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 18 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 circumscribes the plume centre, (2) intrusions emplaced along linear rifts that, in some cases, converge towards the plume centre, and (3) single or 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.

The Magmatic Architecture of Continental Flood Basalts: 2. A New Conceptual Model

“…Third, CFB models should account for pre‐existing tectonic structures and specific crustal properties since these strongly influence the location of magma bodies and their ability to erupt (e.g., presence or absence of a sedimentary basin). Fourthly, non‐magmatic stresses due to uplift from the mantle plume head, continental rifting, and surface loading by lava flows (Blanchard et al., 2017; Ernst et al., 2019; Hieronymus & Bercovici, 2001; Karlstrom et al., 2009; McGovern et al., 2015; Rooney et al., 2014; Saunders et al., 2007; Tibaldi, 2015) are also potentially very important for determining the magmatic architecture and orientation of crustal dike swarms.…”

LIPs and implications for the structure and evolution of continental crust

“…The most successful method for locating paleomantle plumes is using regional dyke swarms of LIPs. Recognition of mantle plumes is significant for continental crust for many reasons including the following: 1) as a locus of lithospheric thinning and continental breakup (or attempted, but failed breakup) (Courtillot et al 1999;Ernst and Bleeker 2010); 2) for locating the central region (within about 500 km of the plume centre) that is the locus of a magmatic underplate and intracrustal intrusions (Blanchard et al 2017;Ernst et al 2018); 3) providing constraints on deep geophysical interpretations based on a knowledge of the LIP plumbing system (Ernst et al 2018); and 4) Influence on resource exploration for ore deposits and oil/gas (Ernst and Jowitt, 2013)---for instance, to predict regions in which heat from the plume destroyed diamond potential in the overlying lithospheric mantle root. In addition, the newly discovered class of giant circumferential swarms can mark the outer edge of the plume at a radius of about 1000 km (Buchan and Ernst, 2018a,b).…”

Recording the largest gabbro-anorthositic complex worldwide: The Kunene Complex (KC), SW Angola

“…The main faults, mapped by Carvalho, 1982 geochemical and geochronological methods, but no gravity modelling has been performed. Some previous works dealing with gravity and magnetic data can be found in Blanchar et al (2017), that reports a magnetic and gravimetric study in the Kibarian Belt; Braitenberg (2015), compiling the Earth gravity data from satellite missions; and Finn et al (2015), mapping the 3D extent of a mafic intrusion in South Africa. The aim of this paper is to decipher the deep geometry of the KC and the crystalline basement of SW Angola in a remote area where the unique public/open access gravity information, covering the whole study area, exists throughout the published data of the Bureau Gravimetrique International (Bonvalot et al, 2012).…”