scholarly journals Mineralogical and Crystal-Chemical Constraints on the Glauconite-Forming Process in Neogene Sediments of the Lower Guadalquivir Basin (SW Spain)

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 578
Author(s):  
Sandra Fernández-Landero ◽  
Juan Carlos Fernández-Caliani
Keyword(s):  
Early Stage ◽  
Passive Margin ◽  
Ion Diffusion ◽  
Forming Process ◽  
Diffusion Controlled ◽  
Neogene Sediments ◽  
Marine Facies ◽  
Single Grain ◽  
End Members ◽  
Highly Evolved

Glaucony is a significant green marine facies in the northwestern passive margin of the Guadalquivir Basin (Spain), where glauconite formed authigenically on a sediment-starved continental shelf, with fecal pellets and benthic foraminiferal tests being the main glauconitized substrates. Results from a study using XRD, TGA-DSC, SEM-EDS, and EPMA have revealed that glauconite is remarkably heterogeneous in mineral composition and chemical maturity, even in a single grain, reflecting a complex interaction of micro-environmental factors, substrate influences and post-depositional alterations. In its early stage, the glauconitization process is consistent with the slow precipitation of a Fe-rich smectite phase, most likely intergrade between nontronite and Fe-montmorillonite end-members, which evolved to a regularly interstratified glauconite-smectite (Gl/S). The Fe-smectite-to-Gl/S transformation is interpreted as a diffusion-controlled reaction, involving sufficient Fe availability in pore water and the constant diffusive transport of seawater K+ and Mg2+ ions towards the substrate. The pelletal glauconite is actually a highly evolved Gl/S consisting almost totally of mica layers, with 0.74 ± 0.05 apfu of K+ in the interlayer, while the Gl/S occurring as replacements of foraminiferal tests contains a mean of 7% of expandable layers in the walls and 16% in the chamber fillings, due to rate-limited ion diffusion.

Refinement of Size Distributions for Primary Crystallizations

1997 ◽  
Vol 481 ◽  
Author(s):  
E. Pineda ◽  
T. Pradell ◽  
D. Crespo ◽  
N. Clavaguera ◽  
J. ZHU ◽  
...  
Keyword(s):  
Grain Size ◽  
Metastable Phase ◽  
Primary Crystallization ◽  
Controlled Growth ◽  
Diffusion Controlled ◽  
Average Grain Size ◽  
Soft Impingement ◽  
Single Grain ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTThe microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled.

scholarly journals A Novel Force Variation Fine Blanking Process for the High-strength and Low-plasticity Material

2021 ◽  
Author(s):  
Huajie Mao ◽  
Han Chen ◽  
Yanxiong Liu ◽  
Kaisheng Ji
Keyword(s):  
Early Stage ◽  
Hydrostatic Stress ◽  
High Strength ◽  
Forming Force ◽  
Forming Process ◽  
Fine Blanking ◽  
Application Range ◽  
Cutting Surface ◽  
Force Variation ◽  
Blanking Process

Abstract Fine blanking is a kind of metal forming process with the advantages of high precision, good surface quality and low cost. Influenced by the concept of lightweight, a large number of metal materials with high strength are widely used in various fields. High strength materials are prone to be cracked during plastic deformation due to their poor plasticity, which limits the application range of them. This paper proposed a force variation fine blanking process for high-strength and low-plasticity materials. At the same time, a method to find the curve of forming force for this novel process was presented. A 2D finite element fine blanking model was established for the TC4 material. Combining genetic algorithm and neural network methods, a model was built up to find the optimal forming force loading curve. The parts fabricated by force variation loading and constant loading fine blanking process were compared through experiments. The mechanism of force variation fine blanking is also revealed. The forming force mainly affects the length of clean cutting surface by affecting hydrostatic stress. According to the ultimate optimal loading curve, the forming force should be kept at a low level in the early stage of blanking stroke, and increased gradually in the ending stage. In the application of force variation fine blanking, the part with long length of clean cutting surface can be obtained with lower die load.

Oxidation Behavior of LPPS MCrAlY Coatings at High Temperature: Part I TGO Growth and β Phase Depletion

2021 ◽  
Vol 1035 ◽  
pp. 539-544
Author(s):  
Zhao Ran Zheng ◽  
Kang Yuan
Keyword(s):  
High Temperature ◽  
Early Stage ◽  
Oxidation Kinetic ◽  
Thermally Grown Oxide ◽  
Temperature Oxidation ◽  
Β Phase ◽  
Mcraly Coating ◽  
Mcraly Coatings ◽  
Diffusion Controlled ◽  
Tgo Growth

MCrAlY can be used as bond coats for thermal barrier coatings (TBCs) with good ductility and excellent resistance against high temperature oxidation and hot corrosion. The behavior of the thermally grown oxide (TGO) scale formed at the MCrAlY coatings plays a key role on the oxidation resistance. In this paper, the oxidation kinetic curves of a MCrAlY coating at 900~1000 °C were obtained by measuring the thickness of the TGO scales. The curves basically conveyed parabolic laws, indicating a diffusion-controlled mechanism of the TGO growth. The thickness of TGO was positively correlated with the consumption of β phase during the early stage of the oxidation processes. After about the half-life of the β phase consumption, the depletion of the β phase significantly accelerated, which was caused by coating-substrate interdiffusion. In addition, the microstructure of the TGO was analyzed

Blueschist facies conditions in Tethyan passive margin metabasaltic rocks of the easternmost Lower Alpujarride Units (Internal Betic Zone, Spain)

2021 ◽  
Author(s):  
Eva Santamaría-Pérez ◽  
Idael Francisco Blanco-Quintero ◽  
Agustín Martín-Algarra ◽  
David Benavente ◽  
Juan Carlos Cañaveras ◽  
...  
Keyword(s):  
Thermal Gradient ◽  
Early Stage ◽  
Passive Margin ◽  
Geochemical Data ◽  
Geodynamic Setting ◽  
Low Grade ◽  
Alkaline Basalt ◽  
Metamorphic Overprint ◽  
Sedimentary Sequences ◽  
Basalt Composition

<p>Jurassic shallow-intrusive basic bodies within the Permian-Triassic Tethyan passive margin sedimentary sequences of the Lower Alpujarride units (Internal Betic Zone, Spain) locally show Alpine low-grade metamorphism in the greenschist and blueschist facies. A small sill-like mafic body near Redován town (Callosa Range) partially preserves igneous ophitic/subophitic texture and relics of augite, ferrohornblende-ferroedenite, kaersutite and K-feldspar (orthoclase). The metamorphic overprint corresponds to high-pressure and low-temperature mineral assemblages that comprise magnesioriebeckite, actinolite, albite, stilpnomelane, phengite and chlorite, with rutile, apatite and titanite as accessory minerals. Major and trace element geochemical data reveal igneous protoliths derived from magmas of alkaline basalt composition enriched in incompatible elements and E-MORB geochemical affinity. The intrusion emplacement occurred at shallow crustal levels in an extensional geodynamic setting (within-plate basalts) related to the breakoff of Pangea. Pressure-Temperature (P-T) conditions estimated by means of pseudosection calculations and the intersection of phengite (Si) and chlorite (Mg#) isopleths indicate a cold thermal gradient with calculated peak metamorphic conditions of ca. 8 kbar at 310 ºC. These conditions are consistent with metamorphism during burial down to ca. 24 km depth and a thermal gradient of ca. 13 ºC/km. Although the easternmost Lower Alpujarride units have been traditionally described as reaching only lower-greenschist to greenschist metamorphic peak conditions, the textures, mineral compositions and P-T conditions of the studied metagabbroic body reveal blueschist facies conditions that attest for a regional early stage (Eocene) of subduction of the lower Alpujarride units. This event predates the late Oligocene - early Miocene subduction-related metamorphism of the Intermediate and Upper Alpujarride units.</p>

scholarly journals Geostatistical Determination of Ore Shoot Plunge and Structural Control of the Sizhuang World-Class Epizonal Orogenic Gold Deposit, Jiaodong Peninsula, China

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 214 ◽  
Author(s):  
Si-Rui Wang ◽  
Li-Qiang Yang ◽  
Jian-Gang Wang ◽  
En-Jing Wang ◽  
Yong-Lin Xu
Keyword(s):  
Gold Deposit ◽  
Structural Control ◽  
Large Scale ◽  
Early Stage ◽  
Eastern China ◽  
Mining Area ◽  
Orogenic Gold ◽  
Forming Process ◽  
Jiaodong Peninsula ◽  
Variogram Modeling

The Jiaodong Peninsula in eastern China is the third largest gold-mining area and one of the most important orogenic gold provinces in the world. Ore shoots plunging in specific orientations are a ubiquitous feature of the Jiaodong lode deposits. The Sizhuang gold deposit, located in northwestern Jiaodong, is characterized by orebodies of different occurrences. The orientation of ore shoots has remained unresolved for a long time. In this paper, geostatistical tools were used to determine the plunge and structural control of ore shoots in the Sizhuang deposit. The ellipses determined by variogram modeling reveal the anisotropy of mineralization, plus the shape, size, and orientation of individual ore shoots. The long axes of the anisotropy ellipses trend NE or SEE and plunge 48° NE down the dip. However, individual ore shoots plunge almost perpendicular to the plunge of the ore deposit as a whole. This geometry is interpreted to have resulted from two periods of fluid flow parallel to two sets of striations that we identified on ore-controlling faults. Thrust-related lineations with a sinistral strike-slip component were associated with early-stage mineralization. This was overprinted by dextral and normal movement of the ore-controlling fault that controlled the late-stage mineralization. This kinematic switch caused a change in the upflow direction of ore-forming fluid, which in turn controlled the orientation of the large-scale orebodies and the subvertical plunge of individual ore shoots. Thus, a regional transition from NW-to-SE-trending compression to NW-to-SE-trending extension is interpreted as the geodynamic background of the ore-forming process. This research exemplifies an effective exploration strategy for studying the structural control of the geometry, orientation, and grade distribution of orebodies via the integration of geostatistical tools and structural analysis.

Mechanism of the Production of the Negative Endocochlear DC Potential in the Guinea Pig

1983 ◽  
Vol 91 (4) ◽  
pp. 427-434 ◽  
Author(s):  
Shizuo Komune ◽  
Musan Huangfu ◽  
James B. Snow
Keyword(s):  
Guinea Pigs ◽  
Early Stage ◽  
Organ Of Corti ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Potassium Ions ◽  
Ion Diffusion ◽  
Ion Conductance ◽  
Dc Potential ◽  
Perilymphatic Space

Changes in endocochlear DC potential (EP) and potassium ion concentrations in endolymph were measured simultaneously during anoxia or during perfusion of the perilymphatic space with furosemide, 10−2 M, in normal and kanamycin-deafened guinea pigs. The potassium ion conductance (Gk) through the cochlear partitions was calculated. Thirty minutes after the onset of anoxia, the Gk is 22.1 μM/min/mV in normal guinea pigs and 4.8 μM/min/mV in kanamycin-deafened guinea pigs. At that time the EP is-29.5 mV in normal guinea pigs and 1.4 mV in kanamycin-deafened guinea pigs. In the early stage of anoxia the rate of potassium ion concentration decrease in the endolymph per unit time is greater in normal guinea pigs than in kanamycin-deafened guinea pigs. These results suggest a rapid increase in the permeability of potassium ions in the organ of Corti in the early stage of anoxia might produce a large negative potassium ion diffusion potential or negative EP in normal guinea pigs and the failure to develop the negative EP in kanamycin-deafened guinea pigs might be due to the lack of such a rapid increase in the permeability because of the loss of the hair cells.

Geological modelling of clay diagenesis in sandstones

Clay Minerals ◽  
1982 ◽  
Vol 17 (1) ◽  
pp. 5-22 ◽  
Author(s):  
Andrew Hurst ◽  
Hilary Irwin
Keyword(s):  
Meteoric Water ◽  
Sea Water ◽  
Water Flux ◽  
Sedimentary Basins ◽  
Hydraulic Head ◽  
Primary Sources ◽  
Diffusion Controlled ◽  
Dissolved Species ◽  
Marine Facies ◽  
Diagenetic Reactions

AbstractPorewater composition is the main control on diagenetic reactions in sandstones. Porewater has two possible contrasting primary sources: (i) fresh meteoric water, which is dilute and acidic, (ii) sea-water, which is alkaline and more concentrated than meteoric water. During burial, unstable minerals equilibrate with these porewaters, thus increasing the concentrations of dissolved species. A simple manometer model is used to describe the diagenesis of interconnected (fluvial or deltaic) sandstones. This model illustrates the following geological relationships: (a) a hydraulic head causes meteoric waters to penetrate deep into sedimentary basins, typically generating authigenic kaolinite; (b) decrease of the hydraulic head (by lowering the land level or by raising sea level) causes concentrated brines to rise within the basin, typically forming illitic cements; (c) enclosed sandstones (marine facies) are isolated from meteoric water flux and only receive fluxes when fault-induced or when uplifted. Kaolinite morphology and distribution are identified as being flux- or diffusion-controlled.

scholarly journals U-Pb ZIRCON DATING OF MIDDLE EOCENE CLASTIC ROCKS FROM THE GERCUS MOLASSE, NE IRAQ: NEW CONSTRAINTS ON THEIR PROVENANCE, AND TECTONIC EVOLUTION

2021 ◽  
Vol 54 (1C) ◽  
pp. 1-15
Author(s):  
Nabaz Aziz
Keyword(s):  
Tectonic Evolution ◽  
Middle Eocene ◽  
Early Stage ◽  
Foreland Basin ◽  
Detrital Zircons ◽  
Passive Margin ◽  
Accretionary Complex ◽  
Depositional Sequence ◽  
Clastic Rocks ◽  
The North

The provenance of Middle Eocene clastic rock from the Gercus Molasse, NE Iraq was determined by detrital zircon (DZ) U-Pb geochronology. The Gercus Molasse in the Iraqi segment of the north-eastern Zagros Thrust Zone provides an ideal example of foreland system evolution with respect to the transition from passive margin to the accretionary complex terrene-flexural foreland basins. The DZ U-Pb age spectra from the Gercus Molasse suggest that the foreland sediments either influx from multiple provenances or are the result of recycling from the accretionary complex terrane. During pre-accretion, however, the radiolarite basin (Qulqula Radiolarite, 221 Ma) located along Arabian passive margin likely acted as an intermediate sediment repository for most or all of the DZ. Representative DZ U-Pb measurements revealed that the Gercus clastic rocks fall into several separable age population ranges of 92-102 (Albian-Cenomanian), 221 (Upper Triassic), 395-511 (Cambrian), 570- 645 (Neoproterozoic), 1111 (Mesoproterozoic), and lesser numbers of Paleoproterozoic (1622-1991 Ma) ages. The source of Proterozoic detrital Zircons is enigmatic; the age peaks at 1.1, 1.5, 1.6, and 1.9 Ga (Proterozoic) does not correspond to any known outcrops of Precambrian rocks in Iraq, and it may be useful to continue to search for such basement. The detrital zircons with age populations at 0.63–0.86 Ga probably originated from the Arabian-Nubian Shield. The age peak at 0.55 Ga correlates with Cadomian Magmatism reported from north Gondwana. The age peaks at ~0.4 Ga is interpreted to represent Gondwana rifting and the opening of Paleotethys. The youngest ages populations at 93 Ma indicate that fraction of DZ were transported directly from the contemporaneously active magmatic arc (Zagros Ophiolite segments). The paleogeography and tectonic evolution of the Neogene Zagros foreland basin were reconstructed and divided into two tectonic stages. The early stage is defined by the Campanian accreted terranes (i.e. orogenic wedge) form loads sufficient to produce flexural basin with a deepest part is situated next to the tip of the loads. This flexural basin is filled by the flysch clastics of the Maastrichtian– Early Eocene (i.e. referred to by the Tanjero-Kolosh flysch sequence). The late stage is marked by a synchronized modification of the clastics fill of the basin and changes in dip directions to compensate for the reduction of the load by both erosion and extension and the basin, therefore, was sealed by a shallowing upwards depositional sequence ending with the terrestrial Gercus Formation.

scholarly journals The early-stage growth and reversibility of Li electrodeposition in Br-rich electrolytes

2020 ◽  
Vol 118 (2) ◽  
pp. e2012071118
Author(s):  
Prayag Biswal ◽  
Atsu Kludze ◽  
Joshua Rodrigues ◽  
Yue Deng ◽  
Taylor Moon ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Early Stage ◽  
Solid Electrolyte Interphase ◽  
Growth Dynamics ◽  
Ion Diffusion ◽  
Reactive Metal ◽  
Metal Anode ◽  
Sem Image ◽  
Fine Control

The physiochemical nature of reactive metal electrodeposits during the early stages of electrodeposition is rarely studied but known to play an important role in determining the electrochemical stability and reversibility of electrochemical cells that utilize reactive metals as anodes. We investigated the early-stage growth dynamics and reversibility of electrodeposited lithium in liquid electrolytes infused with brominated additives. On the basis of equilibrium theories, we hypothesize that by regulating the surface energetics and surface ion/adatom transport characteristics of the interphases formed on Li, Br-rich electrolytes alter the morphology of early-stage Li electrodeposits; enabling late-stage control of growth and high electrode reversibility. A combination of scanning electron microscopy (SEM), image analysis, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and contact angle goniometry are employed to evaluate this hypothesis by examining the physical–chemical features of the material phases formed on Li. We report that it is possible to achieve fine control of the early-stage Li electrodeposit morphology through tuning of surface energetic and ion diffusion properties of interphases formed on Li. This control is shown further to translate to better control of Li electrodeposit morphology and high electrochemical reversibility during deep cycling of the Li metal anode. Our results show that understanding and eliminating morphological and chemical instabilities in the initial stages of Li electroplating via deliberately modifying energetics of the solid electrolyte interphase (SEI) is a feasible approach in realization of deeply cyclable reactive metal batteries.

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