13 October, 2016

Bentonite has its faults, too.

While writing and compiling the doctoral thesis (two chapters complete, hurrah!) I have been screening through many photographs taken during fieldwork. This one was pretty nice because it shows a tiny fault! The fault is almost vertical, strikes almost North, shows almost no displacement (arrows) - recognisable only by relict sedimentary (too pale to be seen on the picture) layers and the occasional root molds (white dotted lines), amounting to maybe 1 cm of movement. Unfortunately this was the only occasion in 5 years of work that I managed to find a fault in the Bavarian bentonite, and I almost missed this one because I thought that it was related to the on-going mining activities.

Front view of the tiny fault in silified bentonite. Hammer for scale. :-)

13 August, 2016

A view of the geothermal plant Oberhaching-Laufzorn

One of the fascinating aspects of our profession is that the geosciences, especially their practical applications, can often be found (almost) in front of your home. Enjoying today's excellent summer day and a bicycle tour through the south-eastern outskirts of Munich unexpectedly lead me to a geothermal plant of Erdwärme Grünwald at Oberhaching-Laufzorn. The plant entered full production capacity in December 2014 and is used for district heating, and minor power generation.

The doublet wells reach a production depth of 4032 m and a re-injection depth of 4453 m below surface. The well taps into the karstified Upper Jurassic Malm aquifer and has a capacity of 140 to 160 l/s at 128 to 130°C; generating about 20 to 50 MW of district heat.

Field impressions:
Rural outskirts of Munich
A look in the other direction reveals the geothermal plant!
Entry and main building.
That is where the thermal waters reach the surface!
Just a minute further down the road. Rural Munich No. 2!

Details and information taken from the local signs at the goethermal plants and the following websites:

Erdwärme Grünwald

Informationsportal Tiefe Geothermie

27 June, 2016

CMS workshop lectures: FILLING THE GAPS – FROM MICROSCOPIC PORE STRUCTURES TO TRANSPORT PROPERTIES IN SHALES

I have been very busy with another publication as part of my doctoral thesis during the last weeks/months. So posting was quiet here and will probably continue to be so for a while.

But I recently noticed another open access resource related to clay science that might be of interested especially to the folks interested in porosity, permeability and fluid flow in shales and clays. This is the CMS Workshop Lecture series vol. 21: Filling the gaps – from microscopic pore structures to transport properties in shales. It is freely available on the CMS website, just follow the link above.

Here is an except from the preface:
This CMS Workshop Lecture Series (WLS) volume is intended to give a summary of the current state-of-the-art of different spectroscopy and microscopy methods, as presented during a workshop held in conjunction with the EUROCLAY 2015 conference in Edinburgh, UK, on the 5th of July 2015. This workshop was initiated by the NEA Clay Club, The Clay Minerals Society, and the Euroclay conference series. This EUROCLAY 2015 workshop is a continuation of the very successful workshop “Clays under Nano- to Microscopic resolution”  which took place from 6th–8thSeptember 2011 in Karlsruhe and documents new developments and the progress made over the past four years concerning research in low-permeability, clay-rich, geological formations (NEA-CLAY- CLUB, 2013). The workshop also provided an excellent opportunity for exchange of knowledge with research communities concerned with the safe long-term management of radioactive waste within argillaceous sediments, and with shale gas and oil exploration.
Enjoy!

15 April, 2016

April reading: isotopes, bentonite, dolomite, clay minerals and zeolites.

Several interesting articles appeared that I find worth and fun to read. The articles are focused on radiogenic and stable isotope compositions of bentonites as well as on dolomite formation associated with clays and zeolites in volcanic ash and soils. The research is nicely situated in the vicinity of my doctoral studies and own interests. So it is a good practise for reading and writing! I hope you enjoy the short and personal list!

Warr et al. (2016) Constraining the alteration history of a Late Cretaceous Patagonian volcaniclastic bentonite - ash - mudstone sequence using K-Ar and 40Ar/39Ar isotopes. Link 

Smectites are often considered unsuitable for radiometric age dating because they only incorporate tiny amounts dateable elements, most of which are easily exchangeable. Warr et al. explore the K-Ar and 40Ar/39Ar dating of smectite from sodium bentonite of Lago Pellegrini in Northern Patagonia, Argentina. They demonstrate that it is possible to date smectites if radiogenic Ar is retained in low-permeability rocks such as bentonites. Results tentatively indicate that a fairly long time (13-17 Ma) was needed for complete alteration. I try something similar using the Rb-Sr system using smectites from bentonites in Southern Germany. Maybe this can be combined...

Bauer et al. (2016) Stable isotope composition of bentonites from the Swiss and Bavarian Freshwater molasse as a proxy for paleoprecipitation. Link

Smectites might be problematic to use in radiometric dating but they are good for reconstructing the stable isotope composition of e.g. the water they formed in. This is especially true for smectite formed in-situ from the alteration of volcanic ash and preserved as bentonite. The isotope fractionation of oxygen and hydrogen is easily affected by temperature, evaporation, or other factors. Bauer et al. utilise this for paleoclimate and -topography reconstructions in the Swiss and German Foreland basin using bentonites from Switzerland and Germany, including some from my own research area in Bavaria. Again an exciting read in my opinion!

Alonso-Zarza et al. (2016) Chabazite and dolomite formation in a dolocrete profile: An example of a complex alkaline paragenesis in Lanzarote, Canary Islands. Link

Zeolites and dolomite are rare minerals in ancient and modern soils that require special conditions of formation. Alonso-Zarza et al. investigated a chabazite- and dolomite-bearing soil profile formed on basaltic rocks of Lanzarote Island with to elucidate its formation conditions, e.g. vadose vs phreatic, Mg distribution, and water sources. The lithostratigraphic distribution of dolomite in the lower and calcite in the upper parts of the profile together with the stable (C and O) and radiogenic (Sr) isotope composition nicely illustrate how carbonate formation was brought about by Mg from local basalt and meteoric water; with chabazite formed during drier, more alkaline periods.

Cuadros et al. (2016) Chemical and textural controls on the formation of sepiolite, palygorskite and dolomite in volcanic soils. Link

This study is about the formation of dolomite and Mg-bearing clay minerals such as palygorskite and sepiolite, and some smectite, in volcanic soil on Gran Canaria Island. Cuadros et al. examined a profile with predominantly sepiolite and calcite towards the top, and palygorskite, dolomite and some smectite towards the base. The dolomite formed related to sepiolite/palygorksite and volcanic ash particles while calcite is located in inter-particle pore-spaces. The study emphasises, among other issues, the role of Mg and Si transported by solutions within the profile but also within volcanic grains. It is a nice addition to the growing number of papers on dolomite formation in soils and terrestrial settings.

Note: Summaries are neither complete article reviews nor guaranteed to be free of misunderstandings. 

07 April, 2016

Online clay science resources: Glossary & Images

As stated in a previous post I like to share freely accessible clay science resources. Today, I want to point out two of them that are immensely useful for figuring out how to call that thing correctly when writing, studying, illustrating, or teaching.

One is the Clay Minerals Society Glossary of Clay Science Project. An ongoing effort to compile a glossary of terms "as used in clay science". The small site also has word- and PDF-file versions for download. I find this very useful for non-native speakers (like me) because not all terms are easily translated.

The other one is more eye-pleasing. It is the Images of Clay archive of the Mineralogical Society of Great Britain and Irland and The Clay Minerals Society. This is a collection of images of (clay) minerals available for non-profit purposes, such as teaching - and I suppose blogging. I especially like the time lapse video of exfoliating vermiculite.

video
Image (Video) reproduced from the 'Images of Clay Archive' of the Mineralogical Society of Great Britain & Ireland and The Clay Minerals Society (www.minersoc.org/gallery.php?id=2.")

12 March, 2016

Old plastic to clay science: super-size Atterberg cylinder

Size fractionation for sediment and clay minerals analysis is done using a centrifuge or Atterberg sedimentation cylinder. Both methods rely on the Stokes' Law to determine the settling time. The usual size fraction for clay analysis is < 2.0 microns. The settling time is determined by the viscosity of the medium - usually a suspension prepared with demineralised water - as well as its density and that of the material (e.g. clay, sand). Densities of quartz and water may be used for general purpose analysis but should be adjusted if high-quality results are needed. The viscosity is temperature dependent. Size separation must be done at constant temperature (e.g. 20°C). Usual set-ups consists of multiple Atterberg glass cylinders of 25 to 30 cm settling height. A typical set-up is shown below.
A dozen of Atterberg cylinders and glass jars to catch the < 2.0 micron suspensions.
Ordinary Atterberg cylinders have a diameter of roughly 5 to 6 cm. This is great for daily operations. But sometimes you need more and want to produce a concentrate of the sand/silt/heavy mineral fraction, as well. Sadly, swelling clays (e.g. bentonites) are awful to sieve either wet or dry. Sieves will be clogged fast. So, with the help of the department technician and using some old, left-over plastic scrap we built a super-size Atterberg cylinder. It has the same settling height but a diameter of 16 cm! This cylinder can hold half a bucket (~ 5 litres) of clay suspension. You can see the super-sized cylinders and the results of the test run in the image below.
Test run of super-sized Atterberg cylinder using 500 g of bentonite. The bentonite was dispersed in several litres of water.
It is great for separating and keeping tens of grams of sand, silt or heavy mineral fractions that can afterwards be sieved without hassle. The clay fractions (in the bucket) can be re-used in ordinary Atterberg cylinders for a more controlled setting. Admittedly, it has a few downsides. Controlling the settling speed of fine fractions is problematic. The suspension must be poured in and cannot be shaken. The internal locomotion of currents  hinders sedimentation. The prototype has the markings on the inside. We have made a replacement from transparent Plexiglas that I will try to get a picture of in action soon.

Costs: A few hours of playing around.

29 February, 2016

Swelling clays and X-ray diffraction

Introduction

Recently, I have been asked by a friend to guide him through a crash course in X-ray diffraction and the identification of swelling clay minerals. Swelling clay minerals are a major issue in formation damage for petroleum/natural gas production but also for natural buildings stones and construction. Since I am ever so often asked how to identify swelling clays by friends or colleagues, I figured that it would make a great blog!

Warning: I keep this very simple. No exceptions, no cutting edge tricks, no rare minerals. Every lab will do things a tiny bit different. So this might not be the exact way you saw it elsewhere. If you are unexperienced and want to do it yourself, you should consult the sources listed at the end of the blog post before proceeding.

Clay minerals

Geoscientists use the term clay in two different contexts that may cause confusion. First, clay sensu lato is any material with a particle diameter < 2.0 µm. So, anything with a grain size smaller 2.0 µm is clay in a physical sense. Second, and more important for the clay scientists, clay sensu strictu is a group of phyllosilicates (Fig. 1) composed of tetrahedral and octahedral sheets. The sheets are the building blocks of layers. There are 1:1 layers and 2:1 layers: meaning a tetrahedral sheet + an octahedral sheet, and an octahedral sheet sandwiched in between two tetrahedral sheets.
Fig. 1: An overview of the classification of clay minerals. Source: Bergaya and Lagaly (2006) General introduction: Clays, clay minerals, and clay science. In: Handbook of Clay Science, Edited by F. Bergaya, B.K.G. Theng and G. Lagaly, Developments in Clay Science, Vol. 1
Based on the site occupancy of the octahedral sheet clay minerals can also be subdivided into di- and trioctahedral. While the first have 2 out of 3 octahedral positions occupied with a cation, the later have all 3 positions occupied with a cation, e.g. Al, Mg, Fe, Li or others. Natural swelling clay minerals are hydrated 2:1 clays with an expandable interlayer such as smectite, interstratified smectite in "another mineral", and vermiculite.

Certain clay minerals have an electrical charge due to substitutions in the octahedral sheet. The charge is neutralised by additional cations (e.g. Na, Ca, Mg) located in the interlayer space between each 2:1 layer stack (Fig. 2). Water (and other useful substances) can enter into the interlayer. The clay swells.
Fig. 2: Basic structure of Montmorillonite, a dioctahedral smectite and hydrous 2:1 swelling clay mineral. Source: USGS Laboratory for X-ray powder diffraction
Determining swelling clay minerals

The clay minerals have to be separated from the rest of the rock. This is usually done by gentle crushing, followed by sedimentation in Atterberg cylinders or by centrifugation. When there is no need to determine the trace element contents or exchangeable cation composition of the clay interlayer the dispersion can be enhanced by adding ammonium (pH control) or sodium pyrophosphate. It is important to keep the suspension in a neutral pH range to prevent flocculation. The < 2.0 µm or any other size fraction can be separated based upon the Stokes Law. So, we are actually working with an equivalent diameter. Doing this we obtain a clay suspension.

A few drops of the suspension are pipetted onto a glass slide and allowed to dry. This is the orientated, air-dried sample. It is measured using X-ray diffraction from 2° to 25° or to 35°2theta. Afterwards, the glass slide is placed into a small container to saturate the interlayer with ethylene glycol vapour - or other substances. The intercalation of EG in the interlayer space (Fig. 2) expands the clay lattice. This can be detected by repeating the XRD measurement. This step must be done fast (~ half an hour to one hour) because the EG will easily escape. The third step is calcination above 500°C but several other temperature steps may be used to gain more detailed information. This will cause the interlayer space to collapse. We repeat the XRD measurement a final time.

How does it looks like in the end?

The best method to immediately see and compare the results is by putting all three measurements into one image. Most XRD devices will have their own internal computer program for data comparison. Alternatively, this can be done using commercial or non-commercial software packages. For illustration purposes I drew three XRD traces (Fig. 3) of one of my own samples (a smectite) treated according to the above explanations and measured as air-dried, EG-solvated and calcined sample. The measurement is shown from 4 to 24° 2theta. There is a clear expansion of the d001 peak from roughly 14.3 to 17.3 Å due to the intercalation of the ethylene-glycol. The calcined sample shows the characteristic collapse of the interlayer. A careful review of the peak positions will confirm that there are no other minerals.
Fig. 3: XRD traces of an orientated, air-dried, EG-solvated, and calcined sample of a smectite. Own sample and data.

References:
Bergaya and Lagaly (2006) General introduction: Clays, clay minerals, and clay science. In: Handbook of Clay Science, Edited by F. Bergaya, B.K.G. Theng and G. Lagaly, Developments in Clay Science, Vol. 1.
Hillier (2003) Quantitative Analysis of Clay and other Minerals in Sandstones by X-Ray Powder Diffraction (XRPD)
Moore and Reynolds (1997) X-Ray Diffraction and the Identification and Analysis of Clay Minerals, 2nd edition.

Internet resources for more detailed instructions: 
USGS - A Laboratory Manual for X-Ray Powder Diffraction
The Cutting Edge - Teaching Clay Science 

16 February, 2016

Amazing geology in Peru: How I found a mythical boiling river in the Amazon - Andrés Ruzo - Ted Talks

My good Peruvian friend and geologist (thanks Jenny!) sent me a link today about a Ted Talk featuring Andrés Ruzo, another geologist, and his search for a mythical boiling river in the Amazon far from any volcanic centre. I liked the talk a lot. Reminds me of my own but not quite that adventureous times in Peru... :-)


13 February, 2016

Top 3 posts 2015

Today I was reviewing my blog posts of 2015 in search for ideas for what topics to write more about. Going through the statistics I found three blog posts that received the most of attention since restarting my blog in 2015. So, I here are the Top 3 posts 2015!

Most viewed was the rather short Online clay science resources post with 2050 views. Seems like there is a need for such information out there! It is great to see that people actually use this. I will try to find and post more clay science resources. If you know some that you can recommend - let me know!

A very close second comes Paper: Dolomite formation in non-marine bentonite deposits with 2027 views. This is a short introductory post on the first publication of my doctoral research. I have more manuscripts in the pipeline, and hope to be able to showcase more of my own work in the future once I got it published. Until then I might have to recycle some old field trips.

The third spot is taken by Old fieldwork pictures from Peru with 1761 views. Just as myself everyone else properly also likes fieldwork pictures and looking at fantastic geology. Sadly, I took very few pictures in those days. I had just bought my first clumsy camera. But I might find a handful of interesting pictures in my back-up harddrive!

Looks like I ought to write more about online clay science resources, my own work and lots of fieldwork pictures! :)

29 January, 2016

Open Access issue in Clay Minerals

Suvrat recently pointed out an open access collection of papers on carbonate sedimentology. Just a few days ago the Clay Minerals Journal of Fine Particle Science (short Clay Minerals) also published an open access issue with a collection of 12 papers from the 7th Mid-European Clay Conference, Dresden, Germany in 2014. The meeting was organized by the German-Austrian-Swiss Clay Group (DTTG). Currently the OA issue seems to be only accessible on ingenta (see link above) but not on GSW. In the editorial the editors summarize the great variability in clay science research from the importance of clays in geotechnical engineering, hydrocarbon production, CO2 and radioactive waste disposal and more classical fields of mineralogy, diagenesis and analytical methods.

From a quick skim through the table of contents, editorial and abstracts all papers appear to be a good read. Though from a purely personal perspective reflecting my own research interests in diagenetic processes, clay mineralogy, and industrial minerals, I find the following papers the most interesting - and I am looking forward to some good (I assume) reads over the weekend.
Wilkinson 2015 Does the nucleation of clay minerals control the rate of diagenesis in sandstones?

Warr & Ferreiro Mählmann 2015 Recommendations for Kübler Index standardization

Garcia-Valles et al. 2015 Kaolin from Acoculco (Puebla, Mexico) as raw material: Mineralogical and thermal characterization
Here is a link the full table of content.

09 January, 2016

Reynolds Cup 2016

Word spread to me that the deadline (January 22nd) for sending out samples for the Reynolds Cup 2016 of the Clay Minerals Society is nearing fast - and that there still are free positions to participate! The Reynolds Cup is a biannual round-robin for qualitative and quantitative phase identification in complex, artifically mixed samples resembling natural, usually clay-rich, rocks. Any analytical method is allowed to be used but the amount of samples is always very small. Although I have not yet partaken myelf, I have personally enjoyed presentations by various previous winners and participants of the Reynolds Cup. It is definitely a round-robin to test your skills to the fullest! The winners always organise and set-up the next Reynolds Cup. Rules on particiption are strict - so read carefully!

Die Beteiligung besonders aus Deutschland-Österreich-Schweiz soll wohl noch zu wünschen übrig lassen!

Here is the original announcement from December 10th, 2015:
REYNOLDS CUP ANNOUNCEMENT via claytalk announcement

Dear colleagues,
the 8th biennial Reynolds Cup competition for quantitative mineral analysis is now open. You can register your interest in participating the contest by sending an email to Reinhard Kleeberg . Information about the competition including guidelines and previous winners can be found at
http://www.clays.org/SOCIETY%20AWARDS/RCintro.html. The competition is free for all to enter, however, those that are not members of the CMS are encouraged (but not obliged) to become members (see http://www.clays.org/MEMBERSHIP/MemberRates.html for details).


Please use the following format when registering:
Subject: Please put "Reynolds Cup 2016 registration" in the subject line in your email request.

In the body of the email please put the following information:
Name:
Institution/organization:
Shipping address: (that works for DHL/Courier delivery, e.g. physical
address not Postal Box)
Phone number (for delivery):
Email address:

A total of approximately 90 sets of samples will be available for
distribution. Each set comprises three samples of approximately 4 g with
mineral mixtures commonly found in clay bearing rocks. All sets of
samples will be distributed in the order of registration. Samples are
expected to be shipped at January 22nd 2016 with the deadline for
submission of results by April 8th 2016. The top three contestants with
the most accurate results will be announced at the 53rd Annual meeting
of the Clay Minerals Society (June 5-8, 2016, Atlanta, Georgia).

Only the names of the top three contestants will be published. The names of the other participants will remain strictly confidential.

The competition is open to anyone interested in quantitative mineral analysis, with particular emphasis on clay mineralogy. Because of the popularity of the Reynolds Cup and the enormous amount of work put into its preparation, potential participants are strongly encouraged to plan ahead and only request samples if they are sure they can complete the analysis and return results to the organizers by the due date. Those who request samples and do not send in results or fail to return the samples unopened WELL BEFORE the due date will not be eligible to
participate in future Reynolds Cups.

A waiting list will be kept to offer returned samples to other potential participants.

To ensure an even wider exposure, we encourage you to forward this
announcement to your national mailing lists and mineralogy associations,
colleagues and friends who might be interested in participating.

We look forward to your participation!
Sincerely,
Reinhard Kleeberg
Reynolds Cup 2016 organizer

Additional information:

Introduction

Rules

Winners

06 January, 2016

Hello 2016

Hello 2016! I hope you all had a merry christmas and a blast of a new years eve! This is a rather personal start into 2016 post. The end of my doctoral thesis project is near. 2016 will see a lot of exciting, important, and life-changing challenges and opportunities. One way or another I will write a lot, finish my doctoral studies, defend my thesis, publish/submit two papers related to my thesis, find a lot of money, write a lot of job applications, finally find a job, move, find a place to live, start a paper on my pet research topic, find funding and support to turn my pet research topic into a real research topic, and while doing all of that I will try to stay a normal human being.

The year began successful: I did not make make a resolution! The first week of 2016 therefore was full with success. I began building/reseaching a literature database for another up-coming project (aka downloading 50+ papers), gave meaningful file names to existing literature collections (extensive use of the rename file function), actually read one paper (4-pagers count), installed Profex for Rietveld-refinement of XRD data (and since wonder how it calculates that chemical composition...), and looked into the manuscript and supervisor comments of my next paper (reading the "publication ready" parts does count).

I am looking forward to defending my doctoral thesis. I am also looking forward to getting out of the office and away from the computer again to do fieldwork. Regarding the blog I want to turn this into a more professional framework. It would be great to show more of what I actually do and work with - at least the parts that can be put online without worries. Having those papers out will be very good for that!