Overturned jointed non-sheared granite block emplaced on sheared non-jointed Alum shale

International Journal of Earth Sciences -     

The formation of phosphoran olivine and stanfieldite from the pyrometamorphic breakdown of apatite in slags from a prehistoric ritual immolation site (Goldbichl, Igls, Tyrol, Austria)

In this study we report P-rich olivine and the tric-calcium phosphate (TCP) stanfieldite in partially molten quartzphyllites from the ritual immolation site at the Goldbichl, near Innsbruck in the Tyrol, Austria. During partial melting, foamy patches of dark glassy material formed at the surface of the rocks and also as layers within the rocks. The pyrometamorphic rocks contain mostly the mineral assemblage olivine + orthopyroxene + plagioclase + spinel + glass. During the investigation of slag samples from this prehistoric ritual immolation site, extremely P-rich, apatite-bearing micro-domains were found. In these domains phosphoran olivine was found whose P contents are approaching the maximum P contents in olivine according to the experimental investigations of Boesenberg and Hewins (Geochim Cosmochim Acta 74:1923–1941, 2010). The textures within these domains indicate strongly disequilibrium conditions. The phosphoran olivines formed due to reactions involving apatite and the mineral assemblage of the quartzphyllites, and coexist with plagioclase and a tri-calcium phosphate phase (TCP) showing stanfieldite Ca₄(Mg, Fe²⁺, Mn²⁺)₅(PO₄)₆ composition. In terms of its chemical composition, olivine shows a wide range in composition with P ranging from 0.3 to 0.54 a.p.f.u, which corresponds to maximal 23 wt.% P₂O₅. These are the highest P-contents in olivine reported from rocks so far. The incorporation of P correlates with decreasing Si contents according to the charge balancing scheme $ 2{{\mathrm{P}}^{5+ }}+□{{\mathrm{M}}_{1,2 }}=2\mathrm{S}{{\mathrm{i}}^{4+ }}+{{\left( {\mathrm{M}\mathrm{g},\mathrm{Fe}} \right)}^{2+ }}{{\mathrm{M}}_{1,2 }} $ . Therefore P can only be incorporated in combination with a vacancy on the M_1,2 position. Micro-Raman spectroscopy of phosphoran olivines indicates that these olivines can easily be identified with this method due to the strong signals of the SiO₄ and PO₄ vibrations. The external vibrations of the M_1,2 sites at low wave-numbers are more complex than for P-free olivine. This might be due to the effect of P⁵⁺ on the M₁ ²⁺ and M₂ ²⁺ positions and the formation of vacancies on these sites. Since micro-Raman investigations of the TCP phase yielded no conclusive match with a known Raman spectrum of a phosphate mineral so far, therefore it is most likely that the TCP phase is stanfieldite, whose Raman spectrum has not been obtained yet. Schematical Schreinemakers analysis in the system CaO-Al₂O₃-FeO-SiO₂-P₂O₅-H₂O shows that P-rich olivine (fayalite-sarcopside solid solution) can form from mineral reactions involving chlorite, apatite and quartz and show that the occurrence of P-rich Fe-olivines spans a large T-range but is restricted to domains with high aSiO₂. The mineral assemblage in the P-rich micro-domains shows that the formation of phosphoran olivine is not only restricted to the interaction between bone material and rocks in slags from ritual immolation sites as suggested by Tropper et al. (Eur J Mineral 16:631–640, 2004) from the immolation site in Oetz but can form locally due to the pyrometamorphic breakdown of a P-rich accessory precursor phase such as apatite.     

The missing half of the subduction factory: shipboard results from the Izu rear arc,IODP Expedition 350

IODP Expedition 350 was the first to be drilled in the rear part of the Izu-Bonin, although several sites had been drilled in the arc axis to fore-arc region; the scientific objective was to understand the evolution of the Izu rear arc, by drilling a deep-water volcaniclastic section with a long temporal record (Site U1437). The Izu rear arc is dominated by a series of basaltic to dacitic seamount chains up to ~100-km long roughly perpendicular to the arc front. Dredge samples from these are geochemically distinct from arc front rocks, and drilling was undertaken to understand this arc asymmetry. Site U1437 lies in an ~20-km-wide basin between two rear arc seamount chains, ~90-km west of the arc front, and was drilled to 1804 m below the sea floor (mbsf) with excellent recovery. We expected to drill a volcaniclastic apron, but the section is much more mud-rich than expected (~60%), and the remaining fraction of the section is much finer-grained than predicted from its position within the Izu arc, composed half of ashes/tuffs, and half of lapilli tuffs of fine grain size (clasts <3 cm). Volcanic blocks (>6.4 cm) are only sparsely scattered through the lowermost 25% of the section, and only one igneous unit was encountered, a rhyolite peperite intrusion at ~1390 mbsf. The lowest biostratigaphic datum is at 867 mbsf (~6.5 Ma), the lowest palaeomagnetic datum is at ~1300 mbsf (~9 Ma), and the rhyolite peperite at ~1390 mbsf has yielded a U–Pb zircon concordia intercept age of (13.6 + 1.6/?1.7) Ma. Both arc front and rear arc sources contributed to the fine-grained (distal) tephras of the upper 1320 m, but the coarse-grained (proximal) volcaniclastics in the lowest 25% of the section are geochemically similar to the arc front, suggesting arc asymmetry is not recorded in rocks older than ~13 Ma.     

A new occurrence of extremely rare Ferro-Chloro-Pargasite in Tudor,Ontario

International Journal of Earth Sciences -     

A representation of Jacchia's thermospheric models in spherical harmonic functions

The Jacchia models are represented in terms of spherical harmonic functions. This representation has the advantage of ease of comparison with other global theoretical and empiric models that use this mathematical form. Furthermore it is analytic, continuous and has continuous derivatives all over the globe. The representation of the exospheric temperatures shows clearly the amplitudes of the various periodic terms and uses relatively few constants. An example of a similar representation for the total mass density at a particular height and level of solar activity is given as well.     

Integral modeling and financial impact of the geothermal situation and power plant at Soultz-sous-Forêts

The science about deep Enhanced Geothermal Systems (EGS) is still an emerging process and for further spreading economics is the key of the technology. To understand the financial situation, a program for economic evaluation was developed. This software (Euronaut) is completely modularized and considers all cash flows. Projects like an EGS are wrapped into tree-like structures. Based on the results which were gained at Soultz-sous-Forêts, two configurations were designed. The first EGS configuration consists of a simplified two well (doublet) system where the dependencies of all components (mainly the reservoir, wells, pumps and the heat-to-power conversion unit) are physically and economically linked together. The realization of these dependencies and their complex interactions enable a sensitivity analysis of the borehole depth and reservoir depth, respectively. As a result, depth dependent effective costs and revenues of an EGS plant with the geohydrological characteristics of Soultz-sous-Forêts are determined. As a future development, the second configuration will adapt the actual situation at Soultz-sous-Forêts with the individual features of all four wells (GPK1 – GPK4). Then, this model can be used for all kinds of sensitivity analyses to clarify the impact of certain components or to optimize the operation scheme; e.g. the flow rates.     

Controls on soil pore water solutes: An approach for distinguishing between biogenic and lithogenic processes

Spatial and temporal variations in pore water compositions are characterized for a deep regolith profile developed on a marine terrace chronosequence near Santa Cruz California. Variations are resolved in terms of the dominance of either a lithogenic process, i.e. chemical weathering, or a biogenic process, i.e. plant nutrient cycling. The concept of elemental fractionation is introduced describing the extent that specific elements are mobilized and cycled as a result of these processes.     

Parameterization of historical earthquakes in Switzerland

Macroseismic earthquake parameters of historical events have been reassessed in the framework of the update of the Earthquake Catalogue of Switzerland ECOS-09. The Bakun and Wentworth method (Bakun and Wentworth 1997) has been used to assess location, magnitude, and, when possible, focal depth. We apply a two-step procedure. Intensity attenuation is assessed first by fitting a model with a logarithmic and a linear term, using a set of 111 earthquakes. The magnitude range is 3 and 5.8. Then, intensity to magnitude relation is developed. A subset of the 111 events, all having an instrumental moment magnitude, was used to perform this intensity to magnitude calibration. Five final calibration strategies were developed based on different intensity calibration datasets, regionalized or non-regionalized models, and fixed or variable source depth. The final assessment of the macroseismic earthquake parameters is based on an expert judgment procedure, using the results derived from all five strategies, and taking into consideration the historical knowledge available for the particular earthquake. A bootstrap procedure has been applied to assess the uncertainty of parameters. Indicative lower and upper bounds of uncertainty are derived from distributions of location and magnitude for a number of events, obtained through bootstrap sampling of the intensity field and of the single intensity values. The final uncertainties are given in terms of parameter uncertainty classes already used in previous versions of the earthquake catalogue of Switzerland.