Michael Bizimis, Ph.D. - US grants

ABSTRACT: 0622827 (Bizimis)

Intellectual merit: This work seeks to understand the origin of the shallow ocean floor around volcanic ocean islands of proposed hotspot origin. The work is crucial to our understanding of plume geodynamics, how plumes interact with the lithosphere, and the origin of plume volcanism. The Hawaiian swell, the most extensively studied of these regions, is the research target. The work tests two different geophysical lithosphere thinning models using detailed geochemical analyses (Hf-Os-Nd-Sr-Pb isotopes, trace and major element concentrations) of peridotite xenoliths from the island of Kaua`i. Chemical data will be used to identify the signatures of peridotites from the Pacific lithosphere and from the mantle plume. If peridotites with both plume-related and in situ Pacific lithosphere compositions are found at Kaua`i, as they are in O`ahu, this is evidence for large-scale erosion and replacement of the Pacific lithosphere by the plume downstream from its present center under the island of Hawai'i. Rare garnet pyroxenite xenoliths from Ka`ula island, and garnet pyroxenites with "majorite" precursors from Salt Lake Crater, O`ahu, which represent some of the deepest samples from the oceanic mantle will also be analyzed to try and identify different proposed origins of the pyroxenites, and identify them as either recycled oceanic crust or high pressure cumulates. The resulting work will provided a new and unprecedented, 4-dimensional (space and time) view of the lithosphere above a plume.
Broader impacts: This research directly complements other ongoing NSF-funded projects, whose objective is to image the root of the Hawaiian swell and determine the origin of the secondary volcanism around the Hawaiian Islands through the study of lavas. Results will be disseminated in the form of publications and presentations at national professional meetings. The research supports an early career scientist in at Florida State University and will involve undergraduate Earth Sciences majors in projects directly related to the main research objectives of this study. This research will also involve and train undergraduate science majors through a NSF-funded REU program at the National High Magnetic Field Lab (NHMFL), and will involve and expose middle school students to research in earth sciences through ongoing outreach programs at the NHMFL. Additional public outreach will occur at the annual NHMFL Open House.

Intellectual merit. Using current estimates for the composition of the Earth's principal reservoirs, mass balance for niobium (Nb) and hafnium (Hf) does not add up and some Nb and Hf is unaccounted for. This proposal is aimed at testing the hypothesis of the existence of a mantle reservoir that contains the balance of the Nb and Hf. This "hidden" reservoir would be high in Nb/Ta and/or low in Lu/Hf. The recognition of such a reservoir would have significant implications for understanding mantle evolution and the recycling of crustal components back into the mantle. Subducted oceanic crust may be the key to solving the apparent mass balance problem. However, for oceanic crust to be the postulated hidden reservoir, it needs to lose Ta compared to Nb in the subduction process. Nb/Ta is an especially useful petrogenetic tracer because very few processes can fractionate these elements (given their similar chemical properties), and thus it can become a very reliable indicator of recycled material. However, because the total variation is limited, high precision analyses are required to recognize the variations. Low-precision analyses of island arc volcanics indicate that there is a significant fractionation in Nb/Ta during subduction. However, the "when" and "where" of the Nb/Ta fractionation is unknown. We propose to determine the behavior of these and other elements in subducted material from various stages of subduction to determine the reaction(s) that result in the fractionation of Nb from Ta and to characterize the material that is subducted. We will work on natural materials as the experimental evidence on elemental partitioning is inconclusive. Once the fractionation process is identified the Nb/Ta can be used as a fingerprint of that process. We complement the analyses of the subducted material with analyses of island arc samples - with the aim to understand where in the subduction process Nb and Ta fractionate.

Broader impacts. One outcome will be development of "new" high precision trace element analytical methods that will have wide applicability. This project will support a young scientist and a graduate student and it will provide core support for the operation of the laboratory, which the PI tries to operate as an open use facility, especially for students. In combination with existing programs at the National High Magnetic Field Laboratory (NHMFL) the proposed research will train and educate undergraduate students as well as teachers. The presence of an active research program is an essential component in being able to expose students and teachers to scientific discovery.

Intellectual Merit
The PIs request funding to acquire single and multi-collector ICP-MS instrumentation, complemented by a solid-state laser-ablation sample introduction system. The proposed instrumentation will serve research efforts covering four academic units at the institution: geological sciences, chemistry and biochemistry, marine science, and public health. These research efforts include investigations into solid earth geochemistry including: mantle geochemistry, subduction magmatism, and U-Pb detrital-zircon geochronology; paleoceanography and paleoclimatology: past ocean circulation and sediment provenance, climate proxy development (Si isotopes), and proxy validation; climate change research: iron fertilization, classification of bloom-forming phytoplankton, and upper ocean particle formation and export; and phase partitioning, transport, and biological uptake of nano-materials in environmental systems.

Broader Impacts
The proposed instrumentation will be incorporated into a suite of education efforts, including inclusion in undergraduate and graduate courses, informal training of undergraduates and graduates as part of research efforts, inclusion in summer programs, including the TRIO Programs Upward Bound (focusing on economically disadvantaged students without a family history of college attendance) and the SPRI program (mentoring high school students in faculty labs). The proposed instrumentation will also support the research efforts of two new hires, including one early career scientist. Cross-institution collaborative efforts with the University of Georgia, University of North Carolina Chapel Hill, and Skidaway Institute of Oceanography would also be enabled should the proposed instrumentation be acquired.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

Hydrothermally altered ocean crust provides a record of heat and mass transfer between seawater and the earth's mantle that takes place during hydrothermal circulation at mid ocean ridges and subduction zones. Hydrothermal vent systems that generate the mineral serpentine are linked to alkaline fluids enriched in organics and are central to generating the energy supply for microbial life at the seafloor. This research uses boron, strontium, and neodymium elemental concentrations as well as boron isotope fractionation to examine the role of water-rock reaction in the conversion of peridotites and other ultramafic rocks common on the seafloor and in the lower crust to serpentine and other minerals. The work involves novel, controlled, hydrothermal, laboratory experiments that examine the pH, temperature and mineral composition controls on boron isotope fractionation and combined B-Sr-Nd mobility and rock-fluid exchange. Targeted geochemical elements were picked because they are recorders of temperature and fluid pH conditions and allow application of the results of the experiments to fossil hydrothermal systems and associated ore deposits. Furthermore, the measurements will constrain the effects of low-temperature serpentinization on the efficiency of elemental recycling across volcanic arcs and enhance our understanding of geochemical fluxes from subducting slabs which impact island arc volcanics. Broader impacts of the work are support of two early career researchers, promotion of a new collaboration, support of students, international collaboration, and support of an institution in an EPSCoR state

0841461
Yogodzinski


This proposal seeks funding of ~$167K to purchase components to upgrade an existing electron microprobe (SX-50) at the University of South Carolina. The probe is 1986 vintage and needs several updated components, both hardware and software. Requested are a new WDS automation system including a Windows-based acquisition and analysis computer, new software to control the probe and integrate EDS and WDS data, a new EDS detector and related acquisition system, and a new cathodoluminescence detector. The University will contribute $50K in matching funds. The upgraded EMP facility will allow the PIs to continue multidisciplinary research projects encompassing geologic, public health, engineering and materials research. The PI studies igneous processes aiming to understand the physical and chemical processes of subduction-related magmas and the conditions leading to their formation. Areas of interest are the Aluetians and Kamchatka. Studies are conducted by measuring whole-rock geochemistry, Pb, Sr, Nd, and Hf isotopic ration, and phenocryst and glass inclusion EMP analysis. Co-PI Bizimis focuses on upper mantle processes using detailed mantel xenolith geochemistry. Planned EMP use involves detailed observations of mineral rim reactions, diffusion profiles, minor matrix phases and student training. Co-PI Barbeau studies sedimentation and tectonics. Foci include determining mineral elemental compositions including CL analysis, resolving sediment provenance, and contraining plate tectonic and kinematic reconstructions. Co-PI Hintz will use the EMP to better understand elemental abundances in foraminifera calcite and aragonite tests. These abundances will be used as proxies for existing environmental conditions in the paleorecord. Co-PI Zhao studies mantle processes and nuclear waste management. The EMP will be critical in determining mantle-related processes, composition and evolution. Additionally, the EMP facility will support materials research. The EMP is incorporated into undergraduate and graduate-level courses in mineralogy and igneous and metamorphic petrology. Professors from other departments (Biology) also teach EMP methods. The current probe supports NSF-sponsored research which produces peer-reviewed publications.

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The funded project provides the first set of measurements of the H2O content of the oceanic mantle and involves collaboration between an academic institution and a private sector firm that has a unique capability to measure H2O in igneous minerals (high-resolution FTIR). The importance of this work lies in the fact that small differences in mantle H2O content can have profound effects on mantle rheology and seismic structure, both of which can impact magma generation and crustal movement and have implications for our understanding and prediction of geohazards. Because the mantle is not directly accessible, the investigators implemented a clever approach in which H2O will be measured in minerals coming from pieces of mantle rock (i.e., xenoliths) that were ripped up during the eruption and upward migration of magma of Hawaiian volcanoes. Using compositional relations of mineral pairs that indicate the depth at which the minerals formed, the depth of origin of the various xenoliths that are to be studied can be determined. Using these, the H2O content of the minerals will be examined by Fourier Transform Infra Red (FTIR) spectroscopy. Xenoliths distributed over 300 km along the Hawaiian Island chain and mantle depths to up to 100 km will be analyzed. Broader impacts of the work are robust and multifaceted. A major impact of the project is the provision of essential data that is needed to better interpret the seismic structure of the ocean crust, which will impact our ability to better model the source areas of geohazards like volcanoes and subduction zone earthquakes. The work also supports collaboration between a public university in an EPSCoR state and private industry. It also has a significant component of in-service teacher training where high school teachers in South Carolina work in the laboratory of the lead PI during the summer, getting a chance to engage in frontline research with academic scientist. The teacher?s research will form the basis for classroom and K-12 instructional materials. Workforce training will be carried through the involvement of graduate and undergraduate students in state-of-the-art geochemical analytical techniques. The Program notes that the graduate student is from a group under-represented in the science.

The proposed work will test the hypothesis that changes in sulfide and metal alloy mineralogy during peridotite alteration will mobilize and fractionate the PGE, Re and Pb relative to their primary magmatic concentrations. Hydrothermal experiments will constrain the solubility of PGE, Re, Pb in mantle Ni-Fe-Ru-Re bearing sulfides and metal alloys as function of temperature and redox conditions, and evaluate PGE alloy exsolution and PGE-Re fractionation under low sulfur fugacity. The natural sample part of the study will constrain the distribution and fractionation of PGE, Re, Pb in sulfides, alloys and bulk rocks from well characterized abyssal peridotites, as function of redox, alteration, sulfide mineralization and primary composition (fertile versus depleted). Through integration of the experimental and natural sample data this work will constrain the fate of PGE, Re, Pb upon recycling of altered oceanic lithosphere and whether altered peridotites can develop, over time, highly heterogeneous 187Os/188Os and 186Os/188Os ratios between refractory (metal alloys) or mobile (sulfide) reservoirs. This project is a collaborative effort between 2 US institutions, and will promote transfer of technology and expertise on novel analytical techniques to a newly established geochemical facility at USC. Researchers will share a suite of state-of-the art instrumentation including FIB-SEM, FE-EMPA, FE-SEM, LA-ICPMS and synchrotron radiation micro-X-Ray fluorescence. All the data collected will be submitted to the PetDB and IEDA, and will be available to the public through a CIW-hosted data repository. A graduate student from USC will participate towards completion of his PhD studies.

Altered mantle rocks exposed at the seafloor (called "serpentinized abyssal peridotites") contain Ni-bearing metal phases associated with secondary plantinum-group element (PGE) sulfur-bearing minerals (sulfides) and PGE metal nuggets. PGEs have unique physical and chemical properties that are critical to many technological applications. Thus, they are often regarded as strategic metals in a wide range of industries including aerospace and fuel cell technology. The proposed research will significantly advance the currently limited understanding of the effects of high-temperature seawater alteration on the distribution of plantinum-group element sulfides hosted in abyssal peridotites. Moreover, abyssal peridotites provide an important record for understanding the composition and evolution of Earth?s mantle now and in the past. The proposed work is a collaborative experimental and natural sample investigation. Experimental data will define the thermodynamic properties of PGE minerals at conditions relevant to modern deep-sea volcanoes and assess critical details of PGE solubility mechanisms in Fe-Ni-Ru-Re sulfides/alloys at elevated temperature/-pressure conditions. The combined experimental results and natural sample data will lead to a fundamental new understanding on the effects of seawater alteration on the siderophile and chalcophile composition of altered peridotite and its effect on the Os and Pb isotope heterogeneity in the Earth?s mantle.

The global process of subduction, which is the sinking of Earth's tectonic plates beneath other plates, is accompanied by physical and chemical processes that cause natural hazards such as earthquakes, magma generation, and volcanic eruptions. It is also the basis of the formation of many economically valuable minerals. Understanding subduction processes in detail is of critical importance for protecting human interests, locating resources, and building a basic knowledge of the Earth. This research focuses on understanding the initial stages of subduction, specifically the geochemical processes, that lead from incipient subduction to a self-sustaining subduction zone and volcanic arc. Samples come from a core drilled in the Izu-Bonin-Mariana area in the western Pacific Ocean as part of a coordinated drilling expedition of the International Ocean Discovery Program (IODP) in 2014. The expedition recovered over 1600 meters of core, preserving seafloor stratigraphy extending from the basaltic foundation of the subducting plate through overlying volcanic arc sediments. Goals of the research are to use the geochemical composition of the basement rocks and volcanic sedimentary processes to understand subduction initiation, the causes of magma formation, and the timing and extent of volcanic arc eruptions. Broader impacts of the work include collaboration with researchers from Japan, Switzerland and the UK. In addition the lead institution is a large, public, Hispanic- and minority-serving institution, which provides the potential for engaging under-represented minority students in the sciences in the research project. Additional impacts include support of an institution in an EPSCoR state (South Carolina) and outreach to Miami, Florida K-12 public schools.

One outcome of this project will be comprehensive geochemical analyses of volcanic rocks recovered on IODP Expedition 351, at Site 1438, which is located just west of the Kyushu-Palau Ridge, the site of Izu-Bonin Mariana (IBM) arc inception. Preliminary findings indicate that oceanic basement at ODP Site 1438 is close to the age of forearc basalts which form the base of the IBM forearc sequences. Prior to the expedition, it was thought that magmas formed at subducting margins were "forearc basalts" of tholeiitic character, similar but not identical, to mid-ocean ridge basalts, followed by boninites. Preliminary findings demonstrate that this initial magmatism may not have been limited to the forearc, but may instead have occurred over a broad area of the plate margin during subduction and arc initiation. This research produces whole-rock major element, trace element, and Hf-Nd isotope geochemical data for basement basalts at Site 1438, at ODP Site 1201, and at DSDP Site 447. Similar studies of clasts separated from volcaniclastic sedimentary rocks that overlie basement at Site 1438 will characterize the earliest products of arc stratovolcanoes and their compositional evolution through time. The proposed studies will establish the full extent of geochemical similarity between forearc and basement basalts. It will also document compositional changes with time that may be recorded at Site 1438. Results of this work will likely lead to a revision of current hypotheses about magma generation during subduction initiation. The overlying volcaniclastic section of Site 1438 provides an unprecedented opportunity to study the chemical evolution of an island arc, from subduction initiation through arc growth and maturity, through the waning/cessation of arc volcanism as the result of rifting and back-arc basin formation.

The chemical compound H2O, which in its liquid state is called water, when it occurs bound in minerals and other solids, influences melting, rheology and plastic behavior of the mineral or material, and the material's thermal and electrical properties. In the case where H2O is bound in minerals deep in the ocean crust, this can result in enhanced generation of magmas, hence volcanic eruptions, and changes in the plasticity, deformation of the lithosphere. In areas where magmas rise to the surface, this H2O is released and forms an important part of the global cycle of H2O. Because most of the H2O on Earth is locked up in minerals in the crust and mantle, the concentration and distribution of H2O in various mantle and lithospheric reservoirs have been inferred primarily from analyses of undegassed glasses and melt inclusions in oceanic basalts through a comparison of their H2O content with incompatible rare earth elements like Cerium. This only provides a rough estimate of the H2O content of the Earth. This research builds off the results of a pilot study and uses a novel new approach to determine how much H2O is stored in minerals in the oceanic mantle and lithosphere, the mechanisms that fractionate H2O from other geochemical tracers in mantle lithologies, and the fate of the H2O and how it impacts the electrical conductivity and rheology of the oceanic lithosphere. Broader impacts of the work include support of a faculty member at an institution in South Carolina, an EPSCoR state (i.e., a state that does not receive significant federal funding), support of a researcher whose gender is under-represented in the sciences, and student training who will get trained on cutting-edge analytical instrumentation at NASA at the Johnson Space Center in Houston, TX. Impacts also include international collaboration with Belgian and Japanese scientists and making the data accessible to the public.

Questions to be addressed by this research include seeing if H2O varies independently from lithophile elements in the lithosphere and if diffusion is responsible if decoupling is observed; looking to see if pyroxenes are typically a high-H2O, low-solidus reservoir; examine if H2O solubility in minerals under lithospheric pressures and temperatures put an upper limit on how much structurally bound H2O is held in the unaltered lithosphere; whether H2O concentrations are reflected in the H2O systematics of lithospheric samples; and whether there are systematic correlations between H2O distribution in the lithosphere and the degree of melting, depth, and lithology and metasomatic agents. To address these issues, Fourier Transform Infrared Spectroscopy (FTIR) will be used to determine the H2O concentrations in well-characterized, fresh (i.e., unaltered) peridotites and pyroxenites from a suite of locations and tectonic settings that include the Canary Islands in the Atlantic Ocean; the Kerguelen Plateau in the South Indian Ocean; the Hawaiian and Samoan Islands and the Ontong Java Plateau in the Pacific Ocean; and the Lena Trough in the Arctic Ocean. Additional geochemical indicators, such as trace element compositions of minerals and radiogenic isotopes of Sr, Hf, Nd, and Pb in minerals and rocks will be used to help determine if there is a link between process, mineralogy, and H2O content/behavior.