Coupling Mantle Volatiles, Eruption Dynamics, and Tectonics on the Mid-Atlantic Ridge (NSF Funded): Mapping and sampling of a portion of the mid-Atlantic spreading center, where a unique geochemical signature was determined for a 1980's 'popping rock' sample, we are taking advantage of recent recognition that tectonic deformation may play a role in focusing volatile fluxing from the mantle. Aboard the R/V Atlantis and using unique tools such as the submersible Alvin and the autonomous underwater vehicle Sentry, we undertake geophysical mapping, targeted sampling, and a complete suite of post-cruise geochemical analyses to determine whether the early quantification of mantle volatiles was representative for the region and/or whether such signatures cluster only near faults, thus implying localized fluxing. Such finding could uproot long-standing inferences about background mantle volatile contents. This project involves collaborations with colleagues at the Woods Hole Oceanographic Institution and Boise State University. The first portion of field work for this project was completed in March 2016 (see video at right) and a second field program will occur from May 11th to June 9th, 2018.
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Emplacement of regularly spaced volcanic centers in the East African Rift: Melt production or melt extraction? (NSF funded): As continental rifts evolve, volcanic centers within rift valleys often develop a characteristic spacing, or wavelength. The surprisingly regular spacing of the volcanic centers within the East African Rift System (EARS) is attributed to lithosphere thickness, pre-existing fault systems, and mantle processes. However, little quantitative assessment of these hypotheses has been undertaken and few studies attempt to include the visco-elastic-plastic rheology of the lithosphere. The primary goal of this work is to use data from coupled numerical and laboratory experiments along with observations from the EARS to quantitatively assess the contribution of both melt production and melt extraction processes on the distribution of volcanic activity along the three main branches of the actively spreading EARS. Post doctoral researcher Aurore Sibrant is the lead on this project. |
Rheologic and tectonic controls on oceanic microplate formation from laboratory models: Using a unique colloidal fluid, Ludox, in laboratory models of seafloor spreading, we examine visco-elastic-plastic deformation and faulting at a simulated ridge axis. By separately varying the rate of spreading and the growth rate of the thickness of the simulated tectonic plates, we examine how tectonic strain rate and plate strength control the formation of oceanic microplates. This project is a collaboration between E. Mittelstaedt and Dr. Anne Davaille at the U. Paris Sud. |
Measuring the Flux of Hydrothermal Fluids at the Seafloor (NSF Funded (2 projects) and Pending): Fluid circulation through the oceanic crust at the axis of mid-ocean ridges is a primary mechanism through which the Earth loses its internal heat. At the seafloor, this circulation releases hot fluids into the deep ocean. These hydrothermal sites typically host ecosystems and life forms found nowhere else on the planet and are thought to be one of the places on Earth where life may have originated. Measuring the rates at which hydrothermal fluids exit the seafloor, and how those rates change over time, is critical for understanding the circulation of fluids through the oceanic crust and the complex linkages between this circulation and geological, biological, and chemical processes both within the crust and in the overlying ocean. The goal of this series of projects is to develop new measurements systems (e.g., Diffuse Effluent Measurement System, left) that will allow a more precise and accurate characterization of hydrothermal heat, volume and chemical fluxes than previously possible. This series of projects involves collaborations with Tim Crone and Jean-Arthur Olive from Lamont Doherty Earth Observatory, Daniel Fornari at the Woods Hole Oceanographic Institution (WHOI), Thibaut Barreyre at IFREMER.
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Magmatic and Tectonic Evolution of Oceanic Transform Faults: Oceanic transform faults are fundamental to accommodating plate motions along mid-ocean ridges. Transforms offset mid-ocean ridges by 10’s to 100’s of kilometers juxtaposing oceanic lithosphere of differing ages, restricting the length scale of passive mantle upwelling, contributing the majority of MOR seismic moment release, and defining the 1st order magmatic and structural segmentation of ridges. Despite their essential role in plate tectonics, however, there is little understanding of the processes that control the dynamic evolution of these plate boundaries. For example, anomalous transform faults can have multiple discrete shear zones, or transform segments, separated by pull apart basins or small intra-transform spreading centers. It is clear that this segmentation dramatically alters the properties and behavior of transforms, and the oceanic lithosphere, but it is unclear what conditions lead to such segmentation. This project aims to quantify the tectonic, magmatic, and rheological processes governing transform fault segmentation.
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Variations in Hotspot Volcanism as a Key to Understanding Deep Mantle Dynamics (NSF Funded): Averaged over millions of years, the rate of lava production at a seamount or island controls its final shape and size. Along seamount chains, such as the Hawaiian-Emperor chain, observed seamount and island volumes change episodically indicating changes in the lava production rate responsible for their formation. The source of lavas forming these islands is believed to be the melting of mantle plumes: upwelling, stationary conduits of hot, chemically enriched material that originate from deep within the Earth's mantle and rise continuously to the surface. However, in contrast to observations, a continuously upwelling conduit would produce a nearly constant lava production rate; this project aims to address the processes that interrupt or perturb a continuously upwelling mantle plume, and, thus, the rate of lava production along hotspot island chains. There are two locations within the mantle where upwelling plumes are likely to be perturbed: 1) the core-mantle boundary, where anomalously dense material may be incorporated into the plume source and change the upwelling rate, and 2) in the mid-mantle, where abrupt changes in the phase, or mineral structure, of mantle rocks can alter the density and, thus, upwelling rate of plumes passing through these transitions. This project aims to use a combination of laboratory experiments and 3D numerical simulations to quantify the magnitude, length, and time scales over which variations in mantle plume upwelling caused by deep mantle processes will affect lava production and compositions at the Earth's surface.
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Modeling hydrothermal recharge and outflow in oceanic crust analogs with sharp permeability gradients (NSF Funded): Hydrothermal venting often occurs at or near major fault or fracture zones, suggesting that these breaks in the ocean crust can act as highly permeable conduits for fluid escape. It is unclear, however, to what extent these breaks in Earth's crust enable fluids to enter and move downward into the seafloor where they get heated. This research uses analog experiments, using a 3-D printer, and numerical modeling to explore how fluid circulation at mid-ocean ridges spontaneously organizes itself and transports heat in highly fractured and faulted crust. By allowing exploration of the relation between venting sites and major tectonic features, this project will improve our understanding of geothermal processes and the search for new hydrothermal sites on the seafloor. This project is a collaborative study between E. Mittelstaedt (U. of Idaho), Jean-Arthur Olive (Lamont Doherty Earth Observatory), and Thibaut Barreyre (IFREMER).
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