Cathodoluminescence imaging and spectral analyses of phosphates in the Martian meteorites: A review.

A. Gucsik1, W. J. Protheroe, Jr. 2, J.A.R. Stirling3, K. Ninagawa4, H. Nishido5, T. Okumura5, N. Matsuda6, Sz. Berczi7, Sz. Nagy7, A. Kereszturi7 and H. Hargitai7

1Max Planck Institute for Chemistry, Mainz, Germany (gucsik@mpch-mainz.mpg.de)2AOL Inc., Houston, USA3Geological Survey of Canada, Ottawa, Canada4Okayama Unversity of Science, Dept. of Applied Physics, Okayama, Japan5Okayama Unversity of Science, RINS, Okayama, Japan6Okayama Unversity of Science, ISEI, Tottori, Japan7Eotvos Lorand University, Budapest, Hungary

NIPR, Tokyo, 07 June 2007

Contents

Basics of the cathodoluminescence signal.

CL properties of some Martian meteorites.

Conclusions.

•Purpose

•Scanning Electron Microscopy-Cathodoluminescence (SEM-CL) techniques provide better spatial resolution images of the minerals than the standard optical microscope ones.

• Moreover, SEM-CL spectral information might give some details on the activator elements presented in the in minerals.

•These observations can aid to understand more about the formation mechanism of different types of phosphates.

•It is important to note, that CL characteristics of the Martian meteorite samples have not been documented in great details, so far.

•Non-destructive method.

based on Goetze, 1999

based on Goetze, 1999

based on Goetze, 1999

based on Goetze, 1999

based on Goetze, 1999

based on Goetze, 1999

based on Goetze, 1999

Mechanism of CL (unshocked)-Band Gap Model

Processes of CL produced in insulator crystals

based on Goetze, 1999

CONDUCTION BAND (Ec)

VALANCE BAND (Ev)

B A N D

G A P (E g)

E N E R G Y (E )

Near UVλ ≤ 200 nm

Near IRλ ≥ 900 nm

1 2 3 1 2

Activator

Trap

3 4

„Extrinsic“„Intrinsic“

External energy source (irradiation)

Photon emission Energy transfers Energy migrations

No photon emission Absence of or closely-spaced electron traps

Mechanism of CL (shocked)-Band Gap Model

based on Nasdala, 2003

Kayama et al. (2007)

Okumura et al. (2007)

CL micrograph and spectrum of apatite

Reference material

based on Goetze, 1999

Samples and Experimental Procedure: We studied two polished thin sections of the Y000593 nakhlite Martian meteorite supplied from the National Institute of Polar Research (NIPR, Tokyo, Japan). SEM-CL imaging and CL spectral analyses were performed on the selected thin sections coated with a 20-nm thin film of carbon in order to avoid charge build-up. SEM-CL images were collected using a scanning electron microscope (SEM), JEOL 5410LV, equipped with a CL detector, Oxford Mono CL2, which comprises an integral 1200 grooves/mm grating monochromator attached to reflecting light guide with a retractable paraboloidal mirror. The operating conditions for all SEM-CL investigation as well as SEM and backscattered electron (BSE) microscopy were accelerating voltage: 15 kV, and 3.0-5.0 nA at room temperature. CL spectra were recorded in the wavelength range of 300-800 nm, with 1 nm resolution by the photon counting method using a photomultiplier detector, Hamamatsu Photonics R2228.

Y-000593 nakhliteSE SEM-CL CL

Apatite (Ap) was found as a mesostasis mineral, which occurs in veinlets between mostly clinopyroxene (Cpx) and plagioclase (Pl). EDS analysis reveals that this apatite is a chloroapatite, which contains minor fluorine, but uncertain of CO2 and OH.

Matsuda et al. (2007)

Research TeamCAN-AMMars MeteoriteResearch Team

Members of the research team are John A. R. Stirling (GSC), Walter J. Protheroe Jr., and Pat A. Hunt (GSC).

GSC – Geological Survey of Canada (Natural Resources Canada)

From left:John A. R. Stirling, Walter J. Protheroe Jr.and Pat A. Hunt

Research TeamPhotograph by: Katherine E. Venance (GSC)

EquipmentCAN-AMMars MeteoriteResearch Team

Equipment used in the research of the Mars meteorites is based at the Geological Survey of Canada, 601 Booth St., 7th floor,Ottawa, Ontario, Canada. The equipment shown below is manufactured by Cameca.

EOS – Electron Optic Service, Inc., Nepean, ONT., CanadaCameca, MBX and Camebax are trademarks of Cameca (France)Kevex is a trademark of Kevex Corporation.

Cameca MBX – Camebax Electron Microprobe This instrument is a fully automatedelectron microprobe with four wavelength spectrometers and a Kevex – Electron Dispersive Spectrometer (EDS). Upgrades to this system have included digital imaging, advanced EDS imaging, and Cathodo-luminescence (CL) spectrometry andimaging system by EOS.

EquipmentCAN-AMMars MeteoriteResearch Team

Also used in the analysis of the Mars meteorites at the Geological Survey of Canada is the Cameca SX-50.

Advance Microbeam - Advance Microbeam CorporationCameca, MBX and Camebax are trademarks of Cameca (France)PGT is a trademark of Princeton Gamma Tech Corporation.

Cameca SX-50 – Camebax Electron Microprobe The SX-50 is a new generation of automated electron microprobes. Thisone has four spectrometers, adigital imaging system and a EDS System by PGT. The software has beenupgraded by Advance Microbeam.

ALH-84001 sample N fragments (#3734, #3738, and #3739)

SE SEM-CL Colour-enhanced CL

Whitlockite (Beta-Ca-phosphate)

Conclusions

CL spectroscopy combined with SEM-CL imaging is a powerful technique to characterize phosphates in the Martian meteorites.

This also can aid to distinguish anhydrous or hydrous phosphates.

This technique also can play a key role in the in-situ measurements of the mineralogical evidences of the atmospheric-rock-fliud interactions on Mars.

Thank you very much for your attention