What tell us the finds of carbon and diamonds in the LDG, other glassy melts and breccias in the Silica-strewnfield
in the Egyptian Great Sand Sea

Norbert Brügge, Germany
Dipl.-Geol.

Upload: April 2018
Update: 23.05.2018

Diamond is a solid form of carbon with a cubic crystal structure. Most of them were formed  in enormeus depths in the Earth's mantle. Under high pressure and temperature, carbon-containing fluids dissolved minerals and replaced them with diamonds. Diamonds are deposited in igneous rocks known as kimberlites and lamproites carried to the surface by volcanic eruptions. Extraterrestrial diamonds, mostly of a microscopic size, are found in carbonaceous chondrites.

In the strewnfield of the Libyan Desert Glass (LDG) is hidden not only the secret of the creation of this unique glass itself, but also the origin of some accumulations of carbon/graphite and diamonds /micro-diamonds embedded in glassy melts within breccias. In the meantime it can be ruled out that these materials are of extraterrestrial origin. To convincing are indications for a connection with the widespread volcanism in the region. Here we have diamonds that have been transported from the earth's mantle to the earth's surface.

The following locations are known so far, and they should not be the last. Unfortunately, all the ludicrous interpretations of the elaborate investigations point in the totally wrong direction, as the citations listed below from the publications prove. The find of kimberlite (Location 3 and 7) bring the impact theory now the death.

 

Location

Position

Characteristics

1

Desert Glass

Strewnfield

Carbonaceous inclusions, polymorphs of graphite and diamond

2

Breccia 1  (Hypatia stone)

25°20"/ 25°29'

Micro-diamonts in a carbonaceous matrix

3

Breccia 3 (Qaret-el-Hanash)

25°04' / 25°55'

Diamonds in a glassy matrix of kimberlite breccia

4

Breccia 4

25°22'51" / 25°27'34"

Glass + graphite

5

Debris in Paleosol

3.8 km SSW of 25°18.11' / 25°29'

Polymetallic and carbonaceous debris

6

Mullite-magnetite-glass melt rock

Southeast of the Silica area

Dark grey mullite-magnetite-glass melt rock with numerous diamonds

7  Crater Zerzura (Kimberlite pipe)  25°16'46"/25°10'05"

Diverse components ( + micro diamonds)

 

The search for kimberlite and diamonds also outside the Silica strewnfield -- on the uplifted cratonal Basement -- can begin

1. Libyan Desert Glass

Crystalline microstructures in Libyan Desert Glass: Effect of microgravity environment
C. Patuelli, R. Serra, S. Coniglione, M. Chiarini
Microgravity and Space Station Utilization, vol. 3, no. 4, 2002


"Samples of Libyan Desert Glass were analyzed by X-ray micro-diffraction technique. It was identified fourteen nano-sized crystalline LDG phases with different colours: Coesite, tridymite, stishovite, baddeleyite, huttonite, yttrium, moissanite, platinium, polymorphs of diamond and graphite.
The four praphite polymorh phases found in LDG samples can be explained by taking into account that the graphite came from the earlier history of the material. The element platinum is extremely scarce in most crustal rocks. The origin of platinum is from ultra-mafic igneous rocks. Its melting point is 1775 °C. The zircon oxide mineral Baddeleyite is the product of the decomposition of zircon at 1775° - 1900°C. Moissanite is a natural silicon carbide (SiC). Huttonite is a low-temperature and low-pressure Thorite-polymorph (ThSiO2).
The identification of nine highbaric phases, the presence of hexagonal diamond with four phases of graphite polymorphs, as well as huttonite and baddeleyite, confirm that LDG formed by "shock metamorphism" at very high pressure and temperature. The nano-sized crystalline phases revealed point out that LDG rapidly solidified.
Preliminary X-ray micro-diffractometry analyses were presented at the “Silica 96” workshop (Patuelli, 1997). High pressure and high temperature phases were identified: including samarium, germanium 12T, thorium beta (this beta phase occurs only at a temperature above 1350°C) and stishovite, which is a high temperature and pressure form of SiO2."
  

Silicate-Silicate liquid immiscibility and graphite ribbons in Libyan Desert Glass
G. Pratesi, C. Viti, C. Cipriani, M. Mellini
Geochimica et Cosmochimica Acta, March 2002

"Transmission electron microscopic (TEM) investigation of the dark (brown or bluish) streaks occurring in Libyan Desert Glass reveals the common presence of small glass spherules. The spherules, mostly 100 nm in size, are homogeneously dispersed within the silica-glass matrix. The complete absence of electron
diffraction effects confirms their amorphous nature. The spherules are Al-, Fe- and Mg-enriched with respect to the surrounding silica matrix and their (Mg+Al+Fe) : Si ratio is close to 1. The silica-glass matrix and amorphous spherules form an emulsion texture (i.e., globules of one glass in a matrix of another glass), which originates from silicate-silicate liquid immiscibility.
The silica glass also contains carbonaceous inclusions consisting of 5–50 nm thick, polygonalized graphite ribbons that form closed structures up to 200 nm in diameter.

Graphite inclusions
Rare carbon-bearing inclusions randomly occur within the silica-glass matrix. Their presence is ubiquitous and not limited to the regions with dark streaks. C-bearing inclusions produce an evident C peak in the EDS spectra. The inclusions consist of ring-shaped polygonalized ribbons, 5–50 nm thick, typically forming closed structures with an overall diameter of ~200 nm. Their SAED patterns consist of rings with d-spacings of 3.35, 2.09 and 1.67 A: these values correspond to graphite (3.36, 2.13-2.03, 1.678 A, JCPDS 23-64). Lattice imaging shows 3.35 A polygonized (002) lattice fringes. The fringes are quite regular, thus indicating good structural order with no evidence of deformation or defects. Dark vertical bands are evident at the polygonal edges and are interpreted as Moire textures."


Graphite polymorphs

2. Hypatia stone

Probably debris of Kimberlite

First paper by Aly Barakat, the discoverer of the stone

5.3-THE MINERALOGICAL COMPOSITION:
The mineralogical composition includes; diamond, graphite, goethite, quartz calcite and halite.

5.3.1-Diamond: Diamond aggregations occur as tiny angular grains (fragments) showing the characteristic lustre and cleavage. Some of these grains show indications of octahedral form), but others are suggestive of partial hexagonal form. EDAX analysis (Fig. 5.3) of some grains indicates that they consist essentially of C (~98 %).
The XRD analysis data are consistent with the presence of diamond of interplanar distances (d) 2.07, 1.259, and 1.881 (JCPDS, card 6-675) as indicated by the Camera method. Moreover, diamond appears through the chart of the other X-ray diffraction method.
Raman spectrometric analysis of the bright aggregates confirms the presence of diamond in a polycrystalline status, as witnessed by the significantly broad peak at 1331 cm-1, spectra b and d). In spectrum (b), diamond is associated with graphite (peak in the 1580 cm-1 region). In spectrum (d), the broad band at 1332 cm-1 is a good evidence for the presence of diamond in the form of microcrystalline aggregates (note the sharp peak of the well crystalline diamond on the reference spectrum c). Thus, the observed large grains represent quite large aggregates of micrometer-sized crystallites.

5.3.2-Graphite: Graphite occurs as thin laminated encrustation coating and embedding the diamond aggregations. The Raman spectroscopy confirms also the intimate association between graphite and diamond (Fig. 5.5, spectrum b). Graphite is also present in the form of microcrystalline grains. In figure (5.5, spectrum a) the single peak at 1580 cm-1 is of crystalline graphite (mean basal plane >>1000 Ĺ). This phase is also known as the G mode. Progressive disorder in graphite is reflected in the Raman spectrum by the broadening and shifting of this band to higher wave numbers, and by development of an additional band near 1360 cm-1 (also known as the D mode) (Pasteris and Wopenka, 1991; Hirlimann, et al., 1992). The peak around 1360 cm-1 in spectrum b (Fig. 5.5) is aconvolution of two peaks. This is due to the presence of both diamond and graphite in intimate association.

 

3. Qaret-el Hanash

Probably the first detected Kimberlite pipe nearby the Silica strewnfield
The most important indication for the emergence of Qaret-el-Hanash, which I postulate now as a eroded kimberlite pipe, are the photos of Ursula Steiner (Switzerland), which come from the top and outside slope of the structure. They document clear the subvolcanic origin of Qaret-el-Hanash impressively. Some photos show a strange, material of a dark (carbonaceous ?) melt with included many diverse fragments, among ferruginous sandstone, basement debris, glass and yellow jasper. The melt contain also visibly large dark brown diamonds.


This piece from the breccia contain large dark brown diamonds

Photographed during
 a trekking-tour in 2012

DISCOVERY OF Fe-Cr-Ni SPECKS WITHIN QARET EL-HANASH BRECCIA OF THE LIBYAN GLASS AREA SOUTH WESTERN EGYPT
A. El-Kammar, I. Arafa, K. A. Soliman & A. Barakat --7th International Conference on the Geology of the Arab World, Cairo University, Feb. 2004, P. 1-7


"The rock consists of various fragments of local sandstone, i.e., from the area of the glass distribution itself. Fragments of igneous source have never been recorded. The rock fragments range from fraction of mm up to 4-cm in diameter, in the collected specimens. The rock fragments vary in colour from creamy white to brownish-red. They are angular to subrounded and embedded in a dull greyish-black matrix. The microscopic investigation and scanning electron microanalysis confirmed the above-mentioned observation and showed that the matrix consists of shattered and fragmented quartz grains of various sizes. In addition to quartz, the matrix contains many other phases, such as glass, zircon, clay minerals, wollastonite, ilmenite, Mg-ilmenite, rutile and Fe-Cr-Ni specks.
There are several metallic specks of various sizes ranging from 1 micron up to about 10 micron, dispersed in the matrix of Qaret el Hanash breccia. They invade some of the quartz grains. These specks are mainly of irregular outlines and some of them show clear fissures. They are associated with glass and intercalated in some cases with halite. EDAX analyses of such specks indicate that they consist of native Fe, Cr and Ni, in addition to subordinate Si and Ca. Finer particles of similar appearance have also been noticed by the petrographical microscope through the fractures of some of the quartz grains.
The most interesting achievement of the chemical analyses is the detection of high Ir content (2.0-2.2 ppb) within the breccias. This value represents the highest reported values for the area. The reported value of Ir in other breccias in the area is around 1.6-1.9 ppb. The highest reported concentration of Ir by the previous studies was detected from the black streak portions from the Libyan glass itself is 1.25 ppb."

Aly Barakat on May 19, 2018: The samples contains tiny particles of Fe-Cr-Ni, and other phases includes tiny grains of moissanite and diamond.

4. Breccia

Aly Barakat, 2004:  At latitude 25°22′51″ N and longitude 25°27′34″ E is present site of a megascopic breccia. The petrographical and mineralogical studies carried out on the breccia  indicate that it represents impact breccia. In addition to the brecciation of the quartz grains some of these grains show PFs and PDFs. The zircon of this breccia shows evidence of deformation as represented by the fragmented nature of some the studied grains and by non-stoichiometric contents of ZrO2 and SiO2. The detection of glass and graphite is accounted also for the impact origin of this breccia.

5. Debris in Paleosol

Polymetallic and carbonaceous debris in paleosol from the Libyan Desert Glass strewn field, SW Egypt: Evidence of a cometary impact.
M. A. G. Andreoli, & M. Di Martino et al. -- Lunar and Planetary Science XLVIII (2017), 1045.pdf

An expedition in November 2011 to the find area of "Hypatia" failed to recover additional hand specimens of "Hypatia" material, but samples of pedogenic (Cenozoic) pebbly deposits. One of these samples was collected 3.8 km SSW of the Hypatia sampling site.
After fractional separations of the sample was identified evidence of hard amorphous carbon and submicron diamonds as well as unusual metallic mineral grains, all those found in the "Hypatia" stone.
The unusual metallic grains and carbonaceous particles tentatively grouped into 4 types
Type I grains and spherules range from 10-20 μm up to 130 μm. SEM-EDX data indicate that the smaller spherules are metallic with a wide compositional range comprising Ti, Ag, Al, and Si in varying porportions, and Ca, O, Na, Mg and S as variable, minor constituents. The largest spherules are pale green and vitreous and consist entirely of P, Si with no detectable oxygen.
Type II grains are much larger (length: 60 μm to 1.2 mm) and consist of
a) sintered aggregates of Pb metal particles
b) strongly sintered clusters of α-Ti (+1.0 at.% Al) subgrains
c) more brittle aggregates of seemingly submicron, Sn-Ca alloy particles.
The Ti metal grains in places host clusters of quenched gas bubbles, blobs of Ti aluminide, veinlets of non-stoichiometric Ti nitride, Al oxycarbonitride, and particles of Zr, Ag, and Zn. A distinctive feature of the Type II grains is their localized coating by (C, O bearing) carbonaceous films and filaments up to 300 μm in length. Although these resemble fungal hyphae and tendrils in SEM images, Raman spectra prove that they comprise partly graphitized kerogen.
Type III grains are shard-like in shape and occur either as partly oxidized branching (70 μm x 50 μm) Al particles decorated by μm-size Bi granules, or as lace-textured Ti particles partly enveloped by Type II grains. Petrographic textural analysis of multiple 3-D sections of the shard indicate that the Type II (and perhaps Type I) grains were derived from the partial to complete melting of the Type III shards.

Type IV grains are morphologically and compositionally diverse, with common characteristics being Carbon as the major constituent. Moissanite (SiC) grains were the first to be positively identified from petrography and Raman spectra. Other grains display a range of textures, including one resembling a honeycomb with N as second major constituent and minor, varying amounts of S and Cl. The Raman spectra of these N-rich grains show faint, indistinct D and G bands but distinctive peaks in the 3000 cm-1 region, indicative of C:H bonds.

6. Mullite-magnetite-glass melt rock

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 (left); 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 in the Silica area, southern of  "Hypatia" stone.


"From available evidence (Raman spectrum) diamonds and disordered graphite are likely to be found in the majority of the dark patches present in the photomicrographs"

 


7. Crater Zerzura

Probably the second detected Kimberlite pipe 
 
Cigolini & Di Martino -- PP-presentation (2013)

Here a spectacular find of a breccia from a crater-like structure is presented, in which probably a swarm of micro-diamonds can be seen. Unfortunately, apart from the identified location of the find (25°16'46 "/ 25°10'05") there are no further comments. The crater is in the Wadi Zerzura, which is located west of the Silica strewnfield. The crater is nearly round and in no case a depression caused by water erosion. In the crater's center there is at least one round hole with a plug of the breccias.
The breccia in the crater may be a kimberlitic emplacement in the decomposition phase. The diamonds (white "sugar") are difficult to recognize in the photos. But some forms seem to be transparent crystals.


Romano Serra
, University of Bologna,
has sent me some new revealing photos from the crater and the breccia. It were only made 30 thin sections to find PDF's.