Gondwana Large Igneous Provinces: plate reconstructions, volcanic basins and sill volumes

Abstract

Gondwana was an enormous supertarrane. At its peak, it represented a landmass of about 100 × 106 km2 in size, corresponding to approximately 64% of all land areas today. Gondwana assembled in the Middle Cambrian, merged with Laurussia to form Pangea in the Carboniferous, and finally disintegrated with the separation of East and West Gondwana at about 170 Ma, and the separation of Africa and South America around 130 Ma. Here we have updated plate reconstructions from Gondwana history, with a special emphasis on the interactions between the continental crust of Gondwana and the mantle plumes resulting in Large Igneous Provinces (LIPs) at its surface. Moreover, we present an overview of the subvolcanic parts of the Gondwana LIPs (Kalkarindji, Central Atlantic Magmatic Province, Karoo and the Paraná–Etendeka) aimed at summarizing our current understanding of timings, scale and impact of these provinces. The Central Atlantic Magmatic Province (CAMP) reveals a conservative volume estimate of 700 000 km3 of subvolcanic intrusions, emplaced in the Brazilian sedimentary basins (58–66% of the total CAMP sill volume). The detailed evolution and melt-flux estimates for the CAMP and Gondwana-related LIPs are, however, poorly constrained, as they are not yet sufficiently explored with high-precision U–Pb geochronology.

Distinct Degassing Pulses During Magma Invasion in the Stratified Karoo Basin—New Insights From Hydrothermal Fluid Flow Modeling

“…Based on borehole data published by Svensen et al (2018), we have estimated that the volume fraction of sills correspond to 19% of the Beaufort Gp. Note that this area is nearly 5 times greater than a previous estimate of 370,000-km 2 sill intrusion area published for the Karoo Basin (Svensen et al, 2017). (see supporting information S1 and Table S3.2 and Table 4).…”

“…2017). Note that we would have obtained an even smaller value if we had considered a sill volume fraction of only 3.4% (i.e., value corresponding to 370,000 km 2 ; Svensen et al, 2017). Note that we would have obtained an even smaller value if we had considered a sill volume fraction of only 3.4% (i.e., value corresponding to 370,000 km 2 ; Svensen et al, 2017).…”

“…The goal is to precisely quantify the amount and rates at which thermogenic gases are mobilized and released by venting into the ocean and/or atmosphere. To provide a potential basin-scale degassing estimate, the surface area of sill intrusions in the sedimentary basin of interest, for example,~85,000 km 2 in the Vøring and Møre Basins (offshore Norway, Svensen et al, 2004) and~370,000 km 2 in the Karoo Basin (South Africa, Svensen et al, 2017), is used to upscale the quantitative results obtained from a single cooling sill model (e.g., Aarnes et al, 2010;Iyer et al, 2013). A calibrated kerogen cracking model considering the breaking of different kerogen bounds (Sweeney & Burnham, 1990) allows to calculate the amount of thermogenic gas that is converted from the total organic carbon (TOC) present in the host-rock.…”

“…This kerogen cracking model has been used to estimate the degassing caused by contact metamorphism within the contact aureole around cooling sills (Iyer et al, 2018;Iyer et al, 2017;Iyer et al, 2013;Aarnes et al, 2015;Aarnes et al, 2011;Aarnes et al, 2010;Kjeldstad et al, 2003). To provide a potential basin-scale degassing estimate, the surface area of sill intrusions in the sedimentary basin of interest, for example,~85,000 km 2 in the Vøring and Møre Basins (offshore Norway, Svensen et al, 2004) and~370,000 km 2 in the Karoo Basin (South Africa, Svensen et al, 2017), is used to upscale the quantitative results obtained from a single cooling sill model (e.g., Aarnes et al, 2010;Iyer et al, 2013). These types of numerical studies establish that the LIP event that intruded the Karoo Basin potentially mobilized~2, 200 Gt CH 4 , while the magmatic event of the North Atlantic Province potentially mobilized~600-3,500 Gt CH 4 from the Vøring and Møre Basins .…”

Emplacement of inflated Pāhoehoe flows in the Naude’s Nek Pass, Lesotho remnant, Karoo continental flood basalt province: use of flow-lobe tumuli in understanding flood basalt emplacement

“…Bryan et al 2010;Self et al 2015), in thick packages spread over areas frequently in excess of a 1 × 10 6 km 2 (Self et al 2015), with very short time spans of emplacement (~1 Ma; Bryan et al 2010). They present challenges to understanding the sources of their magmas, temporal and spatial relationship to supercontinents (Svensen et al 2017), continental rifting and possible mantle plumes (Burke and Torsvik 2004;Ernst and Bleeker 2010), magma supply and distribution systems such as dyke and sill complexes, and not least lava flow emplacement and lava pile construction (Walker 1971;Jay et al 2009). The latter is important and raises a number of questions.…”