Arnold Gucsik

Experimental investigation into the effects of meteoritic impacts on the spectral properties of phyllosilicates on Mars

[1] Phyllosilicates have been identified in some of the most highly cratered Noachian terrains on Mars. To study the effects of such impacts on the properties of phyllosilicates, we experimentally shocked six phyllosilicate minerals relevant to the Martian surface: montmorillonite, nontronite, kaolinite, prehnite, chlorite, and serpentine. The shock-treated samples were analyzed with X-ray diffraction (XRD), near- and mid-infrared (NIR and MIR) spectroscopy, Raman spectroscopy, cathodoluminescence (CL), and the shock pressures and temperatures in some were modeled using Autodyn modeling software. XRD data show that the structure of each mineral, except prehnite, underwent partial structural deformation or amorphization. We also found that while the NIR spectra of shocked samples were very similar to that of the original sample, the MIR spectra changed significantly. This may explain some of the discrepancies between CRISM/OMEGA data (NIR) and TES/THEMIS (MIR) observations of phyllosilicates on Mars. Quartz was identified as a secondary phase in the XRD of shocked chlorite.

Cathodoluminescence and its Application in the Planetary Sciences

1. Physical principles of cathodoluminescence (CL) and its applications in geosciences,- 2.Shock metamorphism of terrestrial impact structures and its application in the Earth and Planetary Sciences,- 3. Petrological modifications in continental target rocks from terrestrial impact structures: Evidence from cathodoluminescence,- 4. Impact diamonds: formation, mineralogical features and cathodoluminescence properties,- 5. Cathodoluminescence microscopy and spectroscopy of lunar rocks and minerals,- 6. Cathodoluminescence instrumentation for analysis of Martian sediments,- 7. Astrobiological aspect of chemolithoautotrophic bacterial activity in the role of black shale-hosted Mn mineralization and cathodoluminescence study of high Mn-bearting carbonates.

Cathodoluminescence and Raman Spectroscopic Characterization of Experimentally Shocked Plagioclase

Cathodoluminescence (CL) spectrum of plagioclase shows four emission bands at around 350, 420, 570 and 750 nm, which can be assigned to Ce3+, Al[Single Bond]O−[Single Bond]Al or Ti4+, Mn2+ and Fe3+ centers, respectively. Their CL intensities decrease with an increase in experimentally shock pressure. The peak wavelength of the emission band related to Mn2+ shifts from 570 nm for unshocked plagioclase to 630 nm for plagioclase shocked above 20 GPa. The Raman spectrum of unshocked plagioclase has pronounced peaks at around 170, 280, 480 and 510 cm−1, whereas Raman intensities of all peaks decrease with an increase in shock pressure. This result suggests that shock pressure causes destruction of the framework structure in various extents depending on the pressure applied to plagioclase. This destruction is responsible for a decrease in CL intensity and a peak shift of yellow emission related to Mn2+. An emission band at around 380 nm in the UV-blue region is observed in only plagioclase shocked above 30 GPa, whereas it has not been recognized in the unshocked plagioclase. Raman spectroscopy reveals that shock pressure above 30 GPa converts plagioclase into maskelynite. It implies that an emission band at around 380 nm is regarded as a characteristic CL signal for maskelynite. CL images of plagioclase shocked above 30 GPa show a dark linear stripe pattern superimposed on bright background, suggesting planer deformation features (PDFs) observed under an optical microscope. Similar pattern can be identified in Raman spectral maps. CL and Raman spectroscopy can be expected as a useful tool to evaluate shock pressure induced on the plagioclase in terrestrial and meteoritic samples.

Micro-Raman study of nanodiamonds from Allende meteorite

We have studied the Raman spectroscopic signatures of nanodiamonds from the Allende meteorite in which some portions must be of presolar origin as indicated by the isotopic compositions of various trace elements. The spectra of the meteoritic nanodiamond show a narrow peak at 1326 cm −1 and a broad band at 1590 cm −1 . Compared to the intensities of these peaks, the background fluorescence is relatively high. A significant frequency shift from 1332 to 1326 cm −1 , peak broadening, and appearance of a new peak at 1590 cm −1 might be due to shock effects during formation of the diamond grains. Such changes may have several origins: an increase in bond length, a change in the electron density function or charge transfer, or a combination of these factors. However, Raman spectroscopy alone does not allow distinguishing between a shock origin of the nanodiamonds and formation by a CVD process as is favored by most workers.

Cathodoluminescence Microscopy and Spectroscopy of Micro- and Nanodiamonds: An Implication for Laboratory Astrophysics

Color centers in selected micro- and nanodiamond samples were investigated by cathodoluminescence (CL) microscopy and spectroscopy at 298 K [room temperature (RT)] and 77 K [liquid-nitrogen temperature (LNT)] to assess the value of the technique for astrophysics. Nanodiamonds from meteorites were compared with synthetic diamonds made with different processes involving distinct synthesis mechanisms (chemical vapor deposition, static high pressure high temperature, detonation). A CL emission peak centered at around 540 nm at 77 K was observed in almost all of the selected diamond samples and is assigned to the dislocation defect with nitrogen atoms. Additional peaks were identified at 387 and 452 nm, which are related to the vacancy defect. In general, peak intensity at LNT at the samples was increased in comparison to RT. The results indicate a clear temperature-dependence of the spectroscopic properties of diamond. This suggests the method is a useful tool in laboratory astrophysics.

Relation between cathodoluminescence and trace-element distribution of magmatic topaz from the Ary-Bulak massif, Russia

Abstract In order to define the cathodoluminescence (CL) properties of magmatic topaz and its relation with traceelement composition, we studied topaz phenocrysts from the Ary-Bulak ongonite massif, Russia using a wide array of analytical techniques. Scanning electron microscopy CL panchromatic images reveal strong variations, which define micrometre-scale euhedral growth textures. Several truncations of these growth textures occur in single grains implying multiple growth and resorption events. The CL spectra of both CL-bright and -dark domains have a major peak in the near-ultraviolet centred at 393 nm. Cathodoluminescence images taken after several minutes of electron bombardment show decreasing emission intensity. Electron microprobe analyses indicate high F concentrations (average OH/(OH + F) = 0.04 calculated by difference, 100 wt.% - total from electron probe microanalyses), consistent with what has been found previously in topaz-bearing granites, and the OH stretching vibration (~3653 cm−1) was detected in Raman spectra. Laser ablation inductively-coupled plasma mass spectrometry traverses performed across the CL textures detected trace elements at ppm to thousands of ppm levels, including: Fe, Mn, Li, Be, B, P, Nb, Ta, W, Ti, Ga, light rare-earth elements, Th and U. Lithium,W, Nb and Ta appear to be correlated with CL intensity, suggesting a role for some of these elements in the activation of CL in topaz. In contrast, no clear correlation was found between CL intensity and F contents, despite the fact that the replacement of OH for F is known to affect the cell parameters of topaz.

Planar Deformation Features in Quartz from the Ries Impact Crater: Advanced by Micro-Raman Spectroscopy

ABSTRACT Shocked quartz grains from the Ries impact structure containing planar microstructures such as Planar Deformation Features (PDFs) were characterized by using micro-Raman spectroscopy. Raman spectrum of shocked quartz shows several bands with an intense peak at 459 cm−1. Low intensity of broad Raman bands near 495 and 800 cm−1, which indicate the presence of silica glass, were detected in the PDFs. 2D Raman mapping of the shocked quartz grain shows various distribution patterns of the integrated intensity of A1 Raman band at 459 cm−1 and thus reveal a difference of crystallinity in shocked quartz. The shift and peak broadening of Raman bands to a lower wave number (459 cm−1) may be due to the degree of disordering in tetrahedral sites affected by shock pressure. The results show distinct changes of the Raman properties of quartz with shock pressure and point to a possible use of this method for the identification and characterization of Planar Deformation Features in quartz.

Shock Metamorphism of Terrestrial Impact Structures and its Application in the Earth and Planetary Sciences

Shock metamorphism is the sum of irreversible chemical, mineralogical and physical changes in the target materials that occur during the hypervelocity impact event (Melosh 1989). The following chapters have been summarized from reviews by French and Short (1968); Sharpton and Grieve (1990); Stöffler and Langenhorst (1994); Grieve et al. (1996); Koeberl (1997) and French (1998). When an extraterrestrial projectile (comet or asteroid) hits target rocks of a planetary surface, geologic materials are subjected to shock pressures above their Hugoniot Elastic Limit (HEL), which is on the order of 5-10 Gigapascals (GPa) (Sharpton and Grieve 1990). Shock metamorphism provides evidence for conditions associated with impact cratering (e.g., French and Short 1968; Stöffler and Langenhorst 1994; Grieve et al. 1996; Koeberl 1997; French 1998, Deutsch 1998 and references therein) including the high pressures, temperatures, and strain rates (106−108 s−1), which lead to as characteristic structural and phase changes in minerals. Figure 2.1 shows that endogenic metamorphism of crustal rocks does not exceed temperatures of 1200◦C and pressures of 2 GPa, except static pressure, which affects specific deep-seated rocks, as for example eclogites (Koeberl 1997). Large impact events differ in many ways from endogenic processes such as volcanic explosions, earthquakes, and plate tectonics (French 1998):

Cathodoluminescence microcharacterization of ballen silica in impactites

The ballen silica shows fairly weak (faint) CL with homogeneous feature in its grain exhibiting almost same spectral pattern with two broad band peaks at around 390 and 650 nm, which might be assigned to self‐trapped excitons (STE) or an intrinsic and nonbridging oxygen hole centers (NBOHC), respectively, recognized in amorphous and crystalline silica. In addition, ballen silica from Lappajarvi crater shows bright and heterogeneous CL with a broad band centered at around 410 nm, presumably attributed to [AlO4/M+]0 centers or self‐trapped excitons (STE). Micro‐Raman and micro‐XRD analyses show that fairly homogeneous CL part is α‐quartz and heterogeneous CL part is composed of α‐cristobalite and α‐quartz. These indicate that ballen silica could be formed in the quenching process from relatively high temperature.

Micro - Raman Spectroscopy of Diamonds from JaH 054 and Sahara 98505 Ureilites, Statistic Research

In this paper Raman spectra of diamonds from two different ureilites, JaH 054 and Sahara 98505, were measured. Obtained results for both ureilites showed the Raman shift ranged between 1321 cm−1 and 1336 cm−1 for JaH 054 and between 1329 cm−1 and 1336 cm−1 for Sahara 98505. FWHM parameter (full width at half maximum) varied also in wide range especially for Sahara 98505. Raman imaging was done for JaH 054 sample and diamonds of different Raman shifts (1321 cm−1, 1328 cm−1, 1330 cm−1) were found in few tens μm sized area of carbon vein. Raman peaks of ureilitic diamonds were compared with literature data of laboratory diamonds produced under high pressure, under low pressure with MW PACVD method and with other ureilites. Presented research showed that even in highly shocked ureilites Raman shift versus FWHM parameter plots are similar with CVD diamonds for ureilites. However, the origin of diamonds in ureilites is not explained based on the obtained results, close coexistence of different diamonds in inves...