Presentation on theme: "High Pressure Mineralogy Minerals Methods & Meaning High Pressure Mineralogy."— Presentation transcript:
High Pressure Mineralogy Minerals Methods & Meaning High Pressure Mineralogy
Quart z poly morp 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 polymorphs of other minerals could occur (e.g., olivine, pyroxene, garnet). High pressure phases of other minerals were historically first found in nature in meteorites. ruby.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. Ni 2 GeO 4 (olivine) Ni 2 GeO 4 (spinel) pressure Later work showed that silicates underwent the same phases changes but at higher pressures: Ni 2 SiO 4 (olivine) Ni 2 SiO 4 (spinel) 55 kbar, °1400 C
High pressure effects Color changes were observed in minerals at pressure indicating that the bonding was changing as well as the density. Olivine becomes black at 270 kbar Laboratory chemicals change oxidation state (Fe 3+ Fe 2+ ) 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 Wadsle yite A new polymorph of olivine was found in the Peace River meteorite. It has a modified spinel structure that was called the -spinel structure. It was given the mineral name, wadsleyite. Wadsley
Ringwoodite Another polymorph of Mg 2 SiO 4 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) Ringwood memoirs/rgwd.htm
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
Caltech’s shock wave lab Pressure in excess of 1.5 Mbar can be achieved. Shock wave lab Extremely 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. -Mg 2 SiO 4 (Mg,Fe)SiO 3 + (Mg,Fe)O spinel perovskite periclase ringwoodite Ringwoo dite to perovskit e 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) 2 Si 2 O 6 Mg 3 (Fe,Si) 2 (SiO 4 ) 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)SiO 3, of the ilmenite structure and other high pressure minerals. Orthopyroxene -> majorite-garnet -> silicate-perovskite -> akimotoite Tenham meteorite with akimotoite
Natural occurrence of MgSiO 3 -ilmenite perovskite in a shocked L5-6 chrondrite. Sharp TG, Lingemann CM, Dupas C, Stöffler D Lunar and Planetary Science XXVIII Akimotoite in Tenham chondrite. Akimotoite, (Mg,Fe)SiO 3, 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 = Mg 3 (Fe,Si) 2 (SiO 4 ) 3
Diamond Inclusions Mark Rivers www-fp.mcs.anl.gov/xray-cmt/rivers/ diamonds.html Inclusions in diamonds bring up samples from the earth’s upper mantle Jill Banfield, Kelsie Dadd, Reshighlights98.htm
Determine the Phases in the Deep Earth Combine data from natural inclusions with laboratory studies
olivine wadsleyite -spinel ringwoodite -spinel (Mg,Fe)SiO 3 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?