David W Peate
Research
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David Peate © 2009
Current Research Projects
Opportunities are available for motivated graduate students (M.S. and Ph.D.) to be involved in research projects in my lab, not necesarily limited to those listed below. Please e-mail me for more information.
click here for a description of facilities available for petrological and geochemical research at Iowa.
*** laser ablation ICP-MS facility (Thermo X-series II + NewWave 213nm laser) is up & running ***
Geochemical Investigations of Impact Processes
I am interested in how the chemical composition of impact materials can be used to infer details of impact processes. I recently received funding from the University of Iowa (Mathematical & Physical Sciences Funding Program) to study metallic spherules in impact melt rock from the Monturaqui impact crater in Chile. Post-doc Chung Wan Lim is working on this project. The metallic spherules are presumed to be derived from the iron meteorite impactor, but have compositions that differ from iron meteorites and show systematic variations with size. We are planning a detailed trace element investigation using our new laser ablation ICP-MS facility to learn more about the processes that cause these compositional variations during the impact event. Together with Ingrid Ukstins Peate (and graduate student Christy Kloberdanz), we are also studying the composition of the target rocks and minerals and the impact melt glass to better quantify what materials contributed to the melt glass. I was fortunate to have an opportunity to visit the Monturaqui impact crater in Dec 2009 and collect samples, together with Ingrid and colleagues as part of their NASA-funded spherules project (see expedition blog).
During the heyday of the K/T boundary controversy, the Manson impact crater in NW Iowa was the prime suspect for the site of the impact that caused the global Ir anomaly. Subsequent geochronological studies demonstrated that the crater age was c. 75 Ma, ten million years eariler that the K/T boundary. The crater site was intensively drilled by the USGS & IGS, and the cores are now archived at the Iowa Geological Survey. There is great potential to develop student projects based on this excellent resource (in collaboration with Ray Anderson and Brian Witzke at the Iowa Geological Survey).
Investigating the rates and mechanisms of crustal assimilation
I am interested in understanding how the compositions of continental basaltic magmas compositions are affected by assimilation of crustal materials en route to the Earth’s surface. Ingrid Ukstins Peate and I have an NSF-funded project to provide fresh constraints on crustal assimilation processes by looking at compositional heterogeneity in monogenetic eruptions from small-volume volcanic fields at different length-scales (whole rock samples vs. melt inclusions in crystals). We chose individual monogenetic systems rather than stratigraphic sequences of flows to give better control over sample ages and to reduce complexities from temporal variations in the assimilation process and magma replenishment episodes. We are using a variety of techniques (melt inclusions, U-series disequilibria, high-precision Pb isotopes) that in combination provide a new approach to the understanding of mechanisms, rates, and relative timing of crustal assimilation and fractionation processes. Jay Thompson has just completed an M.S. thesis on the Ice Springs basaltic lava flow (c. 1290 AD) in SW Utah and post-doc Mike Rowe is studying Paricutin volcano (1943-1952 AD) in Mexico. These are both young (< 1000 years), monogenetic eruptions that preserve compositional variations that can most easily be attributed to crustal assimilation and fractional crystallisation and that also contain partially-melted crustal xenoliths.
Melt inclusions in olivine phenocrysts provide a window into the earlier stages of crustal assimilation and the melt aggregation processes in the magmatic plumbing systems feeding monogenetic eruptions. The diversity of melt inclusion compositions should allow us to determine the extent of crustal assimilation at different stages in the differentiation history of the magma to provide constraints on theoretical and experimental models for the mechanisms of crustal assimilation. Re-homogenized melt inclusions are analysed by EMP (major elements, Cl & S), laser ablation ICP-MS (trace elements), and SIMS or laser ablation MC-ICP-MS (in-situ Pb isotopes). We will use trace element and high-precision Pb isotope data on variably-contaminated whole-rock samples to constrain the assimilant composition and compare this with the trace element and Pb isotope composition of glass and mineral phases in locally-entrained crustal xenoliths as a way to assess bulk versus selective assimilation models. We will use 226Ra/230Th disequilibria in whole rock samples to infer rates of differentiation, and we will measure 226Ra-230Th-238U nuclides in mineral and glass separates from partially-melted crustal xenoliths to provide the first direct observations of the behaviour and relative fractionation of these nuclides during crustal melting.
Origins and Environmental Impact of Large Igneous Provinces
Large igneous provinces represent some of the volumetrically most significant magmatic episodes in the Earth’s history. They are characterised by the rapid eruption of huge volumes of typically tholeiitic basaltic magmas. The ultimate driving force(s) behind the production of such large magma volumes are still the subject of considerable debate, with ideas ranging from impact of a mantle plume head, extension above a mantle plume, melting of lithospheric mantle, melting of recycled fertile eclogite material, small-scale edge convection at lithospheric discontinuities, and even impact melting. As these magmas pass through the crust, assimilation of crustal material can lead to significant modification of their mantle-derived compositional characteristics which complicates interpretations of lava compositions. Large igneous provinces have frequently been invoked as a cause of global climate change, and the coincidence between the eruption of flood basalt sequences and geological stage boundaries in the stratigraphic record is striking. The immense size of many individual eruptive units, often traceable for up to hundreds of kilometers, has led to speculation as to the environmental effects of these eruptions, particularly the extent of volatile emissions during eruption, and the subsequent chemical weathering and impact on ocean chemistry.
I am involved in an ongoing NSF-funded project with Ingrid Ukstins Peate (University of Iowa) and Adam Kent (Oregon State University) to study olivine- and plagioclase-hosted melt inclusions in primitive flood basalts to investigate crustal assimilation processes, and pre-eruptive volatile contents. Ryan Clark completed an M.S. thesis in 2006 on the petrogenesis of high-Ti/Y Paraná flood basalts, and Lee Falkena completed an M.S. thesis in 2009 on melt inclusions in silicic units in the Yemen large igneous province. I am also starting a new project to investigate the possible link between the eruption of the Paraná-Etendeka flood basalt province and the Valanginian Weissert oceanic anoxic event.
Applications of ICP-MS methods, including laser ablation
Laboratory renovations are scheduled for completion in late August 2009, and I hope to have the Thermo X-series II quadrupole ICP-MS and NewWave 213 nm laser abaltion system set up during September 2009.
Current Graduate Students
Opportunities are available for motivated graduate students (M.S. and Ph.D.) to work on projects involving applications of inorganic geochemistry to igneous petrogenesis or environmental topics.
Please e-mail me for more information.
Former Graduate Students (Peate as advisor or co-advisor)
Lee Falkena (M.S. 2007-2009: University of Iowa, USA).
Volatile content of large silicic eruptions in the Oligocene Yemen flood basalt province.Jay Thompson (M.S. 2007-2009: University of Iowa, USA).
Crustal assimilation mechanisms in continental basalts: the Ice Springs flow, Utah.
Ryan Clark (M.S. 2004-2006: University of Iowa, USA).
Petrogenesis of high Ti/Y magma types from the northern Paraná flood basalt province, South America.
current job: Terracon environmental consultants, Cedar Rapids, Iowa.Anna Ladenberger (Ph.D. 2002-2006: Jagiellonian University, Kraków, Poland).
Petrogenesis of Tertiary volcanic rocks from southwestern Poland.
co-advisors: M Michalik (Jagiellonian University)
visited University of Iowa on a Fulbright Scholarship (Sept 2005 - Jan 2006).
current position: Staff Scientist, Swedish Geological Survey.Abigail Barker (Ph.D. 2002-2006: Copenhagen University, Denmark).
Spatial and temporal compositional variations in the Iceland and Cape Verde hot spots.
co-advisors: JA Baker (Victoria University of Wellington, New Zealand), PM Holm (Copenhagen University)
first job after graduation: Post-doctoral researcher, University of Victoria, Canada.
current position: Assistant Professor, Uppsala University, Sweden.
Anja Fonseca (M.Sc. 2001-2005: Copenhagen University, Denmark).
Geochemical development in the upper part of the Skaergaard Intrusion.
co-advisors: C Tegner (Aarhus University), PM Holm (Copenhagen University).
current position: Meteorologist at Denmarks DR1 national TV station.Morten Riishuus (Ph.D. 2000-2004: Aarhus University, Denmark).
Petrogenetic and temporal evolution of the Kangerlussuaq intrusive complex, East Greenland.
co-advisors: C Tegner & R Wilson (Aarhus University), CK Brooks (Copenhagen University).
first job after graduation: Post-doctoral researcher, Stanford University, USA.
current position: Senior researcher scientist, Nordic Volcanological Center, Iceland.Eniko Bali (Ph.D. 2000-2004: Szeged University, Hungary).
Fluid/melt–wall-rock interaction in the upper mantle beneath the central Pannonian basin.
co-advisor: C Szabo (Eotvos University, Budapest, Hungary).
first job after graduation: Post-doctoral researcher, Clermont-Ferrand, France.
current position: Post-doctoral researcher, Bayreuth Research Institute, Germany.
Rasmus Andreasen (M.Sc. 1999-2001: Copenhagen University, Denmark).
Cyclical compositional variations in the Geikie Plateau Formation of the Palaeogene flood basalts, East Greenland: inferences about magma chamber processes.
co-advisor: CK Brooks (Copenhagen University).
first job after graduation: Ph.D. student, Dartmouth College, New Hampshire, USA.
current position: Post-doctoral researcher, Imperial College, London, UK.Yvonne Smit (Ph.D. 1997-2001: Open University, UK).
The Snæfellsnes transect: a geochemical cross-section through the Iceland plume.
co-advisors: CJ Hawkesworth & A Cohen (Open University).
first job after graduation: Post-doctoral researcher, Clermont-Ferrand, France.
current position: Freelance translator, France.Kresten Breddam (Ph.D. 1996-2000: Copenhagen University, Denmark).
The nature of the Iceland mantle plume: evidence from the chemistry of neovolcanic glasses.
co-advisor: CK Brooks (Copenhagen University).
first job after graduation: Post-doctoral researcher, Danish Lithosphere Centre, Denmark.
current position: Head of section, National Institute of Radiation Protection, Denmark.Frances Garland (Ph.D. 1991-1994: Open University, UK).
The Paraná rhyolites, southern Brazil: their petrogenetic relationship to the associated flood basalts.
co-advisor: CJ Hawkesworth (Open University).
Recent or Active Undergraduate Student Research Projects
David Majewski (2009-)
Investigation of magma mixing in dacites from Aguas Calientes volcano, Chile.
Emily Adamek (2008)
Digital image analysis of rock textures.
Funded through an Iowa Research Experiences for Undergraduates award.Kelly Wilhelm (2007-2008)
Compositional investigations of bronze and iron artifacts from the Netherlands.
Funded through an Dewey Stuit scholarship (with Glenn Storey, Anthropology).Kristen Stauffer (2007)
Evaluating the ability of Electric Pulse Disintegration to produce clean mineral separates for geochemical analysis.
Funded through an Iowa Research Experiences for Undergraduates award.Jay Thompson (2006)
Compositional variations within an individual eruptive event: The Ice Springs flow, Utah.Christy Kloberdanz (2005-2006)
PGE and Os isotopes on melt rocks from Manson impact crater, Iowa, and a search for impact diamonds.Shane Behanish (2005-2006)
Olivine-hosted melt inclusions from Vaigat Formation flood basalts, West Greenland.
Funded through an NSF research grant (with Ingrid Ukstins Peate).Jessica Bruse (2005-2006)
Mineral compositional variations in the Tabernacle Hill flow, Utah.
Partly funded through a North-Central GSA Undergraduate research grant (with Ingrid Ukstins Peate).Lee Falkena (2004-2005)
Origin of Pb isotope variations in Fe-Mn nodules from the Izu-Bonin forearc.
Funded through an Iowa Research Experiences for Undergraduates award.