scholarly journals Geochemistry and Texture of Clinopyroxene Phenocrysts from Paleoproterozoic Picrobasalts, Karelian Craton, Fennoscandian Shield: Records of Magma Mixing Processes

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 434 ◽  
Author(s):  
Sergei A. Svetov ◽  
Svetlana Y. Chazhengina ◽  
Alexandra V. Stepanova
Keyword(s):  
Size Distribution ◽  
Crystal Size ◽  
Magma Mixing ◽  
Fennoscandian Shield ◽  
Crystal Size Distribution ◽  
Distribution Analysis ◽  
Trace Element Data ◽  
Magmatic System ◽  
Karelian Craton ◽  
Mixing Processes

This paper presents an integrated major and trace element data and crystal size distribution analysis for zoned clinopyroxene phenocrysts hosted in variolitic and massive picrobasalts of the Suisaari Formation, Karelian Craton, Eastern Fennoscandian Shield. Clinopyroxenes in variolitic and massive lavas occur as unzoned, reverse, and normally zoned crystal. Oscillatory-zoned clinopyroxenes are only observed in variolitic lavas. The obtained data were examined in order to evaluate the contribution of magmatic processes such as magma mixing, contamination and fractional crystallization to the formation of various zoning patterns of clinopyroxene phenocrysts. Clinopyroxene phenocrysts in both variolitic and massive lavas originate from similar primary melts from a single magmatic source. The obtained data on composition and texture of clinopyroxene phenocrysts together with the crystal size distribution (CSD) analysis suggest that crystallization of the massive lavas mainly involves fractionation in a closed magmatic system, whereas the crystallization of the variolitic lavas is determined by processes in an open magmatic system. The results provide novel information on the evolution of Paleoproterozoic magmatic systems in the Karelian Craton.

scholarly journals A Novel Shadowgraphic Inline Measurement Technique for Image-Based Crystal Size Distribution Analysis

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 740 ◽  
Author(s):  
Dominic Wirz ◽  
Marc Hofmann ◽  
Heike Lorenz ◽  
Hans-Jörg Bart ◽  
Andreas Seidel-Morgenstern ◽  
...  
Keyword(s):  
Size Distribution ◽  
Crystal Size ◽  
Elevated Temperatures ◽  
Measurement Techniques ◽  
Potassium Dihydrogen Phosphate ◽  
Crystal Size Distribution ◽  
Thiamine Hydrochloride ◽  
Dihydrogen Phosphate ◽  
Distribution Analysis ◽  
Inline Measurement

A novel shadowgraphic inline probe to measure crystal size distributions (CSD), based on acquired greyscale images, is evaluated in terms of elevated temperatures and fragile crystals, and compared to well-established, alternative online and offline measurement techniques, i.e., sieving analysis and online microscopy. Additionally, the operation limits, with respect to temperature, supersaturation, suspension, and optical density, are investigated. Two different substance systems, potassium dihydrogen phosphate (prisms) and thiamine hydrochloride (needles), are crystallized for this purpose at 25 L scale. Crystal phases of the well-known KH2PO4/H2O system are measured continuously by the inline probe and in a bypass by the online microscope during cooling crystallizations. Both measurement techniques show similar results with respect to the crystal size distribution, except for higher temperatures, where the bypass variant tends to fail due to blockage. Thiamine hydrochloride, a substance forming long and fragile needles in aqueous solutions, is solidified with an anti-solvent crystallization with ethanol. The novel inline probe could identify a new field of application for image-based crystal size distribution measurements, with respect to difficult particle shapes (needles) and elevated temperatures, which cannot be evaluated with common techniques.

A fast X-ray-diffraction-based method for the determination of crystal size distributions (FXD-CSD)

2018 ◽  
Vol 51 (5) ◽  
pp. 1352-1371 ◽  
Author(s):  
Sigmund H. Neher ◽  
Helmut Klein ◽  
Werner F. Kuhs
Keyword(s):  
Size Distribution ◽  
Chemical Engineering ◽  
Crystal Size ◽  
Crystal Size Distribution ◽  
Polycrystalline Materials ◽  
Distribution Analysis ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intensity Scaling

A procedure for a fast X-ray-diffraction-based crystal size distribution analysis, named FXD-CSD, is presented. The method enables the user, with minimal sample preparation, to determine the crystal size distribution (CSD) of crystalline powders or polycrystalline materials, derivedviaan intensity scaling procedure from the diffraction intensities of single Bragg spots measured in spotty diffraction patterns with a two-dimensional detector. The method can be implemented on any single-crystal laboratory diffractometer and any synchrotron-based instrument with a fast-readout two-dimensional detector and a precise sample scanning axis. The intensity scaling is achievedviathe measurement of areferencesample with known CSD under identical conditions; the only other prerequisite is that the structure (factors) of bothsampleandreferencematerial must be known. The data analysis is done with a software package written in Python. A detailed account is given of each step of the procedure, including the measurement strategy and the demands on the spottiness of the diffraction rings, the data reduction and the intensity corrections needed, and the data evaluation and the requirements for the reference material. Using commercial laboratory X-ray equipment, several corundum crystal size fractions with precisely known CSD were measured and analysed to verify the accuracy and precision of the FXD-CSD method; a comparison of known and deduced CSDs shows good agreement both in mean size and in the shape of the size distribution. For the used material and diffractometer setup, the crystal size application range is one to several tens of micrometres; this range is highly material and X-ray source dependent and can easily be extended on synchrotron sources to cover the range from below 0.5 µm to over 100 µm. FXD-CSD has the potential to become a generally applicable method for CSD determination in the field of materials science and pharmaceutics, including development and quality management, as well as in various areas of fundamental research in physics, chemistry, chemical engineering, crystallography, the geological sciences and bio-crystallization. It can be used also underin situconditions for studying crystal coarsening phenomena, and delivers precise and accurate CSDs, permitting experimental tests of various theories developed to predict their evolution.

scholarly journals QEMSCAN as a Method of Semi-Automated Crystal Size Distribution Analysis: Insights from Apollo 15 Mare Basalts

2020 ◽  
Vol 61 (4) ◽  
Author(s):  
S K Bell ◽  
K H Joy ◽  
J F Pernet-Fisher ◽  
M E Hartley
Keyword(s):  
Data Collection ◽  
Size Distribution ◽  
Crystal Size ◽  
Crystal Size Distribution ◽  
Distribution Data ◽  
Nucleation Density ◽  
Distribution Analysis ◽  
Crystal Shape ◽  
Thin Sections ◽  
Crystal Residence

Abstract Crystal size distribution analysis is a non-destructive, quantitative method providing insights into the crystallization histories of magmas. Traditional crystal size distribution data collection requires the manual tracing of crystal boundaries within a sample from a digital image. Although this manual method requires minimal equipment to perform, the process is often time-intensive. In this study we investigate the feasibility of using the Quantitative Evaluation of Minerals by SCANing electron microscopy (QEMSCAN) software for semi-automated crystal size distribution analysis. Four Apollo 15 mare basalt thin sections were analysed using both manual and QEMSCAN crystal size distribution data collection methods. In most cases we observe an offset between the crystal size distribution plots produced by QEMSCAN methods compared with the manual data, leading to differences in calculated crystal residence times and nucleation densities. The source of the discrepancy is two-fold: (1) the touching particles processor in the QEMSCAN software is prone to segmenting overlapping elongate crystals into multiple smaller crystals; (2) this segmentation of elongate crystals causes estimates of true 3D crystal habit to vary between QEMSCAN and manual data. The reliability of the QESMCAN data appears to be a function of the crystal texture and average crystal shape, both of which influence the performance of the touching particles processor. Despite these limitations, QEMSCAN is able to produce broadly similar overall trends in crystal size distribution plots to the manual approach, in a considerably shorter time frame. If an accurate crystal size distribution is required to calculate crystal residence time or nucleation density, we recommend that QEMSCAN should only be used after careful consideration of the suitability of the sample texture and average crystal shape.

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