Scientific Ocean Drilling Accomplishments and Challenges (2011) / Chapter Skim
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3 Scientific Accomplishments: Fluids, Flow, and Life in the Subseafloor
3 Scientific Accomplishments: Fluids, Flow, and Life in the Subseafloor
Pages 27-38
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From page 27... ...
tal crust, hydration of plate boundary faults, initiation of Basement hydrogeology studies initially focused on explosive volcanism, generation of gas hydrates and other quantifying the circulation observed in hydrothermal vents. mineral resources, and distribution of subseafloor microbial Early observations revealed that ocean bottom waters were communities.
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From page 28... ...
Vertical axis is depth into basement, accounting tion of subseafloor microbial communities, the creation of for differences in sediment thickness. Most seafloor measurements have been made in basaltic crust, but two sets of data (ODP Holes ore deposits and gas hydrates, and the overall chemical and 857D and 735B)
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From page 29... ...
In the sedimentary realm, scientific ocean drilling transient, confined-aquifer flow, localized expulsion, and/or focused on identification of flow pathways and fluxes in external fluid sources, but there is still much to be learned passive and active margins. Drilling in active accretionary about specific flow pathways and magnitude, as well as the margins resulted in development of new geochemical tracers role that fluids play in seismicity, chemical alteration, and for inferring fluid flow (ODP Legs 112, 125, 131, 134, 146, volcanism.
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From page 30... ...
Several first-order questions still need to be research to quantify the role that fluids play in controlling addressed in order to resolve the significance of these promechanical processes along both passive and active margins, cesses, including the nature of hydraulic communication including the occurrence and magnitude of large earthquakes between basement and sediments; the effect of diagenetic along plate boundary faults and the distribution and timing of modification of sediments on geochemical and microbial major slope failure events along passive margins. The body processes in the underlying basement; changes in flow as of literature on these topics is growing at a fast rate; Screaton the ocean crust ages; links between marine and continental (2010)
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From page 31... ...
. energy sources that support the chemosynthetic-fueled com- Three years earlier, drilling began at Middle Valley munities seen at vents, in which microorganisms use the huge (ODP Legs 139 and 169)
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From page 32... ...
. It took another 10 years for scientists to visualize and quantify these microbial Until scientific ocean drilling began, the only way cells at depths in excess of 500 m at five ODP sites around to study the chemical reactions and physical stockwork the Pacific Ocean (Parkes et al., 1994)
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From page 33... ...
(2000) summa- 1 rized the findings of these first 15 years of study from 14 marine sediment sites and concluded that while microbial abundances generally decrease with increasing depth, cells 10 are still present at depths in excess of 700 m; they can be stimulated by deep activity, such as subsurface seawater flow or gas hydrates; and they have a strategy of high biomass and low growth rate to guarantee survival (Figure 3.4)
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From page 34... ...
; therefore scientific ocean drilling in gabbroic rocks for the first time as part of IODP Legs 304 is critical to success in understanding microbiology in the and 305 to the Atlantis Massif. An extremely low diversity subseafloor.
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From page 35... ...
In addition, scientists are currently assessing best storage Scientific ocean drilling has been a major factor in practice for cores needed in microbial analysis in conjunc improving understanding of the distribution and dynamics tion with core repositories in the United States and abroad, of gas hydrate in marine sediments. The first gas hydrates and detailed notes on exactly how cores were retrieved and collected in the deep ocean were sediments at the Middle stored are essential in assessing potential contamination, America trench accretionary complex during DSDP Legs even if tracers were not used onboard.
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From page 36... ...
have also found them to be of use. Fields of Inquiry Enabled hydrate proxies and illustrates the strong heterogeneity in vertical gas hydrate distribution (adapted from Tréhu et al., Until gas hydrates were drilled and sampled, geophysi2004)
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From page 37... ...
with the objective of evaluating fossil fuel potential or geo hazards posed by gas hydrates for conventional oil drilling Goals Not Yet Accomplished and recovery. Procedures and protocols for handling and archiving gas hydrate-bearing cores during these expeditions Studies of gas hydrate dynamics on decadal and shorter have been modeled on procedures pioneered during ODP time scales, which require time series observations, will and IODP expeditions (e.g., storage of samples in pressure remain a main focus of the scientific ocean drilling commu vessels or liquid nitrogen; immediate routine scanning of all nity and will require close collaboration between scientific core with infra-digital infra-red cameras)
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From page 38... ...
Several attempts are currently under way tion of methane hydrate studies. A challenge unique to gas to develop probes that could be deployed through scientific hydrate studies is development of sensors that can record ocean drilling to operate in this challenging environment.
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