Quantifying the influence of sill intrusion on the thermal evolution of organic-rich sedimentary rocks in non-volcanic passive margins: an example from ODP 210-1276, offshore Newfoundland, Canada

Abstract

Intrusive magmatism is an integral and understudied component in both volcanic and non-volcanic passive margins. Here, we investigate the thermal effects of widespread (c. 20,000 km2) intrusive magmatism on the thermal evolution of organic-rich sedimentary rocks on the non-volcanic Newfoundland passive margin. ODP 210-1276 (45.41°N, 44.79°W) intersects two sills: an older, upper sill and a younger, lower sill that are believed to correspond to the high amplitude “U-reflector” observed across the Newfoundland Basin. A compilation of previous work collectively provides; 1) emplacement depth constraints, 2) vitrinite reflectance data and 3) 40Ar/39Ar dates. Collectively, these datasets provide a unique opportunity to model the conductive cooling of the sills and how they affect thermal maturity of the sedimentary sequence. A finite differences method was used to model the cooling of the sills, with the model outputs then being entered into the EASY%Ro vitrinite reflectance model. The modelled maturation profile for ODP 210-1276 shows a significant but localised effect on sediment maturity as a result of the intrusions. Our results suggest that even on non-volcanic margins, intrusive magmatism can significantly influence the thermal evolution in the vicinity of igneous intrusions. In addition, the presence of widespread sills on non-volcanic passive margins such as offshore Newfoundland may be indicative of regional-scale thermal perturbations that should be considered in source rock maturation studies.