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
3
4
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
2
a"
P
Laser pit PETH LA ICPMS
Al
Spinel and melt inclusions
200µm
110#
450#
8
350#
90#
80#
70#
60#
300# 250#
150#
50#
40#
50#
40#
50#
60#
70#
80#
Zn,$ppm,$EPMA$
90#
100#
110#
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.
0.045"
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)
5
Analytical conditions: Acc. Volt. 25kV, Beam current: 900 nA
EPMA%
-5
EPMA%
-12
2Vernadsky
TiO2 EPMA
1ISTerre,
1, 2 A.V.SOBOLEV
100#
150#
200#
250#
300#
350#
element,'ppm'EPMA'
400#
450#
500#
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.
