high pressure mineralogy minerals methods & meaning high pressure mineralogy

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?