Geochemistry and origin of Libyan Desert glasses

Barrat, Jean‐Alix; Jahn, B.M.; Amosse, J.; Rocchia, R.; Keller, Francine; Poupeau, Gérard; Diemer, E.

doi:10.1016/s0016-7037(97)00063-x

Cited by 52 publications

(69 citation statements)

References 30 publications

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“…Table 3 reports the compositional data, and (Table 3). Our analyses agree with published data (e.g., Barrat et al 1997). Figures 5b and 5d show that, in some cases, the CL-dark areas have zoned rims (or layers) with variations in the CL intensities.…”

Section: Libyan Desert Glasssupporting

confidence: 92%

Infrared, Raman, and cathodoluminescence studies of impact glasses

Gucsik

Koeberl

Brandstätter

et al. 2004

Meteorit & Planetary Scien

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Abstract-We studied the infrared reflectance (IR), Raman, and cathodoluminescence (CL) spectroscopic signatures and scanning electron microscope-cathodoluminescence (SEM-CL) images of three different types of impact glasses: Aouelloul impact glass, a Muong Nong-type tektite, and Libyan desert glass. Both backscattered electron (BSE) and CL images of the Muong Nong-type tektite are featureless; the BSE image of the Libyan desert glass shows only weak brightness contrasts. For the Aouelloul glass, both BSE and CL images show distinct brightness contrast, and the CL images for the Libyan desert glass show spectacular flow textures that are not visible in any other microscopic method. Compositional data show that the SiO 2 composition is relatively higher and the Al 2 O 3 content is lower in the CL-bright areas than in the CL-dark regions. The different appearance of the three glass types in the CL images indicates different peak temperatures during glass formation: the tektite was subjected to the highest temperature, and the Aouelloul impact glass experienced a relatively low formation temperature, while the Libyan desert glass preserves a flow texture that is only visible in the CL images, indicating a medium temperature.All IR reflectance spectra show a major band at around 1040 to 1110 cm −1 (antisymmetric stretching of SiO 4 tetrahedra), with minor peaks between 745 and 769 cm −1 (Si-O-Si angle deformation). Broad bands at 491 and 821 cm −1 in the Raman spectra in all samples are most likely related to diaplectic glass remnants, indicating early shock amorphization followed by thermal amorphization. The combination of these spectroscopic methods allows us to deduce information about the peak formation temperature of the glass, and the CL images, in particular, show glass flow textures that are not preserved in other more conventional petrographic images.

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Section: Libyan Desert Glasssupporting

confidence: 92%

Infrared, Raman, and cathodoluminescence studies of impact glasses

Gucsik

Koeberl

Brandstätter

et al. 2004

Meteorit & Planetary Scien

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“…The presence of platinum group elements patterned as in chondrites was also detected, which would confirm the presence of extraterrestrial matter and, consistently, an impact as the way of formation [16].…”

Section: The Mystery Of Inclusionssupporting

confidence: 59%

“…The answer to this dilemma was searched for in the LDG inclusions. As far as the minerals inside LDG are concerned, the most abundant and most often presented in the literature is cristobalite [16]. Frischat et al [13] mentioned mineral phases typical for high temperature and high pressure origin (wollastonite, baddeleyite, cristobalite, stishovite).…”

Section: The Mystery Of Inclusionsmentioning

confidence: 99%

Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy

Swaenen¹,

Stefaniak

Frost

et al. 2010

Anal Bioanal Chem

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Several specimens of Libyan Desert Glass (LDG), an enigmatic natural glass fromEgypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO 2 was determined in two polymorphic species, rutile and anatase. MicroRaman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.

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“…3b) concentrations of LDG and sandstone samples from different areas. In both plots, considerable conformity exists between the LDG samples and the sandstones from the LDG strewn field and from Oasis and BP craters in Libya (additional data from Barrat et al, 1997 andAbate et ai., 1999).…”

Section: Geochemistrymentioning

confidence: 91%

“…Isotopic data on LDG by Barrat et al (1997; four samples, the Sr isotopic data were adjusted to 87Sr/86Sr = 0.710248 for NBS 987 to compare them with our data) are included in two isotopic evolution diagrams. For the 14 LDG samples a Rb-Sr regression line indicates an age of557 ± 132 Ma (1a) (Fig.…”

Section: Libyanmentioning

confidence: 99%

Strontium and neodymium isotopic study of Libyan Desert Glass: Inherited Pan‐African age signatures and new evidence for target material

Schaaf

Müller-Sohnius²

2002

Meteorit & Planetary Scien

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Abstract-Libyan Desert Glass (LDG) is an impact-related, natural glass of still unknown target material. We have determined Rb-Sr and Sm-Nd isotopic ratios from seven LDG samples and five associated sandstones from the LDG strewn field in the Great Sand Sea, western Egypt. Planar deformation features were recently detected in quartz from these sandstones. 87Sr/ 86S r ratios and E-Nd values for LDG range between 0.71219 and 0.71344, and between -16.6 and -17.8, respectively, and hence are distinct from the less radiogenic 87Sr/ 86Sr ratios of 0.70910-0.71053 and E-Nd values from -6.9 to -9.6 for the local sandstones from the LDG strewn field. Previously published isotopic ratios from the Libyan BP and Oasis crater sandstones are generally incompatible with our LDG values. LDG formation undoubtedly occurred at 29 Ma, but neither the Rb-Sr nor the Sm-Nd isotopic system were rehomogenised during the impact event, as we can deduce from PanAfrican ages of -540 Ma determined from the regression lines from a total of 14 LDG samples from this work and the literature. Together with similar Sr and Nd isotopic values for LDG and granitoid rocks from northeast Africa west of the Nile, these findings point to a sandy matrix target material for the LDG derived from a Precambrian crystalline basement, ruling out the Cretaceous sandstones of the former "Nubian Group" as possible precursors for LDG.

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Geochemistry and origin of Libyan Desert glasses

Cited by 52 publications

References 30 publications

Infrared, Raman, and cathodoluminescence studies of impact glasses

Infrared, Raman, and cathodoluminescence studies of impact glasses

Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy

Strontium and neodymium isotopic study of Libyan Desert Glass: Inherited Pan‐African age signatures and new evidence for target material

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