TEAM 2:
Organic Geochemical Investigation of Mid-Atlantic Ridge Hydrothermal Systems
PI: Jeffrey Seewald, Tom McCollom and Peter Saccocia
The widespread occurrence of heterotrophic organisms in microbial communities at submarine hydrothermal systems suggests that organic compounds transported by hydrothermal fluids may contribute significantly to metabolic energy sources in these environments. Hydrothermal fluids have also been suggested as a source for prebiotic organic compounds that may have led to the origin of life on early Earth. Despite the prominent role of organic compounds in these and other processes, the composition and source of organic compounds in submarine hydrothermal fluids remains poorly understood, particularly in unsedimented vent environments. During this cruise we will address this issue through sampling and analysis of organic compounds at four unsedimented hydrothermal systems hosted in basaltic (Lucky strike and Snakepit) and ultramafic (Rainbow and Lost City) crust along the Mid-Atlantic Ridge. Hydrothermal activity involving ultramafic rocks is of particular interest because fluid-rock reactions create hydrogen-rich environments that in conjunction with the presence of catalytically active minerals may play a pivotal role in the abiotic synthesis of aqueous organic compounds.
We will be collecting hydrothermal fluids and associated sulfide mineral structures for chemical and isotopic analyses of organic compounds. Complementary analysis of the inorganic composition of the fluids will allow interpretation of the chemical and physical environment in which the organic compounds formed. This information, in conjunction with thermodynamic analyses and insights gained through experimental studies, will allow us to interpret the origin of organic compounds (e.g., abiotic synthesis, thermal maturation, subsurface microbial activities, magmatic degassing) in unsedimented submarine hot-spring systems.
