scholarly journals Partitioning of chromium between garnet and clinopyroxene: first-principle modelling versus metamorphic assemblages

2020 ◽  
Vol 32 (4) ◽  
pp. 387-403
Author(s):  
Sarah Figowy ◽  
Benoît Dubacq ◽  
Yves Noël ◽  
Philippe d'Arco
Keyword(s):  
Partition Coefficients ◽  
Large Scale ◽  
First Principle ◽  
Minor Elements ◽  
Geological Processes ◽  
Mineral Assemblages ◽  
Geochemical Behaviour ◽  
Kinetic Effects ◽  
Trace And Minor Elements ◽  
Element Mapping

Abstract. Understanding the geochemical behaviour of trace and minor elements in mineral assemblages is of primary importance to study small- and large-scale geological processes. Partition coefficients are frequently used to model the chemical evolution of minerals and fluids during melting and in metamorphic rocks of all grades. However, kinetic effects hampering equilibrium partitioning may invalidate the modelling. This study aims at calculating partition coefficients and testing their applicability in natural mineral assemblages, choosing Cr in garnet and clinopyroxene via exchange with Al as a case study. First-principle modelling has been combined with measurements and element mapping to estimate partition coefficients for Cr and the deviation from equilibrium. Results highlight the role of crystal chemistry over the strain field around point defects, controlling the dynamics of the Cr3+ = Al3+ exchange between clinopyroxene and garnet. Ab initio calculations allowed estimation of Cr partition coefficients between garnet and clinopyroxene, using a thermodynamic approach based on endmembers and mixing models simplified for trace element behaviour. The Cr3+ = Al3+ exchange reaction between garnet and the jadeite component of clinopyroxene depends on the grossular and pyrope content, with Cr preferentially incorporated into grossular over jadeite but preferentially incorporated into jadeite over pyrope. Comparison of predicted partition coefficients to measured concentrations in natural samples, together with element mapping, shows large disequilibrium. Cr-rich and Cr-poor sectors exhibit disequilibrium attributed to slow diffusivity of Cr during crystal growth and interface-coupled dissolution–precipitation, even for garnet–clinopyroxene assemblages crystallized around 850 ∘C.

Trace Element Mapping of Minerals and Materials by Electron Microprobe

1999 ◽  
Vol 5 (S2) ◽  
pp. 630-631
Author(s):  
J. Fournelle ◽  
C. Davidson ◽  
F. Spear ◽  
M. Kohn ◽  
H. Guo
Keyword(s):  
Trace Element ◽  
Electron Microprobe ◽  
Trace Element Level ◽  
Element Level ◽  
Faraday Cup ◽  
Minor Elements ◽  
High Detection ◽  
Trace And Minor Elements ◽  
Very High ◽  
Element Mapping

A strength of the modern electron microprobe is its ability to provide 2D compositional information about materials. These images give the ability to observe features that might otherwise pass unseen. Elements at the trace element level are generally ignored due to the high detection limits imposed by mapping under “standard” EMP conditions.Trace element mapping requires beam regulation at high (e.g. 300 nA) to very high (e.g. 3 μA) faraday cup currents, reliable beam and stage control, and suitable samples and mounting media. The ability to operate at high accelerating voltage to maximize Pk2/Bkg is desirable (Robinson and Graham, 1992), although we have encountered column difficulties above 25-30 kV.We are mapping trace and minor elements including Y, Sc, P, Cr, Mn, Ca, in garnets. Fig. 1 shows Y, Sc and Cr maps (Spear and Kohn, 1996; Kohn, Spear and Valley, 1997), and Fig. 2 Y and Sc maps (Cameron, unpub. data), produced with a Cameca SX51.

scholarly journals The Transformation from (111) to (100): A Routine to Large-Scale Epitaxial Diamond

2020 ◽  
Author(s):  
Yang Wang ◽  
Weihua Wang ◽  
Shilin Yang ◽  
Jiaqi Zhu
Keyword(s):  
Large Scale ◽  
Diamond Films ◽  
Diamond Growth ◽  
Nucleation Density ◽  
Diamond Synthesis ◽  
First Principle ◽  
High Quality ◽  
First Principle Calculations ◽  
Large Size ◽  
Experimental Researches

Diamond is a material with excellent performances which attracts the attention from researchers for decades. Pt (111), owing to its catalytic activity on diamond synthesis, is regarded to be a candidate for diamond hetero-epitaxity, which can enhance nucleation density. Molten surface at diamond growth temperature can also improve mobility and aggregation capability of primitive nuclei. Generally, (100)-oriented is welcomed for the achivement of high quality and large size diamond, since the formation of defects and twins are prevented. First-principle calculations and experimental researches were carried out for the study of transformation of orientation. The transformation from {111} to {100}-oriented diamond has been observed on Pt (111) substrate, which can be promoted by the increase of carbon source concentration and substrate temperature. The process is energetic favorable, which may provides a way towards large-scale (100) diamond films.

scholarly journals Drumlin Formation Related to Inverted Melt-Water Erosional Marks

1983 ◽  
Vol 29 (103) ◽  
pp. 461-479 ◽  
Author(s):  
John Shaw
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Ice Sheet ◽  
Fluid Flows ◽  
Minor Elements ◽  
Water Flows ◽  
Melt Water ◽  
Northern Saskatchewan ◽  
Specific Discharge ◽  
Ice Sheet Dynamics

AbstractDrumlin forms are described from maps and air photographs of a part of the Athabasca Plains, northern Saskatchewan. Three major forms, spindle, parabolic and transverse asymmetrical are recognized. These forms, which may show superimposed minor elements, depart from classical descriptions of drumlins, but are similar to moulds of erosional marks created by separated fluid flows. Assemblages of drumlins also show characteristics similar to those of erosional marks. The form analogy between drumlins and moulds of erosional marks is carried to a conclusion that drumlins may be formed by the infilling of erosional marks created on the under-side of glaciers by separated, subglacial melt-water flows. Estimates of specific discharge are obtained by means of an expected range of Reynolds number. Geomorphological evidence is given for large-scale erosion by subglacial melt water. A discussion of the sedimentology, stratigraphy, and deformational structure of the interiors of drumlins shows that they may be explained by the erosional-mark hypothesis. This paper emphasizes the importance of melt water as a geomorphic agent and may have broad implications for ice-sheet dynamics and profiles, rates of deglaciation, and the occurrence of bedrock thrusting by ice.

scholarly journals Trace and minor elements in galena: A reconnaissance LA-ICP-MS study

2015 ◽  
Vol 100 (2-3) ◽  
pp. 548-569 ◽  
Author(s):  
L. George ◽  
N. J. Cook ◽  
C. L. Ciobanu ◽  
B. P. Wade
Keyword(s):  
Minor Elements ◽  
Icp Ms ◽  
Trace And Minor Elements

The partition coefficients of Nd and Sm for the sulphides: first data from Palaeoproterozoic layered Cu-Ni-PGE complexes of Fennoscandian Shield

2021 ◽  
Author(s):  
Pavel Serov ◽  
Tamara Bayanova
Keyword(s):  
Partition Coefficients ◽  
Sulfide Minerals ◽  
Spectrometric Method ◽  
New Mineral ◽  
Mass Spectrometric Method ◽  
Time Data ◽  
Mean Values ◽  
Geological Processes ◽  
Ore Minerals ◽  
Monchegorsk Pluton

<p>The Sm-Nd systematics is one of the most demanded isotope-geochronological tools to study ancient geological complexes. With the accumulation of knowledge about the REE in various geological processes, the question arises of extending the capabilities of the Sm-Nd method by using new mineral geochronometers. The research focused on defining the time of the ore process and its position in the general geochronological scale of formation of the geological site become particularly important. There is a pressing need for defining possible forms of REE occurrence in a lattice of geochronometer minerals in the Sm-Nd study of accessory minerals (e.g. fluorite, burbankite, eudialite, ruthile, etc.) and ore minerals (ilmenite, chrome-spinellid, sulfide minerals). The Sm-Nd method of dating ore processes using sulphide minerals, successfully used on several geological objects, made it possible to determine the main stages of ore formation and confirm geochronologically the conclusions about the syngenetic or epigenetic nature of the ore process.</p><p>Pyrite, pentlandite, chalcopyrite and pyrrhotite from the main industrial fields of the Fennoscandinavian shield were studied: Monchegorsk pluton, Fedorovo-Pansky intrusion, Pechenga, Penicat intrusion and Ahmavaara (Finland). Using a mass-spectrometric method 35 sulphide monofractions were analyzed. The partition coefficients for Nd and Sm were established: for pyrite - 0.229 (Nd) and 0.169 (Sm); for pyrrhotite - 0.265 (Nd) and 0.160 (Sm); for chalcopyrite - 0.229 (Nd) and 0.161 (Sm); for pentlandite – 0.158 (Nd) and 0.082 (Sm). The mean values for D<sub>Nd</sub> are 0.201, for D<sub>Sm</sub>=0.145 and resulting D<sub>Nd</sub>/D<sub>Sm</sub> about 1.4.</p><p>Probably, the distribution of REE in sulfide minerals is inherited from fluids during sulfide formation. REE concentrations in sulphide may reflect the composition of the fluid.</p><p>Thus, for the first time data on Sm and Nd concentrations have been obtained by mass spectrometry. Coefficients of neodymium and samarium distribution in sulfides have been calculated for major Cu-Ni-PGE complexes of Fennoscandia.</p><p> </p><p>This study performed under the theme of scientific research 0226-2019-0053 and were supported by the RFBR  18-05-70082.</p>

No ion is an island: Multiple ions involved during boron incorporation into CaCO3

2021 ◽  
Author(s):  
Michael Henehan ◽  
Christa Klein-Gebbinck ◽  
Gavin Foster ◽  
Jill Wyman ◽  
Mathis Hain ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Isotope Fractionation ◽  
Isotope Composition ◽  
Boron Isotope ◽  
Minor Role ◽  
Growth Mechanisms ◽  
Minor Elements ◽  
Vital Effects ◽  
Biogenic Carbonates ◽  
Trace And Minor Elements

<p>Boron isotope ratios, as measured in marine calcium carbonate, are a proven tracer of past seawater and calcifying fluid pH and thus a powerful tool for the reconstruction of past atmospheric CO<sub>2</sub> and monitoring of coral physiology. For such applications, understanding the inorganic baseline upon which foraminiferal vital effects or coral pH upregulation are superimposed should be an important prerequisite. Yet, investigations into boron isotope fractionation in synthetic CaCO<sub>3 </sub>polymorphs have often reported variable and even conflicting results, implying that we may not fully understand pathways of boron incorporation into calcium carbonate.  Here we address this topic with experimental data from calcite and aragonite precipitated across a range of pH in the presence of both Mg and Ca. We confirm the results of previous studies that the boron isotope composition of inorganic aragonite precipitates closely reflects that of aqueous borate ion, but that calcites display a higher degree of scatter, and diverge from the boron isotope composition of borate ion at low pH. We discuss these findings with reference to the simultaneous incorporation of other trace and minor elements, and highlight a number of mechanisms by which crystal growth mechanisms may influence the concentration and isotope composition of boron in CaCO<sub>3</sub>. In particular, we highlight the potential importance of surface electrostatics in driving variability in published synthetic carbonate datasets. Importantly for palaeo-reconstruction, however, these electrostatic effects are likely to play a much more minor role during natural precipitation of biogenic carbonates.</p>

Studies on some trace and minor elements in blood

1997 ◽  
Vol 57 (3) ◽  
pp. 207-221 ◽  
Author(s):  
T. R. Mahalingam ◽  
S. Vijayalashmi ◽  
R. Krishna Prabhu ◽  
A. Thiruvengadasami ◽  
K. S. R. Murthy ◽  
...  
Keyword(s):  
Minor Elements ◽  
Trace And Minor Elements

scholarly journals Nutrient Analysis of Some Commercially Important Molluscs of Bangladesh

2010 ◽  
Vol 2 (2) ◽  
pp. 390-396 ◽  
Author(s):  
R. L. Baby ◽  
I. Hasan ◽  
K. A. Kabir ◽  
M. N. Naser
Keyword(s):  
Nutrient Content ◽  
Proximate Analysis ◽  
Nutrient Analysis ◽  
Minor Elements ◽  
Crude Fiber Content ◽  
Pila Globosa ◽  
Calcium Phosphorus ◽  
Commercially Important ◽  
Trace And Minor Elements ◽  
Supplementary Feed

This proximate study was carried out to determine the nutrient content of six commercially important molluscs. The selected molluscan species were Pila globosa, Bellamya bengalensis, Melania tuberculata, Lamellidens marginalis, Anisus convexiusculus and Helix sp. These species were assessed for their proximate and mineral compositions designed to establish their nutritive values on the wet weight basis. The analysis of muscles revealed that the composition of crude protein varied from 8.272%±0.05% in Pila globosa to 12.927%±0.57% in Anisus convexiusculus, moisture content varied from 74.6%±0.04% in Melania tuberculata to 85.9%±0.68% in Lamellidens marginalis and in case of ash content it varied from 1.036%±0.02% in Pila globosa to 4.607%±0.01% in Anisus convexiusculus. Carbohydrate content varied from 2.902±0.03% in Pila globosa and 7.566%±0.37% in Melania tuberculata. The fat and crude fiber content was marginally small in all of the species. The concentrations of calcium, phosphorus, iron, sodium and potassium in the flesh and shells of the molluscs were determined. It becomes pretty clear that molluscs are excellent sources of some required trace and minor elements needed for the proper growth and development of human being and can also be used as high-nutrient supplementary feed for domestic animals, birds and even for fish culture. Keywords: Freshwater; Snails; Proximate analysis; Nutrition; Minerals.  © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.DOI: 10.3329/jsr.v2i2.3362                J. Sci. Res. 2 (2), 390-396 (2010) 

Interlaboratory and Interinstrumental Spectrochemical Precision: Comparison of dc Carbon Arc Optical Emission Spectrographic, Atomic Absorption, and X-ray Fluorescence Spectrometric Procedures

1976 ◽  
Vol 30 (3) ◽  
pp. 335-343 ◽  
Author(s):  
Isaac B. Brenner ◽  
L. Gleit ◽  
A. Harel
Keyword(s):  
Atomic Absorption ◽  
Optical Emission ◽  
X Ray ◽  
Minor Elements ◽  
Accuracy And Precision ◽  
Spectrographic Method ◽  
Carbon Arc ◽  
The Common ◽  
Trace And Minor Elements

A cooperative investigation has been performed to test long-term interlaboratory and interinstrumental accuracy and precision of a dc carbon arc optical emission spectrographic method for determining the common trace and minor elements in silicate rocks and minerals. Comparisons are made with determinations by atomic absorption and X-ray fluorescence spectrometric procedures to indicate agreement or bias of the analytical results, and the presence of systematic errors.

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