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High Pressure Mineralogy
MineralsMethods
& Meaning
High Pressure Mineralogy
Quartz
polymorp
hs
Quartz and its high pressure polymorphs, coesite and stishovite were first found made in the laboratory, and later found in nature at the site of the Meteor Crater, AZ, meteorite impact.
Laboratory studies also indicated that high pressure polymorphsof other minerals could occur (e.g., olivine, pyroxene, garnet).
High pressure phases of other minerals were historically first found in nature in meteorites.
www.hppi.troitsk.ru/products/stishovite1.htmruby.colorado.edu/~smyth/ min/tio2.html
Stishovite demonstrates that silicon can assume six-coordination
SM Stishov
Early work on Ni
Early (1950’s) studies of germanate systems indicated that phase changes could occur.
Ni2GeO4 (olivine) Ni2GeO4 (spinel) pressure
Later work showed that silicates underwent the samephases changes but at higher pressures:
Ni2SiO4 (olivine) Ni2SiO4 (spinel) 55 kbar, °1400 C
High pressure effectsColor changes were observed in minerals at pressure indicating that the bonding was changing as well as the density.
Olivine becomes black at 270 kbarLaboratory chemicals change oxidation state (Fe3+ Fe2+)
Seismic velocities suddenly change at 410 and 660 km in the earth
Wadsleyite was first discovered in the Peace River stone-meteorite (ordinary chondrite L6) that fell at Peace River, Alberta, Canada. 31 March 1963
http://www.geo.ucalgary.ca/cdnmeteorites/meteorite/peaceriver1.html
Wadsleyite
A new polymorphof olivine wasfound in the Peace Rivermeteorite. It hasa modified spinelstructure that wascalled the -spinelstructure. It was given the mineralname, wadsleyite.
Wadsley
Ringwoodite
Another polymorph of Mg2SiO4 was found in the Siziangkou (China) and other meteorites. It has the spinel structure. It is named ringwoodite.
Ringwoodite in impact glass from Spain.
(Glazovskaya et al.)
Ringwoodite in the Tenham Meteorite. (Stöffler et al.)
A.E. (Ted) Ringwoodwww.science.org.au/academy/ memoirs/rgwd.htm
olivine polymorphs
-spinelwadsleyite
olivine, Mg2SiO4-spinelringwoodite
Institute for High Pressure Physics, Russian Academy of Sciences
Piston-cylinder high pressure
Rockland piston-cylinder system: 250 ton press
Diamond cell used for high pressure experiments.
Hemley (1997), Geophysical Laboratory,Carnegie Institution of Washington
Diamond Cell
www.geo.lsa.umich.edu/~crib/COURSES/117/Lect17/Lect17.html
Caltech’s shock wave lab
Pressure in excess of 1.5 Mbar can be achieved.
Shock wave labExtremely high pressure can be generated through shock-impact, but for only nanoseconds at a time.
At in laboratory experiments at high pressures ringwoodite breaks down to form a perovskite.
-Mg2SiO4 (Mg,Fe)SiO3 + (Mg,Fe)O spinel perovskite periclase ringwoodite
Ringwoodite to
perovskite
Silicate perovskite may occupy enormous volumes in the earth’s lower mantle. It may be the most abundant mineral in planet earth!
Silicate perovskite periclase (magnesiowustite)
Majorite
Orthopyroxene transforms at high pressure to the garnet structure.
2 Mg,Fe)2Si2O6 Mg3(Fe,Si)2(SiO4)3
The high pressure phase was first found at Coorara meteorite crater, Rawlina, Western Australia, Australia.
It is also found in other meteorites
The natural mineral is named majorite. (1970)
The Tenham meteorite that contains akimotoite, (Mg,Fe)SiO3 ,
of the ilmenite structure and other high pressure minerals.
Orthopyroxene -> majorite-garnet -> silicate-perovskite -> akimotoite
Tenham meteorite with akimotoite
Natural occurrence of MgSiO3-ilmenite perovskite in a shocked L5-6 chrondrite. Sharp TG, Lingemann CM, Dupas C, Stöffler DLunar and Planetary Science XXVIII
Akimotoite in Tenham chondrite.
Akimotoite, (Mg,Fe)SiO3 , a mineral of the ilmenite group, was found in the shock-metamorphosed Tenham chondrite.
World's deepest rocks
They were found at the Earth's surface on the island of Malaita, east of Papua New Guinea. But they originate from deep within the planet, between 400 km and 670 km down.
Professor Ken Collerson, from Queensland University, has shown that the most abundant mineral, garnet, contains a majorite component.
BBC News, 19-May-2000
World's deepest rocks recovered
Majorite = Mg3(Fe,Si)2(SiO4)3
Diamond Inclusions
Mark Riverswww-fp.mcs.anl.gov/xray-cmt/rivers/diamonds.html
Inclusions in diamonds bring up samples from the earth’s upper mantle
Jill Banfield, http://www.geology.wisc.edu/~jill/jpeg/l6sj2.jpeg
Kelsie Dadd, www.es.mq.edu.au/gemoc/annrep1998/
Reshighlights98.htm
Determine the Phases in the Deep Earth
Combine data from natural inclusions with laboratory studies
olivine
wadsleyite -spinel
ringwoodite -spinel
(Mg,Fe)SiO3 perovskite + (Mg,Fe)O periclase
akimotoite ? ilmenite
410 km
660 km
Olivine phases vs.
depth
135 kbar
230 kbar
Depth Pressure
From Stöffer (1997)
Earth Model
10 kbar = l GPa
Silicate Perovskite
Is this the most important mineral in the Earth?
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