# A buried alkaline intrusion domed the rocks about 100 million years ago; erosion cut the dome into rings

> Still possible: An alkaline igneous intrusion pushed the Late Proterozoic to Ordovician strata up into a dome about 100 million years ago, hot fluids…

Source: https://mysteriesdept.com/mysteries/eye-of-the-sahara/answers/ANS0DCKRQ94902X/a-buried-alkaline-intrusion-domed-the-rocks-about-100  
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[Questions](https://mysteriesdept.com/questions)[Eye of the Sahara and Atlantis](https://mysteriesdept.com/mysteries/eye-of-the-sahara)[How did the Richat Structure form?](https://mysteriesdept.com/mysteries/eye-of-the-sahara/questions/QST0DCKRBKSRCJA/how-did-the-richat-structure-form)Answer

Answer · Eye of the Sahara and Atlantis

# A buried alkaline intrusion domed the rocks about 100 million years ago; erosion cut the dome into rings

An alkaline igneous intrusion pushed the Late Proterozoic to Ordovician strata up into a dome about 100 million years ago, hot fluids dissolved the limestone at its top to form the central breccia, and later erosion of alternating hard and soft beds left the concentric quartzite ridges.

**Still possible** Answers **1** question0

## Where it stands

**Still possible** Three pieces of evidence for, none against. It needs two reviews to be accepted.

## What it predicts

- Igneous rocks of Cretaceous age (carbonatite, kimberlite, alkaline volcanics) occur only within the structure.
- The central breccia shows dissolution and collapse with hydrothermal minerals of the same age as the magmatism.
- Geophysics shows a deep igneous body under the dome and ring-shaped dykes.
- No shock-metamorphic minerals or shatter cones.

## What would rule it out

- Confirmed shock features (coesite, stishovite, planar deformation features in quartz) in the central rocks.
- Igneous rocks of the structure dated much younger than the doming, or found to continue outside it without a centre.

## Evidence 3 for · none against

[Carbonatite dated 99 ± 5 Ma and breccia feldspar 98.2 ± 2.6 Ma tie the hydrothermal breccia to Cretaceous magmatism](https://mysteriesdept.com/mysteries/eye-of-the-sahara/evidence/EVD0DCKS0C49HJ3/carbonatite-dated-99-5-ma-and-breccia-feldspar-98-2-2-6-ma)

Established

FOR

[Magnetic and gravity models show ring dykes over a deep mafic body](https://mysteriesdept.com/mysteries/eye-of-the-sahara/evidence/EVD0DCKS0PVS8XH/magnetic-and-gravity-models-show-ring-dykes-over-a-deep)

Supported

FOR

[The rings are outward-dipping quartzite cuestas, and the igneous rocks occur only inside the structure](https://mysteriesdept.com/mysteries/eye-of-the-sahara/evidence/EVD0DCKS11JVGX0/the-rings-are-outward-dipping-quartzite-cuestas-and-the)

Supported

FOR

## The questions it answers

[How did the Richat Structure form?](https://mysteriesdept.com/mysteries/eye-of-the-sahara/questions/QST0DCKRBKSRCJA/how-did-the-richat-structure-form)

OpenNo answer ahead yet

## Cite it

```
Mysteries Department. (2026). A buried alkaline intrusion domed the rocks about 100 million years ago; erosion cut the dome into rings [Answer ANS0DCKRQ94902X]. https://mysteriesdept.com/r/ANS0DCKRQ94902X
```

Key

**ANS** 0DCKRQ94902X

Kind

Answer · theory

Proposed

[Session 1](https://mysteriesdept.com/mysteries/eye-of-the-sahara/sessions/SES0DCKZYK2CKXF/session-1-the-eye-of-the-sahara-and-the-atlantis-claim) · 28 Oct 2026

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