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'Images of Clay'
Mineralogical Society Distinguished Lecturer Programme 2015–16
9th May, University of Glasgow, Lecture C
11th October (5.00 pm), University of Derby, Lecture C
14th October (12.00 pm), Liverpool University, Lecture B
26th October, Exeter University, Lecture C
Lecture A: The lifecycle of caldera-forming volcanoes in the Main Ethiopian Rift: insights from Aluto volcano
The silicic peralkaline volcanoes of the East African Rift are some of the least studied and yet potentially most dangerous volcanoes in the world. We present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in the Main Ethiopian Rift, using new constraints from fieldwork, remote sensing, 40Ar/39Ar geochronology and geochemistry. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at ca. 300 ka developing a ~42 km2 collapse structure. After a hiatus of ~250 kyr, a phase of post-caldera volcanism began. Since ca. 60 ka, highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. The age of the youngest volcanism is not well known. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (>80 %) of typical ‘rift basalt’. Based on the field stratigraphy and the number, style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement of localised pumice cones and effusive obsidian coulees of volumes between 1–100 × 106 m3. Comparisons with other caldera volcanoes in this section of the rift suggest that there may be parallels between Aluto’s behaviour and that of other volcanic centres, both in terms of the volcanic ‘lifecycle’, and broad timings of caldera collapse events. Using Bacteria to Break and Make Minerals
Lecture B: Lessons from a restless caldera: multi-parameter studies to understand the past, present and future of volcanic activity at Santorini volcano, Greece
Understanding the behavior of magma and hydrothermal fluids at restless calderas is important for many reasons. The interplay between the magmatic and hydrothermal systems at caldera-forming volcanoes is key to interpreting many of the geophysical signals measured at the surface used to understand their subsurface state and structure. Several recent studies have highlighted that structural controls may be important in terms of the movements of both types of fluids in the Earth’s crust below volcanoes with implications including hazard management and geothermal prospecting. Caldera-forming systems are often characterized by eruptive activity covering a wide range of size scales and repose intervals. Understanding how these different scales of volcanism at the same system relate to each other is a key science challenge when seeking to understand these types of volcano. This presentation will explore these issues using examples from the caldera-forming system Santorini volcano, Greece. This is a relatively well-studied system that last erupted significantly about 75 years ago and has recently experienced a period of unusual unrest. Lessons from field mapping and geochemistry, high-resolution digital elevation models, interferometric synthetic aperture radar (InSAR) and degassing surveys and compositions can be brought together to yield insights into the behavior of this and similar volcanic systems.
Lecture C: Volcanoes and global change?
Earth’s surface response to volcanism has been suggested to be catastrophic in nature over both shorter and longer timescales. However, volatile outgassing and recycling have also played a major role in the development and maintenance of Earth’s atmosphere, contributing to the persistence of conditions on the planet required for life to emerge and evolve. Since the 1990s there have been some significant advances in our understanding of the ways in which volcanism interacts with our surface environment. This talk will explore some of these advances and explore the ways in which volcanism might have lead to long-term global change during geological history.
Dr Sam Shaw
4th May, Newcastle University, Lecture B
24th November, 6.00 pm, Room M4, Museum Building, Department of Geology, Trinity College Dublin, Lecture A
Lecture A: Mineral formation at the nanoscale: from wastewater treatment to global biogeochemical cycles
Mineral formation and crystallization is a key part of geochemical cycles from the deep earth to terrestrial and marine environmental systems. This includes the formation of ore deposits from hydrothermal fluids, biomineralisation of marine organisms and wastewater treatment using mineral particles. Understanding the fundamentals of how crystals assemble is often challenging because of the atomic/nanoscale at which they occur, the timescales of the reactions (seconds – years) and the range of physical and chemical conditions in which they form (e.g. fluids). Recent developments in electron microcopy technology and synchrotron-based X-ray techniques are opening up the possibility to directly probe mineral formation under environmental conditions. I will present a range of research highlighting the how these next generation state-of-the-art techniques are allowing a new insight into mineralogy, including mineral particle formation during the clean up of radioactive waste, crystallization of carbonates in the ocean and the formation of mineral particles in Arctic rivers.
Lecture B: Trapping contaminants in minerals: understanding atomic scale processes and their application to environmental systems
Contamination of the environment by man-made processes can occur via many pathways, including metal mining, disposal of industrial/radioactive wastes and accidental release (e.g. Fukushima Daiichi nuclear disaster). The chemical form and mobility of heavy metals and radioactive contaminants in environmental systems (e.g. soils) is often controlled by their interaction with mineral particles. Binding of contaminants to mineral surfaces can often slow down their transport, but they have the potential be rereleased. The incorporation of contaminants into the structure of minerals offers a pathway for longer term immobilisation, and the potential to develop new remediation technologies. State-of-the-art X-ray, laser and electron beam techniques can now allow us to identify the exact atomic scale mechanism by which heavy metals and radionuclides can be incorporated into the structure of environmentally important (e.g. iron oxides and clays) mineral phases. This is helping us to underpin our understanding of contaminant migration pathways in the environment (e.g. soils and rivers), and the long-term behavior of radionuclides in a future geological disposal facility for radioactive waste. In this lecture I will show how mineralogist are playing a vital role in understanding the fundamental mechanisms of contaminant/mineral interactions, and how this research is applied to understanding contaminated land.
Use this form (to be added) to apply for a lecture at your institute in 2016 - closing date 5th February 2016. Applications by Societies are welcomed.