Between a Rock and a Hard Place

Conference diaries: Goldschmidt 2013

Charly Stamper October 7, 2013

Following on from Mel Auker’s report on her visit to Japan for the The IAVCEI Scientific Assembly, Bristol PhD students Kate Hibbert and Sorcha McMahon tell us about their recent trip to Florence for Goldschmidt 2013.

What? The annual Goldschmidt conference is a major geochemistry conference, alternating between Europe and North America each year. With over 4,000 delegates from all over the world attending, this year’s gathering consisted of 22 themes, and many sessions within. Topics varied from the geochemistry of bottled water, to a Martian origin for life on Earth, with a new Volcanoes and Hazards session added this year. Talks were given all day every day, with poster sessions and refreshments each evening. Many social events were offered too, including a cheese and wine evening, film showings and a conference banquet.

When? The conference was from the 25^th – 30^th August, 2013, and started with an icebreaker on Sunday 24^th.

Where? Florence, Italy. The conference was held in the Firenze Fiera Congress and Exhibition Centre, just a few minutes walk from the city centre. [Read More]

Science Snap (6): SEM images of a high-pressure experiment

Charly Stamper October 3, 2013

Sorcha McMahon is a third year PhD student in the School of Earth Sciences at the University of Bristol. Sorcha is investigating how strange igneous rocks called carbonatites may have formed, using both natural samples and high-pressure experiments.

Sorcha's SEM SS

These back-scattered electron (BSE) images are a typical view of one of the high-pressure experiments that I run on the piston-cylinder apparatus, here in the BEEST labs at the University of Bristol. Such photographs are taken using the Scanning Electron Microscope (SEM), and are an essential stage in the analysis of run products as the different shades, textures and compositions are used to identify different mineral and melt phases.

The image on the right shows an entire capsule (a metal container that holds the powdered sample) and its contents after it has experienced conditions of 1375^oC and 30 kbar (equivalent to ~100 km depth) for 24 hours. The AuPd capsule (an alloy that can withstand up to ~1400^oC before melting at this pressure) appears brighter than the phases produced because this material has a higher atomic mass than the minerals (more information in Charly’s post).

The two images on the left show closer shots of the same experiment, labelled with the different minerals. In varying shades of grey; garnet, olivine, clinopyroxene (cpx) and orthopyroxene (opx) are typical minerals found in lherzolite (‘normal’ mantle) assemblages. As I am working in a synthetic carbonate-bearing system (CMAS-K₂O-CO₂), my run products contain an abundance of carbonate minerals, such as dolomite. At higher temperatures, melt may be observed, and is identified by its ‘streaky’ quenched texture.

Negative results, have no fear!

Elspeth Robertson September 30, 2013

KT Cooper is a PhD student in the School of Earth Sciences at the University of Bristol. A carbonate geochemist by training, she is currently on a three-month secondment to Houston, Texas, USA working with Exxon Mobil.

Not all research is successful and not all experiments have a positive outcome or even the outcome you first expected. When you are a young researcher, such as a PhD student, this is often very hard to come to terms with. It can feel like its a personal failure on your part and that can knock your confidence. But in the lines of Mel’s previous post on perspective, I hope I can give you some solace.

In carbonate sedimentology we have a problem (well we have many but this one is quite important). Dolomite, which is CaMg(CO3)2, is very prevalent in the rock record, however in the modern environments we can’t find it! Dolomite is thought to form when a fluid has a very high magnesium concentration when compared with calcium. As there are lots of natural fluids that satisfy this criteria so you might think that it would be simple to form dolomite. One researcher thought so and set up an experiment in the 1970’s to precipitate dolomite. After 32 years, he still had no dolomite!

Abstract for a failed 32 year experiment. Credit Springer Link, Published in Aquatic Geochemistry.

This paper (which in my opinion has the best abstract I have ever read) has been cited nearly 100 times and has been the catalyst for a new region of research in carbonates. This negative results, which took 32 years to come about, can only be viewed as a positive thing. So the next time you get a negative result, think to yourself “could this actually be a good thing?”

Science Snap (5): Volcan de Colima’s lava dome

Elspeth Robertson September 27, 2013

Credit: Elspeth Robertson

This photograph, taken from a helicopter, is of the lava dome at Volcan de Colima volcano, Mexico in November 2009. Volcan de Colima has been active throughout history with over 40 eruptions since the sixteenth century. The last explosive Plinian eruption was in 1913 blasting out the summit crater. Nowadays, eruptions tend to be effusive with eruptions of lava flows and the gradual build up of the volcanic dome. The dome is formed through extrusion of viscous lava that builds up into the flat-topped dome seen in the photo. Over time, the dome increases in volume and will eventually start to spill over the volcanic edifice creating spectacular incandescent rock falls.

The wispy looking fog you can see surrounding the dome is steam emanating from the dome, which despite its cool exterior, reaches temperatures of 380 degrees Celsius.