Raman microprobe mineral identification

Hope, Gregory Alan; Woods, R.; Munce, Carolyn G.

doi:10.1016/s0892-6875(01)00175-3

Cited by 116 publications

(66 citation statements)

References 6 publications

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“…These spectra were initially acquired using a relatively low laser intensity (well below 2 mW), whereas in higher power new peaks appeared, probably due to phase modifications during the analysis. The spectrum acquired is very similar to that determined on marcasite by Hope et al (2001), both in terms of identical peak positions at 321 and 384 cm -1 but also with respect to their relative intensities. Moreover, other similar spectra were also measured for marcasite by Mernagh and Trudu (1993), who observed peaks at 324 and 387 cm .…”

Section: Chemical Analysis and Raman Spectroscopy Of Nearby Mineral Psupporting

confidence: 69%

A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology

Chatzitheodoridis

Haigh

Lyon³

2014

Astrobiology

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A conspicuous biomorphic ovoid structure has been discovered in the Nakhla martian meteorite, made of nanocrystalline iron-rich saponitic clay and amorphous material. The ovoid is indigenous to Nakhla and occurs within a late-formed amorphous mesostasis region of rhyolitic composition that is interstitial to two clinopyroxene grains with Al-rich rims, and contains acicular apatite crystals, olivine, sulfides, Ti-rich magnetite, and a new mineral of the rhoenite group. To infer the origin of the ovoid, a large set of analytical tools was employed, including scanning electron microscopy and backscattered electron imaging, wavelength-dispersive X-ray analysis, X-ray mapping, Raman spectroscopy, time-of-flight secondary ion mass spectrometry analysis, high-resolution transmission electron microscope imaging, and atomic force microscope topographic mapping. The concentric wall of the ovoid surrounds an originally hollow volume and exhibits internal layering of contrasting nanotextures but uniform chemical composition, and likely inherited its overall shape from a preexisting vesicle in the mesostasis glass. A final fibrous layer of Fe-rich phases blankets the interior surfaces of the ovoid wall structure. There is evidence that the parent rock of Nakhla has undergone a shock event from a nearby bolide impact that melted the rims of pyroxene and the interstitial matter and initiated an igneous hydrothermal system of rapidly cooling fluids, which were progressively mixed with fluids from the melted permafrost. Sharp temperature gradients were responsible for the crystallization of Al-rich clinopyroxene rims, rhoenite, acicular apatites, and the quenching of the mesostasis glass and the vesicle. During the formation of the ovoid structure, episodic fluid infiltration events resulted in the precipitation of saponite rinds around the vesicle walls, altered pyrrhotite to marcasite, and then isolated the ovoid wall structure from the rest of the system by depositing a layer of iron oxides/hydroxides. Carbonates, halite, and sulfates were deposited last within interstitial spaces and along fractures. Among three plausible competing hypotheses here, this particular abiotic scenario is considered to be the most reasonable explanation for the formation of the ovoid structure in Nakhla, and although compelling evidence for a biotic origin is lacking, it is evident that the martian subsurface contains niche environments where life could develop.

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Section: Chemical Analysis and Raman Spectroscopy Of Nearby Mineral Psupporting

confidence: 69%

A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology

Chatzitheodoridis

Haigh

Lyon³

2014

Astrobiology

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“…They lead to the same conclusion: The product is a mixture of greigite and pyrite. The Raman spectrum of pyrite [41] is made of two sharp peaks at 344 and 380 cm −1 that surround the main peaks of greigite at ∼355 and ∼367 cm −1 , and a smaller one at 430 cm −1 . The XRD pattern is made of only the diffraction lines of pyrite and greigite, except for the line denoted by a star, which could be attributed to (Fig.…”

Section: Evolution Of Mackinawite Prepared With Fe/s = 3/4 and Acidifmentioning

confidence: 99%

The transformation of mackinawite into greigite studied by Raman spectroscopy

Bourdoiseau¹,

Jeannin²,

Rémazeilles³

et al. 2011

J Raman Spectroscopy

120

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In this study, Raman spectroscopy was used to precisely understand the mechanisms of oxidation of mackinawite (FeS). Two experimental conditions were considered: (1) oxidation in air at room temperature and (2) oxidation in acidic anoxic solutions at 80 • C. In both cases, the oxidation process began by the in situ oxidation of Fe(II) cations inside the crystal structure of mackinawite and led to Fe(III)-containing mackinawite, Fe II 1−3x Fe III 2x S. The oxidation in air finally led to Fe(III) oxyhydroxides and elemental sulfur α-S 8 , but greigite (Fe 3 S 4 ) was observed as an intermediate compound. In anoxic acidic solutions, the product of the oxidation was proved to depend on the Fe/S concentration ratio. For Fe/S = 3/4, greigite was the only product obtained, and this allowed us to determine unambiguously the Raman spectrum of this compound. For Fe/S = 1/2, the reaction led to pyrite FeS 2 .

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“…Such instruments have high light throughput, allowing fast analysis of very small areas of minerals. Mernagh and Trudu (1993), Hope et al (2001) and Kharbish (2007) ture of our experiments is that we have synthesized an extended series of Fe x Zn 1Àx S sphalerites in a range of mole fractions of FeS from 0 to 0.5 (which is close to the solubility limit) and with a small increments of 0.05.…”

Section: Introductionmentioning

confidence: 99%