首页 | 本学科首页   官方微博 | 高级检索  
     检索      


Petrography,Sr-isotope geochemistry and geochronology of the Nxau Nxau kimberlites,north-west Botswana
Authors:Farr  Henrietta  Phillips  David  Maas  Roland  de Wit  Michiel
Institution:1.Kimberlites and Diamonds Research Group, School of Earth Sciences, The University of Melbourne, McCoy Building, Corner Swanston & Elgin streets, Parkville, VIC, 3010, Australia
;2.Melbourne Isotope Geochemistry, School of Earth Sciences, The University of Melbourne, McCoy Building, Corner Swanston & Elgin streets, Parkville, VIC, 3010, Australia
;3.Tsodilo Resources Ltd, 161 Bay St, Toronto, ON, M5J 2S1, Canada
;4.Delrand Resources Pty Ltd, 100 King St W, Toronto, ON, M5X 1E3, Canada
;
Abstract:

The Nxau Nxau kimberlites in northwest Botswana belong to the Xaudum kimberlite province that also includes the Sikereti, Kaudom and Gura kimberlite clusters in north-east Namibia. The Nxau Nxau kimberlites lie on the southernmost extension of the Congo Craton, which incorporates part of the Damara Orogenic Belt on its margin. The Xaudum kimberlite province is geographically isolated from other known clusters but occurs within the limits of the NW-SE oriented, Karoo-aged Okavango Dyke Swarm and near NE-SW faults interpreted as the early stages of the East African Rift System. Petrographic, geochronological and isotopic studies were undertaken to characterise the nature of these kimberlites and the timing of their emplacement. The Nxau Nxau kimberlites exhibit groundmass textures, mineral phases and Sr-isotope compositions (87Sr/86Sri of 0.7036?±?0.0002; 2σ) that are characteristic of archetypal (Group I) kimberlites. U-Pb perovskite, 40Ar/39Ar phlogopite and Rb-Sr phlogopite ages indicate that the kimberlites were emplaced in the Cretaceous, with perovskite from four samples yielding a preferred weighted average U-Pb age of 84?±?4 Ma (2σ). This age is typical of many kimberlites in southern Africa, indicating that the Xaudum occurrences form part of this widespread Late Cretaceous kimberlite magmatic province. This time marks a significant period of tectonic stress reorganisation that could have provided the trigger for kimberlite magmatism. In this regard, the Nxau Nxau kimberlites may form part of a NE-SW oriented trend such as the Lucapa corridor, with implications for further undiscovered kimberlites along this corridor.

Keywords:
本文献已被 SpringerLink 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号