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Introduction
Skills and Expertise
Publications
Publications (36)
The chemical composition of formation waters within the upper basaltic crust were calculated or measured at 24 sites on the northwest portion of the Juan de Fuca (JDF) Plate using data from sediment pore waters, scientific boreholes, and seafloor springs. Formation waters differ in composition across this ridge‐flank region because of variations in...
This paper discriminates the source of sediment supply (provenance), degree of chemical weathering, and redox conditions of Holocene sediments cored from the Ankobra and Pra estuaries of Ghana in the Gulf of Guinea using their geochemical characteristics. Considerable stratigraphical variations were observed in major element compositions in the sed...
To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for 1 year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank) as compared to an experiment that was not exposed to subsurface crustal...
Oceanic crust is the largest potential habitat for life on Earth and may contain a significant fraction of Earth's total microbial biomass; yet, empirical analysis of reaction rates in basaltic crust is lacking. Here we report the first assessment of oxygen consumption in young (~8 Ma) and cool (<25 °C) basaltic crust, which we calculate from model...
Systematic differences in sediment thermal and pore water chemical
profiles from Integrated Ocean Drilling Program Site U1363 document
mixing and reaction within the basaltic crust adjacent to Grizzly Bare
outcrop, a site of hydrothermal recharge into 3.6 My-old basaltic crust.
A transect of seven holes was drilled ~50 m to ~750 m away from the bas...
Models of heat flow developed over the last four decades illustrate the
importance of fluid circulation within basaltic crust for Earth's
lithospheric heat loss. Initial conceptual models of this seawater
circulation were idealized with broad sweeping arrows depicting flow
perpendicular to the strike of the ridge axis and penetrating to the
depth o...
The ridge flank environment represents an important habitat for
microbial life on Earth, considering its size and chemical disequilibria
between circulating fluids and rocks. However, the potential for this
habitat to harbor life, and the characteristics that such life might
have, are poorly known at present. Furthermore, the interactions of
microb...
Fluid sampling capabilities associated with borehole observatories
(CORKs) are currently the best mechanism to collect fluids from
subsurface hydrologic zones for evaluating the composition, evolution
and consequence of fluid circulation in oceanic crust. These
capabilities have evolved over the past two decades spanning the Ocean
Drilling Program...
Hydrothermal fluid circulation within oceanic crust at low temperatures affects global biogeochemical cycles, with the volume of fluid circulation rivaling that of the world's water flux to the oceans from rivers. Our work focuses on the best studied low temperature hydrothermal system on the eastern flank of the Juan de Fuca Ridge where a buried b...
Currently, in-situ seafloor and basement pressures are continuously monitored and recorded by an ODP subseafloor hydrogeological observatory (CORK) located in Middle Valley, Juan de Fuca Ridge. Hole 857D was drilled in 1991 in thickly-sedimented crust to a depth of 936 mbsf and instrumented with an original CORK that was replaced in 1996. A small h...
Integrated Ocean Drilling Program (IODP) Hole 1301A was drilled, cased, and instrumented with a long-term, subseafloor observatory (CORK) on the eastern flank of the Juan de Fuca Ridge in summer 2004. This borehole is located 1 km south of ODP Hole 1026B and 5 km north of Baby Bare outcrop. Hole 1301A penetrates 262 m of sediment and 108 m of the u...
Sixteen large, active serpentinite mud volcanoes exist in the Mariana forearc, the region of seafloor between the Mariana Trench and the volcanic island arc. Up to 50 km in diameter and rising as much as 2.4 km above the surrounding seafloor, these seamounts form as a consequence of subduction processes, which generate deep-seated faults that penet...
In 2003, we conducted a survey of 11 serpentinite mud volcanoes in the
Mariana fore arc. Here we report sediment pore water data from navigated
gravity and piston cores and from push cores collected by the ROV system
Jason2-Medea. Systematic variations in profiles of pore water chemical
compositions from these mud volcanoes are consistent with mode...
The research I conducted for my dissertation addresses specifically: (1)
the role of fluid alteration of the ocean crust during its maturing
stages near a spreading center using the Juan de Fuca Ridge as the
model; and (2) the role of fluids in the demise of the crust as it is
recycled within a subduction zone, using the non-accretioanry Mariana
sy...
The Patgon-Masala submarine volcano in the southern-most part of the active Mariana arc has the largest caldera in the Mariana system. The seamount rises to 2300 m above the surrounding 3500-m-deep seafloor. The seamount is 20 km long by 12 km wide, elongate NE-SW, paralleling the southern backarc spreading center. The caldera is 5000 m long by 300...
This paper reports the results of sea trials of the Nereus hybrid underwater robotic vehicle (HROV) conducted in May and June 2009 in the Challenger Deep of the Mariana Trench, where the vehicle successfully performed scientific observation and sampling operations at hadal depths of 10,903 m. The Nereus underwater vehicle is designed to perform sci...
IODP Exp 315 and 316 drilled six sites as part of the first stage of NanTroSEIZE, an international, multi-year endeavor to elucidate earthquake-related processes. These six sites form a transect southeast of the Kumano Basin, Japan with boreholes that penetrated the Kumano forarc basin (C0002), the megasplay fault region (C0001, C0004, and C0008) a...
Holes 1301A and 1301B were drilled, cased, and instrumented with long-term, subseafloor observatories (CORKs) on the eastern flank of the Juan de Fuca Ridge in Summer 2004. These holes penetrate 265 m of sediment and the uppermost 108 to 318 m of 3.5 Ma basaltic basement, in an area of vigorous, warm (64C) hydrothermal circulation. The new borehole...
One of the primary scientific objectives of the NanTroSEIZE expeditions is to test the hypothesis that the earthquake cycle results in systematic changes in the chemical alteration of pore fluids and sediments through which they flow (Tobin and Kinoshita, 2006). Trace elements, particularly the rare earth elements (REE) are sensitive to subtle chan...
The aim of the NanTroSEIZE project is to core through fault rocks at a
range of pressures and temperatures to determine if systematic,
progressive material and state changes control the onset of seismogenic
behavior on subduction zone thrust faults. Fluid chemistry is
predictably altered with increasing pressure and temperature, and can
facilitate...
A sealed borehole observatory (CORK) was deployed on South Chamorro Seamount, an active serpentinite mud volcano in the Mariana forearc to explore subduction-related processes on a non-accretionary, convergent plate margin. Formation fluid was overpressured relative to ambient hydrostatic conditions. Fluid flowed from the borehole at ~0.2 L/s when...
The data presented in this report demonstrate significant improvements in the ability to constrain trace element and Sr isotopic concentrations in sediments overlying ridge-flank hydrothermal systems. Improved sampling methods orchestrated by the Integrated Ocean Drilling Program (i.e., advanced piston coring and anoxic sample processing) enabled t...
Crustal ridge-flank hydrothermal convection of seawater profoundly affects; global geochemical fluxes and cycles, plate tectonics through crustal cooling, and the deep biosphere. Comprehensive assessment of chemical fluxes from this type of hydrothermal circulation has been obscured by sampling artifacts during sample retrieval and extraction from...
The volumetric flux of seawater that flows through the oceanic crust rivals that which flows from rivers into the oceans. As seawater or formation fluid circulates through oceanic basement it is warmed and reacts with basalt and secondary minerals. In addition, diffusive exchange with overlying pore fluids may also impact the composition of the cir...
The southernmost portion of the Mariana Trough is a complex zone of deformation and magmatism. The centerpiece of the trough is the Malaguana-Gadao Spreading Center Ridge, which has a morphology that is inflated relative to all of the other spreading segments in the Mariana Backarc Basin. This inflated morphology is similar to that of the EPR and i...
The Mariana forearc contains tens of seamounts up to 2 km high and 20-50 km in diameter. These seamounts were formed by serpentinite mud volcanism, sometimes in combination with uplift of serpentinized forearc mantle blocks, in which fluids driven off of the subducting slab infiltrated the overlying mantle and serpentinized the harzburgite and duni...
Detailed DSL120 side-scan sonar surveys and Jason2/Medea ROV
observations of the summit areas of several serpentinite mud volcanoes
on the eastern half of the Mariana forearc reveal vent dimensions and
information about the size and dynamics of mud protrusions emanating
from the vents. Some vents appear to be small (a few km in diameter),
which sug...
Borehole observatories developed for long-term sampling and monitoring in the subseafloor of the deep ocean must satisfy design and operation requirements that are similar to systems deployed on land. Many of these systems are used to achieve simultaneous hydrologic, geochemical and microbiological goals, requiring innovative design, installation,...
The upper oceanic crust, composed mainly of basalt, comprises the largest aquifer on Earth. Global fluid fluxes through the upper oceanic crust are at least as large as the annual riverine flux to the ocean, and influence a diverse array of processes and properties, including the thermal state and evolution of oceanic plates; alteration of the lith...
Integrated Ocean Drilling Program (IODP) Expedition 315, part of the multistage Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), provided an excellent opportunity to compare the fluid regime in the old accreted and overlying young forearc sediments. We cored the Kumano forearc basin sediment downhole to the upper accretionary prism in the N...