermal E*ff*ects of Sills*

On reflection seismic data, upper and lower boundaries of sills can be difficult to discern due to limited vertical resolution (cf., [42–45]). Many sills may therefore be left out in seismic interpretations due to sill thicknesses below the detection limit of the data (e.g., [44,45]). Sill thickness, both when sills intrude individually or as clusters, has a large impact on the temperature and maturation in sedimentary basins (e.g., [8,25]). The relative timing between sills emplaced as clusters is especially important if potential source rocks are located between sills [25]. Reported sill thicknesses from the literature vary from ~10 cm to >400 m (e.g., [44,46–55]). In our study a modest sill thickness of ~50 m has been chosen for the modeled sills and we assume the sills to intrude during one pulse with a magma temperature of 1000 ◦C. In BMT this is done by changing the lithology in sill polygon from shale to sill lithology, with related physical properties at time of intrusion. The sills have been modeled to intrude at various times relative to fault slip. This is done to study the interaction of two transient thermal effects simultaneously. As the largest thermal and maturation impact of sill intrusions are found at 3–5 km depths [25], the sills are modeled to intrude within this depth range. Commonly magmatic sills observed in the field and on seismic images (e.g., [7,52]) are layer concordant. Therefore, the sills in the study are modeled accordingly.

Latent crystallization heat introduces an extra source of heat when magma cools and starts to crystallize [56,57]. This extra heat source is not taken into account, as it is the relative di fferences between scenarios that are of interest in our study. Heat advection by fluids in relation to magmatic intrusions is common (e.g., [5,58–61]). However, convection is not accounted for in our modeling, as convection is considered insignificant in low permeability rocks (e.g., [7,8,13,25,62]) and is beyond the scope of this study.
