HR: 0800h
AN: V31D-0687    [Abstracts]
TI: Quantifying Element Mass Transfer at Subduction Zone Conditions by using the Hydrothermal Diamond Anvil Cell and in-situ X-Ray Fluorescence
AU: * Maglio, S J
EM: stevemaglio@gmail.com
AF: High Pressure Science and Engineering Center, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4010, United States
AU: Frank, M R
EM: mfrank@niu.edu
AF: Department of Geology and Environmental Geosciences, Northern Illinois University, Davis Hall 312, Normal Road, DeKalb, IL 60115, United States
AU: Simon, A
EM: adam.simon@unlv.edu
AF: High Pressure Science and Engineering Center, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4010, United States
AU: Tschauner, O
EM: olivert@physics.unlv.edu
AF: High Pressure Science and Engineering Center, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4010, United States
AU: Aarestad, B
EM: aareth2000@yahoo.com
AF: Department of Geology and Environmental Geosciences, Northern Illinois University, Davis Hall 312, Normal Road, DeKalb, IL 60115, United States
AU: Hanchar, J
EM: head@esd.mun.ca
AF: Department of Earth Sciences, Memorial University of Newfoundland, Room 4063, Alexander Murray Building, 300 Prince Philip Drive, St. John's, NL A1B 3X5, Canada
AU: Nicol, M
EM: nicol@physics.unlv.edu
AF: High Pressure Science and Engineering Center, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4010, United States
AB: Our understanding of the physicochemical processes attending prograde metamorphism of subducting oceanic plates derives largely from inferences made from the chemistry of arc volcanics and traditional quench experiments. Using the chemistry of arc volcanics introduces complications owing to the history of melt + crystals during their protracted ascent through the magmatic plumbing system. Quench phenomena may affect measured element abundances in recovered phases, thus, in this project we aim to circumvent these problems by refining a technique using the hydrothermal diamond anvil cell (HDAC) to perform in situ experiments and utilize white synchrotron radiation and X-ray fluorescence (SR-XRF) to quantify element mobility of REE-monazite in H2O ± HCl ± NaCl during simulated prograde heating and compression at relevant P-T conditions of subduction zones. Our first target has been the dissolution of monazite at pressures from 2 to 5 GPa and temperatures to 800 °C. Schmidt et al. (2007; Lithos) report data at 2 GPa which serve as a benchmark for us to evaluate our results. Monazite is a common accessory mineral in a variety of igneous and metamorphic rocks associated with subduction zones and the REE chemistry of monazite has provided insight into processes attending magma evolution in arc systems. The interaction of REE-monazite with an aqueous fluid, generated by dehydration of the subducting oceanic plate, may significantly affect REE ratios in monazite which ultimately complicate geochemical inferences based on monazite chemistry. Solutions of known REE concentration are made and used as standards. The peak areas determined during experiments at slab conditions are compared to the peak areas of the known solutions to resolve the concentration of the REE in the sample. The partitioning of HFSE and LFSE are also of interest, and are being examined in the same experimental procedure. This technique allows us to quantify the fluid mobility of REE, HFSE, and LFSE at the conditions approximating subduction zones.
DE: 1000 GEOCHEMISTRY
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 1065 Major and trace element geochemistry
DE: 1094 Instruments and techniques
DE: 3600 MINERALOGY AND PETROLOGY
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting