An open source book on thin section microscopy

Everything a geology graduate needs to know about thin sections. Fantastic images and totally free: http://www.minsocam.org/msa/openaccess_publications.html

“Guide to Thin Section Microscopy” 

Making a poster for a conference

The first of many wonderful posters

Few weeks ago I went to Spain to participate in a geology conference on mineral replacement reactions. Normally participation in scientific conferences occurs in one of the two ways: either by giving a talk or presenting a poster.

Each of these forms has their advantages and disadvantages. The talks are often considered to be more prestigious than poster presentations so the big professors rarely bother with posters, while it is the most common form of participation for students. The talk allows to reach more people but is limited in time and do not give the opportunity for much discussion. Posters are great for getting direct feedback on project and better suited for work-in-progress but you have to compete for attention with tens, hundreds or sometimes thousands of other enthusiastic posters’ owners in the room. As my main goal was to go for discussion, I went with a poster. Not as I was in a position to choose but …, oh well, the goal was successfully achieved.

But this was also my first poster ever created and quite a few lessons were learned in the process of making it. Unfortunately some of them too late.

Do’s and don’ts:

• It is very useful to go around the department and look on the others’ posters hanging on the walls before even beginning to work on your own. That gives a perspective of a random passerby and helps to understand what attracts the attention, what makes the poster readable or unreadable and which layouts look the best.
• PowerPoint definately is not the best tool for poster making. For basic designs it is kind of okay but generally it is a nightmare. It does not wrap the text around images, sizing and saving reduces the quality of image and options for formatting are very limited. Most people use Photoshop or Adobe Illustrator but these are expensive programs. I often use Inkscape (open source) for most of my graphics but it has problems with handling large images so I went for PowerPowerpoint instead. However the plan for next time is to try some of the other free graphics editors such as LaTeX, Scribus, GIMP, etc.
• Less text, bullet points wherever possible and more pictures. The poster should be fully readable in 5 minutes because no one will spend more time on it. At first my poster contained an extended introduction on all the interesting aspects between the metamorphism and deformation. After realizing that even I am tempted to skip it when going through my own poster, I decided to save it for the master thesis and blog posts.
• The poster should be self-explanatory. Mine was not. I had to guide people through it and explain the images and how different parts are related.  This time it was fine. But there is definitely a better way how to do it.
• Some people consider poster presentation a passive and boring process where you have to stand and wait till somebody will approach you and show some interest. Instead I went around myself and brought anyone who works on similar things to my poster. Either I was lucky or extremely thick-skinned but people seemed to come willingly.
• Never fly with Ryanair! They made me throw away my first poster in the garbage because of baggage limitations. Few things are just unforgivable. This is one of them.

In a month time I have to make another poster so any other comments and tips are welcome!

Guess where was I!

For many religious people this place is a holy site since the 12^th century. For me it is a natural wonder with many secrets to explore.

When I go to geology trips (apart from fieldwork) I intentionally do not check any geological literature beforehand. It is much more interesting to find out everything by myself, wandering around and trying to read millions of years old events in the rocks.

 

The mountains in this area seem to be a thick sedimentary sequence composed mainly of red sandstones at the bottom and conglomerates on the top. Of course when you look in details it is not that simple but roughly speaking these two units determine the landscape and topography on the large scale. In the sandstones on the lower part, erosion dominantly occurs along river beads leading to the formation of canyons and flat topped mountains. The conglomerates on upper part look like human made statues rising highly above the old cloister. But they are not shaped by human. The process takes two steps: first during tectonic activity rocks are fractured forming vertical joint systems and then erosion widens these fractures giving the mountains the peculiar present day shapes.

The sandstones are fine to coarse grained, sometimes with rare pebbles and clay-like material inside. The redish color testifies of terrestrial environment. The red color is basically a rust. Although sandstones are dominated by quartz grains they usually contain smaller fractions of other minerals. If iron bearing minerals in sand comes in contact with oxygen they form rust thus coloring the sand red. It does not happen in deep water because there is not enough oxygen available. But if the water is shallow or gone the sand tend to oxidize. This particular sandstone looks like typical river delta deposits. So what was once beneath the sea now is a high mountain range.

The conglomerates can form in different environments but they often tell that new mountains were growing nearby. In any case the source area should be nearby otherwise long transport would break the rock down to the sand size. The particular conglomerates are well rounded which means they have spent some time in the water where they were polished by currents of waves. Afterwards the limestone and sand filled the voids between pebbles cementing the material and making it persistent to erosion.

In general the area is spectacular. It could keep sedimentologists busy for years because the exposures are excellent.

Guess the place!

Breaking the break

Almost two months of silence here. But, I am making progress with my master thesis. It was a lot of reading, learning and writing during last weeks. I learned the basics in thermodynamic modeling with PerpleX and obtained good results for my samples. I also spent more than a week working with Electron Microprobe, a crazy expensive machine which costs 400 NOK (50 Eur)  in an hour. My supervisor was joking that I am the most expensive master student at the department. But that is not true because one of my coursemates spent a month in Argentina for a fieldwork. I should break the Microprobe to beat that.

And then there was also a short course in Tromsø (northern Norway) about deformation processes. We learned about the rheology of lithosphere and deformation mechanisms, practiced to recognize microtextures in thin-sections, calculated flow laws and learned to use grain size piezometers. All of this in just one week. Fantastic course and excellent teaching by Holger Stünitz. I had a chance to discuss my project and that was a big step forward. There will be another short course by him on rock textures this October. I highly recommend it.

Some afterthoughts (inspired by Andrew Putnis)

A month behind the Polar Circle

Initially, I planned to write a few, more proper articles on Svalbard’s geology but it seems there will never be enough time for this. So better something than nothing and at least few nice pictures:

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For the backstory Svalbard is an archipelago behind the polar circle, about 1000 km north from the northern Norway. This autumn I spend there a month studying geology. There is a university centre (UNIS) which offers various courses and degree programs in Arctic Biology, Geology, Geophysics and Arctic Technology.

You may wonder who had such a crazy idea to put a university centre in the middle of nowhere but considering everything this place can offer the idea is actually pretty sane.

There are only few places on the world where such a rich and diverse geology representing nearly the entire history of the Earth is exposed in such a small area. Svalbard has metamorphic rocks and tillites from Precambrian, trilobites and graptolites from Cambrian and Ordovician, intrusive granites of Silurian age, Devonian fishes and plants, coal and evaporates from Carboniferous, marine reptiles and dinosaur footprints from Mesozoic, Large Igneous Province from Cretaceous, deformed foreland basin deposits from Tertiary, deposits of more than 50 glaciations in Quaternary and excellent modern-day periglacial landscapes. But the main reason why this place attracts many industry-oriented geology students is its post-Devonian sedimentary rocks which are analogues to the hydrocarbon bearing structures in Barents Sea. Svalbard is a part of Barents Sea which was uplifted and exposed due to tectonic processes. Many of the outcrops in Svalbard are seismic scale examples of source and reservoir rocks for hydrocarbons in Barents Sea. Understanding of them is a way how to understand and interpret the seismic sections from Barents Sea.

And besides all of that the place is absolutely wonderful. UNIS is probably the only university on the world teaching geologists to handle weapons because there is a real danger of polar bears outside (and sometimes inside) the city. My course had a 9 day boat trip around the western coast of Svalbard visiting all the best localities, everyday hikes in mountains with a lot of logging practice. We saw a polar bear, heard a landslide, I almost slipped off from the cliff (but that’s fine, I enjoy memories like that) and walked a glacier. That’s almost half of the things on my geology to-do list.

First results from EMP

Today I finally got my hands on EMP (electron microprobe), a hi-tech toy for geochemists which allows to determine the chemical compositions for the tiniest amounts of matter (down to the size of 1 micron).  It works by bombarding the rock sample with an electron beam. The beam causes each element to emit X-rays of a characteristic wave length. Then EMP detects the emitted waves and determines the specific composition of each hit point.

My supervisor had a question of the Earth’s origin on his to-do list today. Fortunately my task of the day was only to characterize the mineral composition of a simple granulite.

EMP image where spinel is partially replaced by corundum. The fractures are filled with reaction products. Then the structure is surrounded by a corona of kyanite and amphibole intergrowth. The kyanite needles extend even farer out in the plagioclase. We saw that kyanite and amphibole intergrowth often makes “bridges” connecting more of these larger corona structures. The transport of the elements mostly occurs along fractures and grain boundaries.

(EMP does not use the light so the image represents the average atomic numbers of the elements in the sample. Thus the heavy minerals appear bright (because they have a high atomic number) and light minerals appear dark (because of their low atomic number)).

Optical microscope image of partially replaced spinel inclusions in granulite. EMP section is framed in red. Spinel here is green, corundum is white and plagioclase is pinkish-gray. The orange stuff is amphibole (light) and biotite (dark).

A treat for Ole (from the comment section):

Guess where am I! #2

I am away from Oslo again for another short course in geology. Guess the city and the mountain in the picture!

photo: L. Spruzeniece

Geological postcard from this “mistery” place  to the lucky winner.

Update: The lucky winner is Zigmārs

Mishmash in the Earth’s crust

Although metamorphic rocks compose a huge part of the Earth’s crust they are less understood than sedimentary or igneous rocks because the depth of the Earth where they form is not accessible for direct study.

For example, if you want to know how the cross-bedding in sandstones forms, go to a river delta and take a look! If you want to know how the odd hexagonal lava pillars take their shape, visit a volcano and observe the cooling of lava. But how can you understand eclogite? The depth of 50 km is probably a bit far to reach.

The metamorphic evolution in Bergen area: (1) Granulite metamorphism during Grenvillian orogeny (900 Ma ago). P≤10 kbar, T= 800-900⁰C. (2) Eclogitisation in Caledonian orogeny Caledonian orogeny 425-460 Ma. P>19 kbar, T=700-750⁰C. (3) Amphibolitisation 420 Ma. P>8 kbar, T=600-650⁰C (base diagram from http://science.jrank.org/pages/47852/metamorphism-metamorphic-facies-metamorphic-rocks.html)

Fortunately there are other powerful tools to apply in this case, such as field observations in outcrops, microscopy examinations, chemical analysis, computer modeling and seismic wave velocity studies. Except of the last one I will try to incorporate all of these methods in my master thesis which is focused on metamorphic rocks in Bergen area.

But let’s start with my pretty outcrops which, I am not going to deny, was a very important reason for choosing this topic for the thesis.

The area

There are 3 main types of metamorphic rocks in my area: granulites, eclogites and amphibolites. All of them can be produced from the same (or different) types of rock just by changing pressure and temperature conditions and fluid content when the rocks goes deeper in the Earth. In Bergen area the source rock probably was something of gabbroic anorthosite composition. Then during multiple tectonic events the rocks were buried or exhumed. The picture above shows the sequence of metamorphic conditions Bergen area has undergone (based on Austrheim and Griffin, 1985; Boundy et al., 1992).

The metamorphic facies 

Granulite facies. The matrix is made of plagioclase (white) and surrounds corona structures which are composed of olivine or pyroxene in the core (black) and garnet rim (red).

Eclogite facies. There is still plagioclase (white) in the matrix because the eclogitisation was not completed and also omphacite (light green). Garnet (red) is disintegrated to individual grains.

 

Amphibolite facies. Matrix consist of plagioclase (white) and corona structures consist of talc or chlorite in the core (light gray) and amphibole in the rim (dark gray). Structurally similar to granulites, mineralogically different.

Each of these events overprinted the previous ones but neither eclogitisation nor amphibolitisation was fully penetrative. They are mostly localised in distinct shear zones. Probably around fractures where fluids got in and accelerated reactions.

So at the end these processes result in amazing outcrops where the transformations between different rocks are captured “in motion” revealing how the minerals and structures change into each other when the rocks experience metamorphism.

More of the pretty pictures:

Granulite blocks embraced by amphibolite facies shear zones

Rotated granulite blocks. Sometimes granulites have pronounced layering marked by elongated coronas. In this case it allows to distinguish rotational domains

Amphibolite shear zone. Note how fluid these rocks look. They should be very ductile at the time of amphibolitisation. Probably large parts of the earth crust is like this at 25 km depth where the amphibolite facies were formed

Initiation of the shear zones in granulites. See how the granulite minerals change the size, shape and colour with deformation and reaction

The shear zones were observed also on large scale

References:

Austrheim H., Griffin W.L. (1985). Shear deformation and eclogite formation within granulite-facies anorthosites of the Bergen Arcs, western Norway. Chemical Geology, 50, 267-281.

Boundy T.M., Fountain D.M., Austrheim H. (1992). Structural development and petrofabrics of eclogite facies shear zones, Bergen Arcs, western Norway: implications for deep crustal deformational processes. Journal of Metamorphic Geology, 10, 127-146.

How to write scientific papers

This video is from the “Scientific writing seminar” which was held at PGP last week. As a master student I found it extremely useful but I think it could be interesting also for more experienced people in academia or even in other fields.

The first part of the seminar was given by Inge Loes ten Kate, an astrobiologist from NASA’s Goddard Space Flight Center who currently is a visiting scientist at PGP. She talked about the goals of writing and publishing research, as well as about the language style for producing compelling papers. The main idea was to keep it as simple and clear as possible.

The second part, which was filmed, was given by Douwe van Hinsbergen, one of the most productive researchers at PGP. He discussed the structure of scientific paper and publication strategies in a very entertaining basketball-coach manner. For example: “If you promise me subduction then give me subduction! Never bluff! Never! Because it will come back and bite you in the ass”

Arrival in Svalbard – lost passport, expelling from airport and hichhiking