Gravity and magnetic modelling of layered mafic-ultramafic intrusions in large igneous province plume centre regions; Case studies from the: 1.27 Ga Mackenzie, 1.38 Ga Kunene-Kibaran, 0.06 Ga Deccan and 0.13-0.08 Ga High Arctic events

Abstract

Gravity and magnetic data from the global EGM2008 and EMAG2 datasets are used to identify geophysical anomalies in Large Igneous Province (LIP) plume centre regions with the goal of characterizing mafic-ultramafic intrusions linked to those LIPs. Geophysical anomalies within eighteen LIPs distributed globally are investigated. Four of these LIPs are selected for detailed modelling: the 1.27 Ga Mackenzie, 1.38 Ga Kunene-Kibaran, 0.06 Ga Deccan and 0.13-0.08 Ga High Arctic LIPs. We recognize three spatial distribution types for intrusions in plume centre regions. These are: 1) intrusions emplaced along a circular fault system that circumscribe the plume centre, 2) intrusions emplaced along linear rifts that, in some cases, converge towards the plume centre, and 3) single/unclassified intrusions. Modelling supports that the geophysical anomalies associated with these LIPs tend to be produced by large (radius > 30 km) and deep-seated crustal intrusions, with densities consistent with mafic-ultramafic rock and magnetic susceptibilities consistent with serpentinized ultramafic rock, except within the Deccan where intrusions are smaller, mainly mafic in composition, and positioned at shallower depths in the crust.