Thangarajan Gowthaman,
The Richat Structure, also known as the Eye of the Sahara and Guelb er Richat, is a prominent circular feature in the Sahara near Ouadane , west – central Mauritania.
The Richat Structure is a deeply eroded , slightly elliptical dome with a diameter of 40 km. The sedimentary rock exposed in this dome ranges in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges. The sedimentary rocks comprising this structure dip outward at 10°–20°. Differential erosion of resistant layers of quartzite has created high - relief circular cuestas. Its center consists of a siliceous breccia covering an area that is at least 30 km in diameter.
Initially interpreted as an asteroid impact structure because of its high degree of circularity , geologists now regard it to be a highly symmetrical and deeply eroded geologic dome. After extensive field and laboratory studies, no credible evidence has been found for shock metamorphism or any type of deformation indicative of a hypervelocity extraterrestrial impact.While coesite, an indicator of shock metamorphism, had initially been reported as being present in rock samples collected from the Richat Structure, further analysis of rock samples concluded that barite had been misidentified as coesite.In addition, the Richat Structure lacks the annular depression that characterizes large extraterrestrial impact structures of this size. Also, it is quite different from large extraterrestrial impact structures in that the sedimentary strata comprising this structure is remarkably intact and "orderly" and lacking in overturned, steeply dipping strata or disoriented blocks.
A more recent multianalytical study on the Richat megabreccias concluded that carbonates within the silica - rich megabreccias were created by low - temperature hydrothermal waters, and that the structure requires special protection and furthe r investigation of its origin.
Nasa describes it on its website: "This prominent circular feature in
the Sahara desert
of Mauritania has attracted attention since
the earliest space missions because it forms a conspicuous bull's-eye in the otherwise rather featureless expanse of the desert."
How it was formed is still up for debate. It was initially though t that it was born as a result of a meteorite impact or volcanic activity, but scientists failed to stump up enough evidence to support these theories. The most plausible explanation that geologists now tend to agree on is that it is simply seismic uplift on display due to erosion that has formed almost symmetrically.The carbonatite rocks have been dated as having cooled between 94 and 104 million years ago. A kimberlitic plug and several sills have been found within the northern part of Richat Structure. The kimberlite plug has been dated to around 99 million years old.
Source : Wikipedia
The Richat Structure is a deeply eroded , slightly elliptical dome with a diameter of 40 km. The sedimentary rock exposed in this dome ranges in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges. The sedimentary rocks comprising this structure dip outward at 10°–20°. Differential erosion of resistant layers of quartzite has created high - relief circular cuestas. Its center consists of a siliceous breccia covering an area that is at least 30 km in diameter.
Initially interpreted as an asteroid impact structure because of its high degree of circularity , geologists now regard it to be a highly symmetrical and deeply eroded geologic dome. After extensive field and laboratory studies, no credible evidence has been found for shock metamorphism or any type of deformation indicative of a hypervelocity extraterrestrial impact.While coesite, an indicator of shock metamorphism, had initially been reported as being present in rock samples collected from the Richat Structure, further analysis of rock samples concluded that barite had been misidentified as coesite.In addition, the Richat Structure lacks the annular depression that characterizes large extraterrestrial impact structures of this size. Also, it is quite different from large extraterrestrial impact structures in that the sedimentary strata comprising this structure is remarkably intact and "orderly" and lacking in overturned, steeply dipping strata or disoriented blocks.
A more recent multianalytical study on the Richat megabreccias concluded that carbonates within the silica - rich megabreccias were created by low - temperature hydrothermal waters, and that the structure requires special protection and furthe r investigation of its origin.
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| Richat Structure from International Space Station |
of Mauritania has attracted attention since
the earliest space missions because it forms a conspicuous bull's-eye in the otherwise rather featureless expanse of the desert."
How it was formed is still up for debate. It was initially though t that it was born as a result of a meteorite impact or volcanic activity, but scientists failed to stump up enough evidence to support these theories. The most plausible explanation that geologists now tend to agree on is that it is simply seismic uplift on display due to erosion that has formed almost symmetrically.The carbonatite rocks have been dated as having cooled between 94 and 104 million years ago. A kimberlitic plug and several sills have been found within the northern part of Richat Structure. The kimberlite plug has been dated to around 99 million years old.
Source : Wikipedia
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