Resan till jordens inre

Resan till jordens inre

Athanasius Kircher(1665) Mundus Subterraneus

Jules Verne (1864)

Nuvarande schematisk bild av jordens inre

Temperatur i jordens inre

Tryck och densitet profiler i jordens inre

Tryck i jordens inre

350

12

300

10

250 8 200 6 150 4

100 50

outer core

mantle 0

inner core

2

0 0

1000

2000

3000

4000

5000

6000

Depth (km)

1 GPa = 100 000 N / cm2

järn 0 GPa

järn 364 GPa

Density (g/cm3)

0.1 GPa 3 GPa 364 GPa 550 GPa 2 TPa 100 TPa 30 000 TPa

Pressure (GPa)

Djupaste hav Industri Max. tryck i Jorden Diamancell Max. tryck i Jupiter Explosion av kärnvapen Solens kärna

14

400

Studier av jordens inre med hjälp av seismiska vågor

Density, pressure and gravity within the Earth

Key questions of the Earth’s deep interior rely on high pressure experiments

fältspat

Silikater

olivin

pyroxen

kvarts granat

hematit (Fe2O3)

koksalt (NaCl)

pyrit (FeS2)

gips (CaSO4 . 2H2O)

Subduktionszon (neddykningszon) - en långsmal zon i jordskorpan längs vilken två litosfäriska plattor kolliderar varvid den ena tvingas ned i manteln Vad händer med strukturen av en silikat mineral när tryck och temperatur ökar vid neddykning i subduktionszonen?

gips

(CaSO4 . 2H2O)

Vatten i jordens inre

Range of water concentrations in mantle-derived samples clinopyroxene orthopyroxene garnet olivine

0

200

400

600

800

1000

ppm H2 O

Olivine, enstatite, diopside and garnet make up 95% of the upper mantle. They all contain water.

1200

1400

• • •

Oceans cover 71% of surface Only 0.025 % of Earth’s mass Chondrites contain 0.10% H2O

Fasövergångar hos olivin olivin

quartz

Coesite inclusions in Pyrope. Size of Pyrope is about 10x7 mm

Coesite inclusion in garnet of eclogite sample

Coesite is a form of silicon dioxide that is formed when very high pressure (2–3 gigapascals) and moderately high temperature (700 °C) are applied to quartz. Coesite was first created by in 1953. In 1960, coesite was found by Eugene Shoemaker to naturally occur in the Barringer Crater, which was evidence that the crater must have been formed by an impact. The presence of coesite in unmetamorphosed rocks may be evidence of a meteorite impact event or of an atomic bomb explosion. In metamorphic rocks, coesite commonly is one of the best mineral indicators of metamorphism at very high pressures (UHP, or ultrahigh-pressure metamorphism). Such UHP metamorphic rocks record subduction or continental collisions in which crustal rocks are carried to depths of 70 km or more. Coesite also has been identified in eclogite xenoliths from the mantle of the earth that were carried up by ascending magmas; kimberlite is the most common host of such xenoliths. The molecular structure of coesite consists of four silicon dioxide tetrahedra arranged in a ring. The rings are further arranged into a chain. This structure is metastable within the stability field of quartz: coesite will eventually decay back into quartz with a consequent volume increase, although the metamorphic reaction is very slow at the low temperatures of the Earth's surface.

Stishovite – a high pressure polymorph of SiO2 The structure is dense-packed. Unlike in quartz, where Si-O are arranged in a tetrahedral coordination, in stishovite each silicon atom has 6 oxygen neighbours (octahedral coordination)

Tiny (< 1 mm) greyish-white, roundish aggregates of the high pressure mineral Stishovite on a matrix of Magadiite-Kenyaite-Coesite. Field of view 3 mm. The source of 'forming' the Stishovite was extreme heat by an meteorite impact near Bisbee, Arizona. The exact location and the year of impact is unknown.

Examples of some high pressure – high temperature phase diagrams of minerals determined in laboratory Phase diagrams depict P-T ranges of stability of various crystallographic forms of minerals.

Phase diagram of MgSiO3 (At ambient conditions, MgSiO3 represents mineral enstatite, belonging to the pyroxene group of silicates)

Examples of some high pressure – high temperature phase diagrams of minerals determined in laboratory

Phase relationships for SiO2 (quartz at ambient conditions)

Phase diagram of NaAlSi3O8 (feldspar albite at ambient conditions)

Diamantcell – ”öppnar ett fönster” till jordens inre

Tryck = kraft / yta

Prov i diamantcell

Laseruppvärmning av material i diamantcell

Laseruppvärmning av material i diamantcell

iron at high pressure in diamond anvil cell

Bilder på glödande provet

50 microner

Omvandling av grafit till diamant i diamantcell vid högt tryck och temperatur

Fasdiagram av kol

Determination of crystal structure by x-ray diffraction

Fig. 5.06 W. W. Norton

By analyzing diffraction pattern, crystal structure of mineral can be determined

Synkrotron anläggningar används ofta för högtryckstudier.

Synkrotron i Argonne, USA.

Synkrotron i Grenoble, Frankrike.

Discovery of post-perovskite transition in MgSiO3 - A new paradigm for core-mantle boundary

CMB

4500

Murakami et al., Science (2004)

4000

Temperature (K)

3500

7.5 MPa/K

3000

2500

2000

1500

1000

Orthorombicperovskite

Post-Pv

500

error ~5 GPa 0 70

80

90

100

110

120

130

140

150

Pressure (GPa)

Valley bottom

Hill top ~8 GPa ~250 km

D” lager

MgSiO3 perovskite

Post-perovskite

Si Mg

Kristallstruktur av post-perovskit

Si Mg

Perovskite

Post-Perovskite

The dominant mineral on the Earth

Forms 150 km thick layer adjacent to the core

Framsteg i forskning om jordens inre

Year-points mark the time and depths, for which corresponding experimentral pressure-temperature conditions were reached in the laboratory.

Modern tomographic 3-D image of the Earth. Colors encode speesd of seismic waves; blue for faster-than average; red for slower-than average speeds. These variations are connected to changes in temperature and/or chemical composition.