Volcanology research program at Monash University - Geological ...

March 2005THE GEOLOGICAL SOCIETY OF AUSTRALIAVictoria DivisionThursday March 31Volcanology research program at Monash UniversityRay Cas, Jill Middleton and Rene LabergeVenue: Building 72 (Engineering) Monash University, Normanby Road, Clayton NorthDrinks and nibbles at 5.30 pm ($2 per person)General Meeting at 6.15 pm – Lecture Theatre E7, Building 72Map Reference Melway 475. Parking adjoining West Ring RoadRay Cas: Introduction.The pure and applied aspects of the volcanology research program at MonashUniversityJill Middleton, PhD student:"The Arico Ignimbrite: the complex facies architecture of a widespread, phonoliticignimbrite produced by a highly explosive plinian eruption from Las CañadasCaldera, Tenerife"Tenerife, in the Canary Islands, northwest of Morocco, is a long lived oceanic, basalticshield volcano, that in the last 4 Ma evolved a highly explosive summit phonolitic calderasystem. The Arico ignimbrite is one of the largest and most extensive phonolitic ignimbriteson Tenerife. It records a complex history of eruption dynamics and depositional processes,and is the only extensively welded ignimbrite on the island. It is composed of severalindividual depositional units emplaced by pyroclastic surges and flows which werechannelled down large barrancos on the upper slopes of the volcano before spreading outonce they reached the coastal plains. The Arico ignimbrite is also highly erosive in natureand commonly erodes its substrate and its own internal units. The initial eruption involvedthe formation of a short-lived plinian eruption column, followed by column collapse and thedeposition of ground surge deposits. A rapid succession of phonolitic pyroclastic flowsWeb address: http://vic.gsa.org.au for up to date GSAV news

THE VICTORIAN GEOLOGIST - 2 - March 2005then ensued with the deposition of several units of differing thicknesses andcharacteristics, some with clearly developed ground layers rich in lithics and others leavingonly thin ash layers. The insulated, continually collapsing column and the selectivechannelling of the flows down barrancos allowed the later pyroclastic flows to retain theirheat and weld.Rene Laberge, PhD Student:"The significance of breccias in the Monte Cimino volcanic system, central Italy:the evolution of a silicic lava dome complex from a series of cryptodomes to apyroclastic flow generating volcano"Explosive eruptions from active lava dome volcanoes pose a serious hazard in severalregions of the world today. Not all domes have explosive eruptions, however, and manydomes appear to experience cycles of explosivity and more passive magma emplacement.The transition of a dome system from non-explosive to explosive is of interest both forunderstanding geologic hazards and to have a fundamental understanding of the growthand evolution of these very complex volcanic systems. One example of the evolution of acryptodome into a lava dome volcano is observed at the Pleistocene Cimini dome complexin central Italy. A variety of breccias record the transformation of the Cimini dome complexfrom an early intrusive phase to later emergence and explosive eruptions. The characterof the breccias provides insight into the eruptive styles and the surface expression of thedome complex through this transition to explosive activity.Ray Cas:"The volcanology of diamond-bearing kimberlites: a snapshot of some of theissues"The eruptions of kimberlite pipes have never been witnessed, so we don’t know what theeruption styles nor volcanoes were like. Volcanological models for kimberlite pipes havebeen based for many years on the geology of southern African pipes, involving narrowtapering pipes. A hypothetically complete pipe would be filled with a deep-seated or rootzone porphyritic, hypabyssal kimberlite, passing upwards into a transitional kimberlitefacies, which in turn is gradationally overlain by tuffisitic kimberlite breccia in the diatremepart of the pipe, and then at the top by crater facies in the crater zone. In addition, largeslumped megablocks of country rock, and perhaps crater rim facies occur, and themargins may include highly brecciated country rock breccia zones. Many newly discoveredCanadian pipes of the “prairies type” are wider, flared and bowl shaped, and appear to bedominated by “crater facies”, rather than the tuffisitic kimberlite breccia that is so prevalentin the diatreme part of the southern African pipes. These differences are prompting areconsideration of many aspects of kimberlite volcanology, especially the physicalprocesses that have been involved in the filling of the pipes. These processes will beconsidered in terms of modern volcanological concepts. In particular, the origins oftransitional facies and tuffisitic kimberlite facies as being the products of in-diatremefluidization processes will be questioned, and the role of alteration in overprinting originaltextural characteristics will be considered. There are also significant problems withkimberlite-specific terminology that clouds understanding of processes. Constraints onvolcanological processes will be discussed.

THE VICTORIAN GEOLOGIST - 3 - March 2005Hear it from the ChairA plea for new blood on the committee: Every year we need to find a few willing helpers.Some positions are presently unfilled and other committee members are certain to stepdown. The work is rewarding, and offers excellent networking opportunities. If you canhelp, please let one of the committee know. If someone asks you to join, please be willingto come on the committee. Ultimately it's our society, so let's make it the best we can.AGM in AprilOur AGM is on April 28th so should send in nominations for a new committee now.Heads of subcommittees should transmit their yearly reports to the Secretary, PeterPritchard, this month.Membership MattersApplied for membership:Applied for Student membership:Transfer to Retired Membership:Transfer to Associate membership:Jackie Anne KlippelMichelle GuzelAlexander Neil McLaurinGary Leonard WallisDr Gideon RosenbaumUpcoming EventsThe Geological Society of Australia Victoria Division and the Southern Grampians Shirecouncil are appearing before the Victorian Civil and Administrative Tribunal on May 18 th topreserve the Recent Byaduk basalt flow in an undisturbed condition.GSAV will take a booth at the Geography Teachers Association Conference atCamberwell High School, August 14 th to 16 th . Volunteers to staff this would be welcome.Contact Noel Schleiger, Education Subcommittee 9435 8408.WANTED. The Committee is calling for a volunteer to take over editing the newsletterafter April. It involves a few hours per month setting out the newsletter, arranging for itsprinting and posting, and coordinating with the Sydney Office on updating mailing lists.Change to an emailed newsletterIt is very much easier to keep you up to date by means of an emailed newsletter. Themajority of our members already receive their newsletters by email and we would like anyothers who have email addresses to transfer to this method of delivery.Just email thomas@unimelb.edu.au and request a changeover.A few email addresses have become obsolete. If this applies to you please sent yourcurrent email address to Lindsay Thomas so you can continue to receive a newsletter.

THE VICTORIAN GEOLOGIST - 4 - March 2005GSA (VICTORIA DIVISION)Please address all correspondence to the GSA, Victoria DivisionGPO Box 2355V, MELBOURNE, VIC 3001Web address: http://vic.gsa.org.auCOMMITTEE 2004OFFICE BEARERS phone COMMITTEE MEMBERS phoneChair: David Moore 9859 9374 Elected Members:Vice Chair: Vacant Geof Fethers 8420 6280Secretary: Peter Pritchard 9439 9582 Leisa Brough 9727 4898Treasurer: Lindsay Thomas 9328 1722 Andy Wilde 9905 1140Promotions: Vacant Fons VandenBerg 9412 5122SUBCOMMITTEESAWARDS: Lex Ferguson 9458 4308 GEOLOGY of VIC: Bill Birch 9270 5049EDUCATION: Noel Schleiger 9435 8408 HERITAGE: Sue White 9328 4154MEMBERSHIP: Leisa Brough 9727 4898 PUBLICATIONS: VacantWEBSITE EDITOR: Jodie Miller NEWSLETTER EDITOR: Lex Ferguson 9458 4308BICENTENNIAL GOLD: Gerhard Krummei 9820 2595.GSA Inc – Subscription and correspondence, address changes etc.Ms Sue Fletcher,ral Business Office, GSA, Suite 706, 301 George St., Sydney NSW 2000Email: sue@gsa.org.au Tel: (02) 9290 2194 Fax: (02) 9290 2198WebsiteThe GSAV Website (www.vic.gsa.org.au) is continuing to evolve.If you have any suggestions on further improvements, or content to be added, send themto thomas@unimelb.edu.au – don’t wait to be invited!