Emanation of fluids at cold seeps, mud volcanoes, and
other types of submarine seepage structures is a typical
phenomenon occurring at continental margins worldwide.
They represent pathways along which volatiles and solutes are
recycled from deeply buried sediments into the global ocean,
and hence they may be considered as a potentially important
link in global geochemical cycles.
In this contribution we present geochemical data from
various geological and tectonic settings such as the Gulf of
Cadiz, the convergent margin off Central America, and/or the
Black Sea and provide approaches how to systemize available
data sets. Clay-mineral dewatering plays a central role in
terms of fluid-mobilization from greater depth, however,
resulting cold seep fluids are typically very different from
each other and cover a large range of geochemical signatures.
This is is due to variations in control parameters such as the
type and thickness of the sediment cover, thermal conditions,
extension of fluid pathways, and the potential for secondary
overprinting. For example, freshened fluids emanating at cold
seeps off Costa Rica indicate dewatering and related
geochemical reactions in subducting sediments, while fluids
sampled at mud volcanoes in the Gulf of Cadiz provide
evidence for a high-temperature fluid source originating in the
underlying oceanic basement. The latter finding provides
evidence for a hydrological connection between buried
oceanic crust and the water column even at old crustal ages.
Varius geochemical tracers were proposed in the past to
decipher relevant processes in the subsurface. In a recent
systematic study, Scholz et al. [1] demonstrated the general
use of Li, reflecting the temperature-dependent isotope
fractionation during early diagenetic Li uptake and burial
diagenetic Li release from sediments. However, additional
approaches are required in order to provide robust geochmical
interpretations of cold seep fluids
