A large number of studies of water in pyroxenes have confirmed that essentially all pyroxenes of terrestrial origin as a rule contain substantial amounts of OH, varying as a function of chemical composition and geological occurrence. The highest OH-concentrations are observed in mantle-derived samples, and it is now well established that both clino- and orthopyroxene can be considered as major host minerals for water in the mantle (e.g., Bell and Rossman 1992; Bell et al. 2004; Bolfan-Casanova 2005).

Understanding magma transport in sheet intrusions is crucial to interpreting volcanic unrest. Studies of dyke emplacement and geometry focus predominantly on low-viscosity, mafic dykes. Here, we present an in-depth study of two high-viscosity dykes (10⁶ Pa·s) in the Chachahuén volcano, Argentina, the Great Dyke and the Sosa Dyke. To quantify dyke geometries, magma flow indicators, and magma viscosity, we combine photogrammetry, microstructural analysis, igneous petrology, Fourier-Transform-Infrared-Spectroscopy, and Anisotropy of Magnetic Susceptibility (AMS). Our results show that the dykes consist of 3 to 8 mappable segments up to 2 km long. Segments often end in a bifurcation, and segment tips are predominantly oval, but elliptical tips occur in the outermost segments of the Great Dyke. Furthermore, variations in host rocks have no observable impact on dyke geometry. AMS fabrics and other flow indicators in the Sosa Dyke show lateral magma flow in contrast to the vertical flow suggested by the segment geometries. A comparison with segment geometries of low-viscosity dykes shows that our high-viscosity dykes follow the same geometrical trend. In fact, the data compilation supports that dyke segment and tip geometries reflect different stages in dyke emplacement, questioning the current usage for final sheet geometries as proxies for emplacement mechanism.

This formula, in which Cr prefers the Y site and Al the Z site, is compatible with the end-member NaCr₃(Al₄Mg₂)(Si₆O₁₈)(BO₃)₃(OH)₃O. Magnesium is disordered over Y and Z, whereas Fe and V³⁺ are ordered at Z. Ideally, chromo-alumino-povondraite is related to oxy-chromium-dravite and oxy-dravite by the homovalent substitution Cr³⁺ ↔ Al³⁺. Tourmaline chemical compositions classified as chromo-alumino-povondraite can be either Cr-dominant or Al-dominant as a result of the compositional boundaries along the solid solution between Cr and Al that are determined at ^Y+Z(Cr₅Al₂), corresponding to Na^Y(Cr₃)^Z(Cr₂Al₂Mg₂)Si₆O₁₈(BO₃)₃(OH)₃O, and ^Y+Z(Cr_1.5Al_5.5), corresponding to Na^Y(Cr_1.5Al_1.5)^Z(Al₄Mg₂)Si₆O₁₈(BO₃)₃(OH)₃O.

The double sided silicon strip detector (DSSSD) is a segmented silicon detector commonly used in the fields of high energy physics and nuclear physics. This type of detector is used for analysis of reactions produced by charged particles. This makes it well suited for a number of analytical methods commonly used in ion beam analysis (IBA), such as Rutherford Backscattering (RBS) and elastic recoil detection (ERDA). One such detector was installed and tested at Lund Ion Beam Analysis Facility (LIBAF) recently. This is a modification to the existing setup used to measure hydrogen concentrations and depth profiles. When completed it will be used primarily for geological applications.Exact knowledge of the hydrogen content is important in a number of fields, but high enough accuracy can be difficult to achieve with most methods. In IBA normally some variant of ERDA, such as the proton–proton (p–p) coincidence method is used. We describe how the p–p coincidence technique was optimized to get the most out of our experimental setup. Previously this type of spectroscopy has been performed with two detector channels. In the present setup we expand that number from 2 to 96 channels, 64 on the front and 32 on the back of the detector. The intersecting strips give 2048 distinct detector elements or 1024 possible coincidences as dictated by the reaction kinematics. This increase in complexity requires a more detailed data analysis but it rewards us with higher sensitivity and a better background suppression