scholarly journals Understanding preservation of primary signatures in apatite by comparing matrix and zircon-hosted crystals from the Eoarchean Acasta Gneiss Complex (Canada)

2020 ◽  
Author(s):  
Emilie Bruand ◽  
Clementine Antoine ◽  
Martin Guitreau ◽  
Jean-Luc Devidal
Keyword(s):  
Pb Isotope ◽  
Crustal Rocks ◽  
Discriminating Power ◽  
Gneiss Complex ◽  
Apatite Crystals ◽  
Chemical Signatures ◽  
The Matrix ◽  
The Impact ◽  
Isotope Systematics ◽  
Melt Evolution

<p>A novel way to investigate the petrogenesis of ancient poly-metamorphosed terranes is to use zircon as a vessel and study protected mineral inclusions which are sensitive to melt evolution such as apatite. Recent contributions have shown that zircon-hosted apatite inclusions of unmetamorphosed granitoids can provide valuable petrogenetic information about a given pluton and, in turn, represent a way to circumvent effects of metamorphism. Yet, the impact of metamorphism on apatite inclusion has never been studied in detail. To address the issue of chemical and isotopic preservation of primary signals in apatite crystals both in the matrix and armored within zircons, we have studied apatite crystals from four 3.6-4.0 Ga orthogneisses of TTG affinity from the Acasta Gneiss Complex (Canada). Our results demonstrate that U-Th-Pb isotope systematics in matrix apatite crystals are reset at the time of the Wopmay orogen (1.8-1.7 Ga) whereas primary REE signatures were preserved in many crystals. On the contrary, zircon-hosted apatite inclusions all preserved primary REE signatures despite U-Th-Pb isotope systematics giving ages between 1.7 and 4.0 Ga. We interpret the variable resetting of these ages as a consequence of radiation damage accumulation in zircon lattice. Only the most pristine zircon has an apatite inclusion with a concordant age consistent with the magmatic age of the zircon (4.0 Ga). In addition, our results show that apatite crystals from TTG have distinct REE composition from post-Archean granitoids apatites, and that even apatites with reset ages preserved some of the chemical signatures characterizing TTG compositions (e.g. HREE). This capacity to retain primary information together with its discriminating power for granitoids makes apatite a very valuable tool for reconstructing the nature and evolution of ancient crustal rocks through the use of either detrital minerals or detrital-zircon hosting inclusions.</p>

scholarly journals U-Pb isotope systematics on minerals from the gneiss complex at Isukasia, West Greenland

1983 ◽  
Vol 112 ◽  
pp. 35-42
Author(s):  
H Baadsgaard
Keyword(s):  
The Other ◽  
Pb Isotope ◽  
West Greenland ◽  
Gneiss Complex ◽  
Data Points ◽  
The Right ◽  
Isotope Systematics

207Pb/204Pb vs. 206Pb/204Pb results from sphenes from Isua gneisses show a scatter of data points between two isochrons, one at 3560 Ma and the other at 2520 Ma. Similar Pb-Pb plots on apatites from Isua show many data points which are doser to the 3560 Ma reference isochron than Pb-Pb apatite data points from Amîtsoq gneisses and Nûk gneisses in the Godthåbsfjord area. Pb from the Isua gneiss apatite and sphene is more radiogenic than that from Amîtsoq gneisses. In concordia plots of zircons all but one of the Isua data points plot to the right of the Amîtsoq zircon discordia line. Assuming a diffusion Pb loss, the 'oldest' Isua gneiss zircon is about 3700 Ma. U-Pb values for sphenes from the Isua gneisses show discordancy which could be the result of partial or local metamorphic effects between 1500 and 2800 Ma. Comparable values from sphenes from Amîtsoq and Nuk gneisses duster fairly dosely to concordant results about 2500 Ma.

Melt evolution beneath a rifted craton edge: 40 Ar/ 39 Ar geochronology and Sr–Nd–Hf–Pb isotope systematics of primitive alkaline basalts and lamprophyres from the SW Baltic Shield

2016 ◽  
Vol 173 ◽  
pp. 1-36 ◽  
Author(s):  
Sebastian Tappe ◽  
Katie A. Smart ◽  
Andreas Stracke ◽  
Rolf L. Romer ◽  
Dejan Prelević ◽  
...  
Keyword(s):  
Baltic Shield ◽  
Pb Isotope ◽  
Isotope Systematics ◽  
Melt Evolution ◽  
Ar Geochronology

Impact Strength, Flexural Modulus and Wear Rate of PMMA Composites Reinforced by Eggshell Powders

2020 ◽  
Vol 38 (7A) ◽  
pp. 960-966
Author(s):  
Aseel M. Abdullah ◽  
Hussein Jaber ◽  
Hanaa A. Al-Kaisy
Keyword(s):  
Impact Strength ◽  
Wear Rate ◽  
Flexural Modulus ◽  
Matrix Material ◽  
Weight Fraction ◽  
Pure Pmma ◽  
Calcination Process ◽  
The Matrix ◽  
The Impact ◽  
Interface Bond

In the present study, the impact strength, flexural modulus, and wear rate of poly methyl methacrylate (PMMA) with eggshell powder (ESP) composites have been investigated. The PMMA used as a matrix material reinforced with ESP at two different states (including untreated eggshell powder (UTESP) and treated eggshell powder (TESP)). Both UTESP and TESP were mixed with PMMA at different weight fractions ranged from (1-5) wt.%. The results revealed that the mechanical properties of the PMMA/ESP composites were enhanced steadily with increasing eggshell contents. The samples with 5 wt.% of UTESP and TESP additions give the maximum values of impact strength, about twice the value of the pure PMMA sample. The calcination process of eggshells powders gives better properties of the PMMA samples compared with the UTESP at the same weight fraction due to improvements in the interface bond between the matrix and particles. The wear characteristics of the PMMA composites decrease by about 57% with increases the weight fraction of TESP up to 5 wt.%. The flexural modulus values are slightly enhanced by increasing of the ESP contents in the PMMA composites.

scholarly journals The Interactions between Polyphenols and Microorganisms, Especially Gut Microbiota

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 188
Author(s):  
Małgorzata Makarewicz ◽  
Iwona Drożdż ◽  
Tomasz Tarko ◽  
Aleksandra Duda-Chodak
Keyword(s):  
Intestinal Bacteria ◽  
Research Data ◽  
Bioactive Metabolites ◽  
Human Organism ◽  
Comprehensive Knowledge ◽  
Bidirectional Relationship ◽  
The Matrix ◽  
Intestinal Pathogens ◽  
The Impact

This review presents the comprehensive knowledge about the bidirectional relationship between polyphenols and the gut microbiome. The first part is related to polyphenols’ impacts on various microorganisms, especially bacteria, and their influence on intestinal pathogens. The research data on the mechanisms of polyphenol action were collected together and organized. The impact of various polyphenols groups on intestinal bacteria both on the whole “microbiota” and on particular species, including probiotics, are presented. Moreover, the impact of polyphenols present in food (bound to the matrix) was compared with the purified polyphenols (such as in dietary supplements) as well as polyphenols in the form of derivatives (such as glycosides) with those in the form of aglycones. The second part of the paper discusses in detail the mechanisms (pathways) and the role of bacterial biotransformation of the most important groups of polyphenols, including the production of bioactive metabolites with a significant impact on the human organism (both positive and negative).

scholarly journals Reliability Assessment of a Multi-State HVDC System by Combining Markov and Matrix-Based Methods

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3097
Author(s):  
Roberto Benato ◽  
Antonio Chiarelli ◽  
Sebastian Dambone Sessa
Keyword(s):  
Current System ◽  
Estimation Method ◽  
Reliability Estimation ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Hvdc System ◽  
Critical Elements ◽  
The Matrix ◽  
The Impact

The purpose of this paper is to highlight that, in order to assess the availability of different HVDC cable transmission systems, a more detailed characterization of the cable management significantly affects the availability estimation since the cable represents one of the most critical elements of such systems. The analyzed case study consists of a multi-terminal direct current system based on both line commutated converter and voltage source converter technologies in different configurations, whose availability is computed for different transmitted power capacities. For these analyses, the matrix-based reliability estimation method is exploited together with the Monte Carlo approach and the Markov state space one. This paper shows how reliability analysis requires a deep knowledge of the real installation conditions. The impact of these conditions on the reliability evaluation and the involved benefits are also presented.

Zircon U-Pb-Hf, geochemical and Sr-Nd-Pb isotope systematics of Late Mesozoic granitoids in the Lantian-Xiaoqinling region: Implications for tectonic setting and petrogenesis

Lithos ◽  
2020 ◽  
Vol 374-375 ◽  
pp. 105709
Author(s):  
Yi-Zeng Yang ◽  
Yan Wang ◽  
Wolfgang Siebel ◽  
Yuan-Shuo Zhang ◽  
Fukun Chen
Keyword(s):  
Tectonic Setting ◽  
Pb Isotope ◽  
Late Mesozoic ◽  
Mesozoic Granitoids ◽  
Isotope Systematics

scholarly journals Evaluating the role of contracting and expanding rainforest in initiating cycles of speciation across the Isthmus of Panama

2012 ◽  
Vol 279 (1742) ◽  
pp. 3520-3526 ◽  
Author(s):  
Brian Tilston Smith ◽  
Amei Amei ◽  
John Klicka
Keyword(s):  
Bird Species ◽  
Tropical Regions ◽  
Isthmus Of Panama ◽  
Species Pairs ◽  
The Matrix ◽  
High Species Richness ◽  
The Rich ◽  
The Tropics ◽  
The Impact

Climatic and geological changes across time are presumed to have shaped the rich biodiversity of tropical regions. However, the impact climatic drying and subsequent tropical rainforest contraction had on speciation has been controversial because of inconsistent palaeoecological and genetic data. Despite the strong interest in examining the role of climatic change on speciation in the Neotropics there has been few comparative studies, particularly, those that include non-rainforest taxa. We used bird species that inhabit humid or dry habitats that dispersed across the Panamanian Isthmus to characterize temporal and spatial patterns of speciation across this barrier. Here, we show that these two assemblages of birds exhibit temporally different speciation time patterns that supports multiple cycles of speciation. Evidence for these cycles is further corroborated by the finding that both assemblages consist of ‘young’ and ‘old’ species, despite dry habitat species pairs being geographically more distant than pairs of humid habitat species. The matrix of humid and dry habitats in the tropics not only allows for the maintenance of high species richness, but additionally this study suggests that these environments may have promoted speciation. We conclude that differentially expanding and contracting distributions of dry and humid habitats was probably an important contributor to speciation in the tropics.

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