IGCP 648 Virtual Seminar Series
This seminar series has been developed by Dr Sheree Armistead as a solution to the reduced connectivity of our IGCP648 members during the COVID-19 global pandemic.
Hosted on Zoom, the IGCP 648 Virtual Seminar Series will initially run for ten (10) weeks with a weekly one hour seminar. The one hour time slot will involve either (i) one ~40 min talk or (ii) two ~20 min talks (depending on speaker preferences), with plenty of time for questions and discussion. The actual time of each presentation will vary each week to suit different time zones. Where possible (and permitted), seminars will also be recorded and hosted here so that everyone can be involved.
To participate in the seminar series please register your interest here.
Once registered, the meeting details will be emailed to you.
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Thursday 28th May at 16:00 GMT
Professor Emeritus Kent Condie from New Mexico Institute of Mining & Technology, US, presenting: Is Plate Tectonics Speeding Up?
Degrees: BS Geology (1959) and MA mineralogy (1960), University of Utah; PhD, University of California, San Diego, geochemistry (1965). Kent Condie is emeritus professor of geochemistry at New Mexico Institute of Mining and Technology, Socorro, NM where he has taught since 1970. Prior to that time he was at Washington University in St. Louis, MO (1964-1970). His textbook, Plate Tectonics and Crustal Evolution, which is widely used in upper division and graduate courses in the Earth Sciences, was first published in 1976 and has gone through four previous editions. In addition Condie has written a beginning historical geology textbook with coauthor Robert Sloan, Origin and Evolution of Earth (Prentice-Hall, 1998), an advanced textbook, Mantle Plumes and Their Record in Earth History (Cambridge University Press, 2001), and a research treatise, Archean Greenstone Belts (Elsevier, 1981). His most recent book, written as an upper division/graduate textbook, is Earth as an Evolving Planetary System has gone through three editions (Elsevier, 2005; 2011; 2016). He also has edited two books, Proterozoic Crustal Evolution (Elsevier, 1992) and Archean Crustal Evolution (Elsevier, 1994). His CD ROM, Plate Tectonics and How the Earth Works is widely used in upper division Earth Science courses in the United States and Europe. Condie’s research, primarily dealing with the origin and evolution of continents and the early history of the Earth, has over the years been sponsored chiefly by the U.S. National Science Foundation. He is author or co-author of over 750 articles published scientific journals, and very frequently, the most cited author at New Mexico Tech by ResearchGate in their weekly survey.
Although cooling of the mantle with time suggests that convection and plate tectonics should slow down with time, the following observations suggest that plate speeds may be increasing with time: The stagnant lid supercontinent stage decreases from 100 to 20 Myr in last 1.5 Ga; the frequency of collisional orogens increases from 1-7/100 Myr since the Archean; the spacing between orogen/zircon age peaks decreases from 700 to <200 Myr since 1.9 Ga; the paleomagnetic average plate speed increases from 15 to 45 deg/100 Myr since the Archean; passive margin duration decreases from 500 to <100 Myr since 1.5 Ga; and the time between LIP center activity and ocean-basin opening decreases from 80 to 30 Myr since 1.5 Ga.
An important factor controlling plate speed is the viscosity contrast across the lithosphere-asthenosphere (L-A) boundary. Although cooling of the mantle will decrease this contrast, which could lead to an increase in plate speed with time, recycling of water into the mantle may have the opposite effect. For plate speeds to increase with time, the L-A viscosity contrast must also decrease with time. To maintain a decreasing viscosity contrast at the L-A boundary, most recycled water must skip the asthenosphere and be carried into the deep mantle, perhaps by hydrous high-P phases.
Friday 5th June, 12 GMT: Craig Storey (University of Portsmouth) – The collisional history of continents through detrital rutile.
Friday 12th June; time TBA: Lucía Pérez-Díaz (Halliburton/Oxford University) – Plate-driving forces: pushing plumes into the background.
Friday 19th June; time TBA: Jo Whittaker (University of Tasmania) – Tasman Gateway – attempts to link tectonics, plumes and ocean circulation.
Thursday 25th June; 12:00 GMT: Geoff Grantham (University of Johannesburg) – Neoproterozoic to Cambrian granitoids of northern Mozambique and Dronning Maud Land Antarctica: Implications for the assembly of Gondwana.
Thursday 2nd July; time TBA: Bénédicte Cenki-Tok (Montpellier Uni, visiting Sydney Uni) – Formation and preservation of HT/UHT terranes.
Date and time TBA: Anna Gülcher (ETH Zürich) – In search of the perfect recipe of Earth’s lower mantle: the formation, preservation and dynamics of chemical heterogeneities.
Seminar 1 - Dr Chris Spencer Continuous continental growth as constrained by the sedimentary record.
Chris Spencer is an assistant professor at Queen’s University (Canada). His research is focused on the secular evolution of tectonic, magmatic, and sedimentary processes through geologic time.
Analysis of a database of ~600,000 detrital zircon ages constrained by the depositional ages of the respective sedimentary units reveals a dynamic evolution of zircon age peaks through time. This analysis demonstrates that zircon age peaks from ancient sedimentary successions are often out of phase with the detrital zircon record obtained from modern sediments. The growth and diminishment of the zircon age peaks through time implies the presence of continental crust whose age is not proportionately represented in the modern record, and therefore that the current crustal archive is biased. However, when the detrital zircon record is viewed in terms of its evolution through time, that is taken as a time-lapse view of continental growth, it appears there never was a time in Earth history without an associated zircon age peak. The analysis of detrital zircon age peaks presented herein also reveals an evolution that can be broadly divided into three temporal groupings that broadly correspond with phases of Earth’s tectonic evolution, namely pre-supercontinent continental growth (pre-2.1 Ga), Earth’s middle age (2.1-0.8 Ga), and post-onset of modern-day plate tectonics (post-0.8 Ga). These three groupings each display increasing degrees of zircon age diversification with time, and are a likely result of a net increase of preserved continental crust through time. The presence of these three tectonic states in multiple geologic proxies (detrital zircon ages, changing styles of metamorphism, paleogeography/supercontinents) suggests that while the growth of the continental crust is continuous, the tectonic processes that shape the long-term preservation of the crust have evolved over geologic time.
Gilby Jepson did his PhD at the University of Adelaide exploring Central Asian tectonics. In 2019; Gilby joined the University of Arizona, USA, as a post-doctoral researcher. Gilby uses thermochronology and geochemistry to investigate the modern landscape in order to answer a range of tectonic questions.
Central Asia is one of the most orographically diverse regions in the world, hosting the world’s highest mountains and largest orogenic systems. Understanding the crustal evolution of Central Asia can thus provide insights in to global tectonic and erosional processes. The growth of the Eurasian continent can be described by frequent Phanerozoic collision accretion events along its Tethyan Ocean margin. The upper crustal response to this complex and dynamic tectonic evolution can be resolved by exploring the cooling history of a rock as a function of erosion, tectonics, and thermal evolution. We present the first regional scale analysis of 2,526 published low-temperature thermochronometric ages from Central Asia spanning the Altai-Sayan, Tian Shan, Tibet, Pamir, and Himalaya. We compare these dates to tectonic, climatic and crustal thickness proxies in order to constrain the thermo-tectonic evolution of Central Asia. Our results indicate that the main control on cooling ages, and by inference erosion, is tectonics and their proximity to major plate boundaries. Climate plays an important role locally by enhancing erosion in areas with strong orographic barrier effects (e.g. Himalaya). The predominance of pre-Cenozoic ages in much of the Central Asia interior suggests that much of Central Asia was largely exhumed prior to the India-Eurasia collision, experiencing only localized Cenozoic reactivation. We observe a general decrease of cooling ages with latitude supporting second order climatic control on erosion.
Renata da Silva Schmitt is a Brazilian researcher who completed a bachelor in Geology at Federal University of Rio Grande do Sul (UFRGS-1991) and in Journalism at Pontifical Catholic University of Rio Grande do Sul (PUCRS -1991), master in Geosciences at UFRGS (1995) and doctorate in Geology at Federal University of Rio de Janeiro (UFRJ-2001), with a period at the University of Kansas (USA – 1998-1999). Geology professor since 2002, professor on structural geology and tectonics at UFRJ since 2009. She has the CNPq research productivity grant, and completed two post-docs: at Max Planck Institut fur Chemie (2004 – Germany) and at Australian National University (2013-Australia). During 2020, she is in a sabbatical period at University of Bern (Switzerland) working with a SNSF project on deformation and melting in shear zones. Her main line of research is the tectonic evolution of Neoproterozoic-Paleozoic orogens, with focus on correlation along South American and African margins. She coordinates the Gondwana Digital Center of Geoprocessing at UFRJ, built up during the cooperation project “Review of the geological map of Gondwana”, with CENPES (PETROBRAS 2010-2019). She was the leader of IGCP-628 – The Gondwana Map Project – The geological map and tectonic evolution of Gondwana (2013-2018).
Gondwana lasted as a merged landmass ca. 320 m.y, from the Cambrian (ca. 500 Ma) until the Jurassic (ca. 180 Ma), comprising more than 60% of today´s continental crust, including five major continents (South America, India, Africa, Antarctica, Australia) and smaller fragments widespread in Asia, Europe and North America. Its tectonic evolution comprises three main evolutionary stages: amalgamation (670-480 Ma), development (480-180 Ma) and fragmentation (180- 85 Ma). On the 30th year anniversary of the geological map of Gondwana, scale 1:10M, by De Wit et al. (1988), an updated map will be launched as a major product from the IGCP-628 “The Gondwana Map Project– the geological map and the tectonic evolution of Gondwana”. This map emerges from an 8-year working group at the Gondwana Digital Center of Geoprocessing (GDCG), in UFRJ, Rio de Janeiro (Brazil), with collaboration of more than two hundred scientists from all over the world. We present here the new reconstruction model for Gondwana in the Jurassic, enlightening key issues: (1) the link between ancient orogenic sutures and rifted continental margins; (2) alternative tectonic fit solutions for the critical regions; (3) contrasting non-volcanic and volcanic margins with continental lithosphere inheritance. Scientific data from all Gondwana-derived fragments provided a better fit in a new reconstruction model for 180 Ma timeframe. Crustal scale shear zones, juvenile terranes, rift basins and dyke swarms were used as major onshore piercing points. Offshore data available was added to undo the actual continental margins and critical regions were partially sorted out with compilation and focused new research. Even though, some regions are still matter of debate, such as the Malvinas/Falklands plateau, Sri Lanka-Antarctica-India continental margins, India-Madagascar-Mauritia continental margins, West Antarctica-Patagonia terranes and the Southeastern Brazilian hyperextended margin.