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VERSION:2.0
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X-WR-CALNAME:Earth Planetary Science Seminar - Dr. Glenn Gaetani "Experimen
 tal constraints on the damp peridotite solidus and potential temperature o
 f the oceanic mantle".
X-WR-TIMEZONE:Pacific Time (US & Canada)
BEGIN:VEVENT
DTSTAMP:20260714T132105Z
UID:tag:localist.com\,2008:EventInstance_52594795409276
DTSTART:20260414T190000Z
DTEND:20260414T201500Z
DESCRIPTION:Ocean crust is formed by magmatism along 65\,000 km of divergen
 t plate boundaries known as mid-ocean ridges. Decompression partial meltin
 g of mantle peridotite ascending beneath these ridges produces the basalti
 c magma that forms the crust. The depth at which partial melting begins is
  controlled by a combination of mantle potential temperature and the perid
 otite solidus. Knowledge of the solidus combined with geophysical observat
 ions indicating the presence of partial melt can be used to constrain mant
 le temperature. However\, the peridotite solidus is sensitive to the prese
 nce of small amounts of hydrogen dissolved in the nominally anhydrous mine
 rals that comprise upper mantle peridotite. At H2O-undersaturated (“damp
 ”) conditions the melting point of peridotite is dramatically lower than
  the anhydrous solidus\, increasing the depth at which partial melting beg
 ins for a given potential temperature. Partial melting that begins beneath
  a ridge at the “damp” solidus involves a larger volume of peridotite 
 and produces a higher mean pressure of melting and lower mean extent of me
 lting. The oceanic upper mantle is estimated to contain 50 to 200 μg/g H2
 O\, but its influence on the onset of peridotite melting has proven challe
 nging to quantify experimentally. Despite meticulous drying protocols\, an
  unknown amount of H2O is present in high-pressure melting experiments. Me
 asuring the concentrations of H2O in nominally anhydrous minerals grow dur
 ing partial melting experiments is hindered by the small grain size. We de
 veloped an experimental approach that leverages the rapid diffusivity of H
 + in olivine to overcome this difficulty by using large (~300 µm in diame
 ter) olivine spheres as hygrometers. We used this approach to quantify the
  solidus temperature for peridotite containing ~145 μg/g dissolved H2O at
  1.0 to 2.5 GPa. Our data reveal that the H2O-undersaturated peridotite so
 lidus is hotter than previously thought. Reconciling our experimental resu
 lts with geophysical observations of the melting regime beneath the East P
 acific Rise requires that existing estimates for the oceanic upper mantle 
 potential temperature be adjusted upward by ~60 °C.\n \n\nGaetani Bio\n\n
 Director of the Northeast National Ion Microprobe Facility (2010 – Prese
 nt)\n\nScientific Staff Woods Hole Oceanographic Institution (2000 – Pre
 sent)\n\nResearch Scientist Rensselaer Polytechnic Institute (1998-2000)\n
 Advisor Bruce Watson\n\nPostdoctoral Scholar California Institute of Techn
 ology (1996-1998)\nAdvisor: Ed Stolper\n\nPh.D. Massachusetts Institute of
  Technology (1996)\nAdvisor: Tim Grove\n\nM.S. State University of New Yor
 k at Albany (1990)\nAdvisor: Steve DeLong\n\nB.S. University of Massachuse
 tts at Amherst (1985)
LOCATION:Building 320\, Geology Corner\, Room 220
SUMMARY:Earth Planetary Science Seminar - Dr. Glenn Gaetani "Experimental c
 onstraints on the damp peridotite solidus and potential temperature of the
  oceanic mantle".
URL;VALUE=URI:https://events.stanford.edu/event/copy-of-earth-planetary-sci
 ence-seminar-dr-glenn-gaetani-experimental-constraints-on-the-damp-peridot
 ite-solidus-and-potential-temperature-of-the-oceanic-mantle
CATEGORIES:Class/Seminar
END:VEVENT
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