Geodynamic assessment of heat flow evolution in the Porcupine basin, Irish Offshore

Abstract

The Porcupine basin, on the Irish Atlantic Margin, has experienced a complex history, including multiple inversion phases (Corcoran and Clayton, 2001) and significant magmatic activity, particularly emplacement of sills (Fernandes, 2011). Additionally, numerous authors (e.g. Calvès et al, 2012) have described a large elongated structure, the Porcupine Median Volcanic Ridge (PMVR). There are similarities in this respect to the Norwegian Vøring basin where a large underplating body has been identified (Wangen et al., 2011 and Fjeldskaar et al, 2003) as having a great influence on the source rock maturation. The geological and geodynamic history in the Porcupine basin, including the local intrusions (sills) and the basin scale magmatic bodies, have created variation in the thermicity of the basin.

In this project, we model the evolution of the basin at several key locations to understand the impact of the geological and geodynamic variations on maturation. We model the geodynamic evolution at the lithospheric scale of the basins on the Atlantic Margin. The modelling methodology is a thinning model updated from McKenzie (1978) with variable amount of thinning in the crust and lithospheric mantle (Royden and Keen, 1980). The tectonic subsidence curves, combined with lithospheric parameters (e.g. thermal conductivity and heat production), allow the creation of an inverted tectonic model from which we obtain heat flow evolution through time. This is compared to the thermal and maturity indicators (i.e., Vitrinite Reflectance and present day temperature). The model takes into account a two-layer approach for the stretching of the lithosphere and considers the sediments, which allows a better representation of the basin. The impact of intrusions and underplating or any other magmatic activity during the lifetime of the basin is also considered in the model, allowing an accurate understanding of the complex evolution of the basin.

The objective of this work is to discriminate between the thermal sources through time in the basin in order to have a better understanding of the geological evolution of the Irish Atlantic Margin.

This is project no. IS13/18 financed by the Irish Petroleum Infrastructure Programme.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015