june 4no 17-范大伟hpstar长春 _20150601_W

1、Effects of Hydration on the ElasticProperties of Pyrope at High P and TDawei Fan (范大伟)HPSTAR ChangchunJune 4th, 2015HPSTAR Annual Conference1Outline 1. Research Background 2. Elasticity of Hydrous Pyrope 3. Conclusions2Outline 1. Research Background 2. Elasticity of Hydrous Pyrope 3. Conclusions3Man

2、tle MineralogyGarnetLin and Wheat, 2011 The major minerals in the Earths upper mantle are olivine, opx, cpx, and garnet; Silicate garnet is an important mantle mineral and knowledge of its elastic property reliable compositional models of the upper mantle (Isaak et al., 2006;Perrillat et al., 2007).

3、is crucial to construct4Pyrope in the Earths MantleCa3Cr2Si3O12UvaroviteSome important garnet end-member composition(Alm)(Gr)(Py)(Uv)(An)(Maj)(Spe)Geiger, 2013Pyrope in the Earths interiorGarnet inclusion in diamondGarnet peridotite xenolithEclogite xenolithTwo solid solution series: Py-Alm-SpeUv-Gr

4、-AnWood et al., 2013Huang and Chen, 2014Bulk modulus data of almandine-pyrope binary system5 Garnets in peridotite and eclogite are usuallyrich in pyrope (Lu and Keppler, 1997). Pyrope is the major end-member garnets and an abundant constituent of the upper mantle ofEarth (Pavese et al., 2001).Hydro

5、gen in the Earths InteriorSchematic model for global water circulationHydrous phases exist in the deep Earthnominally anhydrous mineralsOhtani, 2005Hydrogen is the simplest and most abundant element in the universeHydrous PyropeWaterPyrope=upper mantle.6 Pyropecontainssmallamountsof structural OH-;

6、Affectthephysicalpropertiesofpyrope (such as elasticity, rheology, and electrical conductivity ); The physical properties of EarthsOutline 1. Research Background 2. Elasticity of Hydrous Pyrope 3. Conclusions7Fe compositional effects on the Elasticity of PyropeLu et al., 2013, EPSL Addition of 25 mo

7、l% Fe in pyrope increases the pressure derivative of the bulk modulus by 7 %, but has a negligible effect on other elastic parameters; Knowledge about the effect of hydrogen on the thermo-elasticity of pyrope is not clear.8Synthetic Experiments and AnalysisStarting material:Magnesium hydroxide Mg(OH

8、)2Aluminum oxide Al2O3Silica SiO21 mm Hydrous Pyrope YJ-3000TAverage H2O concentration 900 ppmHydrous PyropeEPMAMg3Al2Si3O129FTIRSynchrotron Experiments at BSRF and SSRFBeijing Synchrotron Radiation Facility, BSRFExternal heating diamond anvil cell4W21.Diamond anvil; 2. Heater;3. Rhenium gasket; 4.

9、Sample;5. ThermocoupleFan et al., 2010Powder XRDShort symmetric diamond anvil cellShanghai Synchrotron Radiation Facility, SSRFBL15UDuffy s websiteSingle crystal XRD10Room-Temperature EoS of hydrous PyropeVolume Eulerian strain-normalized pressure (FE-fE) plotVolume compression of hydrou pyrope at h

10、igh pressure compared with the previous studythird-order BM-EoS The effect of hydration is to decreasebulk modulusK0 and increase its pressure derivative K0 .11High-Temperature EoS of hydrous PyropeVariations of the isothermal bulk modulus of hydrous pyrope against temperature.P=16.75 GPa, T=900 K12

11、 Theeffectofhydrationandcomposition to the temperaturederivative of bulk modulus and thermal expansion coefficient of pyrope are limited.Seismic model of EarthPREM model Seismic waves passing through the Earth can directly probe the Earths deep interior; Seismic observations have well established th

12、e sound velocities and density relations with depth as well as with pressure.Dziewonski and Anderson, 198113Modeled densities of the upper-mantle mineralsDensity profile of upper-mantle minerals compared with PREM modelUpper mantle Modeled the density profile of piclogite and pyrolite for the Earths

13、 upper mantle region along a normal continenta geotherm (Katsura, 2010); The hydrogen effect on elasticity of pyrope leads to a 1% decrease in the density; The density profile of hydrous pyrope and dry pyrope are respectively 6% and 7% more dense than the PREM model.14Modeled densities of the upper-

14、mantle mineralsDensity profile of Pyrolite and Piclogite with hydrous pyrope compared with PREM modelDensity profile of Pyrolite model compared with PREM model The density profile both of pyrolite uncertainties; The density profile of pyrolite model with hydrous pyrope appears to have slightly small

15、er density than the pyrolite with dry pyrope.and piclogitemodels match well each other within their15Water solubility in pyrope as a function of pressureFrom Huang and Chen 2014 AGU16Experimental Outlook BLS is an accurate method formeasuring the materials.elasticpropertiesof13-BMD13-BMD at GSECARS

16、(Bass et al., 2005)Sinogeikin et al., 2006Brillouin scattering system17Outline 1. Research Background 2. Elasticity of Hydrous Pyrope 3. Conclusions183. Conclusions(1) The effect of hydration is to decrease K0 and increase K0 of pyrope.(2) The (K/T)P and 0 of pyrope may not be significant affected b

17、y the composition and hydrogen.(3) Thehydrogeneffectonelasticityofpyropeleadstoa1%decrease in the density.(4) Thedensityprofileofpiclogitemodelmatchwellwiththepyrolite model within their uncertainties.19AcknowledgementsHPSTAR: Qingxin Chu, Bin Yang, Bingmin YanInstitute of Geochemistry, CAS: Jingui Xu, Yunqian Kuang, Hongsen XieUniversity of Science and Technology of China