Singida kimberlites25 Oct 2023 12:27
Fifty-four kimberlite pipes and dykes cut Precambrian granite in the Singida region. The pipes range from 60 to 2500 feet in diameter, and occur in clusters and lines. The lines follow fracture zones. In addition to intrusive kimberlite, the pipes contain massive to stratified kimberlite tuff and sedimentary light porous rock beds. Some pipes have jackets of explosion breccia. The Singida pipes represent the upper parts of kimberlite volcanoes. The kimberlite consists mostly of serpentine which has replaced olivine. Magnesium ilmenite, pyrope, dark green diopside and perovskite are characteristic accessory minerals. After consolidation, the kimberlite was entirely serpentined, and partly carbonated and silicified. The absolute age of the pipes is not known. Indirect evidence suggests an early Tertiary age. The Singida kimberlites may have been emplaced during an early ultrabasic phase of Tertiary-Recent alkaline volcanism of the Eastern Rift Valley.
[Yuri's opinion would be valuable here. The old geologists had amazing knowledge with their skills. The "clusters" were determined >70 years ago and if memory serves me correctly there is another group north of Singida town at Ikungi. If Mang'onyi is indeed a cluster the kimberlites will reach down >1mile.
A comparison with Welkom/Odendaalsrus (if it can be found) might be useful. The idea of "clusters" seems to support Eric's interpretation of GoldTree, Gustav, Cornpatch, etc.]