EPMA

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160. Albite. TAPJ GPC. 9. 15. Ca. 180. 180. Wollastonite. TAPH GPC. 3. 6. P. 160. 160. Apatite Durango PETH XPC. 5. 4. Co. 160. 160 pure CoO. LIFL. XPC. 5. 8.
A high precision EPMA data of olivine: comparison with LA ICP-MS 1,2 V.G.BATANOVA ,

AND

D.

3 KUZMIN

University J. Fourier, Grenoble, France, [email protected]; GEOKHI RAS, Moscow, Russia; 3VS Sobolev Inst. of Geol. and Miner. SB RAS, Novosibirsk, Russia New Electron Probe MicroAnalyser (EPMA) laboratory in ISTerre, University J. Fourier, Grenoble, France   1  

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The  primary  causes  for  most  systema5c  accuracy  errors  in  trace  elements  measurements  are   poorly  placed  spectrometer  posi5on  for  determina5on  intensity  of  background  (Donovan  et  al.,   2011).  To  choose  op5mal  backgrounds  posi5ons  we  performed  high-­‐sensi5vity  wavelength  scan   on  each  side  of  the  peak  of  the  analysed  trace  element.  This  figure  shows  such  scan  from  both   sides  of  Al  Ka  line  in  San  Carlos  OL    standard  (USNM111312-­‐44)  and  Al-­‐free  OL  from  mantle   perido5te.  We  use  linear  interpola5on  method  with  two  background  measurements  on  each   side  of  the  peak.  To  avoid  underes5ma5on  of  Al  concentra5on  due  to  curvature  of  the   con5nuum  in  the  Al  peak  region,  we  selected  background  posi5ons  close  to  the  peak.    

JEOL JXA-8230: W- electron source. Probe current range: 10 to 10 A and Beam current stability: ±0.05% / h, ±0.3% / 12h Acc. voltage: 0.2 to 30 kV; 5 wavelength dispersive spectrometers (WDS); Energy dispersive spectrometer (EDS) - a silicon-drift detector (SDD). Combining the SDD with the remote controlled aperture mechanism enables simultaneous WDS/EDS analysis. Probe facility is equipped by climate system capable to keep constant temperature (± 0.5oC) and humidity (± 5%) in the room Phosphorus and aluminum zoning in olivine crystals

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a"

P

Laser pit PETH LA ICPMS

Al

Spinel and melt inclusions

200µm

110#

450#

8  

350#

90#

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60#

300# 250#

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50#

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50#

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50#

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Zn,$ppm,$EPMA$

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120#

TiO2 in Olivines from different types of basalts. EPMA and LA ICP MS data

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0.015

0.01

0.005

TiO2 LA ICP MS 0 0

0.005

0.01

0.015

SUMMARY

200#

100#

50#

5 9 3 5 5 6 3 5 4 5

The combination of modern Jeol JXA-8230 electron probe microanalyser equipped with 5 wavelength dispersive X-ray spectrometers (WDS) and an energy dispersive SDD X-ray spectrometer (EDS) with highly efficient climate conditioning delivers precision down to 5 ppm 2 standard error of electron probe microanalysis of olivine.

400#

100#

element,'ppm,'LA+ICPMS'

Melt inclusions The  olivine  is  principal  source  of  petrological  and  geochemical  informa5on.  Especially  informa5ve   are  minor  and  trace  elements  Ni,  Mn,  Ca,  Al,  Cr,  Co,  Ti,  Zn,  P,  Na  with  concentra5on  range  over  10   ppm.  The  maps  show  the  typical  olivine  grain  from  MORB  with  fine  oscillatory  zoning  in   phosphorus  and  from  Iceland  with  oscillatory  zoning  in  Al.  It  demonstrates  necessity  of  high   spa5al  resolu5on  (in  order  of  few  microns)  for  analysis  of  such  grains.    LA  ICP  MS  and  SIMS  which   recently  applied  to  understanding  trace  element  concentra5on  in  olivine  do  not  provide  such   spa5al  resolu5on.  Today  only  EPMA  can  give  us  this  kind  of  resolu5on.      

Zn, Co, Al in Ol from MORB, LA ICP MS and EPMA data 500#

GPC GPC GPC XPC XPC XPC XPC XPC XPC XPC

400 500 155 Fo 150 5 15 6 4 8 6 5 8 8 5

 Acc.  V  25  kV,  beam  current  900  nA.  At  this  condi5on  major  element  can  not  be  analysed  on   WDS  because  of  extremely  high  coun5ng  rates  and  oversatura5on  of  counters.  The  only  way   to  measure  the  major  and  trace  elements  together  is  to  use  EDS  for  major  elements   measurement.  Precision  (2  sigma)  obtained  by  repeated  measurement  of  olivine  standards   are  for  major  element  equvalent  of  Fo  -­‐150  ppm  and  for  trace  elements  4-­‐15  ppm.  Total   5me  of  analysis  -­‐  12  minutes.  

0.5"     0.45" 0.04"   0.4" 0.035"   0.35"   0.03"   0.3" 0.025"   0.25"   0.02"   0.2" SCOL"   0.015" XEN"" 0.15"   SCOL" 0.01"   0.1" XEN"   0.005" 0.05"   0" 0"   0" 0.05" 0.1" 0.15" 0.2" 0.25" 0.3" 0.35" 0.4" 0.45" 0.5" 0" 0.005" 0.01" 0.015" 0.02" 0.025" 0.03" 0.035" 0.04" 0.045"   LA%ICP%MS% LA%ICP%MS%   SCOL  –  San  Carlos  Olivine  USNM111312-­‐44  (Jarosewich  et  al.,  1980);  LA  ICP  MS  data  from  De  Hoog  et  al.,  2010  and  E.   Hauri  et  al.,  (under  prepara5on);  XEN  –  internal  ISTerre  EPMA  lab  standard.  ERROR  BAR=  2  standard  devia5ons.  

120#

detection 2 StDev Type of limit (ppm) counter (ppm)

 Finally  we  developed  our  op5mal  protocol  shown  on  this  figure.  

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7   100µm

On peak Background count times Count Standard Crystal (sec) Times (+/-) Elements on EDS Si 500 OL USNM111312-44 SDD Mg 500 OL USNM111312-44 SDD Fe 500 OL USNM111312-44 SDD Elements on WDS Al 180 180 pure Al2O3 TAPJ Na 160 160 Albite TAPJ Ca 180 180 Wollastonite TAPH PETH

P 160 160 Apatite Durango PETH Co 160 160 pure CoO LIFL Zn 180 180 ZnS LIFL Ti 180 180 pure TiO2 PETH Ni 80 80 pure NiO LIFH Mn 160 160 Rhodonite LIFH 90 90 pure Cr2O3 LIFH   Cr

EPMA and LA ICP MS data comparison, OLIVINE STANDARDS

Zn,$ppm,$LA)ICPMS$

                             

Elemental distribution maps (WDS)

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Analytical conditions: Acc. Volt. 25kV, Beam current: 900 nA

EPMA%

-5

EPMA%

-12

2Vernadsky

TiO2 EPMA

1ISTerre,

1, 2 A.V.SOBOLEV

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element,'ppm'EPMA'

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References:     De  Hoog  et  al.,  Chem.Geol.,  v270,  196-­‐215,  2010;  Donovan  et  al.,  Amer.Miner.v   96,  274-­‐282,  2011;    Hauri  et  al  (under  prepara5on);  Jarosewich  et  al,  Geostand.   Newsleh.,  v4,  40-­‐43,  1980;  Sobolev  et  al,  Science,  v  316,  412-­‐417  2007.