Volcanological and structural aspects of the Venetia kimberlite cluster - a case study of South African kimberlite maar-diatreme volcanoes

Abstract

Research Article| September 01, 2003 Volcanological and structural aspects of the Venetia kimberlite cluster – a case study of South African kimberlite maar-diatreme volcanoes Stephan Kurszlaukis; Stephan Kurszlaukis De Beers GeoScience Centre, PO Box 82232, Southdale 2135, South Africa, e-mail: Stephan.kurszlaukis@debeersgroup.com Search for other works by this author on: GSW Google Scholar Wayne Peter Barnett Wayne Peter Barnett DeBeers Consolidated Mines Limited, Premier Mine P.O. Box X1015, Cullinam 1000, South Africa, South Africa, e-mail: wayne.barnett@debeersgroup.com Search for other works by this author on: GSW Google Scholar Author and Article Information Stephan Kurszlaukis De Beers GeoScience Centre, PO Box 82232, Southdale 2135, South Africa, e-mail: Stephan.kurszlaukis@debeersgroup.com Wayne Peter Barnett DeBeers Consolidated Mines Limited, Premier Mine P.O. Box X1015, Cullinam 1000, South Africa, South Africa, e-mail: wayne.barnett@debeersgroup.com Publisher: Geological Society of South Africa First Online: 07 Mar 2017 Online ISSN: 1996-8590 Print ISSN: 1012-0750 © 2003 Geological Society of South Africa South African Journal of Geology (2003) 106 (2-3): 165–192. https://doi.org/10.2113/106.2-3.165 Article history First Online: 07 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Stephan Kurszlaukis, Wayne Peter Barnett; Volcanological and structural aspects of the Venetia kimberlite cluster – a case study of South African kimberlite maar-diatreme volcanoes. South African Journal of Geology 2003;; 106 (2-3): 165–192. doi: https://doi.org/10.2113/106.2-3.165 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract The paper summarises an investigation of the volcanology of the Venetia kimberlite cluster and the country rock structures in the immediate vicinity of the pipes. Our study shows that the pre-existing country rock structure and the stress field prevailing during emplacement control the position and morphology of the pipes. The pipes were formed along pre-existing zones of weakness, and the pipe shapes are elongated in the direction of fractures and faults. The highest degree of vertical and lateral pipe shape irregularity is found in the vicinity of country rock structural weaknesses. The understanding of this relationship between pipe geometry and country rock structure can significantly affect mineral resource models.The most important volcanological feature of the cluster is the presence of bedded fragmental rocks filling the main pipes K1 and K2. These rocks are readily interpreted as volcaniclastic in origin, yet are petrographically identified as typical Southern African tuffisitic kimberlite breccias ("TKB"). These observations contradict the hypothesis that "TKB's" are intrusive rocks, which are expected to be massive and unstructured in nature.The presence of accretionary (armoured) lapilli, soft sediment deformation, and signs of reworking within the volcaniclastic deposits suggest a high moisture content of the volcaniclastic material during and after emplacement of the pipe. Monolithic talus fans as well as contact breccias represent significant facies types within the Venetia kimberlite cluster. The contact breccias show signs of downward movement along the pipe walls, suggesting a considerable volume deficit at depth. These volcanological observations need to be accounted for in a comprehensive emplacement model for the Venetia kimberlite pipes.The observed structures, internal textures and facies suggest that the Venetia pipes were emplaced in several violent volcanic phases, separated by periods of relative inactivity. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.