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High Pressure Mineralogy Minerals Methods & Meaning High Pressure Mineralogy.

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Presentation on theme: "High Pressure Mineralogy Minerals Methods & Meaning High Pressure Mineralogy."— Presentation transcript:

1 High Pressure Mineralogy Minerals Methods & Meaning High Pressure Mineralogy

2 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. min/tio2.html Stishovite demonstrates that silicon can assume six-coordination SM Stishov

3 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

4 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

5 Wadsleyite was first discovered in the Peace River stone- meteorite (ordinary chondrite L6) that fell at Peace River, Alberta, Canada. 31 March 1963 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

6 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

7 olivine polymorphs  -spinel wadsleyite olivine, Mg 2 SiO 4  -spinel ringwoodite

8 Institute for High Pressure Physics, Russian Academy of Sciences Piston-cylinder high pressure Rockland piston-cylinder system: 250 ton press

9 Diamond cell used for high pressure experiments. Hemley (1997), Geophysical Laboratory, Carnegie Institution of Washington Diamond Cell

10 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.

11 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)

12 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)

13 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

14 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.

15 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

16 Diamond Inclusions Mark Rivers diamonds.html Inclusions in diamonds bring up samples from the earth’s upper mantle Jill Banfield, Kelsie Dadd, Reshighlights98.htm

17 Determine the Phases in the Deep Earth Combine data from natural inclusions with laboratory studies

18 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

19 From Stöffer (1997) Earth Model 10 kbar = l GPa

20 Silicate Perovskite Is this the most important mineral in the Earth?

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