**1. Introduction**

Hydrocarbon discoveries associated with magmatic intrusions are common in many sedimentary basins throughout the world [1–3], and these intrusions may potentially a ffect all parts of the petroleum system [4]. The impact of magmatic intrusions has been studied in several basins worldwide, e.g., Vøring Basin, Norway (e.g., [5–7]), Karoo Basin, South Africa (e.g., [8–10]), Gunnedah Basin, Australia [11], Neuquén Basin, Argentina (e.g., [12,13]), Bohai Bay Basin, China (e.g., [14,15]). All these studies conclude that magmatic intrusions significantly influence the basin thermal history and thus the maturation of organic material in their vicinity.

Several studies have identified the pre-intrusion temperature of the host rock as an important variable for the ultimate thermal and maturation levels of sedimentary basins with magmatic intrusions [8,10,13,16–18]. However, this variable is one of the most di fficult parameters to constrain, as the traces of pre-intrusion temperature and maturation are erased instantly in the thermal aureole of magmatic intrusions when magmatic emplacement occurs [19] and the basin has been subject to later geological development. As magmatic intrusions often are emplaced into structurally complex sedimentary basins, it is crucial to understand how the basin's structural evolution a ffects the

temperature development. With such knowledge it should be possible to discern temperature e ffects of the structural development from temperature e ffects of magmatic intrusions. This is important as the pre-intrusion temperatures have implications for the magnitude of the thermal e ffect of sills, i.e., size and temperatures of the thermal aureole, which eventually will have implications for the estimated maturation of the basin.

Magmatic intrusions and their e ffect on temperature and maturation in the surrounding host rocks have been subject of several studies (e.g., [8,13,19–24]). Only a few studies model sills intruding into structurally complex basins under development, while taking the temporary host-rock temperature and maturation into consideration (e.g., [7,25]). Structurally complex basins are characterized by numerous faults, changing lithologies with di fferent physical properties and area specific heat flow. To estimate the basin's thermal development as a function of time, the geohistory of the basin must first be established by reconstruction. In standard basin modeling, the impact of the structural development on the temperature history is seldom taken into account and this may give incorrect thermal and maturation predictions [26].

Several studies exist on temperature modeling in fault zones, but many of these focus on the e ffects related to uplift and erosion observed in the footwall part of the fault zone and not on the thermal transients in the hanging wall section (e.g., [27–34]). To our knowledge no studies includes magmatism in a fault setting. In our study the main focus is on the transient thermal e ffects of normal faults with syn- and post-rift deposits, and the influence such structural development has on the thermal e ffects of sills. Possible transient thermal e ffects due to erosion have not been pursued in this study.

The calculated pre-intrusion temperatures are dependent on the representation of the basin's structural development [13,25,26]. The purpose of this study is to quantify the thermal e ffects of the most important factors a ffecting the thermal history in structurally complex sedimentary basins with magmatic sill intrusions. We do this by running a series of simple models. A more realistic model would require higher structural resolution with variation of lithological and geometrical properties in space and time. However, many simultaneously varying factors a ffecting the thermal evolution would obscure the magnitude and impact of the individual factors. We therefore first study the thermal e ffects on structural complex basin on a simple, synthetic profile followed by analysis of the subsequent sensitivity sets: (1) fault displacement, (2) time span of faulting and deposition, (3) fault angle, (4) thermal conductivity and specific heat capacity, (5) basal heat flow and (6) restoration method. The overall goal is to test the sensitivity of faulting, physical properties of the lithologies and choice of fault restoration method on the thermal e ffect of magmatic intrusions in complex sedimentary basins. We aim for some general conclusions that are applicable to sedimentary basins with normal faults and magmatic sill intrusions.
