scholarly journals Crystal size and shape distribution systematics of plagioclase and the determination of crystal residence times in the micromonzogabbros of Qisir Dagh, SE of Sabalan volcano (NW Iran)

2015 ◽  
Vol 66 (4) ◽  
pp. 257-268 ◽  
Author(s):  
Hamed Pourkhorsandi ◽  
Hassan Mirnejad ◽  
Davoud Raiesi ◽  
Jamshid Hassanzadeh
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
Crystal Size ◽  
Magma Mixing ◽  
Crystal Size Distribution ◽  
Distribution Data ◽  
Near Surface ◽  
Shape Distribution ◽  
Size And Shape ◽  
Sabalan Volcano

AbstractThe Qisir Dagh igneous complex occurs as a combination of volcanic and intrusive rocks to the south-east of the Sabalan volcano, north-western Iran. Micromonzogabbroic rocks in the region consist of plagioclase, alkaline feldspar and clinopyroxene as the major mineral phases and orthopyroxene, olivine, apatite and opaque minerals as the accessory minerals. Microgranular and microporphyritic textures are well developed in these rocks. Considering the importance of plagioclase in reconstructing magma cooling processes, the size and shape distribution and chemical composition of this mineral were investigated. Based on microscopic studies, it is shown that the 2-dimensional size average of plagioclase in the micromonzogabbros is 538 micrometers and its 3-dimensional shape varies between tabular to prolate. Crystal size distribution diagrams point to the presence of at least two populations of plagioclase, indicating the occurrence of magma mixing and/or fractional crystallization during magma cooling. The chemical composition of plagioclase shows a wide variation in abundances of Anorthite-Albite-Orthoclase (An=0.31–64.58, Ab=29.26–72.13, Or=0.9–66.97), suggesting a complex process during the crystal growth. This is also supported by the formation of antiperthite lamellae, which formed as the result of alkali feldspar exsolution in plagioclase. The calculated residence time of magma in Qisir Dagh, based on 3D crystal size distribution data, and using growth rate G=10−10mm/s, varies between 457 and 685 years, which indicates a shallow depth (near surface) magma crystallization and subvolcanic nature of the studied samples.

scholarly journals Nucleation and Initial Growth of Garnet in Low-Grade Metamorphic Rocks of the Sanbagawa Metamorphic Belt, Kanto Mountains, Japan

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 292 ◽  
Author(s):  
Mutsuko Inui ◽  
Yumenosuke Wakai ◽  
Hiirou Sakuragi
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
Crystal Size ◽  
Crystal Size Distribution ◽  
Garnet Growth ◽  
Low Grade ◽  
Initial Growth ◽  
Metamorphic Belt ◽  
The Core ◽  
Log Normal

The beginning of the recrystallization of minerals within a subducting oceanic plate provides a valuable record of dehydration within the subduction zone. Pelitic schists of the Nagatoro area, Kanto Mountains, Japan, record the initial stages of garnet growth. Consequently, these rocks were studied to analyze garnet nucleation and growth during metamorphism of the Sanbagawa metamorphic belt, one of the world’s most comprehensively studied subduction complexes. The garnet grains are small, euhedral, and occur only within micaceous lamellae that define the schistosity. Crystal size distribution analyses revealed most of the garnet grains follow the log-normal size distribution, indicating that they formed in the same event. A few exceptionally large garnet grains exist that do not seem to follow the log-normal distribution. The latter garnet grains contain a rounded fragmental area with a different chemical composition inside the core. It is possible that detrital fragments of garnet contribute to the irregular crystal size distribution of garnet in the studied area. Many of the smaller (log-normal) garnet grains have relatively large, homogeneous Mn-rich cores. The lack of chemical zoning within the garnet cores suggests that they grew under constant pressure and temperature in response to overstepping of the garnet-in reaction. The chemical composition changes very sharply at the boundary between the core and the surrounding mantle. The size of the Mn-rich core is different from sample to sample, suggesting that the nucleation was controlled by the local chemical condition of each sample.

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.

scholarly journals Modeling of Nucleation, Growth, Dissolution, and Disappearance of Paracetamol in Ethanol Solution for Unseeded Batch Cooling Crystallization with Temperature-Cycling Strategy

2020 ◽  
Author(s):  
Youngjo Kim ◽  
Yoshiaki Kawajiri ◽  
Ronald W. Rousseau ◽  
Martha A. Grover
Keyword(s):  
Size Distribution ◽  
Crystal Size ◽  
Process Analytical Technology ◽  
Ethanol Solution ◽  
Temperature Cycling ◽  
Crystal Size Distribution ◽  
Balance Model ◽  
Distribution Data ◽  
Concentration Data ◽  
Nucleation Growth

A population balance model (PBM) is developed for unseeded batch crystallization, with temperature-cycling strategies to control the crystal size distribution. The model is able to predict the evolution of crystal size distributions of crystallizing paracetamol from ethanol solutions considering the characteristics of primary nucleation, secondary nucleation, growth, dissolution, and disappearance of crystals. Process analytical technology (PAT) tools were employed to collect solute concentration data and crystal size distribution data. This model employs a boundary condition to describe the disappearance of crystals in temperature-cycling strategies where the temperature is increased and decreased repeatedly. As a result, the obtained model can describe the evolution of crystal size distribution when repetition of cooling and heating is carried out. Moreover, this model can be applied to investigate phenomena that are challenging to explain with experimental data alone, thereby we can gain insight and optimize the operation of the process.

scholarly journals Modeling of Nucleation, Growth, Dissolution, and Disappearance of Paracetamol in Ethanol Solution for Unseeded Batch Cooling Crystallization with Temperature-Cycling Strategy

2020 ◽  
Author(s):  
Youngjo Kim ◽  
Yoshiaki Kawajiri ◽  
Ronald W. Rousseau ◽  
Martha A. Grover
Keyword(s):  
Size Distribution ◽  
Crystal Size ◽  
Process Analytical Technology ◽  
Ethanol Solution ◽  
Temperature Cycling ◽  
Crystal Size Distribution ◽  
Balance Model ◽  
Distribution Data ◽  
Concentration Data ◽  
Nucleation Growth

A population balance model (PBM) is developed for unseeded batch crystallization, with temperature-cycling strategies to control the crystal size distribution. The model is able to predict the evolution of crystal size distributions of crystallizing paracetamol from ethanol solutions considering the characteristics of primary nucleation, secondary nucleation, growth, dissolution, and disappearance of crystals. Process analytical technology (PAT) tools were employed to collect solute concentration data and crystal size distribution data. This model employs a boundary condition to describe the disappearance of crystals in temperature-cycling strategies where the temperature is increased and decreased repeatedly. As a result, the obtained model can describe the evolution of crystal size distribution when repetition of cooling and heating is carried out. Moreover, this model can be applied to investigate phenomena that are challenging to explain with experimental data alone, thereby we can gain insight and optimize the operation of the process.

Magma chamber evolution of the Ardestan pluton, Central Iran: evidence from mineral chemistry, zircon composition and crystal size distribution

2019 ◽  
Vol 83 (6) ◽  
pp. 763-780 ◽  
Author(s):  
Shahrouz Babazadeh ◽  
Tanya Furman ◽  
John M. Cottle ◽  
Davood Raeisi ◽  
Ianna Lima
Keyword(s):  
Size Distribution ◽  
Crystal Size ◽  
Magma Mixing ◽  
Mineral Chemistry ◽  
Crystal Size Distribution ◽  
Plagioclase Feldspar ◽  
Magmatic Origin ◽  
Field Evidence ◽  
History Of ◽  
Chemical Conditions

AbstractThe Oligo–Miocene Ardestan quartz diorite to tonalite is part of widespread Cenozoic magmatism within the Urumieh–Dokhtar Magmatic Assemblage of Iran. The Ardestan pluton is composed mainly of varying proportions of plagioclase feldspar (normally zoned from bytownite to andesine), amphibole (magnesio-hornblende) and biotite. Biotite exhibits a range of Al values (~2–2.8 apfu) over very restricted Fe# ratios (0.42–0.56) which are characteristic of continental arc magmatic suites. High Ti2O contents of biotite (<6.1 wt.%) suggest a magmatic origin. Ti-in-biotite geothermometery gives a mean crystallisation temperature of 730 ± 56°C, slightly higher than calculated TZr.Ti°C (716 ± 50°C) and similar to the average TZr.sat°C (735 ± 26°C). These results are consistent with the low bulk-rock SiO2 contents, which provide minimum estimates of temperature and indicate zircon crystallised from a fractionated magma. Zircons from the Ardestan pluton have high (Sm/La)N (>10) ratios suggesting a magmatic origin. T–$f_{{\rm O}_{\rm 2}}$ calculations of oxygen fugacity between –13.6 to –16.9 indicate oxidising crystallisation conditions between the Ni–NiO (NNO) and Fe2O3–Fe3O4 (HM) buffers. Tight linear trends of log (XF/XOH), log (XCl/XOH) and log (XCl/XOH) vs. XMg represent a narrow range of $f_{{\rm H}_2O}$, fHF and fHCl, clearly indicating that physico-chemical conditions were essentially constant throughout the formation of magmatic biotite. The shape of crystal size distribution curves along with the medium Al and Mg contents in amphibole and biotite, respectively, are consistent with a history of magma mixing involving injections of basic magma into the evolving felsic chamber. Calculated residence time for Ardestan plagioclase crystals of ~630 years support field evidence that these plutons were emplaced at shallow depths.

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.

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