scholarly journals Polygenic Nature of Olivines from the Ultramafic Lamprophyres of the Terina Complex (Chadobets Upland, Siberian Platform) Based on Trace Element Composition, Crystalline, and Melt Inclusion Data

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 408
Author(s):  
Anastasiya Starikova ◽  
Ilya Prokopyev ◽  
Anna Doroshkevich ◽  
Alexey Ragozin ◽  
Vasily Chervyakovsky
Keyword(s):  
Melt Inclusions ◽  
Melt Inclusion ◽  
Trace Element Composition ◽  
Mantle Metasomatism ◽  
Negative Slope ◽  
Positive Slope ◽  
Melt Evolution ◽  
Different Sources ◽  
Two Populations ◽  
Silicate Carbonate

Olivine from the deep mantle-derived rocks, such as ultramafic lamprophyres, carries important information about the composition of the mantle source, the processes of mantle metasomatism, the origin of specific silicate-carbonate melts, as well as the composition and mechanisms of crystallization of these rocks. Textures and compositions of olivine from the carbonate-rich ultramafic lamprophyres (aillikites) of the Terina complex, along with their mineral and melt inclusions, exposed that olivines have different sources. Two populations of olivines were considered: macrocrysts (>1 mm) and groundmass olivines (<1 mm). Groundmass olivines are phenocrysts and characterized by weak variations in Mg# (84–86.5), a sharp increase in Ca and Ti contents, and a decrease in Ni and Cr from core to rim. They have higher concentrations of Li, Cu, Ti, and Na compared to macrocrysts. Among the macrocrysts, the following populations are observed: (1) high-Mg olivines (Mg# 89–91) with high Ni and low Ti contents, which are interpreted as xenocrysts from the slightly depleted lherzolite mantle; (2) high-Ca olivines (Mg# 84–88, CaO 0.13–0.21 wt %), which have patterns similar to groundmass olivines and are interpreted as cumulates of early portions of aillikite melt; (3) macrocrysts with wide variations in Mg# (73–88), low CaO contents (0.04–0.11 wt %), and positive slope in Ca vs. Al and negative slope in Ca vs. Mn, which are interpreted as disintegrated megacrysts from the Cr-poor megacryst suite. The megacryst suite could have been formed in the pre-trap period during the melting of the metasomatized subcontinental lithospheric mantle (SCLM). The aillikite melt evolution is traced by secondary melt inclusions in olivine macrocrysts: early phlogopite-diopside-calcite-apatite association, containing Ti-magnetite and ilmenite, is followed by an association with magnetite and sulfides (pyrrhotite and pentlandite); finally, at a late stage, inclusions with a predominance of Ca-Na-carbonates and sulfates and enriched in U, Th, Y, REEs, Sr, and Ba were captured.

Melt inclusions in olivines from phoscorites and olivinites of the Kovdor massif.

2020 ◽  
Author(s):  
Anna Redina ◽  
Cora Wohlgemuth-Ueberwasser ◽  
Julia Mikhailova ◽  
Gregory Ivanyuk
Keyword(s):  
Melt Inclusions ◽  
Trace Element Composition ◽  
Russian Science ◽  
Silicate Mineral ◽  
Mineral Phases ◽  
Icp Ms ◽  
Kola Alkaline Province ◽  
Negative Crystal ◽  
The Baltic ◽  
Silicate Carbonate

&lt;p&gt;The Kovdor massif is a part of the Paleozoic Kola alkaline province and located in the eastern part of the Baltic Shield. Kovdor carbonatites host a unique complex baddeleyite-apatite-magnetite deposit from which iron ores and zirconium have been mined. New data on melt inclusions in olivine crystals from phoscorites and olivinites of the ore complex are presented in this contribution. Daughter minerals in crystallized melt inclusions were identified by Raman spectroscopy and scanning electron microscopy. The trace element composition of inclusions was determined using LA-ICP-MS.&lt;/p&gt;&lt;p&gt;Melt inclusions in olivine from Kovdor phoscorites are negative crystal or round in shape, with sizes ranging from 5 to 50 microns. They form groups or line up. According to the mineral composition, two types of melt inclusions can be distinguished: carbonate and silicate-carbonate. In the first type, Ca-Na-Mg- (Sr?) - REE carbonates are dominant among daughter phases. In the second one, silicate phases (phlogopite, monticellite, diopside), Ca-Na-Mg carbonates and magnetite are found together. Melt inclusions in olivine from olivinites are isometric or elongated, 5&amp;#8211;25 &amp;#956;m in size. They form groups or occur as isolated inclusions. Benstoneite, geylussit, ankerite, calcite and hydroxyl-bastnesite along with phyllosilicates (phlogopite, paragonite?) were identified among daughter minerals.&lt;/p&gt;&lt;p&gt;The rare earth elements composition of melt inclusions from both types of rocks is characterized by the predominance of light REE. The content of REE, especially light ones, in inclusions from phoscorites is higher. Strontium and barium contents in most melt inclusions have negative correlations with niobium and zirconium concentrations.&lt;/p&gt;&lt;p&gt;Melt inclusions from phoscorites and olivinites contain carbonate and silicate mineral phases in various proportions, which may imply heterogeneous trapping of crystalline phases and two immiscible melts, silicate and carbonatite. Inclusions from phoscorite represent a more evolved magma with higher concentrations of rare metals.&lt;/p&gt;&lt;p&gt;This work was supported by the Russian Science Foundation, grant No 19-17-00013.&lt;/p&gt;

A myriad of melt inclusions: a synchrotron microtomography study of melt inclusions and vapour bubbles from Colli Albani (Italy)

2021 ◽  
Author(s):  
Corin Jorgenson ◽  
Luca Caricchi ◽  
Michael Stueckelberger ◽  
Giovanni Fevola ◽  
Gregor Weber
Keyword(s):  
Melt Inclusions ◽  
Melt Inclusion ◽  
Fluid Phase ◽  
Volcanic Eruptions ◽  
Mineral Chemistry ◽  
Magma Ascent ◽  
Vapour Bubble ◽  
Electron Synchrotron ◽  
Colli Albani ◽  
Synchrotron Microtomography

&lt;p&gt;Melt inclusions provide a window into the inner workings of magmatic systems. Both mineral chemistry and volatile distributions within melt inclusions can provide valuable information about the processes modulating magma ascent and preceding volcanic eruptions. Many melt inclusions host vapour bubbles which can be rich in CO&lt;sub&gt;2&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt;O and must be taken into consideration when assessing the volatile budget of magmatic reservoirs. These vapour bubbles can be the product of differential volumetric contraction between the melt inclusion and host phase during an eruption or indicate an excess fluid phase in the magma reservoir. Thus, determining the distribution of volatiles between melt and vapour bubbles is integral to our fundamental understanding of melt inclusions, and by extension the evolution of volatiles within magmatic systems.&lt;/p&gt;&lt;p&gt;A large dataset of 79 high-resolution tomographic scans of clinopyroxene and leucite phenocrysts from the Colli Albani Caldera Complex (Italy) was recently acquired at the German Electron Synchrotron (DESY). These tomograms allow us to quantify the volume of melt inclusions and associated vapour bubble both glassy and microcrystalline melt inclusions. Notably, in the glassy melt inclusions the vapour bubbles exist either as a single large vapour bubble in the middle of the melt inclusion or as several smaller vapour bubbles distributed around the edge of the melt inclusion. These two types of melt inclusions can coexist within a single crystal. We suggest that the occurrence of these rim- bubbles is caused by one of two exsolution pathways, either pre-entrapment and bubble migration or post entrapment with preferential exsolution at the rims. By combining the analysis of hundreds of melt inclusions with the chemistry of the host phase we aim to unveil magma ascent rates and distribution of excess fluids within the magmatic system of Colli Albani, which produced several mafic-alkaline large volume ignimbrites.&lt;/p&gt;

scholarly journals What lies beneath? Reconstructing the primitive magmas fueling voluminous silicic volcanism using olivine-hosted melt inclusions

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 504-508 ◽  
Author(s):  
Simon J. Barker ◽  
Michael C. Rowe ◽  
Colin J.N. Wilson ◽  
John A. Gamble ◽  
Shane M. Rooyakkers ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Melt Inclusion ◽  
Taupo Volcanic Zone ◽  
Mantle Dynamics ◽  
Silicic Volcanism ◽  
Depleted Mantle ◽  
Basaltic Magmas ◽  
Show Evidence ◽  
Basaltic Melts ◽  
Eruptive Centers

Abstract Understanding the origins of the mantle melts that drive voluminous silicic volcanism is challenging because primitive magmas are generally trapped at depth. The central Taupō Volcanic Zone (TVZ; New Zealand) hosts an extraordinarily productive region of rhyolitic caldera volcanism. Accompanying and interspersed with the rhyolitic products, there are traces of basalt to andesite preserved as enclaves or pyroclasts in caldera eruption products and occurring as small monogenetic eruptive centers between calderas. These mafic materials contain MgO-rich olivines (Fo79–86) that host melt inclusions capturing the most primitive basaltic melts fueling the central TVZ. Olivine-hosted melt inclusion compositions associated with the caldera volcanoes (intracaldera samples) contrast with those from the nearby, mafic intercaldera monogenetic centers. Intracaldera melt inclusions from the modern caldera volcanoes of Taupō and Okataina have lower abundances of incompatible elements, reflecting distinct mantle melts. There is a direct link showing that caldera-related silicic volcanism is fueled by basaltic magmas that have resulted from higher degrees of partial melting of a more depleted mantle source, along with distinct subduction signatures. The locations and vigor of Taupō and Okataina are fundamentally related to the degree of melting and flux of basalt from the mantle, and intercaldera mafic eruptive products are thus not representative of the feeder magmas for the caldera volcanoes. Inherited olivines and their melt inclusions provide a unique “window” into the mantle dynamics that drive the active TVZ silicic magmatic systems and may present a useful approach at other volcanoes that show evidence for mafic recharge.

scholarly journals Petrogenesis of Ultramafic Lamprophyres from the Terina Complex (Chadobets Upland, Russia): Mineralogy and Melt Inclusion Composition

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 419 ◽  
Author(s):  
Ilya Prokopyev ◽  
Anastasiya Starikova ◽  
Anna Doroshkevich ◽  
Yazgul Nugumanova ◽  
Vladislav Potapov
Keyword(s):  
Mineral Composition ◽  
Fractional Crystallization ◽  
Fluid Inclusions ◽  
Siberian Craton ◽  
Melt Inclusions ◽  
Melt Inclusion ◽  
Inclusion Composition ◽  
Accessory Minerals ◽  
Secondary Minerals ◽  
Peridotite Mantle

The mineral composition and melt inclusions of ultramafic lamprophyres of the Terina complex were investigated. The rocks identified were aillikites, mela-aillikites, and damtjernites, and they were originally composed of olivine macrocrysts and phenocrysts, as well as phlogopite phenocrysts in carbonate groundmass, containing phlogopite, clinopyroxene and feldspars. Minor and accessory minerals were fluorapatite, ilmenite, rutile, titanite, and sulphides. Secondary minerals identified were quartz, calcite, dolomite, serpentine, chlorite, rutile, barite, synchysite-(Ce), and monazite-(Ce). Phlogopite, calcite, clinopyroxene, Ca-amphibole, fluorapatite, magnetite, and ilmenite occurred as daughter-phases in melt inclusions. The melt inclusions also contained Fe–Ni sulphides, synchysite-(Ce) and, probably, anhydrite. The olivine macrocrysts included orthopyroxene and ilmenite, and the olivine phenocrysts included Cr-spinel and Ti-magnetite inclusions. Crystal-fluid inclusions in fluorapatite from damtjernites contain calcite, clinopyroxene, dolomite, and barite. The data that were obtained confirm that the ultramafic lamprophyres of the Terina complex crystallized from peridotite mantle-derived carbonated melts and they have not undergone significant fractional crystallization. The investigated rocks are considered to be representative of melts that are derived from carbonate-rich mantle beneath the Siberian craton.

Effect of Intermediate Support on Instabilities of a Cantilever With Terminal Dynamic Moment

2019 ◽  
Author(s):  
Mahmoud Abdullatif ◽  
Ranjan Mukherjee
Keyword(s):  
Negative Slope ◽  
Positive Slope ◽  
Critical Stability ◽  
Flutter Instability ◽  
Intermediate Support ◽  
Instability Modes ◽  
Stability Point ◽  
The Stability ◽  
The Moment ◽  
Dynamic Moment

Abstract The stability characteristics of a cantilever beam, with and without an intermediate support, subjected to a dynamic terminal moment, is investigated. The moment is assumed to be proportional to the slope of a point along the length of the beam. The proportionally constant, which can be positive or negative, is varied to find the critical stability point. In the absence of intermediate support, stability is lost through divergence when the dynamic moment is proportional to the positive slope, and through flutter when the dynamic moment is proportional to the negative slope. In contrast, the nature of instability switches between divergence and flutter, and between different flutter instability modes while undergoing flutter, in the presence of an intermediate support.

scholarly journals A Plethora of Epigenetic Minerals Reveals a Multistage Metasomatic Overprint of a Mantle Orthopyroxenite from the Udachnaya Kimberlite

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 264
Author(s):  
Dmitriy I. Rezvukhin ◽  
Taisia A. Alifirova ◽  
Alexander V. Golovin ◽  
Andrey V. Korsakov
Keyword(s):  
Melt Inclusions ◽  
Kimberlite Pipe ◽  
Mantle Metasomatism ◽  
Crystal Chemical Formula ◽  
Mineral Inclusions ◽  
Reaction Zones ◽  
Geochemical Analyses ◽  
Individual Grains ◽  
Kimberlite Field ◽  
Intergranular Space

More than forty mineral species of epigenetic origin have been identified in an orthopyroxenite from the Udachnaya-East kimberlite pipe, Daldyn kimberlite field, Siberian platform. Epigenetic phases occur as: (1) Mineral inclusions in the rock-forming enstatite, (2) daughter minerals within large (up to 2 mm) crystallized melt inclusions (CMI) in the rock-forming enstatite, and (3) individual grains and intergrowths in the intergranular space of the xenolith. The studied minerals include silicates (olivine, clinopyroxene, phlogopite, tetraferriphlogopite, amphibole-supergroup minerals, serpentine-group minerals, talc), oxides (several generations of ilmenite and spinel, rutile, perovskite, rare titanates of the crichtonite, magnetoplumbite and hollandite groups), carbonates (calcite, dolomite), sulfides (pentlandite, djerfisherite, pyrrhotite), sulfate (barite), phosphates (apatite and phosphate with a suggested crystal-chemical formula Na2BaMg[PO4]2), oxyhydroxide (goethite), and hydroxyhalides (kuliginite, iowaite). The examined epigenetic minerals are interpreted to have crystallized at different time spans after the formation of the host rock. The genesis of minerals is ascribed to a series of processes metasomatically superimposed onto the orthopyroxenite, i.e., deep-seated mantle metasomatism, infiltration of a kimberlite-related melt and late post-emplacement hydrothermal alterations. The reaction of orthopyroxene with the kimberlite-related melt has led to orthopyroxene dissolution and formation of the CMI, the latter being surrounded by complex reaction zones and containing zoned olivine grains with extremely high-Mg# (up to 99) cores. This report highlights the utility of minerals present in minor volume proportions in deciphering the evolution and modification of mantle fragments sampled by kimberlitic and other deep-sourced magmas. The obtained results further imply that the whole-rock geochemical analyses of mantle-derived samples should be treated with care due to possible drastic contaminations from “hiding” minor phases of epigenetic origin.

The chlorine-isotopic composition of lunar KREEP from magnesian-suite troctolite 76535

2020 ◽  
Vol 105 (8) ◽  
pp. 1270-1274
Author(s):  
Francis M. McCubbin ◽  
Jessica J. Barnes
Keyword(s):  
Isotopic Composition ◽  
Melt Inclusions ◽  
Melt Inclusion ◽  
Isotopic Fractionation ◽  
Magma Ocean ◽  
Geochemical Composition ◽  
Isotopic Compositions ◽  
Stable Isotopic ◽  
Lunar Samples

Abstract We conducted in situ Cl isotopic measurements of apatite within intercumulus regions and within a holocrystalline olivine-hosted melt inclusion in magnesian-suite troctolite 76535 from Apollo 17. These data were collected to place constraints on the Cl-isotopic composition of the last liquid to crystallize from the lunar magma ocean (i.e., urKREEP, named after its enrichments in incompatible lithophile trace elements like potassium, rare earth elements, and phosphorus). The apatite in the olivine-hosted melt inclusion and within the intercumulus regions of the sample yielded Cl-isotopic compositions of 28.3 ± 0.9‰ (2σ) and 30.3 ± 1.1‰ (2σ), respectively. The concordance of these values from both textural regimes we analyzed indicates that the Cl-isotopic composition of apatites in 76535 likely represents the Cl-isotopic composition of the KREEP-rich magnesian-suite magmas. Based on the age of 76535, these results imply that the KREEP reservoir attained a Cl-isotopic composition of 28–30‰ by at least 4.31 Ga, consistent with the onset of Cl-isotopic fractionation at the time of lunar magma ocean crystallization or shortly thereafter. Moreover, lunar samples that yield Cl-isotopic compositions higher than the value for KREEP are likely affected by secondary processes such as impacts and/or magmatic degassing. The presence of KREEP-rich olivine-hosted melt inclusions within one of the most pristine and ancient KREEP-rich rocks from the Moon provides a new opportunity to characterize the geochemistry of KREEP. In particular, a broader analysis of stable isotopic compositions of highly and moderately volatile elements could provide an unprecedented advancement in our characterization of the geochemical composition of the KREEP reservoir and of volatile-depletion processes during magma ocean crystallization, more broadly.

scholarly journals Volume-timing relationships during cough and resistive loading in the cat

2000 ◽  
Vol 89 (2) ◽  
pp. 785-790 ◽  
Author(s):  
Donald C. Bolser ◽  
Paul W. Davenport
Keyword(s):  
Linear Relationship ◽  
Negative Slope ◽  
Inspiratory Time ◽  
Positive Slope ◽  
Single Breath ◽  
Resistive Loading ◽  
Resistive Loads ◽  
The Relationship ◽  
Pattern Regulation ◽  
Pulmonary Volume

The relationship between pulmonary volume-related feedback and inspiratory (CTi) and expiratory (CTe) phase durations during cough was determined. Cough was produced in anesthetized cats by mechanical stimulation of the intrathoracic tracheal lumen. During eupnea, the animals were exposed to single-breath inspiratory and expiratory resistive loads. Cough was associated with large increases in inspiratory volume (Vi) and expiratory volume (Ve) but no change in phase durations compared with eupnea. There was no relationship between Viand CTi during coughing. A linear relationship with a negative slope existed between Vi and eupneic inspiratory time during control and inspiratory resistive loading trials. There was no relationship between Ve and CTe during all coughs. However, when the first cough in a series or a single cough was analyzed, the Ve/CTe relationship had a positive slope. A linear relationship with a negative slope existed between Ve and eupneic expiratory time during control and expiratory resistive loading trials. These results support separate ventilatory pattern regulation during cough that does not include modulation of phase durations by pulmonary volume-related feedback.

scholarly journals Application of Starch-Stabilized Silver Nanoparticles as a Colorimetric Sensor for Mercury(II) in 0.005 mol/L Nitric Acid

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Penka Vasileva ◽  
Teodora Alexandrova ◽  
Irina Karadjova
Keyword(s):  
Silver Nanoparticles ◽  
Optical Sensor ◽  
High Selectivity ◽  
Localized Surface Plasmon ◽  
Negative Slope ◽  
Positive Slope ◽  
Plasmon Absorption Band ◽  
Relative Standard ◽  
Mechanism Of Interaction ◽  
Redox Interaction

A sensitive and selective Hg2+optical sensor has been developed based on the redox interaction of Hg2+with starch-coated silver nanoparticles (AgNPs) in the presence of 0.005 mol L−1HNO3. The relative intensity of the localized surface plasmon absorption band of AgNPs at 406 nm is linearly dependent on the concentration of Hg2+with positive slope for the concentration range 0–12.5 μg L−1and negative slope for the concentration range 25–500 μg L−1. Experiments performed demonstrated that metal ions (Na+, K+, Mg2+, Ca2+, Pb2+, Cu2+, Zn2+, Cd2+, Fe3+, Co2+, and Ni2+) do not interfere under the same conditions, due to the absence of oxidative activity of these ions, which guarantees the high selectivity of the proposed optical sensor towards Hg2+. The limits of detection and quantification were found to be 0.9 µg L−1and 2.7 µg L−1, respectively, and relative standard deviations varied in the range 9–12% for Hg content from 0.9 to 12.5 μg L−1and 5–9% for Hg levels from 25 to 500 μg L−1. The method was validated by analysis of CRM Estuarine Water BCR505. A possible mechanism of interaction between AgNPs and Hg2+for both concentration ranges was proposed on the basis of UV-Vis, TEM, and SAED analyses.

scholarly journals Two Light-Induced Processes in the Photoreceptor Cells of Limulus Ventral Eye

1971 ◽  
Vol 58 (5) ◽  
pp. 544-561 ◽  
Author(s):  
J. E. Lisman ◽  
J. E. Brown
Keyword(s):  
Voltage Clamp ◽  
Photoreceptor Cell ◽  
Reversal Potential ◽  
Membrane Conductance ◽  
Photoreceptor Cells ◽  
Negative Slope ◽  
Induced Current ◽  
Positive Slope ◽  
Current Voltage ◽  
Lower Slope

The dark-adapted current-voltage (I-V) curve of a ventral photoreceptor cell of Limulus, measured by a voltage-clamp technique, has a high slope-resistance region more negative than resting voltage, a lower slope-resistance region between resting voltage and zero, and a negative slope-resistance region more positive than 0 v. With illumination, we find no unique voltage at which there is no light-induced current. At the termination of illumination, the I-V curve changes quickly, then recovers very slowly to a dark-adapted configuration. The voltage-clamp currents during and after illumination can be interpreted to arise from two separate processes. One process (fast) changes quickly with change in illumination, has a reversal potential at +20 mv, and has an I-V curve with positive slope resistance at all voltages. These properties are consistent with a light-induced change in membrane conductance to sodium ions. The other process (slow) changes slowly with changes in illumination, generates light-activated current at +20 mv, and has an I-V curve with a large region of negative slope resistance. The mechanism of this process cannot as yet be identified.

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