UK IODP Moratorium Award for Jennifer Lington - Expedition 502
Lead Research Organisation:
University of Southampton
Abstract
Ocean crust is produced during submarine volcanism along mid-ocean ridges, repaving two-thirds of Earth's surface every 200 million years. Yet it remains relatively unexplored, accessible only using submersibles or scientific ocean drilling. Such exploration revealed that seawater circulates through the cooling crust and reacts with the rocks, transporting heat and chemicals to the oceans. This “hydrothermal circulation” makes important contributions to Earth’s long-term biogeochemical cycles.
During submarine volcanism carbon dioxide (CO2) is released from the magma to the oceans and atmosphere, but during subsequent hydrothermal circulation, calcium carbonate minerals form storing CO2 from seawater in the rock. Consequently, the formation and evolution of ocean crust affects atmospheric CO2 levels and hence climate. The role of ocean crust in the planetary carbon cycle depends on the balance between the CO2 released during formation of new crust and the CO2 sequestered during hydrothermal reactions throughout the crust's lifetime. Global variations in the extent and timing of hydrothermal calcium carbonate formation therefore have the potential to drive significant changes in the Earth system.
Along mid-ocean ridges hydrothermal circulation occurs through spectacular “black smoker” hot springs, but it can occur wherever heat drives fluid flow through the ocean crust. Consequently, gaining a complete understanding of the full complement of hydrothermal exchanges between the crust and overlying oceans across all tectonic settings is key to determining past hydrothermal contributions to global biogeochemical cycles and their role in driving global change.
Until recently volcanism was thought to occur in three geodynamic settings: divergent plate boundaries (including mid-ocean ridges), convergent plate boundaries (including subduction zones) and hotspots. However, a new type of volcanism that occurs due to flexure and fracturing of oceanic plates before they subduct, termed ‘petit-spot volcanism’, was discovered in the Japan Trench in 2006. Petit-spot volcanism, now known to be ubiquitous where ocean plates flex, is predicted to make important contributions to Earth’s CO2 emissions because the magmas are enriched in CO2 relative to elsewhere in the oceans. However, the overall role of petit-spot volcanism in the global carbon cycle depends on the extent to which these emissions are balanced by subsequent hydrothermal reactions. International Ocean Drilling Programme Expedition 502 will recover the first in-situ section through petit-spot lavas, allowing their role in Earth’s long-term carbon cycle to be quantified. This research will use these unique cores to:
-Quantify the exchanges between petit-spot lavas and the oceans, including the extent of carbon-uptake, due to different styles of hydrothermal alteration.
-Determine the ages of hydrothermal minerals and hence the timing and duration of these exchanges.
These results will allow us to achieve our overall objective of evaluating the role of petit-spot volcanism in long-term global biogeochemical cycles, including the carbon cycle. The resultant more complete understanding of Earth’s past carbon cycle will benefit efforts to model past climate change due to elevated atmospheric CO2, and hence our ability to predict potential future climate change due to anthropogenic CO2 emissions. The knowledge of how petit-spot lavas and their reactions with seawater affect the characteristics of crust entering subduction zones will also aid studies of these plate boundaries where major earthquakes and their associated natural hazards (e.g., tsunamis) occur.
During submarine volcanism carbon dioxide (CO2) is released from the magma to the oceans and atmosphere, but during subsequent hydrothermal circulation, calcium carbonate minerals form storing CO2 from seawater in the rock. Consequently, the formation and evolution of ocean crust affects atmospheric CO2 levels and hence climate. The role of ocean crust in the planetary carbon cycle depends on the balance between the CO2 released during formation of new crust and the CO2 sequestered during hydrothermal reactions throughout the crust's lifetime. Global variations in the extent and timing of hydrothermal calcium carbonate formation therefore have the potential to drive significant changes in the Earth system.
Along mid-ocean ridges hydrothermal circulation occurs through spectacular “black smoker” hot springs, but it can occur wherever heat drives fluid flow through the ocean crust. Consequently, gaining a complete understanding of the full complement of hydrothermal exchanges between the crust and overlying oceans across all tectonic settings is key to determining past hydrothermal contributions to global biogeochemical cycles and their role in driving global change.
Until recently volcanism was thought to occur in three geodynamic settings: divergent plate boundaries (including mid-ocean ridges), convergent plate boundaries (including subduction zones) and hotspots. However, a new type of volcanism that occurs due to flexure and fracturing of oceanic plates before they subduct, termed ‘petit-spot volcanism’, was discovered in the Japan Trench in 2006. Petit-spot volcanism, now known to be ubiquitous where ocean plates flex, is predicted to make important contributions to Earth’s CO2 emissions because the magmas are enriched in CO2 relative to elsewhere in the oceans. However, the overall role of petit-spot volcanism in the global carbon cycle depends on the extent to which these emissions are balanced by subsequent hydrothermal reactions. International Ocean Drilling Programme Expedition 502 will recover the first in-situ section through petit-spot lavas, allowing their role in Earth’s long-term carbon cycle to be quantified. This research will use these unique cores to:
-Quantify the exchanges between petit-spot lavas and the oceans, including the extent of carbon-uptake, due to different styles of hydrothermal alteration.
-Determine the ages of hydrothermal minerals and hence the timing and duration of these exchanges.
These results will allow us to achieve our overall objective of evaluating the role of petit-spot volcanism in long-term global biogeochemical cycles, including the carbon cycle. The resultant more complete understanding of Earth’s past carbon cycle will benefit efforts to model past climate change due to elevated atmospheric CO2, and hence our ability to predict potential future climate change due to anthropogenic CO2 emissions. The knowledge of how petit-spot lavas and their reactions with seawater affect the characteristics of crust entering subduction zones will also aid studies of these plate boundaries where major earthquakes and their associated natural hazards (e.g., tsunamis) occur.