Insights to magmatic–hydrothermal processes in the Manus back-arc basin as recorded by anhydrite

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 74 (2010): 5514-5536, doi:10.1016/j.gca.2010.07.004.Microchemical analyses of rare earth element (REE) concentrations and Sr and S isotope ratios of anhydrite are used to identify sub–seafloor processes governing the formation of hydrothermal fluids in the convergent margin Manus Basin, Papua New Guinea. Samples comprise drill–core vein anhydrite and seafloor massive anhydrite from the PACMANUS (Roman Ruins, Snowcap and Fenway) and SuSu Knolls (North Su) active hydrothermal fields. Chondrite–normalized REE patterns in anhydrite show remarkable heterogeneity on the scale of individual grains, different from the near uniform REEN patterns measured in anhydrite from mid–ocean ridge deposits. The REEN patterns in anhydrite are correlated with REE distributions measured in hydrothermal fluids venting at the seafloor at these vent fields and are interpreted to record episodes of hydrothermal fluid formation affected by magmatic volatile degassing. 87Sr/86Sr ratios vary dramatically within individual grains between that of contemporary seawater and that of endmember hydrothermal fluid. Anhydrite was precipitated from a highly variable mixture of the two. The intra–grain heterogeneity implies that anhydrite preserves periods of contrasting hydrothermal– versus seawater–dominant near–seafloor fluid circulation. Most sulfate δ34S values of anhydrite cluster around that of contemporary seawater, consistent with anhydrite precipitating from hydrothermal fluid mixed with locally entrained seawater. Sulfate δ34S isotope ratios in some anhydrites are, however, lighter than that of seawater interpreted as recording a source of sulfate derived from magmatic SO2 degassed from underlying felsic magmas in the Manus. The range of elemental and isotopic signatures observed in anhydrite records a range of sub–seafloor processes including high–temperature hydrothermal fluid circulation, varying extents of magmatic volatile degassing, seawater entrainment and fluid mixing. The chemical and isotopic heterogeneity recorded in anhydrite at the inter– and intra–grain scale captures the dynamics of hydrothermal fluid formation and sub–seafloor circulation that is highly variable both spatially and temporally on timescales over which hydrothermal deposits are formed. Microchemical analysis of hydrothermal minerals can provide information about the temporal history of submarine hydrothermal systems that are variable over time and cannot necessarily be inferred only from the study of vent fluids.This study received financial support from an Ocean Drilling Program Schlanger Fellowship (P.R.C.), NSF grant OCE–0327448 (W.B.), and DFG–Research Center/Excellence Cluster ‘The Ocean in the Earth System’ (W.B.

Research challenges for energy data management (panel)

This panel paper aims at initiating discussion at the Second International Workshop on Energy Data Management (EnDM 2013) about the important research challenges within Energy Data Management. The authors are the panel organizers, extra panelists will be recruited before the workshop

Brucite formation and dissolution in oceanic serpentinite

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Klein, F., Humphris, S. E., & Bach, W. Brucite formation and dissolution in oceanic serpentinite. Geochemical Perspectives Letters, 16, (2020): 1-5, doi:10.7185/geochemlet.2035.Brucite is an important, albeit elusive, hydrous mineral formed during serpentinisation, a vector of Mg from the mantle to seawater, and possibly a significant host of water in oceanic serpentinite. However, the abundance of brucite has not been quantified in oceanic serpentinite and its fate and related chemical fluxes remain uncertain. We used thermal analysis and confocal Raman spectroscopy to determine the abundance and distribution of brucite in serpentinite recovered by seafloor drilling (n = 48) and dredging (n = 22). Almost all (90 %) of the drilled serpentinite samples contained brucite. The brucite contents increased with increasing extent of serpentinisation and constituted up to 15.6 wt. % of the altered rock. In contrast, dredged serpentinites were devoid of brucite and lost 4.0 wt. % MgO on average, which translates to an estimated average annual flux of 1.3 × 1010 mole Mg and about 2 × 1010 mole alkalinity during seafloor weathering of serpentinite globally. Our data suggest that, on average, brucite stores ∼20 % of the water in unweathered serpentinite, making brucite one of the largest water carriers in slow and ultra-slow spreading oceanic lithosphere.Support for this project was provided by the Independent Research & Development Program at Woods Hole Oceanographic Institution, the US National Science Foundation (NSF Award # 1059534 and 9986135), and the Special Priority Program 1144 of the German Science Foundation (BA 1605/1-1 and BA 1605/1-2). This research would not have been possible without samples supplied by the Ocean Drilling Program and the Seafloor Samples Laboratory at WHOI

Enhanced olivine weathering in permeable sandy sediments from the North Sea – a laboratory study using flow-through reactors

The Earth’s climate is increasingly warming due to ongoing anthropogenic carbon dioxide (CO2) emissions. In order to mitigate the human-made climate change and to meet the Paris Agreement goals of limiting the warming below 2°C, active carbon dioxide removal (CDR) from the atmosphere is of great importance in addition to massive CO2 emission reductions. A possible CDR method is rock weathering and the associated dissolution of minerals in the ocean, which leads to marine alkalinity enhancement and, thus, an enhanced flux of CO2 from the atmosphere into the ocean. In the framework of the project RETAKE, a consortium of the German Marine Research Alliance (DAM) research mission CDRmare, we investigate the potential, feasibility and side effects of olivine dissolution in high-energy coastal environments where strong currents and advection of seawater through permeable sediments have been proposed to accelerate weathering of silicate rocks. Here, we present data from laboratory experiments with flow-through reactors that are filled with permeable sandy sediments from the North Sea amended with different amounts and grain sizes of olivine. Permeable sediments are generally characterized by advective pore-water flow. Under advective conditions, higher weathering rates than those found in diffusion-controlled depositional settings are expected since the reaction products are rapidly removed and the formation of authigenic mineral coatings on olivine grains is prevented. The flow-through experiments are conducted under oxic conditions whereby air-saturated natural seawater is continuously pumped through the reactors. In addition to the permanent measurement of oxygen, pH and temperature, the circulating water is regularly sampled and alkalinity, dissolved inorganic carbon, major cation and trace metal (e.g., nickel) concentrations are analyzed. Preliminary results indicate an increase in alkalinity up to 3.2 mM in the reactor with the largest amount of olivine while the alkalinity in the control reactor (without olivine addition) is close to background seawater concentrations of 2.3 mM. Similarly, highest dissolved nickel concentrations were found in the reactor with highest olivine contents added. In order to detect and characterize secondary minerals that possibly formed, the sediment/olivine mixtures are sampled after completion of the experiments and analyzed with respect to the mineralogical and chemical composition

Optimizing Notifications of Subscription-Based Forecast Queries

Integrating sophisticated statistical methods into database management systems is gaining more and more attention in research and industry. One important statistical method is time series forecasting, which is crucial for decision management in many domains. In this context, previous work addressed the processing of ad-hoc and recurring forecast queries. In contrast, we focus on subscription-based forecast queries that arise when an application (subscriber) continuously requires forecast values for further processing. Forecast queries exhibit the unique characteristic that the underlying forecast model is updated with each new actual value and better forecast values might be available. However, (re-)sending new forecast values to the subscriber for every new value is infeasible because this can cause significant overhead at the subscriber side. The subscriber therefore wishes to be notified only when forecast values have changed relevant to the application. In this paper, we reduce the costs of the subscriber by optimizing the notifications sent to the subscriber, i.e., by balancing the number of notifications and the notification length. We introduce a generic cost model to capture arbitrary subscriber cost functions and discuss different optimization approaches that reduce the subscriber costs while ensuring constrained forecast values deviations. Our experimental evaluation on real datasets shows the validity of our approach with low computational costs

Comprehension of action sequences : The case of paper, scissors, rock

Bach, P., Knoblich, G., Friederici, A. D., & Prinz, W. (2001). Comprehension of action sequences: The case of paper, scissors, rock. In K. Stenning & J. D. Moore (Ed.), Proceedings of the 23rd Annual Conference of the Cognitive Science Society (S. 39-44). Mahwah, NJ: Erlbaum.Publisher PD

Subaqueous cryptodome eruption, hydrothermal activity and related seafloor morphologies on the andesitic North Su volcano

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Volcanology and Geothermal Research 323 (2016): 80-96, doi:10.1016/j.jvolgeores.2016.04.041.North Su is a double-peaked active andesite submarine volcano located in the eastern Manus Basin of the Bismarck Sea that reaches a depth of 1154 m. It hosts a vigorous and varied hydrothermal system with black and white smoker vents along with several areas of diffuse venting and deposits of native sulfur. Geologic mapping based on ROV observations from 2006 and 2011 combined with morphologic features identified from repeated bathymetric surveys in 2002 and 2011 document the emplacement of a volcanic cryptodome between 2006 and 2011. We use our observations and rock analyses to interpret an eruption scenario where highly viscous, crystal-rich andesitic magma erupted slowly into the water-saturated, gravel-dominated slope of North Su. An intense fragmentation process produced abundant blocky clasts of a heterogeneous magma (olivine crystals within a rhyolitic groundmass) that only rarely breached through the clastic cover onto the seafloor. Phreatic and phreatomagmatic explosions beneath the seafloor cause mixing of juvenile and pre-existing lithic clasts and produce a volcaniclastic deposit. This volcaniclastic deposit consists of blocky, non-altered clasts next, variably (1-100 %) altered clasts, hydrothermal precipitates and crystal fragments. The usually applied parameters to identify juvenile subaqueous lava fragments, i.e. fluidal shape or chilled margin, were not applicable to distinguish between pre-existing non-altered clasts and juvenile clasts. This deposit is updomed during further injection of magma and mechanical disruption. Gas-propelled turbulent clast-recycling causes clasts to develop variably rounded shapes. An abundance of blocky clasts and the lack of clasts typical for the contact of liquid lava with water is interpreted to be the result of a cooled, high-viscosity, crystal-rich magma that failed as a brittle solid upon stress. The high viscosity allows the lava to form blocky and short lobes. The pervasive volcaniclastic cover on North Su is partly cemented by hydrothermal precipitates. These hydrothermally-cemented breccias, crusts and single pillars show that hydrothermal circulation through a thick layer of volcaniclastic deposits can temporarily increase slope stability through precipitation and cementation.The RV Melville work was funded by a combination of the US National Science Foundation grant OCE-0327448 and a collaborative research funding grant from Nautilus Minerals for the ABE surveys. The RV Sonne research cruise was funded through the BMBF (Grant G03216a). Additional funding, including salary support for JT, was provided by the German DFG Research Centre/Excellence Cluster ―The Ocean in the Earth System‖. WB acknowledges support from DFG research grant BA1605/4-1.2018-05-1

Optische Erscheinungen und andere ungewöhnliche Wetterphänomene auf der Wetterwarte Fichtelberg

Der Fichtelberg im Erzgebirge ist mit 1215 Metern die höchste Erhebung Sachsens und liegt an der Grenze zu Tschechien. Gemeinsam mit dem nahe gelegenen Keilberg (heute tschechisch Klínovec; 1244 m) auf böhmischer Seite bildet er den höchsten Punkt des Erzgebirgskamms. Die von Südwest nach Nordost ansteigende Pultscholle des Gebirges fällt nach Süden hin steil ins Egertal (heute tschechisch Údolí Ohře) ab. In diesem, nach Süden vom Duppauer Gebirge (heute tschechisch Doupovské hory) und dem Kaiserwald (heute tschechisch Slavkovský les) eingerahmten Tal sammelt sich bei herbstlichen und winterlichen Hochdruckwetterlagen die Kaltluft (Böhmischer Nebel). Durch diese Konstellation liegt der Fichtelberg entweder in einer trockenen warmen Luftmasse darüber (Inversion) oder er wird direkt vom Böhmischen Nebel beeinflusst, wenn dieser über den Kamm fließt. Das führt zu zahlreichen optischen Erscheinungen, die es sonst in dieser Fülle nur selten gibt. So besticht der Gipfel bei Inversionswetterlagen nicht nur mit einer außergewöhnlichen Fernsicht,Der Fichtelberg im Erzgebirge ist mit 1215 Metern die höchste Erhebung Sachsens und liegt an der Grenze zu Tschechien. Gemeinsam mit dem nahe gelegenen Keilberg (heute tschechisch Klínovec; 1244 m) auf böhmischer Seite bildet er den höchsten Punkt des Erzgebirgskamms. Die von Südwest nach Nordost ansteigende Pultscholle des Gebirges fällt nach Süden hin steil ins Egertal (heute tschechisch Údolí Ohře) ab. In diesem, nach Süden vom Duppauer Gebirge (heute tschechisch Doupovské hory) und dem Kaiserwald (heute tschechisch Slavkovský les) eingerahmten Tal sammelt sich bei herbstlichen und winterlichen Hochdruckwetterlagen die Kaltluft (Böhmischer Nebel). Durch diese Konstellation liegt der Fichtelberg entweder in einer trockenen warmen Luftmasse darüber (Inversion) oder er wird direkt vom Böhmischen Nebel beeinflusst, wenn dieser über den Kamm fließt. Das führt zu zahlreichen optischen Erscheinungen, die es sonst in dieser Fülle nur selten gibt. So besticht der Gipfel bei Inversionswetterlagen nicht nur mit einer außergewöhnlichen Fernsicht, sondern auch mit ungewöhnlich starken Refraktionseffekten wie Luftspiegelungen, stark deformierter oder geteilter Sonnenscheibe sowie mehrfachen Grünen, Blauen und Roten Strahlen an der horizontnahen Sonne. Die Dämmerungsfarben sind bei derartigen Wetterlagen sehr intensiv und neben Purpur- und Gegenpurpurlicht und stark ausgeprägtem Erdschattenbogen zeichnen sich manchmal auch die Schatten weit entfernter Berge oder Wolken am Himmel ab (Crepuscularstrahlen). Fließt der Böhmische Nebel über den Erzgebirgskamm, entstehen bei gleichzeitigem Sonnenschein im Sommer Glorie und Nebelbogen und im Winter atemberaubende Eisnebelhalos. sondern auch mit ungewöhnlich starken Refraktionseffekten wie Luftspiegelungen, stark deformierter oder geteilter Sonnenscheibe sowie mehrfachen Grünen, Blauen und Roten Strahlen an der horizontnahen Sonne. Die Dämmerungsfarben sind bei derartigen Wetterlagen sehr intensiv und neben Purpur- und Gegenpurpurlicht und stark ausgeprägtem Erdschattenbogen zeichnen sich manchmal auch die Schatten weit entfernter Berge oder Wolken am Himmel ab (Crepuscularstrahlen). Fließt der Böhmische Nebel über den Erzgebirgskamm, entstehen bei gleichzeitigem Sonnenschein im Sommer Glorie und Nebelbogen und im Winter atemberaubende Eisnebelhalos

Model-based Integration of Past & Future in TimeTravel

We demonstrate TimeTravel, an efficient DBMS system for seamless integrated querying of past and (forecasted) future values of time series, allowing the user to view past and future values as one joint time series. This functionality is important for advanced application domain like energy. The main idea is to compactly represent time series as models. By using models, the TimeTravel system answers queries approximately on past and future data with error guarantees (absolute error and confidence) one order of magnitude faster than when accessing the time series directly. In addition, it efficiently supports exact historical queries by only accessing relevant portions of the time series. This is unlike existing approaches, which access the entire time series to exactly answer the query. To realize this system, we propose a novel hierarchical model index structure. As real-world time series usually exhibits seasonal behavior, models in this index incorporate seasonality. To construct a hierarchical model index, the user specifies seasonality period, error guarantees levels, and a statistical forecast method. As time proceeds, the system incrementally updates the index and utilizes it to answer approximate and exact queries. TimeTravel is implemented into PostgreSQL, thus achieving complete user transparency at the query level. In the demo, we show the easy building of a hierarchical model index for a real-world time series and the effect of varying the error guarantees on the speed up of approximate and exact queries