Solidification timescale for the Dufek Intrusion, Antarctica determined by U-Pb zircon ages

2020 ◽  
Author(s):  
Jill VanTongeren ◽  
Aidan Taylor ◽  
Blair Schoene
Keyword(s):  
Bushveld Complex ◽  
Lower Section ◽  
Magma Chambers ◽  
Skaergaard Intrusion ◽  
Mafic Intrusion ◽  
Three Samples ◽  
Two Samples ◽  
Mineral Compositions ◽  
Layered Mafic Intrusion ◽  
Stratigraphic Thickness

<p>The 8-9 km thick Dufek layered mafic intrusion of Antarctica was emplaced at approximately 182 Ma associated with the Ferrar dolerites and the breakup of the supercontinent Gondwana.  It is rivaled in thickness only by the Bushveld Complex of South Africa and shows a similar progression in mineral compositions all the way to the uppermost contact with an overlying granophyre layer.  This progression in mineral composition suggests that it crystallized from the bottom to the top and did not form an upper solidification front (a.k.a., Upper Border Series) typical of smaller intrusions such as the Skaergaard Intrusion.  Unlike the Bushveld Complex, however, the Dufek Intrusion is exposed in only two ~1.8 km thick sections: the lowermost Dufek Massif, and the uppermost Forrestal Range, which are separated from one another by a ~50km wide snowfield.  The remainder of the stratigraphy is inferred from geophysics, evolution of mineral compositions, and projection of the dip of the layering through the snowfield. </p><p> </p><p>            We obtained precise CA-ID-TIMS U-Pb zircon ages from samples from the Dufek Massif and Forrestal Range in order to determine the timescale of solidification of a large layered mafic intrusion.  What we found is surprising - zircons from the bottom of the intrusion record younger ages than those from the top of the intrusion.  Two samples from the Dufek Massif have zircon U-Pb ages of 182.441±0.048 Ma and 182.496±0.057 Ma; whereas three samples from the Forrestal Range have zircon U-Pb ages of 182.601±0.064 Ma, 182.660±0.10 Ma, 182.78±0.21 Ma.  Thus, the lower section of the Dufek Intrusion solidified approximately 160,000 years after the upper.  We explore two possibilities for this reverse-age stratigraphy, (1) that the ages reflect the solidification of interstitial melt in a single magma chamber cooling from the top down, or (2) that the Dufek Massif and Forrestal Range are two separate magma chambers that are not connected at depth.  Our results have implications for the stratigraphic thickness estimates of the Dufek Intrusion as well as the duration of magmatism associated with continental breakup.</p><p> </p><p> </p>

A 5-km-thick reservoir with >380,000 km3 of magma within the ancient Earth's crust

2021 ◽  
Author(s):  
Rais Latypov ◽  
Sofya Chistyakova ◽  
Richard Hornsey ◽  
Gelu Costin ◽  
Mauritz van der Merwe
Keyword(s):  
Bushveld Complex ◽  
Earth’S Crust ◽  
Magma Chambers ◽  
Crystallization Sequence ◽  
Igneous Provinces ◽  
Research Concept ◽  
History Of ◽  
Mineral Compositions ◽  
Earth's Crust ◽  
Chamber Floor

Abstract Several recent studies have argued that large, long-lived and molten magma chambers1–10 may not occur in the shallow Earth’s crust11–23. Here we present, however, field-based observations from the Bushveld Complex24 that provide evidence to the contrary. In the eastern part of the complex, the magmatic layering was found to continuously drape across a ~4-km-high sloping step in the chamber floor. Such deposition of magmatic layering implies that the resident melt column was thicker than the stepped relief of the chamber floor. Prolonged internal differentiation within such a thick magma column is further supported by evolutionary trends in crystallization sequence and mineral compositions through the sequence. The resident melt column in the Bushveld chamber during this period is estimated to be >5-km-high in thickness and >380,000 km3 in volume. This amount of magma is three orders of magnitude larger than any known super-eruptions in the Earth’s history25 and is only comparable to the extrusive volumes of some of Earth’s large igneous provinces26. This suggests that super-large, entirely molten and long-lived magma chambers, at least occasionally, occur in the geological history of our planet. Therefore, the classical view of magma chambers as ‘big magma tanks’1–10 remains a viable research concept for some of Earth’s magmatic provinces.

scholarly journals Biosystematic Study on Some Egyptian Species of Astragalus L. (Fabaceae)

Agriculture ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 125
Author(s):  
Monier M. Abd El-Ghani ◽  
Ashraf S. A. El-Sayed ◽  
Ahmed Moubarak ◽  
Rabab Rashad ◽  
Hala Nosier ◽  
...  
Keyword(s):  
Genetic Relationships ◽  
Dna Barcode ◽  
Plant Morphology ◽  
Its Region ◽  
Its2 Region ◽  
Whole Plant ◽  
Three Samples ◽  
Two Samples ◽  
Region 10 ◽  
Unique Banding Pattern

Astragalus L. is one of the largest angiosperm complex genera that belongs to the family Fabaceae, subfamily Papilionoideae or Faboideae under the subtribe Astragalinae of the tribe Galegeae. The current study includes the whole plant morphology, DNA barcode (ITS2), and molecular marker (SCoT). Ten taxa representing four species of Astragalus were collected from different localities in Egypt during the period from February 2018 to May 2019. Morphologically, identification and classification of collected Astragalus plants occurred by utilizing the light microscope, regarding the taxonomic revisions of the reference collected Astragalus specimens in other Egyptian Herbaria. For molecular validation, ten SCoT primers were used in this study, producing a unique banding pattern to differentiate between ten samples of Astragalus taxa which generated 212 DNA fragments with an average of 12.2 bands per 10 Astragalus samples, with 8 to 37 fragments per primer. The 212 fragments amplified were distributed as 2 monomorphic bands, 27 polymorphic without unique bands, 183 unique bands (210 Polymorphic with unique bands), and ITS2 gene sequence was showed as the optimal barcode for identifying Astragalus L. using BLAST searched on NCBI database, and afterward, analyzing the chromatogram for ITS region, 10 samples have been identified as two samples representing A. hauarensis, four samples representing A. sieberi, three samples representing A. spinosus and one sample representing A. vogelii. Based on the ITS barcode, A. hauarensis RMG1, A. hauarensis RMG2, A. sieberi RMG1, A. sieberi RMG2, A. sieberi RMG3, A. sieberi RMG4, A. spinosus RMG1, A. spinosus RMG2, A. spinosus RMG3, A. vogelii RMG were deposited into GenBank with accession # MT367587.1, MT367591.1, MT367593.1, MT367585.1, MT367586.1, MT367588.1, MT160347.1, MT367590.1, MT367589.1, MT367592.1, respectively. These results indicated the efficiency of SCoT markers and ITS2 region in identifying and determining genetic relationships between Astragalus species.

scholarly journals A Comparison of the Composition of Selected Commercial Sandalwood Oils with the International Standard

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2249
Author(s):  
Malgorzata Kucharska ◽  
Barbara Frydrych ◽  
Wiktor Wesolowski ◽  
Jadwiga A. Szymanska ◽  
Anna Kilanowicz
Keyword(s):  
Mass Spectrometry Analysis ◽  
Santalum Album ◽  
Benzyl Benzoate ◽  
Spectrometry Analysis ◽  
Correct Information ◽  
Three Samples ◽  
Two Samples ◽  
High Street ◽  
Chromatographic Profile ◽  
Sandalwood Oil

Sandalwood oils are highly desired but expensive, and hence many counterfeit oils are sold in high street shops. The study aimed to determine the content of oils sold under the name sandalwood oil and then compare their chromatographic profile and α- and β santalol content with the requirements of ISO 3518:2002. Gas chromatography with mass spectrometry analysis found that none of the six tested “sandalwood” oils met the ISO standard, especially in terms of α-santalol content. Only one sample was found to contain both α- and β-santalol, characteristic of Santalum album. In three samples, valerianol, elemol, eudesmol isomers, and caryophyllene dominated, indicating the presence of Amyris balsamifera oil. Another two oil samples were found to be synthetic mixtures: benzyl benzoate predominating in one, and synthetic alcohols, such as javanol, polysantol and ebanol, in the other. The product label only gave correct information in three cases: one sample containing Santalum album oil and two samples containing Amyris balsamifera oil. The synthetic samples described as 100% natural essential oil from sandalwood are particularly dangerous and misleading to the consumer. Moreover, the toxicological properties of javanol, polysantol and ebanol, for example, are unknown.

Magnetic study of Fe3O4/Ag nanoparticles

2018 ◽  
Vol 83 (1) ◽  
pp. 10402
Author(s):  
Janusz Typek ◽  
Nikos Guskos ◽  
Grzegorz Zolnierkiewicz ◽  
Zofia Lendzion-Bielun ◽  
Anna Pachla ◽  
...  
Keyword(s):  
Antibacterial Properties ◽  
Blocking Temperature ◽  
Precipitation Method ◽  
Magnetic Clusters ◽  
Mass Ratio ◽  
Three Samples ◽  
Two Samples ◽  
Magnetic Resonance Technique ◽  
Silver Nps ◽  
Multi Mode

Nanocomposites of Fe3O4 nanoparticles (NPs) impregnated with silver NPs display antibacterial properties and may be used in water treatment as disinfection agent. Three samples were synthesized: Fe3O4 NPs obtained by the precipitation method and additionally two samples with added silver NPs with mass ratio of Ag:Fe3O4 equal to 1:100 and 2:100. Magnetic properties of these samples were studied by SQUID magnetometry (in temperature range 2–300 K and magnetic fields up to 70 kG) and magnetic resonance technique at RT. Temperature dependence of dc susceptibility revealed the blocking temperature close to RT in all three samples and allowed to determine the presence of single or multi-mode distribution of NP sizes in a particular sample. Isothermal magnetisation measurements showed that the presence of silver NPs, especially those with smaller sizes, decreases the saturation magnetisation. The shape of ferromagnetic loop registered at T = 2 K was used to discuss the sizes of NP magnetic clusters in our samples. Conclusions obtained from analysis of the ferromagnetic resonance spectra were consistent with the propositions based on the magnetometric studies.

scholarly journals The influence of high pressure on the properties of natural alumino-silicates

2002 ◽  
Vol 34 (2) ◽  
pp. 163-168
Author(s):  
N. Susic
Keyword(s):  
High Pressure ◽  
Thermal Behaviour ◽  
Amorphous Layer ◽  
New Materials ◽  
Crystalline Phases ◽  
Amorphous Phases ◽  
Long Period ◽  
Two Samples ◽  
Mineral Compositions

The effect of the application of high-pressure (up to 12 GPa) on natural alumino-silicates has been studied. Chemical and mineral compositions and thermal behaviour have been analyzed of two samples of alumino-silicates. Results obtained indicate that the application of high pressure causes notable changes. A particularly significant one is the formation of amorphous phases on account of crystalline phases. An amorphous layer formed on particle surfaces with its diverse physical, mechanical, chemical, and other properties, especially over a long period of time, can influence the processes provoking or activating land slides or soil settlements. This enables derivation of many new materials with entirely new properties important for use in the ceramic and brick industries.

scholarly journals Ultrasonic Shaking of Glauconite Pellets with Diverse Reagents for a Comparison of Their K–Ar with Already Published Rb–Sr Results

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 439
Author(s):  
Norbert Clauer ◽  
Edward Keppens ◽  
I. Tonguç Uysal ◽  
Amélie Aubert
Keyword(s):  
Clay Material ◽  
Similar Data ◽  
X Ray Diffraction ◽  
Metallic Trace Elements ◽  
Three Samples ◽  
Isotopic Studies ◽  
Mineral Assemblages ◽  
Preparation Step ◽  
Mineral Compositions ◽  
Sr Method

A combined ultrasonic treatment, with de-ionized H2O, dilute HAc or dilute HCl, of three Mid-Miocene glauconite samples was applied to K–Ar date the different separates in order to compare the results with those obtained by the Rb–Sr method using the same three samples and that were analyzed strictly in the same way. Two aliquots yield opposite elemental and K–Ar trends, which suggests different initial mineral compositions for the various pellets. The K–Ar data of two untreated and leached L7 and L8 aliquots are almost within analytical uncertainty from 17.3 ± 0.6 Ma to 19.6 ± 0.7 Ma (2σ), while those of the third L10 sample are slightly higher at 22.1 ± 1.2 Ma (2σ). Comparatively, the earlier published Rb–Sr ages of the three untreated samples and of the leached aliquots gave similar data for the L7 aliquots by an isochron at 18.1 ± 3.1 (2σ) Ma and for the sample L8 by an isochron with an age of 19.6 ± 1.8 (2σ) Ma, while the untreated L10 aliquot yields a very high Rb–Sr date of 42.1 ± 1.6 (2σ) Ma. This untreated L10 glauconite fraction contains blödite, a Sr-rich carbonate that impacted the two isotopic systems differently. Generally, dilute HCl or HAc acids dissolve carbonates, sulfates, sulfites and oxides, while they do not affect the clay-type crystals such as glauconites. These soluble minerals can be identified indirectly, as here, by X-ray diffraction and the amounts of leached Na2O, CaO and Fe2O3 contents. Together with the leaching of some metallic trace elements, those of NaO confirm the leaching of metals and of blödite that are both hosted by the glauconite pellets. The occurrence of this Sr-enriched mineral explains the age differences of the non-treated aliquots and suggests a systematic leaching of any glauconite separate before isotope determination and, possibly, a comparison of the Rb–Sr and K–Ar results. Ultrasonic shaking appears appropriate for physical disaggregation of any contaminating grains that may remain hosted within the pellets, even after a preliminary H2O wash, which may dissolve and remove the soluble minerals but not the H2O-insoluble silicates. The K–Ar study completed here as a complement to a previous Rb–Sr study highlights, again, the importance of the preparation step in isotopic studies of glauconite-type and, by extension, of any clay material, as all occurring minerals can interfere in the final age determinations and, therefore, differently in the mineral assemblages. All those not in isotopic equilibrium need to be removed before analysis, including the soluble Sr or alkali-enriched ones.

Misinterpretation of zircon ages in layered intrusions

2021 ◽  
Author(s):  
R. Latypov ◽  
S. Chistyakova
Keyword(s):  
Phase Equilibria ◽  
High Precision ◽  
Bushveld Complex ◽  
Classical Model ◽  
Layered Intrusions ◽  
Isotopic Data ◽  
Magma Chambers ◽  
Stratigraphic Position

Abstract A recent re-interpretation of the Bushveld Complex and other layered intrusions as stacks of randomly emplaced, amalgamated sills is mostly fuelled by finding of zircon ages that are not getting progressively younger from the base upwards, as expected from a classical model for the formation of layered intrusions. Rather, they display several reversals from older to younger ages and vice-versa with moving up-section through the layered intrusions. Here, we show that the reported zircon ages are at odds with the relative ages of rocks as defined by cross-cutting relations in potholes of the Bushveld Complex. This indicates that interpretation of the zircon isotopic data as the emplacement age of the studied rocks/units is incorrect, making a new emplacement model for layered intrusions baseless. This conclusion is further buttressed by the phase equilibria analysis showing that regular cumulate sequences of layered intrusions are not reconcilable with a model of randomly emplaced sills. In this model, the late sills are free to intrude at any stratigraphic position of the pre-existing rocks, producing magmatic bodies with chaotic crystallization sequences and mineral compositional trends that are never observed in layered intrusions. There are thus no valid justifications for the re-evaluation of the current petrological model of the Bushveld Complex and other layered intrusions as large, long-lived and largely molten magma chambers. A fundamental implication of this analysis is that the current high-precision U-Pb TIMS ages from layered intrusions are inherently unreliable on the scale of several million years and cannot therefore be used for rigorous estimations of the timing of crystallization, duration of magmatism, and cooling of these intrusions.

scholarly journals The Effect of Weathering on Salt Release from Coal Mine Spoils

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 760
Author(s):  
Melinda Hilton ◽  
Mandana Shaygan ◽  
Neil McIntyre ◽  
Thomas Baumgartl ◽  
Mansour Edraki
Keyword(s):  
Particle Size ◽  
Coal Mine ◽  
Chemical Weathering ◽  
Physical Weathering ◽  
Particle Size Fractions ◽  
Mine Spoils ◽  
Weathering Processes ◽  
Three Samples ◽  
Two Samples ◽  
Physical And Chemical

Coal mine spoils have the potential to create environmental impacts, such as salt load to surrounding environments, particularly when exposed to weathering processes. This study was conducted to understand the effect of physical and chemical weathering on the magnitude, rate, and dynamics of salt release from different coal mine spoils. Five spoil samples from three mines in Queensland were sieved to three different particle size fractions (<2 mm, 2–6 mm, and >6 mm). Two samples were dispersive spoils, and three samples were nondispersive spoils. The spoils were subjected to seven wet–dry cycles, where the samples were periodically leached with deionised water. The rate, magnitude, and dynamics of solutes released from spoils were spoil specific. One set of spoils did not show any evidence of weathering, but initially had higher accumulation of salts. In contrast, broad oxidative weathering occurred in another set of spoils; this led to acid generation and resulted in physical weathering, promoting adsorption–desorption and dissolution and, thus, a greater release of salts. This study indicated that the rate and magnitude of salt release decreased with increasing particle size. Nevertheless, when the spoil is dispersive, the degree of weathering manages salt release irrespective of initial particle size. This study revealed that the long-term salt release from spoils is not only governed by geochemistry, weathering degree, and particle size but also controlled by the water/rock ratio and hydrological conditions of spoils.

scholarly journals A Study of the Micropore Structure of Carbonized Rayon Yarn by Nitrogen Adsorption and Nonane Pre-Adsorption

1985 ◽  
Vol 2 (2) ◽  
pp. 89-95 ◽  
Author(s):  
J. N. Bohra ◽  
K. S. W. Sing
Keyword(s):  
External Surface ◽  
Nitrogen Adsorption ◽  
The Other ◽  
Adsorption Method ◽  
Micropore Structure ◽  
Surface Areas ◽  
Three Samples ◽  
Two Samples ◽  
Before And After ◽  
Gain Access

Adsorption isotherms of nitrogen have been determined at 77 K on three samples of carbonized rayon yarn, both before and after the pre-adsorption of n-nonane. In their original state the three samples were all highly microporous. Application of the αs-method of isotherm analysis reveals that their micropore volumes were 0·17–0·19 cm3g−1 and their external surface areas 20–27 m2g−1 (the corresponding BET areas being 427–483 m2g−1). Nonane pre-adsorption resulted in blockage of the entire micropore structure only in the case of one sample: micropore volumes ∼0·1 cm3g−1 were still available for nitrogen adsorption in the other two samples. It appears that nitrogen molecules were able to gain access to some parts of these micropore structures through wider pore entrances which were not completely blocked by the pre-adsorbed nonane. The work has shown that the nonane pre-adsorption method requires further investigation before it can be used with confidence for the assessment of microporosity.

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