Connecting the Deep Earth and the Atmosphere

Abstract

Most hotspots, kimberlites, and large igneous provinces (LIPs) are sourced by plumes that rise from the margins of two large low shear-wave velocity provinces in the lowermost mantle. These thermochemical provinces have likely been quasi-stable for hundreds of millions, perhaps billions of years, and plume heads rise through the mantle in about 30 Myr or less. LIPs provide a direct link between the deep Earth and the atmosphere but environmental consequences depend on both their volumes and the composition of the crustal rocks they are emplaced through. LIP activity can alter the plate tectonic setting by creating and modifying plate boundaries and hence changing the paleogeography and its long-term forcing on climate.Extensive blankets of LIP-lava on the Earth's surface can also enhance silicate weathering and potentially lead to CO2 drawdown (cooling), but we find no clear relationship between LIPs and post-emplacement variation in atmospheric CO2 proxies on very long (>10 Myrs) timescales.Subduction is a key driving force behind plate tectonics but also a key driver for the long-term climate evolution through arc volcanism and degassing of CO2. Subduction fluxes derived from full-plate models provide a powerful way of estimating plate tectonic CO2 degassing (sourcing) and correlate well with zircon age frequency distributions through time. This suggest that continental arc activity may have played an important role in regulating long-term climate change (greenhouse vs. icehouse conditions) but only the Permo-Carboniferous icehouse (~330-275 Ma) show a clear correlation with the zircon record.

The Magmatic Architecture of Continental Flood Basalts I: Observations From the Deccan Traps

“…Typically, full CFB sequences have an overall duration of about 5–15 Ma (Courtillot & Fluteau, 2014; Courtillot & Renne, 2003; H. Svensen et al., 2018), with the much briefer main‐phase eruptions accounting for the majority of the erupted volume (e.g., $$ > 60\%$$ for the Deccan Traps, Richards et al., 2015, ≈87% for the Columbia River Basalt, Kasbohm & Schoene, 2018). CFBs are also important events for solid earth‐climate interaction, since they are frequently temporally correlated with significant environmental perturbations on a global scale, including major mass extinctions and rapid climate change (e.g., Clapham & Renne, 2019; Ernst & Youbi, 2017; M. T. Jones et al., 2016; Torsvik et al., 2021; Wignall, 2001).…”

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

“…Continental flood basalt provinces (CFBs) are some of the largest magmatic events in Earth history and their “main eruptive phase” (durations ∼1 Ma; Bryan et al., 2010; Courtillot & Fluteau, 2014; Courtillot & Renne, 2003; Ernst & Youbi, 2017; Svensen et al., 2018) are associated with eruption of millions of km 3 of dominantly pāhoehoe basaltic lava flows over vast areas (e.g., Bryan & Ferrari, 2013; Ernst, 2014; Mahoney & Coffin, 1997; Self et al., 1998, and references therein). CFBs are critical events in the interaction between the solid Earth and surface environment since the volatile emissions from degassing of erupted lavas (as well as intrusives) can strongly perturb the ecosystem (Clapham & Renne, 2019; Torsvik et al., 2021). This relationship is illustrated by the frequently temporal correlation of CFBs with significant environmental perturbations on a global scale, including major mass extinctions and rapid climate change (e.g., Clapham & Renne, 2019; Ernst & Youbi, 2017; Jones et al., 2016; Wignall, 2001).…”

Hemispheric Geochemical Dichotomy of the Mantle Is a Legacy of Austral Supercontinent Assembly and Onset of Deep Continental Crust Subduction

“…(2020) reconstruction, this does not exist. Moreover, there is disagreement whether to use a mantle reference frame with true polar wander around hypothesized fixed LLSVPs (Torsvik & Cocks, 2017; Torsvik et al., 2021), or if the LLSVPs are mobile on 100 Myr timescales (Rudolph & Zhong, 2013).…”

“…We argue that subduction of continental crust in the northern hemisphere during the last 300 Ma was unlikely to generate extreme EM domains sampled by modern hotspots (Jackson et al., 2021) because it has not had sufficient time to return to the surface in northern hemisphere mantle plumes. Down‐going slabs require ∼200 Ma to reach the CMB (Domeier et al., 2016; Van der Meer et al., 2010), then they reside at the CMB for a period of time, and finally they require 10’s to 100 Ma to be transported from the CMB to the near surface in upwelling plumes (Steinberger et al., 2019; Torsvik et al., 2021). This mechanism may help explain why northern hemisphere oceanic hotspots do not exhibit geochemical signatures associated with northern hemisphere continental crust subduction that occurred from 300 Ma to present (Jackson et al., 2021).…”