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The Roots of a Flood Basalt Province: Expedition to Antarctica

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The Roots of a Flood Basalt Province: Expedition to Antarctica Travelogue The Roots of a Flood Basalt Province: Expedition to Antarctica Jean H. Bédard Natural Resources Canada, Québec In January 2005, I participated in an Antarctic field mapping workshop with a group of researchers under the leadership of Bruce Marsh (Johns Hopkins University), who had obtained a generous grant from the National Science Foundation (Office of Polar Programs, Geology and Geophysics) covering all field and travel expenses. The focus was the plumb- ing system feeding the continental flood basalts that erupted when the South Atlantic Ocean opened 185 million years ago (Kirkpa- trick Basalts, Ferrar Dolerites, Dufek Intrusion). Flood basalts are important features of the geological record, and their emplacement is one of the mechanisms proposed for mass Group photo taken at McMurdo Station. Front row Sam Mukasa, Dougal Jerram, Taber Hersum. 3rd row: (L to R): Andrew Feustel, Dennis Geist, Tom Fleming, extinction. The subvolcanic intrusions that Karen Harpp, Jean Bédard, Michael Garcia, Dick Alan Boudreau, Dave Elliott, Jill van Tongeren, Justin Naslund, Adam Simon, Bruce Marsh. Not present: feed flood basalts are also important sources Durrell, Amanda Charrier. 2nd row: Jennifer Cooper, George Bergantz, Stu McCallum, Michael Manga, of nickel and platinum-group elements (e.g. Ron Fodor, Scott Paterson, Ed Mathez, Jon Davidson, Simon Katterhorn. Noril’sk). However, despite their importance, many issues about the genesis of cumulate postcumulus textural and chemical reequili- rocks remain unresolved. The origin of cumu- bration, which largely obliterates the evidence late rocks being one of my principal interests, of the early processes, making it difficult to the trip prospectus, published in EOS, decipher how cumulate rocks and associated attracted my attention. With my employer’s ore deposits form. blessing I applied, and was very pleased to be Travel to Antarctica requires an intensive among those selected for the workshop. medical screening process, since evacuation is expensive and can be subject to long delays because of the weather. Extra-cold-weather gear is issued at the efficient US Antarctic Program’s clothing distribution centre in Christchurch, New Zealand. Our first attempt to reach “The Ice” aboard a US Military Air Command C-141 Starlifter failed due to inclement weather. A frustrating week of postponements followed, with a nightly 3 a.m. knock on the door of the “Bed and Breakfast.” The refrain of “24-hour delay” was greeted by curses and groans by those of us with tight schedules. Finally, the weather cleared, and after an The author in front of the Beacon sandstone at the Dais intrusion, Basement sill, ~400 m thick. The pale uncomfortable eight-hour flight, we were head of Taylor Glacier. The icecap is visible behind material at the summit is Precambrian basement. Note sitting on the Ross Ice Shelf, where McMurdo the icefalls. the pale subhorizontal layers, which correspond to Station is situated, looking at the smoking feldspar-enriched cumulates. In the foreground, orthopyroxenitic cumulates are sculpted by the wind. cone of Mount Erebus, an active alkaline “beakers”) fly in two or three times a week. volcano forming the spine of Ross Island. Helos (helicopters) are constantly taking off McMurdo (or Club Mac, as some call it) is the and landing, and in good weather, US and NZ The workshop was to target the mechanics of main US base, and its population swells from Hercules transports take off a dozen times a sill emplacement and the diversity of magma about 250 in winter to over 1000 scientists day to ferry fuel down to the Pole. differentiation mechanisms, including crystal and workers in the austral summer. McMurdo The first item on the agenda upon our arrival transport and sorting, deposition, postcumu- is situated at approximately 78oS, and in was an intensive cold-weather survival course, lus melt transfer, and assimilation of wall- January there are 24 hours of sunshine, which which included a night out in a Quonzie/Igloo. rocks. The plumbing system of the Jurassic is somewhat disorienting when leaving the At –5°C, the weather was mild compared to flood basalts is extraordinarily well preserved pub at midnight. A lounge provided in each what I left behind in Canada (−30). After and exposed in the Dry Valleys of Antarctica block has all the amenities of home, including “graduating” we were authorized for deploy- (Marsh 2004). Lavas, dikes, and chilled mar- satellite TV, pool tables, washing machines, ment to our Dry Valleys camp. The Dry gins contain microphenocrysts that can serve etc. Food is served in a huge cafeteria-style Valleys receive essentially no precipitation, as points of comparison with the cumulate galley. There are a gym and three bars—one and the principal geomorphic process is the rocks occurring in the lowermost of three for beer-drinking smokers, one for beer- wind. Wind-blown dust carves the cliffs into feeder sills (300–500 m thick), in which the drinking non-smokers, and a café–wine bar weird, elephant-graveyard-like ventifacts. earliest stages of cumulate formation and for effete intellectuals. Most importantly, the maturation are recorded. In contrast, the long station boasts a superbly equipped laboratory. The environmental rules in Antarctica are cooling times of large layered intrusions like McMurdo is a veritable hive of activity in the very strict, and no waste of any kind is the Bushveld Complex allow extensive summer as plane-loads of scientists (known as allowed to touch the ground. This means that E LEMENTS 316 DECEMBER 2005 Calendar 2006 March 26–29 18th Industrial Minerals PO Box 979, 1444 S. Boulder Avenue, e-mail: [email protected] (subject: 2006 International Congress & Exhibition, Tulsa, OK 74101-0979, USA. Tel.: 918- Joint Assembly); web page: http://www. January 5–6 Mineralogical Society San Francisco, CA, USA. Details: Metal 560-2679; fax: 918-560-2684; e-mail: agu.org/meetings/ja06 Winter Meeting – Micro- and Nano- Bulletin Plc, 16 Lower Marsh, London, [email protected]; web page: http:// June 3–7 Joint 43rd Annual Meeting geosciences: Advances and SE1 7RJ, UK. Tel.: + 44 (0) 20 7827 www.aapg.org/houston/index.cfm of The Clay Minerals Society and Applications, Bath Spa University, Bath, 9977; fax: + 44 (0) 20 7827 5292; e- April 17–21 Materials Research Annual Meeting of the Groupe UK. Details: e-mail: m.lee@earthsci. mail: [email protected]; web Society 2006 Spring Meeting, San Français des Argiles (French Clay gla.ac.uk; web page: www.minersoc. page: http://www.indmin.com/conf_ Francisco, CA, USA. Tel.: 724-779-3003; Group), Oléron Island, France. Details: org/pages/meetings/Bath2006.htm details.asp?ref=C046 fax: 724-779-8313; e-mail: info@mrs. Sabine Petit, Université de Poitiers, CNRS January 5–6 Mineral Deposits Studies March 26–30 American Chemical org; web page: www.mrs.org/meetings/ Hydr’ASA, 40 Av. du Recteur Pineau, Group (MDSG) 29th Annual Winter Society 231st Annual Meeting, Atlanta, future_meetings.html 86022 Poitiers Cedex, France. Tel.: 33- Meeting, London, UK. Details: John GA, USA. Details: ACS Meetings, 1155, (0)5-49-45-37-56; e-mail: sabine.petit@ May 13–14 Melt Inclusions in Chapman, e-mail john.chapman@ 16th Street NW, Washington, DC 20036- hydrasa.univ-poitiers.fr; web page: Plutonic Systems: Mineralogical imperial.ac.uk; web page: www.huxley. 4899, USA. Tel.: 202-872-4396; fax: www.clays.org or www.c2s-organisation. Association of Canada Short Course, ic.ac.uk/research/Basins/MDSG 202-872-6128; e-mail: natlmtgs@acs. com/gfacms06 Montreal, Canada. Details: Jim Webster; org; web page: www.chemistry.org/por- January 11–13 Workshop on e-mail: [email protected]; web page: June 12–17 Walker Memorial tal/a/c/s/1/acsdisplay.html?DOC=meet- Nanoscale Processes in the Earth and www.mineralogicalassociation.ca/index. Meeting: Advances in Volcanology, ings%5catlanta2006%5chome.html Planetary Sciences (NanoPEPS), php?p=120 Volcanic and Magmatic Studies Alberquerque, NM, USA. Details: Adrian March 27–29 Society for Mining, Group, Mineralogical Society, Reykholt, May 14–16 Society of Economic Brearley, University of New Mexico; e- Metallurgy and Exploration (SME) Iceland. Details: [email protected]. Geologists 2006 Conference, Keystone, mail: [email protected]; web page: Annual Meeting & Exhibit, St. Louis, uk; web page: www2.norvol.hi.is/page/ Colorado, USA. Tel.: 720-981-7882; fax: http://epswww.unm.edu/nanopeps Missouri, USA. Web page: www.smenet. nordvulk_walker 720-981-7874; e-mail: seg2006@seg- org/meetings/AnnualMeeting2006/index January 23–27 Cities on Volcanoes 4, web.org; website: www.seg2006.org June 25–29 First International .cfm Quito, Ecuador. Details: tel.: 593-2-222- Congress on Ceramics, Toronto, May 14–17 Planet Earth in Montreal: 5655; fax: 593-2-256-7847; e-mail: April 1–3 Volcanic and Magmatic Canada. Details: Dr. Stephen Freiman, Geological Association of Canada and [email protected] or citiesonvolca- Studies Group: LASI II – Physical tel.: 301-975-5658 or Mark Mineralogical Association of Canada [email protected]; website: Geology of Subvolcanic Systems: Mecklenborg, ACerS Staff Director, Joint Annual Meeting, Montreal, www.citiesonvolcanoes4.com Laccoliths, Sills and Dykes, Isle of Skye, Technical Publications and Meetings, Canada. E-mail: [email protected], UK. Details: Ken Thomson or Nick tel.: 614-794-5829. E-mail: stephen. March 3–6 Annual Meeting of the web page: www.gacmac2006.ca Petford; e-mail: [email protected] [email protected] or mmecklenborg@ DGK (Deutschen Gesellschaft für or [email protected]; web page: ceramics.org; web page: www.ceram- Kristallographie), Freiburg/Breisgau, May 14–18 IAVCEI 2006: Continental www.gees.bham.ac.uk/LASI_web_3.htm ics.org/?target=/meetings/icc/home.asp Germany. Website: www.dgk-2006.de Basalt Volcanism, Guangzhou, China. Details: Dr. Yigang Xu, Guangzhou April 2–7 European Geosciences July 2–6 Australian Earth Sciences March 5–8 Earth and Space 2006, Institute of Geochemistry, Chinese Union (EGU) General Assembly, Convention, Melbourne, Australia.
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