Miriam Kastner, Geology - US grants

This award will provide one-half of the funds required to purchase a precision isotope ratio mass spectrometer for the Scripps Institution of Oceanography at the University of California in San Diego. The instrument will be housed and operated in the Scripps Analytical Facility where it will be available for research use by members of the UC-San Diego campus. The Principal Investigator and her colleagues at Scripps are at the forefront of research on stable isotope variations in submarine hydrothermal vents and gases dissolved in sea water, natural ice and sediments. The isotope analyses made possible by this equipment acquisition will lead to knowledge about the deep origins of gases and their role in ocean, sedimentary basin, and atmospheric chemistry.

Three major types of phosphorites occur off Peru: (1) friable light-colored laminae, including small peloids and nodules, (2) phosphatic sands dominated by peloids, and (3) generally darker, well lithified dense nodules and hard-grounds. The cores recovered during Ocean Drilling Project (ODP) Leg 112 contain all three phosphorite types and allow expansion of the existing information on many aspects of the older Cenozoic to Quaternary sediments of this region. Accordingly, the primary aims of this project are to (1) improve the understanding of oceanographic and sedimentologic factors which control the episodic deposition of phosphorites in the geologic record, and (2) to develop geochemical and isotopic criteria which may distinguish primary properites derived in the original depositional environment, from modified properties, those acquired by the influence of a subsurface saline brine or during later burial diagenesis, or by reworking and concentration through sedimentologic processes. %%% Phosphorites on continental margins are an interesting and potentially economical mineral deposit. This study will examine the controlling factors for the formation of these deposits. Sediments from drill cores on the Peruvian margin will be examined by a variety of geochemical techniques for clues to the climatic influences on formation as well as the post- depositional effects of fluid flow and diagenesis.

The mineral barite BaSO4) is an ubiquitous component of particulate material in the water column, and of pelagic sediments. Many workers have noted a correlation between the abundance of barite in sediments and productivity in overlying surface waters. Barite is clearly important in the geochemical cycle of Ba, and it is also quite insoluble and therefore resists dissolution and diagenetic exchange in sediments. Furthermore, three elements for which the seawater isotopic composition is important for solving many paleoceanographic problems (Sr, S and Nd) occur in barite in amounts that permit precise isotopic measurements to be made on very small amounts of the separated phase. For all of these reasons, barite appears to be an important tracer of productivity, geochemical cycling, and a host of processes that may affect seawater chemical and isotopic compositions, e.g. climate, tectonics, sealevel change and rates of marine hydrothermal activity. Nevertheless, the present understanding of the sites and mechanisms of barite formation, transport, and fate in the sedimentary column is very incomplete and the linkage between Ba, barite and C fluxes need to be clarified. In this research a mass- balance, morphological, geochemical and isotopic approach to the study of the cycling of barite in upper sedimentary layers of the equatorial Pacific and its relation to the C cycling will be made Novel aspects of the work include the use of Nd, Sr and S isotopes as clues to the environment of formation and possible recycling of barite. This study will make use of sediment trap, filtered and bottom sediment samples, and will be closely coordinated with geochemical and isotopic investigations of the water column by other workers. It will also be undertaken with close attention to the potential of barite as a contemporary as well as a paleo monitor of biogeochemical and isotopic characteristics of seawater.

The nature and origin of fluids and digenetic solids in accretionary complexes can be inferred from geochemical, isotopic and mineralogical studies of convergent margins. The Barbados Ridge, Peru margin, Nankai Trough and New Hebrides island arc to be studied in this project are different in structure, thermal regime, sedimentology and geochemistry. The objective of the project is to constrain the fluid-rock interactions in these four contrasting settings and to quantify the flow of water and solutes through the accretionary prism. Fluids being expelled from such settings play a key role in controlling the deformational, thermal, and geochemical evolution of these margins. A synthesis of the fluid systems will be important in planning future ODP drilling in accretionary wedges.

9316460 Kastner This award provides 72% of the funds required for the acquisition of a heating and freezing stage for optical microscopy of fluid inclusions in rock and mineral samples. The equipment will be installed and operated in the Geological Research Division of the Scripps Institute of Oceanography at the University of California, San Diego. The institution is committed to providing the remaining funds necessary to acquire the instrument system. Research to be conducted with this apparatus includes the study of fluid inclusions in rocks brought up from the mantle and in ancient oceanic accretionary complexes. The interpretation of such fluid inclusions yields information regarding the nature and origin of fluids trapped in the mantle and on the evolution of the chemistry of ancient oceans. ***

9521258 Kastner Kastner will develop Nd isotopes in marine barite to trace fluctuations of water masses. This technique should be useful in understanding the development of water masses and their movement during glacial-interglacial cycles. This research should also lead to an understanding of what depth barite forms in the water, which has been a puzzle for some time. This is important because barite in sediments has been used to indicate the productivity of the surface waters. ***

9529953 Kastner Fluid and solid samples will be analyzed for Cl concentration and isotopic composition from six sites in three geologically, sedimentology, and hydrologically different subduction systems: Barbados, Nankai, and Mariana. On the basis of previous extensive geologic, mineralogic, chemicals, and isotopic characterizations, samples of pore waters, sediments, altered basalts, and their related mineral separates have been carefully selected for this study. Emphasis will be placed on the important and abundant ocean floor hydrous silicates, especially clay minerals (e.g., smectite, illite, chlorite), other micas, serpentine, talc, and amphibole. Potential precursor phases of authigenic hydrous minerals will also be analzyed (e.g. volcanic arc glass and tuffs). This new data set will be interpreted in terms of kinetic isotopic enrichment (i.e., diffusion), advective mass transport, and fluid-rock reaction models and applied to processes occuring in convergent margins.

9712135 Kastner At accretionary margins sedimentary carbon is recycled as pore waters are squeezed from the compacting sediments. These pore waters are discharged at natural seeps where some of the carbon is deposited as thick surface and subsurface layers, additional carbon may be sequestered in gas hydrates, and some of the carbon is lost to the water column in gaseous form. The relative proportions and magnitude of these processes, however, are poorly understood. The present project will begin an in situ , experimental approach to examining and quantifying these processes on the Oregon margin. Sampling chambers will be fitted to sealed borehole drilled by the Ocean Drilling Program and will be used to collect precipitate and fluid flow out of the sedimentary section. Samples from the year long experiment will be subsequently analyzed to provide information on the kinetics of carbon sequestration during fluid expulsion. Not only will the research define chemistry of the fluids and associated digenetic deposits, it also will relate the mass deposited over time to a known volume of fluid, and measure the affect of that deposition on sediment permeability. Microbial research will examine the potential role and importance of organisms in controlling the carbon partitioning. ***

OCE 98-11557 Kastner OCE 98-12121 Wheat The recommended Collaborative project involves retrieval in 1999 of four OsmoSamplers deployed by the JOIDES Resolution in holes drilled in 1996 on the eastern flank of the Juan de Fuca Ridge during ODP Leg 168. In addition, liter-volume samples will be collected at the base of the boreholes, and borehole fluid temperature measurements will also be made. These holes were sealed with the ODP CORKs, which allow instrument retrieval and data readout through ports and interfaces to instrument strings on their top surface. Retrieval involves five days of use of the Alvin submersible in association with a Wireline Re-entry Tool (WRT), further development of which will be funded by this proposal. After retrieval, the OsmoSampler samples, representing a continuous record of borehole fluid composition for three years, will be analyzed for a large range of major, minor and trace elements, including Na, K, Li, Rb, Sr, Si, B, Ba, Mn, Fe, Br, F, NH4, NO3, PO4, SO4, and the rare earth elements. They will also be analyzed for a wide range of isotopic compositions, including those of H, O, Sr, B, Li, Cl, and Be. The large volume samples will be analyzed for tritium (to check for borehole fluid contamination with ambient seawater), Ar, Xe, CO2, and CH4 concentrations, for He isotopic composition, and for C isotopes if enough CO2 and CH4 are present. The holes in the CORK will be capped after retrieval, with emplacement of a new instrument "cap" at one hole (Site 1026) for evaluation of the chemical response to local hydrographic changes where over-pressured basement fluids are currently venting. This project will represent the best opportunity to date to obtain actual formation fluids that are circulating within the oceanic crust. These samples will allow a fundamental examination of alteration processes occurring within the crystalline oceanic crust as it ages, providing a means for testing models of chemical flux between oceanic basement and seawater essential t owards understanding the composition of both. ***

9730477 The proposed instrumentation project requests funds to develop a low cost, versatile and adaptable fluid sampler for deployment in depths up to 6000 m. It will be designed to 1) determine the relative importance of fluid expulsion via diffuse and focused flow, 2) quantify the geochemical fluxes associated with each of the modes of fluid flow, and 3) establish the importance of episodic flow. The experimental fluid chamber will capture and isolate fluids escaping the sediment-water interface with little or no disturbance of the flow regime. It will consist of a long, thin-walled cylindrical chamber of narrow bore, and a length to diameter ratio of 10:1 or greater. A frame will convey the chamber to near the bottom and support it from a wide-spread tripod. After tripod emplacement, the chamber will be deployed to rest just on the sediment-water interface with no near-by surfaces to disturb or redirect the normal upward advection of fluids from the sediment surface. No back-pressure is created in the system by avoiding flow area restrictions. Normal flow will enter the chamber through the bottom of the cylinder and continue through, exiting at the top. Two tracers will be continuously injected into the system to help determine the direction and rate of flow. Intended duration of initial deployments will be weeks to months, and eventually years.

Kastner OCE-9817612 The Pis will conduct research on the concentration of trace gases in seafloor methane hydrates and on dating them with state-of-the-art geochemical instrumentation. Dating hydrates is essential for under- standing the mechanisms and rates of hydrate formation and dissociation and because methane hydrates constitute a major transient sink of oceanic carbon. Pb-210/Pb-206, C-14, CfC11/12, Kr-85 and Th-230 analyses are planned.

This technology development project addresses methane hydrates, which represent the most abundant hydrocarbon source on Earth. Decades of geochemical studies have established the importance of anaerobic methane oxidation (AMO) in methane hydrate containing marine sediments, but the organisms responsible for this major process in the Carbon cycle have never been isolated; and no pure cultures of microbes capable of net AMO have yet been obtained. The project entails an interdisciplinary integrated experimental and field program to determine the mechanism of AMO by following AMO under controlled variable-defined laboratory conditions that provide a thermodynamically favorable environment for microbial methane consumption over methane production. In order to create conditions which support AMO, newly designed anaerobic high pressure/low temperature bioreactors will be constructed and tested. The source of microorganisms inoculated into the bioreactors will come from sediment samples with AMO activity. These sediments will be recovered under in situ conditions from the Cascadia Margin off the Oregon coast. A variety of geochemical assays on the culture medium and the resulting methane hydrate will be performed during enrichments in the bioreactor, and the biogeochemistry of the environment will be continuously monitored and characterized. The bioreactors will provide an experimental platform for future analyses of isotopically labeled biogeochemical equilibrium and kinetic experiments under well defined controlled conditions.

This project will continuously monitor the pressure, fluid chemistry, and hydrology in two instrumented boreholes at the Costa Rica subduction zone, using long-term observatories (CORK and ACORK) installed during ODP Leg 203. The field program will 1) deploy pressure gauges and data loggers, OsmoSamplers, and osmotic flow meters in 3 CORKed boreholes along a transect across the deformation front of the subduction zone and 2) retrieve the OsmoSamplers, data stored in the data loggers and deploying new OsmoSamplers and pressure gauges, with the submersible Alvin. The fluid stored in the OsmoSamplers will provide a continuous 1.3 year record of fluid conditions collected at in situ conditions at weekly resolution, in three distinct hydrogeologic systems. The first flow system is the upper oceanic crust of the incoming Cocos Plate, the second is the return of a deeply sourced fluid along the decollement and the third is in the underthrust sediment section driven by compaction dewatering. By documenting the nature of these hydrogeologic systems it will be possible to better understand the effects of fluid flow at convergent margins on the shallow thermal structure and fluid content of the downgoing plate, the physical properties of the subduction zone interface, deformation style and transport of elements to the oceans.

0216643
Charles
This Major Research Instrumentation award to University of California at San Diego provides funds for acquisition of an isotope ratio mass spectrometer for shared use in studies of climate and global climate change, ocean sciences and anthropology at the Scripps Institution of Oceanography and other UCSD departments. The award is supported by the Division of Ocean Sciences at NSF. UCSD will provide cost-share support from non-federal funds for 33% of total project costs.
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Funds are provided to the PIs from three oceanographic institutions for a collaborative project to investigate fluid expulsion processes in the large-scale elongated gas blowouts, offshore Virginia and North Carolina. Large-scale evacuations resulting from massive gas expulsion were discovered offshore in the area in year 2000. Progressive downslope creep within the shelf-edge delta was considered to be responsible for updip movement of gas and its eventual expulsion. The PIs will undertake a new shipboard program to acquire high-resolution multibeam bathymetric data over the blowout sites, survey suspected fluid discharge sites, and collect gravity cores from shelf edge delta for age control and sediment and pore-water samples. The objective of the study is to determine if there is present-day discharge of gas-rich fluids through the floors or sidewalls of the blowouts, or whether these seepage sites and relict features. The study will contribute to knowledge of methane venting processes on the margins, which have climatic, geotechnical, hazards and resource implications.

The PIs propose to evaluate Porous Silicon (pSi) sensors for marine applications. Porous Silicon sensors will be fabricated and tested in a laboratory pressure cell, to simulate ocean pressures and temperatures. Optical nanostructures can be precisely fabricated in pSi sensors; the presence of an analyte will produce readily detectable changes in the nanostructure's optical properties such as the reflectivity spectrum. pSi sensors have been used on land to detect a number of chemical and biological signals, and have also been used in liquid solutions for biomedical applications. The PIs feel that pSi sensors could be developed for ocean science applications with the desirable qualities of inherent pressure tolerance, high sensitivity, small size, low power consumption and low cost. For this test, the chemical target will be methane, due to a) the importance of methane in the oceans, and b) the limitations of existing deep ocean methane sensors. There are significant unknowns concerning marine applications for pSi sensors, particularly biofouling and corrosion. The oceans will be a new and untested operating environment for pSi sensors.

Broader Impacts
The PIs proposed to develop a new observational measurement technology for the ocean sciences. New ocean sensors would also have immediate applications in environmental monitoring and industrial processes. In addition, the proposed activity will provide training and education for graduate students and promote crossdisciplinary research.

Kastner

Abstract

The PI will measure of Cl concentrations and isotope systematics in subduction-related aqueous fluids and rocks. The main objectives are to determine Cl concentrations and isotope compositions in: 1) pore fluids and sediments from the Costa Rica subduction zone; and 2) serpentine samples from subduction zones and transform faults. The work would result in an improved understanding of the cycling of volatiles (Cl, H2O) during tectonic processes and is of broad scientific interest.

During Leg 205 of the Ocean Drilling Program (ODP) two boreholes were drilled into active hydrologic formations on the Costa Rica margin west of the Nicoya Peninsula. One borehole penetrated through the overriding plate into the décollement at ODP Site 1255. The other borehole penetrated through the subducting sediment section and plate into permeable igneous basement at ODP Site 1253. These two boreholes were sealed and instrumented with a borehole observatory (CORK), allowing pressure, temperature, fluid flow velocity, and fluid chemical composition to be measured within the formation. The 1.5-yr pressure and two-year temperature, fluid velocity, and fluid chemical composition records collected to date have provided a basic knowledge of formation properties, although fluids within the boreholes had yet to reach steady state with the surrounding formations. The data also provide evidence that tectonic forcing related to subduction results in measurable transients in pressure, temperature, fluid velocity, and fluid composition within the décollement. While the initial data provide a baseline for approaching several important scientific and technical questions, they have raised new key questions that will be addressed from additional continuous borehole data. The investigators will a 6-day submersible operation to retrieve instruments and stored data that will provide a continuous record of formation temperature, pressure, fluid flow rate, and chemical composition for an additional five years, from the time of the last visit in 2004 to 2009. This project will result in an extremely valuable long-term synchronous record of hydrologic, geochemical, and geodynamic activity at this subduction zone, and establish a technical and scientific foundation for future borehole studies in a broad range of tectonically and hydrologically active settings.

Tectonic plate boundaries where ocean crust subducts beneath continental crust are associated not only in the Earth's most active earthquake zones, but also with the largest concentration of land volcanoes. Our understanding of these areas (also called subduction zones) and the processes that cause associated seismic and volcanic hazards is therefore needed for us to be able to better protect coastal communities and prepare effective land use and hazard mitigation strategies. Because both volcanism and earthquakes are affected by, and many times triggered by, fluids and the dehydration of minerals exposed to increasing temperatures and pressures as subduction occurs, our knowledge of how subduction zone fluids change with space, time, and composition across and between subduction zones is critical to our understanding of how these important areas behave and evolve over time. This research completes the geochemical data sets of subduction zones off the northwestern US, Japan, South and Central America, and the Caribbean. It also compiles all relevant laboratory experimental data, pore fluid, and deep sea bore hole fluid data with a focus on synthesizing this voluminous dataset and seeking new insights into how the geochemistry of fluids can reveal processes occurring at depth in the subduction process. Where identified, gaps in the geochemical record of these fluids will be completed, including creating an isotopic dataset for oxygen, deuterium, strontium, lithium, boron. The collective data will be used to examine mass balances of elements, the contribution of subduction fluids to the make-up of present day seawater, the role of compaction and dehydration/hydration reaction on fluid chemistry, and insights on the evolution of pore fluid pressures. Broader impacts of the work include support of a more than 15 year NSF investment in subduction zone characterization and dynamics and support of a PI whose gender is under-represented in the sciences.