Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion

Abstract

Earth’s carbon cycle is strongly influenced by subduction of sedimentary material into the mantle. The composition of the sedimentary subduction flux has changed considerably over Earth’s history, but the impact of these changes on the mantle carbon cycle is unclear. Here, we show that the carbon isotopes of kimberlite magmas record a fundamental change in their deep-mantle source compositions during the Phanerozoic Eon. The 13 C/ 12 C of kimberlites before ~250 Ma preserves typical mantle values, whereas younger kimberlites exhibit lower and more variable ratios—a switch coincident with a recognized surge in kimberlite magmatism. We attribute these changes to increased deep subduction of organic carbon with low 13 C/ 12 C following the Cambrian Explosion when organic carbon deposition in marine sediments increased significantly. These observations demonstrate that biogeochemical processes at Earth’s surface have a profound influence on the deep mantle, revealing an integral link between the deep and shallow carbon cycles.

Microdroplets initiate organic-inorganic interactions and mass transfer in thermal hydrous geosystems

“…In addition, apart from carbonate minerals, water and aluminosilicates may also serve as sources of oxygen for the generation of deep CO 2 13 , 23 , 68 . Furthermore, in conjunction with the frequently documented process of transferring carbon from organic sources to carbonate minerals 4 , the hydrogen originating from organic compounds, in combination with water-derived hydrogen, could become integrated into hydrous minerals at elevated temperatures, implying a potential impact of surface-level biogeochemical processes on the deeper geosphere 69 , 70 . We are not intent to dismiss the catalytic models that may significantly accelerate organic–inorganic interactions.…”

Proterozoic supercontinent break-up as a driver for oxygenation events and subsequent carbon isotope excursions

“…Although the isotopic composition of CO 2 emitted at ocean islands remains poorly constrained, there are suggestions that CO 2 in samples from the Pitcairn hotspot may be isotopically light compared to mid-ocean ridges ( 38 ). Additionally, a recent study on kimberlites, which may be derived from mantle plumes similar to ocean island basalts, showed that δ 13 C in many Phanerozoic examples exhibit low values, which the authors attribute to subducted organic C ( 39 ). The model assumes that organic C is released on the order of hundreds of millions of years after subduction, corresponding to the timescale of convective overturn in the mantle ( 24 , 40 ).…”

Desilicification Rims of Zircon Xenocrysts Record the Timing of Kimberlite Emplacement

“…These xenocrysts and xenoliths can provide key information regarding the composition and history of the lithosphere at the time of magma emplacement (e.g., Dalton et al., 2020; Gardiner et al., 2020; Giuliani & Pearson, 2019; Xiang et al., 2022). Furthermore, the temporal distribution of kimberlites throughout Earth's history, which encompasses a period of more than 2.5 Gyr (Heaman et al., 2019; Woodhead et al., 2019), may record secular cooling of the mantle, geodynamic processes (i.e., the onset and evolution of plate tectonics), and supercontinent cycles (e.g., Giuliani et al., 2022; Stern et al., 2016; Tappe et al., 2018). As such, it is essential to obtain reliable kimberlite ages.…”

“…, may record secular cooling of the mantle, geodynamic processes (i.e., the onset and evolution of plate tectonics), and supercontinent cycles (e.g., Giuliani et al, 2022;Stern et al, 2016;Tappe et al, 2018). As such, it is essential to obtain reliable kimberlite ages.…”