QUARTERLY NEWS BULLETIN ~ Geoplaque atChapmansPeakDrive ICDP approvesfundingfordrillingproject Komatiite 50 th Anniversary DECEMBER 2 0 1 9 ........................................................................................................................................................................................................................ VOLUME 62 NO. 4 ............................... CENTREFOLD: Viljoens, a lifetime with komatiite. 3 Photos: David Reid, Komatiite in Barberton and Nondweni Volume 62 ~ Number FOUR ~ DECEMBER 2019 contents Society News GSSA MANDELA MINING PRECINCT (FORMERLY CSIR MININGTEK), 2 From the Editor’s desk - Chris Hatton CORNER RUSTENBURG & CARLOW ROADS, 3 Executive Manager’s Corner - Craig Smith MELVILLE, SOUTH AFRICA. 4 President’s Column - Sifiso Siwela 8 The Professional (Affairs) Corner P.O. Box 9230 CRIRSCO Auckland Park 2006 Johannesburg, South Africa University News Tel: +27 11 358 0028 9 Wits e-mail: [email protected] 16 Stellenbosch Web: www.gssa.org.za Articles COMMITTEE 20 Unveiling of the Geoplaque at Chapman’s Peak Drive Convener & Editor: Chris Hatton .................... 082 562 57 23 Sea Point Contact Advertising: Jann Otto ........................ 082 568 0432 25 Save the date! Geocongress Design & Layout: Belinda Boyes-Varley ........ 079 29 7748 26 REI Fund Printing: Seriti Printing (Pty) Ltd ....... 02 43 7632 27 IUGS and IGCP All submissions to (in order of preference): 3 ICDP approves funding for drilling project on the Bushveld email attachments (in Word .doc) to: [email protected] Complex disc/hard copy to: Chris Hatton 32 New dinosaur species fossil discovered in South Africa Postal Address: Council for Geoscience 33 Natal Colony Gold Rush of 853 Private Bag X112 Pretoria 35 Rapidly shifting magnetic north pole South Africa 000 36 Komatiite 50th Anniversary Geoheritage Field Excursion Tel : + 27 (0) 2 84 1149 47 The First International Kimberlite Conference 973 General Fax: 086 679 859 Centre fold Contributions for the next issue should be submitted by: 50 Viljoens, a lifetime with komatiite. 15th FEBRUARY, 2020. Book review 66 Mining in Zimbabwe: From the 6th to the 2st Centuries Geobulletin is provided free to members of the GSSA. Non-member subscriptions per four issue volume are R350.00 for South Africa. 69 Minerals & Gemstones of East Africa Overseas and rest of Africa, R350 plus postage. Surface mail, R200.00. Airmail, R300.00. The views expressed in this magazine Obituaries are not necessarily those of the GSSA, its editor or the publishers. 7 Felix Mendelsohn ADVERTISING RATES (Excl. VAT & Agency Commission): Geobulletin 73 Aylva Schoch is published by the Geological Society of South Africa (GSSA) and 76 Anton Hales appears quarterly during March, June, September and December 78 John Gurney each year. 82 William David Northrop 2019 RATES: Jann Otto 082 568 0432 (inside back cover) Mineral Scene For detailed prices, mechanical and digital submission requirements, please contact the GB advertising co-ordinator, editor (see Contents 84 Schizolite, Kalahari Manganese Field, South Africa Page for contact information) to obtain an up-to-date Rates Card or other information. The Geotraveller DEADLINES FOR COPY AND ADVERTISING MATERIAL are 86 Malvern Hills Geopark, England 5th February (March 2020 issue), 5th May (June 2020 issue), 5th August (September 2020 issue) and 5th November (December 2020 Other Business issue). 96 Rates card 2020 Please note that the design and layout of adverts and inserts is 97 GSSA Events from January 2020 – November 2020 entirely the responsibility of the advertiser. If you wish to contract 98 Classifieds the services of the GB graphics and layout supplier for this service, please contact Belinda Boyes-Varley directly, well in advance of the advert submission deadline to make arrangements. Front Cover: Geobulletin © 2019 The Geological Society of South Africa. All rights ‘The mantle has gone dark….’ Kinked twin planes in a deformed olivine reserved. Geobulletin is available as gratis open access. Issues may crystal included within garnet. Crossed polars. FOV = 3mm. Mantle be downloaded from the Geobulletin Archive: Peridotite nodule collected from the Boshof Road dumps, Kimberley. https://gssa.pub/gb/content Photo by D.L. Reid. (ISSN 0256-3029) publisher-id: gb.62.4 geobulletin DECEMBER 2019 from the editor’s desk ‘You’ve never had it so good’ is one way of looking The proliferation of the farming culture is in large at our current climate of blistering heat and drought measure due to the stable temperature regime of the alternating with incessant rain last six thousand years. During this time, the average and flooding. The basis for annual temperature has varied by less than 5 degrees. this questionable perspective By comparison the beginning of the Younger Dryas is the emerging picture of saw much large temperature variations within a matter the world as it was relatively of years. Although one might take comfort in a belief recently. 2 800 years ago that meteorite impacts are infrequent, wild temperature a remarkably abrupt cold swings, with or without a meteorite impact, are not snap ushered in the Younger unusual. The warming at the end of the Younger Dryas Dryas glaciation, rudely was almost as abrupt as the cooling at the beginning, interrupting the warming trend and it was the feedback loops that are associated with SOCIETY NEWS which followed the end of the relatively mundane events such as glacier melting and Older Dryas glaciation. One shifts in storm patterns that drove this heating. The take explanation for this sudden away message from the Younger Dryas is that wild swings cooling, initially regarded as quite far-fetched, is that in temperature are the rule rather than the exception. a meteorite struck the Earth, producing wild fires on The stable climate that currently prevails cannot last. a global scale, darkening the sky and demolishing The relatively miniscule temperature increase associated human populations. The evidence for this apparently with current global warming, whether anthropogenic or outrageous explanation is actually quite considerable, not, may be just the beginning of a feedback loop which including a sample of an iron meteorite in Greenland, will escalate to the frightening fluctuation at the end of the nearby Hiawatha impact site with an appropriately the Younger Dryas. The question is, what should we do juvenile morphology, soot deposits across the globe, during these good times? How do we make hay while and to cap it all, platinum spikes within these soot the sun shines? deposits. Francis Thackeray of the University of the Witwatersrand presents the most recent description of Whilst an individual geologist can certainly make a a platinum spike, found within the Wonderkrater peat difference to the world, the greatest impact arises when deposit. The timing of the Wonderkrater spike appears the geologist and society act in concert. For a South to correspond remarkably closely with the demise of the African geologist the interaction between geology spear-wielding Robberg culture and the colonisation and the wider society begins with our microcosm, the of their erstwhile hunting grounds by humans who are Geological Society of South Africa. Strengthening of effectively indistinguishable from the San, using the bow the local branches of the Society is one of the aims and poisoned arrow to bring down their prey. In the of our new President, Sifiso Sexwale. Pp. 20-24 of Cape the transition is as abrupt as the Younger Dryas this issue illustrate the activities of a local branch that impact hypothesis would predict. Only in KZN does the is already flourishing. The Western Cape branch has transition appear more gradual but the use of the bow updated plaques on Chapman’s Peak and Sea Point. and arrow in this part of the world dates back to more The association of the Sea Point site with the geological than sixty thousand years, showing that the use of this activities of Charles Darwin provides a bridge between weapon was no new thing for this culture. DNA evidence geology, biology and evolution, inviting exploration of suggests that the hunter-gatherer culture originated here the links between these interrelated aspects of science. so this culture might have spread from KZN when the rest Another vehicle for communication among geologists is of Africa was reeling from the impact at the beginning of the conference. The revival of Geocongress, begun last the Younger Dryas. At the end of the Younger Dryas to year at the University of Johannesburg continues next year the north, the domestication of the auroch in the Middle at Stellenbosch University (p.25). Another conference, East saw the beginning of the farming culture. The with a narrower focus than Geocongress but nonetheless southward spread of nomadic farmers would ultimately with wide appeal began when a collaboration between overwhelm the hunter-gatherer culture. the late Barry Hawthorne († previous issue) and the late 2 geobulletin DECEMBER 2019 Volume 62 ~ Number FOUR ~ DECEMBER 2019 John Gurney (†pp.78-8) led to the staging of the First which together with kimberlite, is one of the only two International Kimberlite Conference at the University of rock types to be named after a South African locality. Cape Town in 973. John Gurney’s scrapbook of this The quench needles of orthopyroxene and olivine in event is on pp. 47-64. This was the beginning of a career komatiite (spinifex texture, see centrefold and p. 38) which inspired many to join in a lifelong intellectual attest to the much higher temperature of the earth as adventure grappling with the many facetted mysteries it was three and a half billion years ago. From their of diamonds, their inclusions, the peridote and eclogite beginnings in komatiites the Viljoens’ careers diversified xenoliths that contain diamonds and the kimberlites that into multitudinous areas of geology and business, brought xenoliths and diamonds to surface. Although including major roles in the successful organisation of rare the diamond content of intact diamondiferous the 32nd International Geological Congress held in Cape xenoliths is sufficient to induce most diamond miners Town in 206 (see centrefold).