The first morning we went on a field trip with a geologist from a nearby uranium mine. Namibia produces 15% of the world's uranium anda. Boom is occurring in the deposits not far from Swakopmund. They are primary deposits found in granite, meaning that the uranium is held in the very rocks that brought it up from the earth's interior. Here a geologic map shows the field relationships to trip participants.
As my structural geology teacher once told me, "Rocks don't suffer metamorphism, they enjoy it!" If so, these rocks have had quite an enjoyable ride. They began life about 800 Ma as sandstone, shale and limestone deposits, only to be caught up in the Pan-African Orogeny, about 650 Ma. This is when the Kalihari craton (ancient continental fragment) collided with the Congo craton. The rocks between the two were squeezed and accordion-folded, such that some of them were brought down 18 to 20 miles below the surface. The folds and metamorphism can be seen in this outcrop along the Swakop River.
More dikes. The uranium host rocks are seen in the light-colored granite bands trending to the upper left.
This is a showy little gem called Everlasting. The species name is Helichrysum roseaniveum.
No comments:
Post a Comment
If your comment will not post, email me with the problem.