Source: Andras Zboray

The Mystery of the Kimberlite Breccia on the Zerzura Plateau

(northern of the Egyptian Gilf Kebir)

Norbert Brügge, Germany
Dipl.-Geol.

Upload: May 2018

Geological setting: The little explored Zerzura (or Saad) plateau is located north of the Gilf Kebir on the latitude to the Silica strewnfield in the Great Sand Sea in the east. The plateau is divided into two halves by a distinctive wadi. The plateau is to be shaped according to the geological map by sandstones of the Upper Cretaceous (Saad Form.). That is not verifiable. It should be Devonian sandstones. Under the loss (erosion) of Ordovician-Silurian strata, would follow the Archean Basement of the East Sahara Ghost Craton. This scenario is likely because the Zerzura Plateau is placed, like the Gilf Kebir, on the Uweinat - Howar Uplift. Mesozoic layers are generally absent on the uplift. Layers south of the Zerzura Plateau are probably also not of Cretaceous. Findings of Lepidosigillaria indicate Carboniferous layers. Also regarding the Gilf Kebir plateau the geological map is therefore mostly wrong. The entire mapping is based on a misinterpretation of a Carboniferous plant imprint (Paleoweichselia halfa BRÜGGE, 2017) and which was erroneously determined as Weichselia reticulata BRNGT.



Zerzura plateau on air



Zerzura plateau on geological map (brown)


The Zerzura Plateau has become interesting in recent time because we have to solve another of the many puzzles in the Gilf Kebir region. Romano Serra and his companions found a crater in 2011, with a peculiar breccia at its center. The author found a photo of it at an Italian PP-presentation. Thankfully, Romano Serra has now provided the author with additional photos.

In this spectacular breccia from the crater-like structure (crater Zerzura-1) we can see probably a swarm of
micro-diamonds. Unfortunately, apart from the identified location of the find (25°16'46 "/ 25°10'05") there are no further comments. Now, the author found a further such characteristic crater in the satellite overview in the surrounding. Five of them (Zerzura-2, 3, 4, 5, 6) are located:
 
25°17'47"/ 25°11'37" 25°17'20" / 25°11'50" 25°12'49" / 25°03'32" 25°19'57" / 24°58'39" 25°25'14" / 25°01'42"

The crater Zerzura-1 is nearly round and in no case a depression caused by water erosion. There are only two narrow cuts in the wall, typical of craters in Gilf Kebir Crater Field. Characteristic of the structures in the GKCF are tilted layers at the edges, which suggests slow upward movements. But the walls of Zerzura-1 crater are flat as after an explosion. In the crater itself is a hole with a plug of breccias therein.
The author believes that 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.
 

PP-presentation

Zerzura-1

Zerzura-2

Zerzura-3

Zerzura-4

Zerzura-5

Zerzura-6

Zerzura-1

Zerzura-1 breccias


In addition of this, there are some pictures from a trekking tour from the year 2003 available, which has thankfully made available to me by Andras Zboray (fjexpeditions.com). In the southern part of the plateau, in a hole in the sandstone, strange hollow cracks can be seen on the wall, on which light mineral deposits stick on the inside. Remarkable are also the round small openings in the floor and in the walls of the hole through which obviously iron-rich solutions have flowed. There is no doubt that hydrovulcanic solutions have risen here under high pressure and have left their signature.



Location of the hole: 25°07'28"N / 25°19'43"E


 
  



 

Further mysteries
 

1.) Crater-shaped structures with central hill eastern of the northern tip of Gilf Kebir Plateau
(unnamed and unexplored)

In the just found new "Eastern Gilf Crater Field" (EGCF) there are craters that are not comparable to the craters in the Gilf Kebir Crater Field (GKCF) in the southeast. A accordance with the craters on the Zerzura Plateau is more obvious. The structure of the craters will soon be clarified by Egyptian geologists (Aly Barakat).
  


 

2.) The find of pinkish Silica, 50 km southwest of the LDG strewnfield
 

Libyan Desert Glass : New field and Fourier transform infrated data
Francois Fröhlich et al. -- Meteoritics & Planetary Science 48, Nr 12, 2517–2530 (2013)

"Are the Wadi Qubba LDG blocks in situ or were they transported here from the Great Sand Sea by Prehistoric men? Several observations and analyses are consistent with the assignment of this new LDG occurrence to the LDG strewn field.
1. The color (pink) of all the Wadi Qubba specimens is quite different from the Great Sand Sea ones (yellow to green);
2. The molecular structure is clearly slightly different;
3. No large artifacts were found at Wadi Qubba; only one small blade was found that was made from the same glass as the other LDG found in the neighborhood (size, color, molecular structure).
Thus, we infer that the Wadi Qubba LDG blocks are in place and hence they are included in the LDG strewn field."

   
24°52.189' / 25°27.044'

Note: The piece is found in a unknown Wadi (not Wadi Qubba). It could not have been transported out of the strewnfield field to this place. The valley floor is 50m higher. The pinkish color of the piece is extraordinary and was never found in the LDG strewnfield. The quality of the finds does not indicate that they were attractive for humans. Apparently, there is another tectonic structure somewhere outside the known Silica strewnfield.
Of interest in this context are the unknown bright deposits in the valleys. These may correspond with the new craters. Craters 3 and 4 show such bright rocks in the central hill.