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


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.

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.

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.")