A not credible message about the discovery of cometary material in the Egyptian desert
 (Libyen Desert Glass area)

Norbert Brügge, Germany
Dipl.-Geol.

Update: 14.03.2017

Published message (Abstract)

Unique chemistry of a diamond-bearing pebble from the Libyan Desert Glass strewnfield, SW Egypt; Evidence for a shocked comet fragment

Jan D. Kramers et al. -- Earth and Planetary Science Letters (2013), Volume 382, Pages 21–31
http://www.sciencedirect.com/science/article/pii/S0012821X13004998


Published colored photo of the piece (30 gram)

"We have studied a small, very unusual stone, here named “Hypatia”, found in the area of southwest Egypt where an extreme surface heating event produced the Libyan Desert Glass 28.5 million years ago. It is angular, black, shiny, extremely hard and intensely fractured. We report on exploratory work including X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy with EDS analysis, deuteron nuclear reaction analysis, C-isotope and noble gas analyses. Carbon is the dominant element in Hypatia, with heterogeneous O/C and N/C ratios ranging from 0.3 to 0.5 and from 0.007 to 0.02, respectively. The major cations of silicates add up to less than 5%. The stone consists chiefly of apparently amorphous, but very hard carbonaceous matter, in which patches of sub-μm diamonds occur. δ13C values (ca. 0‰) exclude an origin from shocked terrestrial coal or any variety of terrestrial diamond. They are also higher than the values for carbonaceous chondrites but fall within the wide range for interplanetary dust particles and comet 81P/Wild2 dust. In step heating, 40Ar/36Ar ratios vary from 40 to the air value (298), interpreted as a variable mixture of extraterrestrial and atmospheric Ar. Isotope data of Ne, Kr and Xe reveal the exotic noble gas components G and P3 that are normally hosted in presolar SiC and nanodiamonds, while the most common trapped noble gas component of chondritic meteorites, Q, appears to be absent. An origin remote from the asteroid belt can account for these features."

"We propose that the Hypatia stone is a remnant of a cometary nucleus fragment that impacted after incorporating gases from the atmosphere. Its co-occurrence with Libyan Desert Glass suggests that this fragment could have been part of a bolide that broke up and exploded in the airburst that formed the Glass. Its extraordinary preservation would be due to its shock-transformation into a weathering-resistant assemblage."
  

The international reactions to the statements in the article of the South African scientists are euphoric. The investigated piece (it is a dark glassy fragment of 30 gram, and was found in 1996 by the Egyptian geologist Dr. Aly A. Barakat in the area of the silica glass) should be cometary material. This message in a short time has already been inflationary widespread.

Because this euphoria I can not empathize, I present my concerns at this point. The conclusions of the South Africans must be wrong.

In the entire area exist no evidences of significant exo-terrestrial events. The numerous crater-like structures which are visible in this region (including the Libyan crater Oasis, BP and Arkenu) belong to a large area with subvolcanic inventory from this period before 28.5 million years. Included is the strewn field with the Libyan Desert Glass. The Libyan Desert Glass belongs as much to the inventory of this subvolcanic events such as other specials (Jasper Mountain, Dakhla Glass).

The emergence of the desert glass, with an estimated total mass of about 1400 tons, is definitely NOT caused by an airburst or an impact, but is an exceptional "volcanic" glass. For the melting of sand masses at the surface by an airburst, there were no conditions in the Oligocene period. The land surface was a rocky ablation area. A sandy desert did not exist.

In contrast to the obsidian is the desert glass not a conventional volcanic glass because it contains 96-99% SiO2. It must be presumed that it before 28.5 million years as a pure glass melt along a deep fissure in the earth's crust flowed. Corresponding flowing structures are visible in the glass. In the glass were identified fourteen nano-sized crystalline, also polymorphs of diamond and graphite.

In this context also should be classified the analyzed "shocked comet fragment". If we follow the results of the investigation, then this material could be from the deep and hidden interior of the earth.

The arguments for cometary origin of "Hypatia"

-It contains sub-micrometer diamonds in an amorphous, carbon-dominated matrix.
-Carbon isotope data (δ13C~0) do not fit terrestrial coal or carbonaceous chondrites.
-Argon, Kr and Xe isotope data show extraterrestrial origin different from chondrites.

are not convincing, because ultimately our planet was created by aggregation of exo-terrestrial material (even cometary material). What we know about the Earth's interior, is not enough. Surprises are always possible. Predestined seems to be the area in the southwestern Egyptian desert. It was affected by a magmatic "hotspot" in the Tertiary period. The findings of "sub-micrometer diamonds in an amorphous, carbon-dominated matrix" are a clear indication for the origin of the material at great depths.

What's new

About the Occurrence of micron-sized diamonds in the mullite-magnetite-silica glass boulders in the Gilf Kebir area of western Egypt
M.A.G. Andreoli -- School of Geosciences, University of the Witwatersrand, South Africa; Unpublished document (2017)

"Dark grey mullite-magnetite-glass melt rock (right); numerous diamonds were found in the polished, light sandy grey slab (bottom left) but found absent in the core of the dark, glassy patch." The location is south of the Silica area.

Comment: For me a puzzling, how the numerous diamonds were be enclosed in the sedimentary rock. I believe it is a igneous dike-rock.

PIXE micro-mapping of minor elements in "Hypatia", a diamond bearing carbonaceous stone from the Libyan Desert Glass area, Egypt: Inheritance from a cold molecular cloud?
M. Andreoli et al.-- Article in Nuclear Instruments and Methods in Physics Research, Section B, Beam Interactions with Materials and Atoms (2015)
Publisher: Elsevier; DOI: 10.1016/j.nimb.2015.09.008

Matter originating from space, particularly if it represents rare meteorite samples, is ideally suited to be studied by Particle Induced X-ray Emission (PIXE) as this analytical technique covers a broad range of trace elements and is per se non-destructive. We describe and interpret a set of micro-PIXE elemental maps obtained on two minute (weighing about 25 and 150 mg), highly polished fragments taken from "Hypatia", a controversial, diamond-bearing carbonaceous pebble from the SW Egyptian desert. PIXE data show that "Hypatia" is chemically heterogeneous, with significant amounts of primordial S, Cl, P and at least 10 elements with Z > 21 (Ti, V, Cr, Mn, Fe, Ni, Os, Ir) locally attaining concentrations above 500 ppm. Si, Al, Ca, K, O also occur, but are predominantly confined to cracks and likely represent contamination from the desert environment. Unusual in the stone is poor correlation between elements within the chalcophile (S vs. Cu, Zn) and siderophile (i.e.: Fe vs. Ni, Ir, Os) groups, whereas other siderophiles (Mn, Mo and the Platinum group elements (PGEs)) mimic the distribution of lithophile elements such as Cr and V. Worthy of mention is also the presence of a globular domain (Ø S 120 lm) that is C and metals-depleted, yet Cl (P)-enriched (>3 wt.% and 0.15 wt.% respectively). While the host of the Cl remains undetermined, this chemical unit is enclosed within a broader domain that is similarly C-poor, yet Cr–Ir rich (up to 1.2 and 0.3 wt.% respectively). Our data suggest that the pebble consists of shock-compacted, primitive carbonaceous material enriched in cold, pre-solar dust.

A comprehensive study of noble gases and nitrogen in "Hypatia", a diamond-rich pebble from SW Egypt
G. Avice et al. -- Earth and Planetary Science Letters (2015), Volume 432, Pages 243–253
https://arxiv.org/ftp/arxiv/papers/1510/1510.06594.pdf

In 1996 a very unusual ~30 g sized pebble was found in the Libyan Desert Glass strewn field where abundant fragments of impact-related silica-rich glass are found. This brittle black stone consists of ~70 wt. % carbon, and has a hardness comparable to diamond, reminiscent of carbonados. These authors performed an exploratory analytical study on "Hypatia", including XRD, SEM, Raman spectroscopy, TEM, and analyses of C and noble gas isotopes motivated by the fact that this stone was found in the area of the Libyan Desert Glass (LDG). Noble gas isotope analysis is central to the study of meteorites because these rocks formed from multiple components with distinct noble gas isotopic signatures that help to constrain their origin and evolution. Among these components, the so-called Q phase dominates the budget of heavy noble gases (Ar, Kr Xe) in chondrites originating from the asteroid belt.
 Kramers et al. (2013) concluded that Hypatia is extra-terrestrial, based on 40Ar/36Ar ratios as low as about 40. They noted that O/C ratios (0.19 - 0.51) in Hypatia are higher than in chondritic Insoluble Organic Matter (IOM). In addition, they reported that the trapped Ne, Kr, and Xe in "Hypatia" indicate the occurrence of the nucleosynthetic P3 and G components of presolar origin known from meteorites (Ott, 2014), while the Q (and HL) components ubiquitous in chondrites were absent in "Hypatia". The combined evidence led them to conclude that "Hypatia" did not originate in the asteroid belt where chondrites likely formed. They suggested instead that it formed in a more external region of the solar accretion disk, such as the Kuiper Belt, where presolar components might be more abundant, i.e., that "Hypatia" could be of cometary origin. They further proposed that the airburst of the parent comet of "Hypatia" resulted in the formation of the Libyan Desert Glass.
In this work we extend the study by Kramers et al. (2013) with isotopic analyses of all five noble gases in several mg-sized fragments of "Hypatia" in two different laboratories (CRPG Nancy, France and ETH Zürich, Switzerland) and with a nitrogen isotope investigation performed both at CRPG (Nancy) and IPG-Paris. We also describe results from X-ray diffraction (XRD) experiments and transmission electron microscopy (TEM) observations performed at the University of Jena (Germany). An attempt to determine the oxygen isotopic composition in "Hypatia" by the Nancy Cameca 1280 ion probe failed because of the reduced size of oxygen-bearing phases and because of the presence of contaminants and important amounts of water.

High resolution TEM image showing the onion-shaped graphite (0001)gr in the surface of diamond (111)dia. The absence of orientation relationship suggests that graphite is here a product of retrograde annealing of diamond.

This new study confirms and provides new evidence for the earlier conclusion that "Hypatia" is a fascinating new type of extra-terrestrial material. In contrast to the exploratory work reported by Kramers et al. (2013), we did find noble gases with isotopic signatures closely resembling the Q component. We also found nitrogen with an isotopic signature clearly distinct from primitive chondrites and closely resembling those of various differentiated meteoritic materials. In particular, we compare our data with noble gas and nitrogen signatures in three known types of carbon-rich extraterrestrial materials: carbon-rich veins in ureilite meteorites, graphite nodules in iron meteorites, and carbon-rich lithologies in acapulcoites and lodranites, and we discuss a possible link of "Hypatia" with each of these materials.