Chemical zoning of calcium aluminoferrite formed during melt crystallization in CaO–SiO2–Al2O3–Fe2O3 pseudoquaternary system

AbstractDehydration reactions in the subducting slab liberate fluids causing major changes in rock density, volume and permeability. Although it is well known that the fluids can migrate and interact with the surrounding rocks, fluid pathways remain challenging to track and the consequences of fluid-rock interaction processes are often overlooked. In this study, we investigate pervasive fluid-rock interaction in a sequence of schists and mafic felses exposed in the Theodul Glacier Unit (TGU), Western Alps. This unit is embedded within metaophiolites of the Zermatt-Saas Zone and reached eclogite-facies conditions during Alpine convergence. Chemical mapping and in situ oxygen isotope analyses of garnet from the schists reveal a sharp chemical zoning between a xenomorphic core and a euhedral rim, associated to a drop of ~ 8‰ in δ18O. Thermodynamic and δ18O models show that the large amount of low δ18O H2O required to change the reactive bulk δ18O composition cannot be produced by dehydration of the mafic fels from the TGU only, and requires a large contribution of the surrounding serpentinites. The calculated time-integrated fluid flux across the TGU rocks is 1.1 × 105 cm3/cm2, which is above the open-system behaviour threshold and argues for pervasive fluid flow at kilometre-scale under high-pressure conditions. The transient rock volume variations caused by lawsonite breakdown is identified as a possible trigger for the pervasive fluid influx. The calculated schist permeability at eclogite-facies conditions (~ 2 × 10–20 m2) is comparable to the permeability determined experimentally for blueschist and serpentinites.

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Melt Crystallization of Ammonium Dinitramide (ADN) Investigated by Means of X‐ray Diffraction

Chemie Ingenieur Technik ◽

10.1002/cite.202000185 ◽

2021 ◽

Author(s):

Michael Herrmann ◽

Ulrich Förter‐Barth ◽

Thomas Heintz

Keyword(s):

Melt Crystallization ◽

Ammonium Dinitramide ◽

X Ray Diffraction ◽

X Ray

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Effect of Electrical Aging on the Trap Parameter of HVAC XLPE Cable Insulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.672-674.769 ◽

2014 ◽

Vol 672-674 ◽

pp. 769-772

Author(s):

Wei Wei Li ◽

Qiang Shi ◽

Chi Wu

Keyword(s):

Crystallization Process ◽

Melt Crystallization ◽

Depolarization Current ◽

Cable Insulation ◽

Trap Charge ◽

Xlpe Cable ◽

Trap Parameter ◽

Start Up ◽

Electrical Aging ◽

Two Peaks

The effect of electrical aging on the trap parameter of HVAC XLPE cable insulation was investigated in this work. Thermally Stimulated Current (TSC) was used to measure depolarization current. The variation of trap parameter was calculated by means of start-up method based on the Gaussian fitting curve of TSC data. It was found that, the activation energy and the amount of trap charge obtained from TSC peak at 243K and 348K were increased after electrical aging, which may be benefit to characterize the degree of aging. The amount of trap charge in the two peaks increases as the increase of oxide dipole after electrical aging. And charge trapped described by the TSC peak at melting temperature increased after aging. It is considered that the increase of charge in the TSC peak can be attributed to the release of trap charge in the melt crystallization process, which corresponds to the α relaxation process in XLPE insulation.

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Chemical zoning and crystallization mechanisms in the magma chamber of the Pomici di Base plinian eruption of Somma-Vesuvius (Italy)

Contributions to Mineralogy and Petrology ◽

10.1007/s004100050505 ◽

1999 ◽

Vol 135 (2-3) ◽

pp. 179-197 ◽

Cited By ~ 40

Author(s):

P. Landi ◽

A. Bertagnini ◽

M. Rosi

Keyword(s):

Magma Chamber ◽

Plinian Eruption ◽

Chemical Zoning

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The Effect of WS2 Nanosheets on the Non-Isothermal Cold- and Melt-Crystallization Kinetics of Poly(l-lactic acid) Nanocomposites

Polymers ◽

10.3390/polym13132214 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2214

Author(s):

Mohammed Naffakh ◽

Pablo Rica ◽

Carmen Moya-Lopez ◽

José Antonio Castro-Osma ◽

Carlos Alonso-Moreno ◽

...

Keyword(s):

Lactic Acid ◽

Transition Metal Dichalcogenides ◽

Crystallization Rate ◽

Melting Behavior ◽

Hybrid Nanocomposites ◽

Melt Crystallization ◽

Heating Rates ◽

Solution Blending ◽

New Perspective ◽

Ws2 Nanosheets

In the present work, hybrid nanocomposite materials were obtained by a solution blending of poly(l-lactic acid) (PLLA) and layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS2) as a filler, varying its content between 0 and 1 wt%. The non-isothermal cold- and melt-crystallization and melting behavior of PLLA/2D-WS2 were investigated. The overall crystallization rate, final crystallinity, and subsequent melting behavior of PLLA were controlled by both the incorporation of 2D-WS2 and variation of the cooling/heating rates. In particular, the analysis of the cold-crystallization behavior of the PLLA matrix showed that the crystallization rate of PLLA was reduced after nanosheet incorporation. Unexpectedly for polymer nanocomposites, a drastic change from retardation to promotion of crystallization was observed with increasing the nanosheet content, while the melt-crystallization mechanism of PLLA remained unchanged. On the other hand, the double-melting peaks, mainly derived from melting–recrystallization–melting processes upon heating, and their dynamic behavior were coherent with the effect of 2D-WS2 involved in the crystallization of PLLA. Therefore, the results of the present study offer a new perspective for the potential of PLLA/hybrid nanocomposites in targeted applications.

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Rejuvenation events recorded in alkali feldspar from the Tuolumne Intrusive Complex

10.5194/egusphere-egu21-14918 ◽

2021 ◽

Author(s):

Susanne Seitz ◽

Guilherme Gualda ◽

Luca Caricchi

Keyword(s):

Trace Elements ◽

Hierarchical Clustering ◽

Alkali Feldspar ◽

Growth Conditions ◽

Major And Trace Elements ◽

Sem Analysis ◽

Intrusive Complex ◽

Cluster Number ◽

Chemical Zoning ◽

Chemical Signatures

Zoned minerals preserve information about their growth conditions, by changing their composition as function of temperature, pressure and melt composition. By carefully looking at a zoned minerals we can determine characteristics of the main stages of the evolution of magmatic systems.We study alkali feldspar megacrysts from the Tuolumne Intrusive Complex in California, with the aim of deciphering chemical signatures of rejuvenation events. We characterize the chemical zoning of alkali feldspar using X-ray tomography, BSE imaging, EDS-SEM analysis and LA-ICPMS analysis along profiles. We use hierarchical clustering based on major and trace elements to objectively identify compositional groups for each chemical profile. By reducing the complexity of chemical zoning to one dimension (i.e. cluster number) we can trace the evolution of the conditions of growth and identify rejuvenation events.Alkali feldspar megacrysts (up to 20 cm in size) from the Cathedral Peak unit of the Tuolumne Intrusive Complex occur predominantly disperse and only make between 8 - 12 % of the total crystal population. They are mostly homogeneous in major element, and markedly oscillatory zoned in trace elements such as Ba, Sr, and Rb. Using hierarchical clustering we identify four different chemical groups within the alkali feldspar crystals. Each chemical group is repeated multiple times in a single crystal. Overall the crystals show a decreasing trend of Ba towards the rim. Extended alkali feldspar crystallization would lead to a depletion of Ba in the melt and consequently to the growth of low Ba-zones of alkali feldspar. In some crystals the sequence of decreasing Ba is repeated twice. We propose that this reflects melt recharge in a melt-rich magmatic system.

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