Transition from hydrothermal vents to cold seeps records timing of carbon release in the Guaymas Basin, Gulf of California
Journal
Biogeosciences Discussions
Pages
1--34
Date Issued
2018-02
Author(s)
Christian Hensen
Mark Schmidt
Volker Liebetrau
Florian Scholz
Mechthild Doll
Longhui Deng
Mark A. Lever
Stefan SchlA?mer
Sudipta Sarkar
Volker Thiel
Christian Berndt
Abstract
Abstract. The Guaymas Basin in the Gulf of California is an ideal site to test the hypothesis that magmatic intrusions into organic-rich sediments can cause the release of large amounts of thermogenic methane and CO2 that may lead to climate warming. In this study pore fluids close (~ 500 m) to a hydrothermal vent field and at cold seeps up to 20 km away from the northern rift axis were studied to determine the influence of magmatic intrusions on pore fluid composition and gas migration. Pore fluids close to the hydrothermal vent area show predominantly seawater composition, indicating a shallow circulation system transporting seawater to the hydrothermal catchment area rather than being influenced by hydrothermal fluids themselves. Only in the deeper part of the sediment core, composed of hydrothermal vent debris, Sr isotopes indicate a mixture with hydrothermal fluids of ~ 3 %. Also cold seep pore fluids show mainly seawater composition. Most of the methane is of microbial origin and consumed by anaerobic oxidation in shallow sediments, whereas ethane has a clear thermogenic signature. Fluid and gas flow might have been active during sill emplacement in the Guaymas Basin, but ceased 28 to 7 thousand years ago, based on sediment thickness above extinct conduits. Our results indicate that carbon release depends on the longevity of sill-induced, hydrothermal systems which is a currently unconstrained factor.
SDGs
Type
journal article