ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Unbekannt

Determination of phase relations of the olivine–ahrensite transition in the Mg2SiO4–Fe2SiO4 system at 1740 K using modern multi-anvil techniques (2021)

Chanyshev, Artem ; Bondar, Dmitry ; Fei, Hongzhan ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-07-04

Beschreibung: The phase relations of iron-rich olivine and its high-pressure polymorphs are important for planetary science and meteoritics because these minerals are the main constituents of terrestrial mantles and meteorites. The olivine–ahrensite binary loop was previously determined by thermochemical calculations in combination with high-pressure experiments; however, the transition pressures contained significant uncertainties. Here we determined the binary loop of the olivine–ahrensite transition in the (Mg,Fe)2SiO4 system at 1740 K in the pressure range of 7.5–11.2 GPa using a multi-anvil apparatus with the pressure determined using in situ X-ray diffraction, compositional analysis of quenched run products, and thermochemical calculation. Based on the determined binary loop, a user-friendly software was developed to calculate pressure from the coexisting olivine and ahrensite compositions. The software is used to estimate the shock conditions of several L6-type chondrites. The obtained olivine–ahrensite phase relations can also be applied for precise in-house multi-anvil pressure calibration at high temperatures.

Beschreibung: BMBF

Beschreibung: H2020 European Research Council http://dx.doi.org/10.13039/100010663

Beschreibung: Deutsches Elektronen-Synchrotron (DESY) (4201)

Schlagwort(e): ddc:549 ; Experimental ; Olivine ; Ahrensite ; Phase transition ; Thermobarometry ; Meteorites

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

2

Unbekannt

Numerische Simulationen des Ausbreitungsverhaltens von Wärmeträgerfluid-Inhaltsstoffen aus Erdwärmesonden in Trinkwassereinzugsgebieten (2020)

Struß, Janine ; Schäfer, Dirk ; Dahmke, Andreas ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-06-20

Beschreibung: Aufgrund deutlich erhöhter Wärmebedarfsdichten urbaner Räume besteht in besonderem Maße hier die Möglichkeit und Erfordernis, durch eine nachhaltige Wärmeversorgung und saisonale Wärmespeicherung im geologischen Untergrund einen wesentlichen Beitrag zu den national und international gesetzten Klimaschutzzielen zu liefern. Eine effiziente Möglichkeit zur Wärmegewinnung und -speicherung bieten hierfür Erdwärmesonden, die jedoch aus Gründen des vorbeugenden Grundwasserschutzes in Bereichen der Trinkwassernutzung heutzutage meist nicht oder nur beschränkt genehmigt werden. Numerische Simulationen einer Erdwärmesondenleckage für Randbedingungen eines zur Trinkwassergewinnung genutzten norddeutschen Aquifers auf Grundlage von aufgearbeiteten stoffspezifischen Abbauratenkonstanten zeigen, dass Grenzwerte für die meisten handelsüblichen Wärmeträgerfluid-Inhaltsstoffe bereits bei einem Abstand von nur 100 m zwischen Erdwärmesonde und Trinkwasserentnahme aufgrund starker Verdünnung und mikrobiellen Abbaus mit einem Faktor 〉 10 unterschritten werden. Vor dem Hintergrund dieser Ergebnisse und angesichts der Zielsetzung einer Reduktion fossiler Primärenergiequellen um 80–95 % bis 2050, erscheinen pauschale Abstandsvorgaben (von zurzeit 〉 1000 m) daher zumindest hinsichtlich der Trinkwassergefährdung durch Erdwärmesondenleckagen diskussionswürdig.

Beschreibung: Christian-Albrechts-Universität zu Kiel (3094)

Schlagwort(e): ddc:549 ; Borehole heat exchanger ; Heat transfer fluids ; Additives ; Groundwater ; Risk assessment

Sprache: Deutsch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

3

Unbekannt

Lateral variations in the Unit 7–8 boundary zone of the Rum Eastern Layered Intrusion, NW Scotland: implications for the origin and timing of Cr-spinel seam formation (2020)

Kaufmann, Felix E. D. ; O’Driscoll, Brian ; Hecht, Lutz ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-06-23

Beschreibung: The Rum Layered Suite, NW Scotland, hosts Cr-spinel seams at the bases of peridotite–troctolite macro-rhythmic units in the eastern portion of the intrusion. Here, we present detailed field observations together with microstructural and mineral chemical analyses for the Unit 7–8 Cr-spinel seam and associated cumulates in the Eastern Layered Intrusion. Detailed mapping and sampling reveal significant lateral variations in the structural characteristics and mineral compositions of the Unit 7–8 boundary zone rocks. Although the Cr-spinel seam is laterally continuous over ~ 3 km, it is absent towards the centre and the margins of the intrusion. The compositional characteristics of Cr-spinel and plagioclase vary systematically along strike, exhibiting a chemical evolution towards more differentiated compositions with increasing distance from the main feeder conduit of the Rum intrusion; the Long Loch Fault. On the basis of our combined datasets, we propose that the upper part of the troctolite, the anorthosite layer underlying the Cr-spinel seam and the seam itself formed during a multi-stage magma replenishment event. The stages can be summarised as follows: (1) peridotite schlieren and anorthosite autoliths formed following melt infiltration and cumulate assimilation in the crystal mush of the Unit 7 troctolite. (2) The anorthosite layer then formed from the Unit 7 troctolite crystal mush by thermal erosion and dissolution due to infiltrating magma. (3) Subsequent dissolution of the anorthosite layer by new replenishing magma led to peritectic in situ crystallisation of the Unit 7–8 Cr-spinel seam, with (4) continued magma input eventually producing the overlying Unit 8 peridotite. In the central part of the Rum Layered Suite, the aforementioned assimilation of the troctolitic footwall formed the anorthosite layer. However, the absence of anorthosite in close proximity to the Long Loch Fault can be explained by enhanced thermochemical erosion close to the feeder zone, and its absence close to the margins of the intrusion, at maximum distance from the Long Loch Fault, may be due to cooling of the magma and loss of erosion potential. In line with other recent studies on PGE-bearing chromitites in layered intrusions, we highlight the importance of multi-stage intrusive magma replenishment to the formation of spatially coupled anorthosite and Cr-spinel seams, as well as the lateral mineral chemical variations observed in the Unit 7–8 boundary zone cumulates.

Beschreibung: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347

Schlagwort(e): ddc:549 ; Mineralogy ; Cr-spinel seam

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

4

Unbekannt

Reassessing zircon-monazite thermometry with thermodynamic modelling: insights from the Georgetown igneous complex, NE Australia (2020)

Volante, S. ; Collins, W. J. ; Blereau, E. ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-06-23

Beschreibung: Accessory mineral thermometry and thermodynamic modelling are fundamental tools for constraining petrogenetic models of granite magmatism. U–Pb geochronology on zircon and monazite from S-type granites emplaced within a semi-continuous, whole-crust section in the Georgetown Inlier (GTI), NE Australia, indicates synchronous crystallisation at 1550 Ma. Zircon saturation temperature (Tzr) and titanium-in-zircon thermometry (T(Ti–zr)) estimate magma temperatures of ~ 795 ± 41 °C (Tzr) and ~ 845 ± 46 °C (T(Ti-zr)) in the deep crust, ~ 735 ± 30 °C (Tzr) and ~ 785 ± 30 °C (T(Ti-zr)) in the middle crust, and ~ 796 ± 45 °C (Tzr) and ~ 850 ± 40 °C (T(Ti-zr)) in the upper crust. The differing averages reflect ambient temperature conditions (Tzr) within the magma chamber, whereas the higher T(Ti-zr) values represent peak conditions of hotter melt injections. Assuming thermal equilibrium through the crust and adiabatic ascent, shallower magmas contained 4 wt% H2O, whereas deeper melts contained 7 wt% H2O. Using these H2O contents, monazite saturation temperature (Tmz) estimates agree with Tzr values. Thermodynamic modelling indicates that plagioclase, garnet and biotite were restitic phases, and that compositional variation in the GTI suites resulted from entrainment of these minerals in silicic (74–76 wt% SiO2) melts. At inferred emplacement P–T conditions of 5 kbar and 730 °C, additional H2O is required to produce sufficient melt with compositions similar to the GTI granites. Drier and hotter magmas required additional heat to raise adiabatically to upper-crustal levels. S-type granites are low-T mushes of melt and residual phases that stall and equilibrate in the middle crust, suggesting that discussions on the unreliability of zircon-based thermometers should be modulated.

Beschreibung: Centre of Excellence for Core to Crust Fluid Systems, Australian Research Council http://dx.doi.org/10.13039/100012537

Beschreibung: Ruhr-Universität Bochum (1007)

Schlagwort(e): ddc:549 ; Zircon and monazite thermometry ; Water content ; Granitic melts ; Complete crustal section ; Phase equilibria diagrams

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

5

Unbekannt

Mineralogical and geochemical investigation of megaspherulites from Argentina, Germany, and the USA (2021)

Breitkreuz, Christoph ; Götze, Jens ; Weißmantel, Alexandra ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-06-14

Beschreibung: Textures and whole-rock chemistry, as well as mineral composition, were analyzed in megaspherulites (high-temperature crystallization domains [HTCDs]) that formed in different geographical and geotectonic contexts and during different geological periods (Silver Cliff, CO, USA—Paleogene; El Quevar, Argentina—Miocene; Meissen Volcanic Complex, Germany—Late Carboniferous). All of these megaspherulites have formed exclusively in rhyolitic lava, and their mineral composition is dominated by K-feldspar (sanidine) and SiO2 phases (quartz, cristobalite, tridymite). All megaspherulites represent composite HTCDs, comprising three zones: inner domain (ID), outer domain (OD), and a marginal domain (MD). Early evolution of megaspherulites is characterized by either central cavities and sector- to full-sphere spherulites or dendritic quartz-sanidine domains. The latter consist of bundles of fibrils each radiating from a single point reflecting relatively high growth rates. A common feature of OD and MD of all three megaspherulite occurrences is autocyclic banding. It mainly comprises fibrous (≤ 100 μm length), radially oriented sanidine and quartz, which formed at a temperature close to glass transition temperature (Tg). The termination of megaspherulite growth is marked by centimeter-sized sector-sphere spherulites on the surface. Megaspherulite formation requires limited nucleation, which is probably related to the low phenocryst content of the hosting lava. Latent heat from overlying crystallizing lithoidal rhyolite maintained low undercooling conditions keeping nucleation density low and facilitating high diffusion and growth rates. Late megaspherulite growth and its termination under low diffusion conditions is controlled by cooling close to Tg. Calculations based on literature data suggest that the megaspherulite growth presumably lasted less than 60 years, perhaps 30 to 40 years.

Schlagwort(e): ddc:549 ; Rhyolitic lava ; SEM ; CL ; XRD ; EPMA ; Cristobalite ; Tridymite

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

6

Unbekannt

The provenance signal of climate–tectonic interactions in the evolving St. Elias orogen: framework component analysis and pyroxene and epidote single grain geochemistry of sediments from IODP 341 sites U1417 and U1418 (2021)

Huber, Barbara ; Bahlburg, Heinrich ; Huber, Barbara; Institut für Geologie und Paläontologie, Westfälische Wilhelms-Universität, Münster, Germany ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-08-17

Beschreibung: The St. Elias orogen and the Surveyor Fan in the adjacent Gulf of Alaska are a coupled source to sink system recording the interplay of tectonics and variable degrees of glaciation during the collision of the Yakutat terrane with the southern Alaska margin since the Miocene. The Miocene to Holocene sediments of the Surveyor Fan were drilled during IODP expedition 341. The recovered material is used to constrain information on changes in erosion centers during the last 10 Ma to study the impact of climatic and tectonic processes on orogen evolution. Point counting of sand- and silt-sized light framework components and geochemical single grain analysis of heavy mineral groups epidote and pyroxene is applied to analyze patterns of sedimentary provenance of two sites on the distal and proximal Surveyor Fan (Site U1417 and U1418, respectively). The studied sands and silts of Miocene to Pleistocene age are slightly enriched in feldspar (plag 〉〉 kf) at the proximal site, compositions at both sites do not show systematical changes with time of deposition. Framework component spectra uniformly reflect the expected active margin provenance. Epidote and pyroxene compositions are very consistent and show no change with time of deposition. Associations of epidote and pyroxene with albite, titanite and pumpellyite are in line with near-shore sources in the Chugach Metamorphic Complex and the metabasite belt at its southern border, and in units of recycled detritus exposed in the fold and thrust belt on the western Yakutat Terrane, respectively. Rock fragments indicate input from mainly metamorphic sources during the Miocene and Pliocene and an increase of input from low-grade metamorphic and sedimentary rocks in the Pleistocene, a finding also indicated by the abundance of epidote and pyroxene. This implies increasing erosion of the near-shore areas of the fold and thrust belt with advance of glaciers to the shore since the Miocene, being enhanced by the onset of the Northern Hemisphere glaciation at the beginning of the Pleistocene. Climate changes connected to the mid-Pleistocene transition did not result in appreciable changes in the petrographic compositions. Glaciers seem to have remained nested in their topographically predefined positions, continuously feeding material with uniform characteristics into the fan.

Beschreibung: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Beschreibung: Westfälische Wilhelms-Universität Münster (1056)

Schlagwort(e): ddc:549 ; Alaska ; Provenance ; Framework components ; Pyroxene ; Epidote ; Climate–tectonic interactions

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

7

Unbekannt

Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier (2021)

Schönig, Jan ; von Eynatten, Hilmar ; Tolosana-Delgado, Raimon ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-07-20

Beschreibung: The major-element chemical composition of garnet provides valuable petrogenetic information, particularly in metamorphic rocks. When facing detrital garnet, information about the bulk-rock composition and mineral paragenesis of the initial garnet-bearing host-rock is absent. This prevents the application of chemical thermo-barometric techniques and calls for quantitative empirical approaches. Here we present a garnet host-rock discrimination scheme that is based on a random forest machine-learning algorithm trained on a large dataset of 13,615 chemical analyses of garnet that covers a wide variety of garnet-bearing lithologies. Considering the out-of-bag error, the scheme correctly predicts the original garnet host-rock in (i) 〉 95% concerning the setting, that is either mantle, metamorphic, igneous, or metasomatic; (ii) 〉 84% concerning the metamorphic facies, that is either blueschist/greenschist, amphibolite, granulite, or eclogite/ultrahigh-pressure; and (iii) 〉 93% concerning the host-rock bulk composition, that is either intermediate–felsic/metasedimentary, mafic, ultramafic, alkaline, or calc–silicate. The wide coverage of potential host rocks, the detailed prediction classes, the high discrimination rates, and the successfully tested real-case applications demonstrate that the introduced scheme overcomes many issues related to previous schemes. This highlights the potential of transferring the applied discrimination strategy to the broad range of detrital minerals beyond garnet. For easy and quick usage, a freely accessible web app is provided that guides the user in five steps from garnet composition to prediction results including data visualization.

Beschreibung: deutsche forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Beschreibung: Georg-August-Universität Göttingen (1018)

Beschreibung: http://134.76.17.86:443/garnetRF/

Schlagwort(e): ddc:549 ; Garnet major-element composition ; Database ; Host-rock discrimination ; Machine-learning ; Provenance ; Web app

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

8

Unbekannt

Clay mineral formation in Permian rocks of a geothermal borehole at Northern Upper Rhine Graben, Germany (2021)

Nguyen-Thanh, Lan ; Mählmann, Rafael Ferreiro ; Hoang-Minh, Thao ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2023-07-19

Beschreibung: Hydrothermally altered rhyolite rocks in the Permian Donnersberg Formation of a geothermal borehole in the Northern Upper Rhine Graben (Germany) were investigated to find out answers for the low hydraulic conductivity of the rocks. The composition of clay minerals and the temperature of smectite–illite transformation were carried out using X-ray diffraction, X-ray fluorescence, transmission electron microscopy, Fourier transform infrared spectroscopy, and polarized-light microscopy analyses. Clay mineral (CM) composition includes illite/muscovite (1M and 2M1 polytypes), illite–smectite interstratifications (IS-ml), smectite, and chlorite; and non-clay minerals such as quartz, feldspars, epidote, calcite, dolomite, and hematite were detected. The 2M1-polytype mica might be the only primary sheet silicates from the parent rocks, while the others occur as authigenic neo-formed CMs under heat flow and geothermal gradient. The development of CMs indicates different mechanisms of illitization and smectitization. Based on the texture, morphology, structure/polytype, and chemistry of rocks and minerals, in particular CMs, the study grouped the CM formation into three transformation processes: smectitization during magma cooling and possible contact metamorphisms with decreasing and low temperature, smectite illitization controlled by burial diagenesis and hydrothermal alteration, and illite smectitization followed exhumation and Cenozoic subsidence with decreasing temperature. The rhyolites were altered to all of the orders IS-R0, IS-R1, and IS-R3 by the dissolution-precipitation and layer-to-layer mechanisms. The first one supported small xenomorphic plates and flakes of 1Md, elongated particles of 1M, and pseudo-hexagonal forms of 2M1. The second one could lead to the platy particles of 1Md and 2M1 polytypes. The dominant temperature range for the transformation in the area has been 140–170 °C– ~ 230 °C.

Beschreibung: Technische Universität Darmstadt (3139)

Schlagwort(e): ddc:549 ; Geothermal borehole ; Clay mineral ; Smectite illitization ; Thermal gradient ; Upper Rhine Graben ; Donnersberg Formation

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext

9

Unbekannt

Interspinifex Ni sulfide ore from Victor South-McLeay, Kambalda, Western Australia (2020)

Staude, Sebastian ; Barnes, Stephen J. ; Markl, Gregor ; [weitere]

Springer Berlin Heidelberg

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2024-02-12

Beschreibung: Spinifex-textured olivine plates hosted in sulfides are usually named “interspinifex ore” in komatiite-hosted sulfide deposits. This ore type is rare but provides important genetic information on sulfide deposits, komatiite volcanology and thermomechanical erosion processes. Occurrences in Victor South-McLeay and Moran South (Kambalda, Western Australia) differ significantly from previously reported occurrences in their stratigraphic location, position within the ore profile and textural appearance. Thus, their formation process has to be reconsidered. Interspinifex ore reported here is situated in the lower portion of the basal lava flow between massive and net-textured sulfides in the centre of the embayment and between massive sulfides and older basalt in a “pinchout” where the sulfides melted sideways into older basalt on the embayment edge. Interspinifex ore is composed of up to 10-cm-long aggregates of parallel plates in the upper portion of massive sulfides and is overlain by barren komatiite. The texture does not allow for a classic single explanation. Thus, two possible formation mechanisms are envisaged: (1) A younger komatiite melt intrudes into its own olivine and sulfide liquid cumulate pile, while the sulfides are still liquid. The injection on top of the sulfides causes the formation of an emulsion, from which the spinifex forms due to the temperature gradient between the melts. (2) Interspinifex ore is a relic of an early komatiite flow formed in a series of successive pulses of komatiite and sulfide liquid. The spinifex of the komatiite is invaded by a younger batch of sulfide liquid replacing interstitial silicate melt.

Beschreibung: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Schlagwort(e): ddc:549 ; Interspinifex ore ; Kambalda ; Komatiite-hosted Ni sulfide deposit ; Emulsion ; Sulfide infiltration

Sprache: Englisch

Materialart: doc-type:article

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

CITATION GEO-LEO

S·F·X

Volltext