08 December, 2015

User meeting “Rietveld analysis with BGMN”

For XRD enthusiasts or students who need BGMN out of pure necessity, and do not want to wait for the DTTG Workshop 2017, there is a 2-day course in Rietveld-analysis with BGMN at the TU Bergakademie Freiberg, Germany, on March 1st and 2nd, 2016. The course has recently been announced on the DTTG website together with the first circular (click for a detailed PDF to load).

P.S. I use BGMN on a regular basis during my doctoral studies, mostly for the quantification of clays (bentonite) and carbonates. It is a great and easy to understand programm used especially by people from clay science. Though it can just as well be used to work on any other kind of material.

This is the course description from the cicurlar:

This workshop is addressed at persons using the BGMN Rietveld program in research and education. Basic knowledge in X-ray powder diffraction is assumed. The content focuses on  the use of laboratory powder diffractometers and the application of BGMN in phase analysis.
Examples in the tutorials are mainly from minerals and rocks.
Computer exercises will be performed on the participants’ own laptop computers. The BGMN and Profex software are under GNU GPL and will be distributed for free. Versions for Windows and Mac OS X systems will be available. Copies of the presentations will be distributed as PDF files. Participation is limited to 20 persons and will be decided by the organizers on a first-come-first-served basis. Individual confirmation will be sent after the pre-registration deadline

29 November, 2015

DTTG Workshop 2017

It passed my attention but now I noticed the first announcement for the next and 7th international DTTG (German-Austrian-Swiss Clay Group) Workshop on qualitative and quantitative analysis of clays and clay minerals to be held in at the University of Greiswald, February 20th to 27th 2017. Georg Grathoff and Lawrence Warr will be the organisers, whom I met at several occasions and they are both great clay scientists. The announcement comes way ahead of time but I can recommend this workshop whole-heartedly. It is extremely popular and places will fill-up fast. I have been lucky enough to personally participate in the 5th DTTG Workshop 2013 at the KIT Karlsruhe. It was great! Having all the people you usually only know from paper titles concentrated for a week into one room makes for an excellent atmosphere of knowlege transfer, networking with other clay science PhD students, and great conversations! I have also been to Greifswald some years ago, and it is a quiet but very nice town located at the Baltic Sea. Well worth a visit!

The course summary from the DTTG website:
The workshop focuses on the needs of graduate students and PhD students in the field of clay science. The workshop is also open for scientists and people working in industry who are interested in clay science. The workshop will be consist of theoretical lectures and laboratory exercises. Therefore, the number of participants is limited to 15 persons.

Topics of the workshop are: Different aspects of XRD of clay minerals including QPA with the Rietveld method, physicochemical properties of clay minerals and their quantification (CEC, charge, surface), simultaneous thermal analysis, aspects of sorption, as well as the application of electron microscopy and infrared spectroscopy in clay research.

07 November, 2015

Fossil roots in tuffites & bentonite deposits, Southern Germany

Yesterday I joined #FossilFriday on Twitter. It made me realize how many images of fossil roots I actually have. I am not a palaeontologist, most of them will never make it into a publication. So, let's share here! All images were taken during my doctoral research in bentonite mines in Southern Germany. The Mid-Miocene bentonite deposits of the Upper Freshwater Molasse are often associated with so called "Harte Platte" (English: hard plate) - a descriptive term for hard clay of little economic value. The hard clays are usually composed of partially altered tuffites, silified bentonite or sandstone-like horizons, and are common in deposits of a thickness of roughly 3 meters and more. While the hard clays are economically useless, their reduced shrink-swell capacity and stiffer composition is probably the reason for an often excellent preservation of fossil root features! Unfortunately, I lack the in depth palaeobotanical expertise to identify the plants they are from. However, based on their large size they must once have been quite impressive trees or shrubs that, based on the literature on depositional settings, grew in wetland settings. I also have a number of thin-sections and SEM images of well-preserved root features that I use as side-notes in an upcoming publication. But if anyone knows if it is possible to use root morphology to do more than "tree" or "shrub" let me know! The upside is always at the top of each image.

This is the image I used for #FossilFriday depicted a loam-filled root mold. It is one of the largest root molds I found.

This down-ward branching examples is part of a finely bedded, almost laminated tuffite. The tiny circular objects are sectional views of more "roots". These examples were replaced by silica.

More branching root features. Filled with a mix of loam and carbonates.

Cross-section of silica-rich root trace with central root channel? Diameter ~ 1.5 cm.

Fe-Mn-stained roots about 1 cm in diameter.

Almost vertical loam-filled root features in an almost 4 m thick tuffite.

27 September, 2015

Old fieldwork pictures from Peru

Things have been quiet here recently due to job hunting and working on my doctoral thesis and related publications. Going through my back-up files I came upon a number of fieldwork images from my ore exploration student internship in Peru. It ignited some nostalgia about those great times in the Andes! Here are some pictures...

Trujillo cathedral.
Trujillo city hall.
Desert and cactus.



We need to get up there!
Traveling off-road!

27 August, 2015

Online clay science resources

When I began my doctoral research I was lacking a really good knowledge of clay rocks and clay minerals. So, during the years I have been looking for easy to understand resources on clay minerals and methods. Oddly enough I found the most useful resources now that I am closing in on finishing my project!

Anyways, I decided to share the best online resources. The first I found only last week. It is the YouTube channel of the Virtual Soil Science Learning Resources group initiated by Dr. Maja Krzic (UBC) in 2004. Their channel hosts dozens of short videos by soil experts on anything a starter might look for. I especially found the videos about methods, e.g. determining cation exchange capacity or salinity, the most useful.

22 August, 2015

Paper: Dolomite formation in non-marine bentonite deposits


On August 6th the first of three publications that are a part of my doctoral research was finally published online in the Clay Minerals Journals at GSW (alternatively via ingentaconnect - abstract also available on RG). The study explores the role of authigenic carbonate formation during bentonitization. We used a combination of X-ray diffraction, micromorphology (based on thin-sections and SEM) and stable isotope analysis to investigate bentonite-associated dolomite and calcite formation.

Bentonites in the Upper Freshwater Molasse formed from practically Ca- and Mg-free, calc-alkaline, rhyolitic air-fall tuffites. The presence of abundant authigenic dolomite (one deposit is capped by 1 m thick dolomite horizon) was a major surprise, and we extensively used XRD to confirm the mineralogical composition. The combination of methods enabled us to distinguish both dolomite-rich and calcite-rich pedogenic, palustrine and groundwater facies within bentonite deposits. The figures taken from the paper illustrates some of the carbonate microfabrics.

The carbon and oxygen stable isotope results (figure from paper shown below) were essential in resolving formational environments. The carbon isotope ratios imply a C3-plant-dominated carbon source with small additions from dissolved carbon from groundwater and atmospheric carbon in upper "soil horizons". However, the bi-modal distribution of carbon isotope results is consistent with carbonate formation in both water-logged and non-water-logged conditions, and suggests repeated wetting and drying cycles. The oxygen isotope data the impact of evaporation and temperature on δ18OV-SMOW values of meteoric water of -7.0 to -4.8 per mil during carbonitization, and hence bentonite formation.
We concluded that dolomitization was a syngenetic to early diagenetic process - perhaps on the time-scale of soil formation. Both dolomite and bentonite formation occurred in non-saline, non-arid and repeatedly partially-oxygenated and reducing soil and groundwater environments. That actually comes as a small surprise because carbonates were so far dismissed as unrelated to bentonite formation. It also places bentonite formation into a soil and groundwater environment, and not later diagenesis. We, however, cannot rule out that smectite formation continued after blanketing of deposits with younger sediments.

References:

M. H. Köster and H. A. Gilg (2015) Pedogenic, palustrine and groundwater dolomite formation in non-marine bentonites (Bavaria, Germany) Clay Minerals, June 2015, v. 50, p. 163-183, published online August 6, 2015, doi:10.1180/claymin.2015.050.2.0

19 August, 2015

Aesthetic calcite

Regular readers will have noticed that I like posting pretty pictures. Today, I felt like posting the next one! This time it is a calcite crystals found in the voids of a carbonate nodule from the Bavarian bentonite deposits - as usually. The picture was made purely for aethetic enjoyment.

A wonderfully smooth calcite crystal.

01 August, 2015

Mining machinery in action

During many visits to bentonite mines in Bavaria my doctoral supervisor, me, and our students usually had to arrange ourselves with active mining activity. This meant taking good care of communications with the mine manager, surveyor, and most importantly the machine operators. You do not want to get your head hit by the bucket of an excavator or run over by one of the trucks! Having a bulldozer and excavator around does of course have its benefits for taking samples and outcrop documentation. What a hand shovel will get done in 2 hours, the bucket excavator will get done in 5 minutes! So having good relationships with the mining folks will save you hours and days of tedious work! Anyways, over time, I managed to capture a lot of the machinery at work and I decided to put some of the better images online. Enjoy!

A track-driven scraper in action. Although slower they are more cost efficient in small-scale operations.

The bucket excavator was so kind to excavate the base of the bentonite deposit for us.

Same as above. Taking a break.

Hauling and loading of Volvo trucks with overburden.

Preparing the terrain and removing overburden with bulldozers and another bucket excavator.

Hauling and loading again with the aim of clearing a nice profile for us. View from the freshly excavated pit.

26 July, 2015

Fithian Illite, lllinois, US

Fithian Illite at Salt Fork of Vermilion River near Fithian, IL

Illite is one of the most frequent clay minerals and is an important constituent of many sedimentary rocks. It was named after the state of Illinois, United States, by Grim, Bray and Bradley in 1937. The type locality of the Late Pennsylvania Fithian cyclothem is also the type locality of the clay mineral illite. In October 2013 I had the chance to actually visit the locality when participating in the 50th Anniversary Annual Meeting of the Clay Minerals Society at the University of Illinois at Urbana-Champaign. The trip was lead by Stephan Altaner and Shane Butler.

The image I made shows the succession of Pennsylvanian mudstone or underclay with carbonate concretions, and of course illite, towards a fossil soil horizon. Besides illite the mudstone also contains chlorite, kaolinite, illite-smectite, quartz and jarosite from pyrite weathering. The bituminous Flannigan coal is about 40 to 50 cm thick. Above it is a thinly bedded black shale and then marls & limestones. The sandstone units above and below the described sequence are not visible in the picture or obscured by the trees.

Fithian cyclothem with illite-bearing mudstone
Reference:
Altaner & Butler, 2013: Geologic Field Trip to the Fithian Illite, Fithian, Illinois Guidebook for field trip held on October 10, 2013 in conjunction with the 50th Anniversary Annual Meeting of The Clay Minerals Society held at the University of Illinois at Urbana-Champaign

25 July, 2015

Let's XRD something unusual: What's in my ghassoul?

X-ray diffraction is an incredibly versatile method not restricted to rocks and minerals. While the material scientist and engineers among you might use it to examine concrete or thin-films in photovoltaics, I tried it on cosmetics from the organic supermarket. Actually, I picked a ready-to-use mixture of ghassoul that can be used as a shampoo. I will not disclose the brand or producer. But as far as I can tell from my very quick-and-dirty analysis: what is written on it - it is actually inside! But I make no guarantee!

Ghassoul is a natural clay rock found in the Atlas mountains of Morocco. Depending on the sources and literature it is either a bentonite, a stevensite-rich or a hectorite-rich clay rock. The clay has been mixed with oils, alcohol, and perfumes. So I was sceptical about identifying anything. I put the clay into a cup of water, stirred, and pipetted a few drops onto a glass slide to make an orientated texture mount. That is usually done for the clay fraction less than 2 microns and therefore probably only qualifies as playing around in the lab. 

The XRD trace was recorded from 2° to 70° 2θ and CuKα radiation. Measuring time is rather short with about 50 minutes. The characteristic peaks for several minerals are visible in the XRD trace. There is a large smectite 001 peak at about 14 Å and a small peak at about 1.52 Å characteristic for trioctahedral smectites. So this very likely contains a trioctahedral smectite such as hectorite, stevensite or saponite. I do not know if and how oils and perfumes intercalate into the smectite interlayer but assuming that they have not, the 001 position indicates an interlayer dominated by divalent cations, most likely Ca and Mg. If there would be Na or even K it would rather be around 10 to 12 Å.

XRD trace of ghassoul smear slide.
A lot of other peaks are visible at higher angles. I only marked the most important main peaks of easily recognisable phases, such as quartz, feldspar, calcite, mica, dolomite, and some kaolinite or chlorite. The later two are hard to distinguish without further work. There also are some peaks that would require more work, perhaps they are pyrite/hematite, more feldspar, etc. 

So, the ghassoul really does look like it contains natural clays and minerals! I cannot, however, determine if this is the natural composition or if minerals have been added.

Finally, as the stuff is very expensive I am putting it to practical trials on head and beard. :-)

13 July, 2015

Euroclay 2015

Yesterday I returned from the EuroClay 2015  in Edinbugh, UK. It was one of the largest clay science meetings in years - with over 500 participants. Topics ranged from rad waste, pharmaceutical applications to out of this world topics on Mars and its clay mineralogy. I, however, had the honor of starting the bentonite session on July 9th with a talk about boron and boron isotopes in smectites from bentonite deposits. Despite a slight fear of public presentations it went absolutely fantastic and I received plenty of good feedback from scientists coming from Italy, Germany, Greece, the UK, the US, and many others. It was great to hear positive but honest feedback. I really enjoyed the comments that specifically addressed what the audience really liked. The meeting was also well organised and the conference dinner location was excellent.

Some impressions:
Our latest results...

...me summing-up what we now know.

Edinburgh castle.

Salisbury Crags.

Centre of Edinburgh.

24 June, 2015

Guest posting on the Traveling Geologist

Today I have a guest post about my doctoral research on Bavarian bentonite on the Traveling Geologist blog!

Go take a look at their interesting and informative blog. It is host to a large collection of geologist's impressions.

Thanks a lot for the opportunity!

06 June, 2015

Dolomite growing inside mica

Working on the electron microscope always gets me excited. Exploring the world of the tiny and tinier is both scientifically interesting and aesthetically rewarding. The image shows authigenic dolomite crystals growing between the sheets of a detrital mica (probably muscovite) flake in Bavarian bentonite. Enjoy!
Dolomite rhombs growing and destroying mica.

01 June, 2015

Elements Magazine: The Lost Geologist in the Students Research Spotlight

The June issue of Elements magazine appeared online today. All contributing geoscience societies have a Society News Section. In June, I have the great pleasure of being one of three students portrayed in the Clay Minerals Society Student Research Spotlight, showcasing a short discreption of my doctoral work. This link leads directly to the CMS News Section.

31 May, 2015

Zeolite pirate face

A potential spin-off of the almost finished doctoral project are lithium-rich hectorite deposits. Thanks to cool people at the Bundeswehr (German Armed Forces) University Munich I recently had the opportunity to use their Environmental Scanning Electron Microscope.

Here is what we found - a zeolite pirate face!

Zeolite pirate face composed of tiny, lath- and brick-shaped zeolite.

28 May, 2015

Short anatomy of a bentonite deposit

Bentonite deposits in Bavaria, Southern Germany, are located in a 10 by 40 km wide belt between Mainburg, Moosburg and Landshut, roughly northeast of Munich. Among non-geologists the region is more famous for its hop fields, and bentonite mines are scenically located between hop and gently rolling green hills. Underneath the hop, bentonites are hosted in fluviatile-lacustrine gravels of the Nördlicher Vollschotter (Northern Main Gravel) unit.

In the image you see one of the many small, lenticular bentonite deposits. This particular deposit was  part of my last Bachelor student's thesis in 2014 and the samples were a good test for a portable X-ray fluorescence unit a few months later. The pit nicely shows how a thin lenticular bentonite is hosted in micaceous footwall sands and hanging-wall fluviatile sand and gravels of the Nördliche Vollschotter. The region is blanketed by Quaternary loess of high agricultural value.

Bentonite in unconsolidated Miocene sediments. Bucket excavator and Bachelor student (left from center) for scale.

The sand and gravels are themselves a wonderful sedimentogical units with textbook-like depositional structures. Igneous, metamorphic and sedimentary clasts are derived from Mesozoic, Cenozoic and crystaline rocks of the Bavarian Forest, Swabian Alb, and from the Alps.

Cross-cutting sedimentary structures in fluviatile, sand-rich gravels. A sharp erosional contact separates loess and gravel.

In this deposit gray-greenish bentonite is sandwiched between thin floodplain marls and hanging-wall gravels. Upper contacts in bentonites are almost always erosional in nature. What is very unusual in Bavarian bentonite deposits is that they contain abundant authigenic dolomite. Two up-coming publications are dealing with those, and I can already reveal that dolomite and calcite formation are syn- to very early postgenetic to bentonitization. Using micromorphological, carbon and oxygen stable isotopes we can also show that bentonite-associated carbonates formed in pedogenic, palustrine and groundwater settings.

Bentonite, rather unspectacular, sandwiched between marl (part of the sand unit below) and gravel.

Last but not least a dolomite nodule from underneath the bentonite. Most of the sediments are rich in swelling clay minerals (smectites) and show typical shrink-swell features, such as slickesides. Carbonate precipitation is often related to these structures. The outer shapes of nodules often are perfect imprints of slickensides surfaces.

A medium-sized dolomite nodule from the marl bed. Macroscopically identical to those in bentonite.

17 May, 2015

Arizona impressions

Early in 2014 I applied for a student research grant at the Clay Minerals Society. I asked for a boron isotope campaign to be partially funded. To my great pleasure the CMS granted enough support to fund a visit to the Arizona State University SIMS facility im Tempe, AZ. So in august 2014 I spent a week in the basement doing SIMS measurements. Besides wonderful data I also brought back home a suitcase full of pictoral landscape impressions that still feed my desire to return. 

First evening in Tempe, AZ. A lovely view from my appartment.
SIMS lab. Time spent: 7 days watching the screens.
After several days of countless boron isotope ratio measurements I sneaked out. Took a car and drove north!
On the interstate. Endless driving. A very meditating activity.
Grand Canyon South Rim! Worth every hour on the road! Note the perfect weather for monsoon season.
If you watch closely you will find the Colorado river in the lower left.
Making contact to the locals.


After spending a long detour...
...I got to see my first hectorite mine! The owner was so kind to meet-up with me. We spent an hour talking and filling  sample bags (Which almost got me arrested a few days later. But I will share that anecdote another time).

The mine owner recommend a country-side route away from the interstate to return to Phoenix. No other car for two full hours. Amazing!

The boron isotope data will be presented at the EuroClay2015 in Edinburgh, Scotland. 

The hectorite has since been XRDed, cut into thin-sections, and looked at by ESEM/EDX. 

Thanks for watching!

15 May, 2015

Returning to life

This blog has been idle for eons.

The doctoral thesis and project is in its final year. My first publication has been accepted in early 2015 for publication in the Clay Minerals Journal. The 2nd publication is in the pipeline. Data for the 3rd is complete. Searching for a new job. Before christmas, I hope, I willl defend my thesis. Then move on to new adventures in geoscience - or should I say clay science?

I ought to change the blog name. No longer feeling lost!

Enough for today. Blog is alive again!