Project

Discipline

Infrared spectroscopy; Deep water cycle; Petrology; Volcanic glasses; Nominally anhydrous minerals; Diffusion

Lead
Wasser spielt eine fundamentale Rolle in biologischen als auch geologischen Prozessen und ist von enormer Wichtigkeit für die Entwicklung des Lebens auf der Erde. Wasser tritt nicht nur als Flüssigkeit oder Eis auf, es kann auch in die Struktur von Mineralien eingebaut werden und ist in dieser Form stabil bis in sehr grosse Tiefen von mehreren hundert Kilometern. Dieses Wasser ist von grösster Bedeutung für Stoffkreisläufe im Inneren der Erde welche sich über Jahrmillionen abwickeln. Die Analyse von Wasser in Mineralien und Gläsern, besonders wenn es nur in einer Quantität von einigen Mikrogrammen pro Gramm Mineral vorkommt, ist extrem schwierig. Im Rahmen dieses Projektes wird ein Labor an der Universität Bern eingerichtet mit dem man Spuren von Wasser in Mineralien und vulkanischen Gläsern bestimmen kann.
Lay summary
Ziel dieses Projektes ist die Bestimmung von Wasserstoff als Spurenelement in geologischen Materialien. Wegen der geringen Masse ist es unmöglich Wasserstoff mit Röntgenfluoreszenzmethoden nachzuweisen, welche üblicherweise gebraucht wird für Mineralanalysen. Es ist jedoch möglich Schwingungen zwischen Wasserstoff- und Sauerstoffatomen mit Hilfe von Infrarotspektroskopie zu erfassen. Im Rahmen dieses Projektes wird ein Infrarotspektroskopie Labor aufgebaut in welchem Mineralien und Gläsern mit einem speziellen Mikroskop untersucht werden können. Es werden dabei Methoden entwickelt, um das Wasser in diesen Materialien zu quantifizieren. Folgende Fragestellungen sollen dann anschliessend mit dem neun Labor erforscht werden: 1) Wie kann Wasser entlang von Subduktionszonen in den Erdmantel transportiert werden? Wieviel Wasser ist in Mineralien des Erdmantels enthalten? Wie verändern Magmen ihren Wassergehalt durch den Aufstieg an die Erdoberfläche? Kann die Diffusion von Wasser in Gläsern und Mineralien gebraucht werden als Stoppuhr für geologische Prozesse? Zudem dient das Labor auch um Standards für die Wasseranalyse von Festkörpern mit der SwissSIMS zu entwickeln.

Direct link to Lay Summary

Last update: 11.11.2015

Communication	Title	Media	Place	Year

Number	Title	Start	Funding scheme

It is well known that water plays a crucial role in all biological processes and is a key ingredient for the initiation and evolution of Life on planet Earth. Water is also essential in all surface related geological processes from weathering to sedimentation. Less intuitive but of similar importance, water is also involved in many geological process acting in the deep Earth. The melting temperature of rocks is lowered by several hundred degrees in the presence of water and the amount of melt produced increases as a function of water content. Water in magmas has a huge influence on the way magmas flow. Water-rich lavas have the potential for catastrophic eruptions whereas volcanos with water-poor lavas represent a much lesser natural hazard. Water can be stored in the interior of the Earth in the form of hydrous minerals such as biotite, muscovite, serpentine, chlorite and amphibole, highly influencing the strength of the rocks. However, hydrous minerals have a limited pressure-temperature stability and thus it remained enigmatic how water could be stored in the mantle below ~ 100 km depth. The discovery that water in the form of OH can be incorporated into nominally anhydrous minerals (NAMs) such as olivine and pyroxene completely changed the way we look at the deep water cycle. Tiny amounts of water (a few parts per million in weight) in mantle rocks can have profound influence on a wide range of physical properties such as electric conductivity, strength of the rocks, element diffusion and propagation of seismic waves. It is likely that the involvement of water in all these geological processes is key to the unique plate tectonic regime operating on Planet Earth compared to other planets. Despite the importance of water in geological processes, microanalysis of water in geological materials has proven to be a challenge. X-ray based methods such as the electron-microprobe are unable to detect the weak X-rays emitted by hydrogen atoms. Instead H is best measured by spectroscopic methods such as infrared and Raman spectroscopy. Fourier Transform Infra Red (FTIR) Spectroscopy coupled to a microscope is the most powerful micro-analytical technique to quantify trace amounts of water in minerals, to determine volatile contents in volcanic glasses and experimental run products. Infra red spectroscopy is based on the absorption of energy by molecules that twist, rotate or vibrate. The energy of absorption contains information about the bonding energy and thus local structural environment of atoms. IR light is particularly absorbed by bonding including the light elements C-O-H-N, and represents the main analytical technique to study the incorporation of these elements in solid matter. Absorption not only provides information on the structural context (qualitative information) but, when properly calibrated, it can reveal quantitative information as well.In this proposal I ask a SNF contribution to establish a FTIR laboratory that includes a spectrometer coupled to a highly sensitive microscope equipped with a mapping stage to analyse trace amounts of water in geological materials at the Geological Institute at the University of Berne. To my knowledge this would represent the first such facility fully dedicated to geosciences in Switzerland. FTIR spectroscopy will be important for projects including water in the deep Earth, volatiles in volcanic glasses and melt inclusions, diffusion studies as well as the role of water in the rheology of rocks. Thus the facility will serve a wide Earth science community in the fields of magmatic and metamorphic petrology, volcanology, ore deposits and geochemistry and it might be also useful for other disciplines such as archaeology. Calibration of standard materials by FTIR for water is a prerequisite for successful water analyses at higher resolution at the SWISS SIMS, adding additional strategic value to a FTIR laboratory. Given the wide interest on the influence of water on geological processes, such research might lead to a Centre of Competence at the Institute of Geological Sciences in Bern. Considering the key role of water in the evolution of Planet Earth, such a facility would fit perfectly into the broad research topics of “Matter and the Universe”, especially in the fields of development and habitability of planets and the origins of life, which have been individuated as one of main research strategies for the future at the University of Bern.