995 research outputs found
Insights to magmaticâhydrothermal 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 subâseafloor processes governing the formation of
hydrothermal fluids in the convergent margin Manus Basin, Papua New Guinea. Samples
comprise drillâcore vein anhydrite and seafloor massive anhydrite from the PACMANUS
(Roman Ruins, Snowcap and Fenway) and SuSu Knolls (North Su) active hydrothermal
fields. Chondriteânormalized REE patterns in anhydrite show remarkable heterogeneity on
the scale of individual grains, different from the near uniform REEN patterns measured in
anhydrite from midâocean 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 intraâgrain
heterogeneity implies that anhydrite preserves periods of contrasting hydrothermalâ versus
seawaterâdominant nearâseafloor fluid circulation. Most sulfate ÎŽ34S values of anhydrite
cluster around that of contemporary seawater, consistent with anhydrite precipitating from
hydrothermal fluid mixed with locally entrained seawater. Sulfate ÎŽ34S 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 subâseafloor processes including highâtemperature hydrothermal fluid
circulation, varying extents of magmatic volatile degassing, seawater entrainment and fluid
mixing. The chemical and isotopic heterogeneity recorded in anhydrite at the interâ and
intraâgrain scale captures the dynamics of hydrothermal fluid formation and subâseafloor
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 OCEâ0327448 (W.B.), and DFGâResearch Center/Excellence Cluster âThe
Ocean in the Earth Systemâ (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 (nâ=â48) and dredging (nâ=â22). 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 1.3âĂâ1010 mole Mg and about 2âĂâ1010 mole alkalinity during seafloor weathering of serpentinite globally. Our data suggest that, on average, brucite stores âŒ20 % 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 â a laboratory study using flow-through reactors
The Earthâs 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 âThe Ocean in the Earth Systemâ. WB acknowledges support from DFG
research grant BA1605/4-1.2018-05-1
Optische Erscheinungen und andere ungewöhnliche WetterphÀnomene 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 KlĂnovec; 1244 m) auf böhmischer Seite
bildet er den höchsten Punkt des Erzgebirgskamms. Die von SĂŒdwest nach Nordost
ansteigende Pultscholle des Gebirges fĂ€llt nach SĂŒden hin steil ins Egertal
(heute tschechisch ĂdolĂ OhĆe) ab. In diesem, nach SĂŒden vom Duppauer Gebirge
(heute tschechisch Doupovské hory) und dem Kaiserwald (heute tschechisch
SlavkovskĂœ 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 darĂŒber (Inversion) oder er wird direkt vom Böhmischen Nebel
beeinflusst, wenn dieser ĂŒber den Kamm flieĂt. Das fĂŒhrt zu zahlreichen
optischen Erscheinungen, die es sonst in dieser FĂŒlle nur selten gibt. So
besticht der Gipfel bei Inversionswetterlagen nicht nur mit einer
auĂergewöhnlichen 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 KlĂnovec; 1244 m) auf
böhmischer Seite bildet er den höchsten Punkt des Erzgebirgskamms. Die von
SĂŒdwest nach Nordost ansteigende Pultscholle des Gebirges fĂ€llt nach SĂŒden hin
steil ins Egertal (heute tschechisch ĂdolĂ OhĆe) ab. In diesem, nach SĂŒden vom
Duppauer Gebirge (heute tschechisch Doupovské hory) und dem Kaiserwald (heute
tschechisch SlavkovskĂœ 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 darĂŒber (Inversion) oder er wird direkt vom Böhmischen Nebel
beeinflusst, wenn dieser ĂŒber den Kamm flieĂt. Das fĂŒhrt zu zahlreichen
optischen Erscheinungen, die es sonst in dieser FĂŒlle nur selten gibt. So
besticht der Gipfel bei Inversionswetterlagen nicht nur mit einer
auĂergewöhnlichen Fernsicht, sondern auch mit ungewöhnlich starken
Refraktionseffekten wie Luftspiegelungen, stark deformierter oder geteilter
Sonnenscheibe sowie mehrfachen GrĂŒnen, Blauen und Roten Strahlen an der
horizontnahen Sonne. Die DĂ€mmerungsfarben sind bei derartigen Wetterlagen sehr
intensiv und neben Purpur- und Gegenpurpurlicht und stark ausgeprÀgtem
Erdschattenbogen zeichnen sich manchmal auch die Schatten weit entfernter
Berge oder Wolken am Himmel ab (Crepuscularstrahlen). FlieĂt der Böhmische
Nebel ĂŒber 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 GrĂŒnen, Blauen und Roten Strahlen an der horizontnahen Sonne. Die
DĂ€mmerungsfarben sind bei derartigen Wetterlagen sehr intensiv und neben
Purpur- und Gegenpurpurlicht und stark ausgeprÀgtem Erdschattenbogen zeichnen
sich manchmal auch die Schatten weit entfernter Berge oder Wolken am Himmel ab
(Crepuscularstrahlen). FlieĂt der Böhmische Nebel ĂŒber den Erzgebirgskamm,
entstehen bei gleichzeitigem Sonnenschein im Sommer Glorie und Nebelbogen und
im Winter atemberaubende Eisnebelhalos
Educational data comics:What can comics do for education in visualization?
This paper discusses the potential of comics for explaining concepts with and around data visualization. With the increasing spread of visualizations and the democratization of access to visualization tools, we see a growing need for easily approachable resources for learning visualization techniques, applications, design processes, etc. Comics are a promising medium for such explanation as they concisely combine graphical and textual content in a sequential manner and they provide fast visual access to specific parts of the explanations. Based on a first literature review and our extensive experience with the subject, we survey works at the respective intersections of comics, visualization and education: data comics, educational comics, and visualization education. We report on five potentials of comics to create and share educational material, to engage wide and potentially diverse audiences, and to support educational activities. For each potential we list, we describe open questions for future research. Our discussion aims to inform both the application of comics by educators and their extension and study by researchers
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