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Microtexture Characterization of Rocks and Minerals

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (30 June 2020) | Viewed by 45476

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Special Issue Editor

Prof. Dr. Yungoo Song

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Guest Editor

Department of Earth System Sciences, Yonsei University, 03722 Seoul, Korea
Interests: clay mineralogy; ore mineralogy; microtexture; illite polytype; illite-age analysis (IAA); SEM–BSE; 3D micro-CT; XRD; EPMA; fault gouge

Special Issue Information

Dear Colleagues,

Microtextures, the physical or structural aspects of minerals and rocks, may include the interrelationships of minerals, the preferred orientation of grains, the internal textures of minerals, etc., which reflect the histories of crystallization, dissolution–precipitation, and deformation of minerals. Therefore, the detailed study of processes by characterizing microtextures in minerals and rocks at the microscopic scales is now a major area of research and particularly provides a fundament for interpreting the chemical and isotopic results of minerals. Moreover, new observational facilities and techniques, such as FE–SEM–BSE imaging, 3D micro-CT imaging using synchrotron, and microscale elemental mapping of trace elements using LA–ICP–MS, are being developed and used for characterizing various microtextures with high resolution quality. In the light of these considerations, this Special Issue invites the latest advances in the microtextural characterization of minerals and rocks in order to understand their forming processes. Consequently, submissions dealing with microtextural aspects of minerals and rocks are welcome and encouraged.

Prof. Dr. Yungoo Song
Guest Editor

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Keywords

microtexture
structural aspects
preferred orientation
crystallization
dissolution–precipitation
deformation
FE–SEM–BSE
3D micro-CT
synchrotron
elemental mapping

Published Papers (13 papers)

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Editorial

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3 pages, 161 KiB

Open AccessEditorial

Editorial for Special Issue “Microtexture Characterization of Rocks and Minerals”

by Yungoo Song

Minerals 2021, 11(5), 526; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050526 - 17 May 2021

Viewed by 1359

Abstract

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

Research

Jump to: Editorial

16 pages, 7940 KiB

Open AccessArticle

3D Fabric Analysis in Fault Rock Using Synchrotron μ-CT: A Statistical Approach to SPO (Shape Preferred Orientation) for Estimation of Fault Motion

by Ho Sim, Yungoo Song, Seongsik Hong and Sung-Ja Choi

Minerals 2020, 10(11), 994; https://0-doi-org.brum.beds.ac.uk/10.3390/min10110994 - 09 Nov 2020

Cited by 2 | Viewed by 2274

Abstract

This study provides information about fault motion by statistically presenting shape and orientation information for tens of thousands of grains. The recently developed shape preferred orientation (SPO) measurement method using synchrotron micro-computed tomography was used. In addition, various factors that were not considered in previous SPO analysis were analyzed in-depth. The study area included the Yangsan and Ulsan fault zones, which are the largest fault zones in the southeastern part of the Korean Peninsula. Samples were collected from five outcrops in two regions. According to the field observation results, the samples in the area were largely divided into fault gouge and cataclasite, and as a result of SPO analysis, we succeeded in restoring the three-dimensional fault motion direction for each outcrop and identified the fault type. In addition, the analysis results of the fault gouge and cataclasite samples collected from the thin fault zone were interpreted using the focal mechanism solution. As a result, the statistical SPO analysis approach supplements the shortcomings of previous research methods on two-dimensional planes and can quantitatively infer the three-dimensional fault motion for various fault rock samples in the same sequence, thus, presenting useful evidence for structural analysis. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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20 pages, 13710 KiB

Open AccessArticle

Microstructure of Vein Quartz Aggregates as an Indicator of Their Deformation History: An Example of Vein Systems from Western Transbaikalia (Russia)

by Dmitry V. Lychagin, Elvira N. Kungulova, Evgeny N. Moskvichev, Anatoly A. Tomilenko and Platon A. Tishin

Minerals 2020, 10(10), 865; https://0-doi-org.brum.beds.ac.uk/10.3390/min10100865 - 30 Sep 2020

Cited by 6 | Viewed by 3340

Abstract

We investigated the microstructural and crystallographic features of quartz from complex vein systems associated with the development of thrust and shear deformations in Western Transbaikalia using electron back scatter diffraction (EBSD) and optical microscopy. Vein quartz systems were studied to obtain insights on the mechanisms and localization of strains in quartz, in plastic and semibrittle conditions close to the brittle–ductile transition, and their relationship to the processes of regional deformations. Five types of microstructures of vein quartz were distinguished. We established that the preferred mechanisms of deformation of the studied quartz were dislocation glide and creep at average deformation rates and temperatures of 300–400 °C with subsequent heating and dynamic and static recrystallization. The formation of special boundaries of the Dauphiné twinning type and multiple boundaries with angles of misorientation of 30° and 90° were noted. The distribution of the selected types in the differently oriented veins was analyzed. The presence of three generations of vein quartz was established. Microstructural and crystallographic features of vein quartz aggregates allow us to mark the territory’s multi-stage development (with the formation of syntectonic and post-deformation quartz). Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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18 pages, 6126 KiB

Open AccessArticle

Fluid Infiltration and Mass Transfer along a Lamprophyre Dyke–Marble Contact: An Example from the South-Western Korean Peninsula

by Jungrae Noh, Changyeob Kim, Vinod O. Samuel, Yirang Jang, Seung-Ik Park and Sanghoon Kwon

Minerals 2020, 10(9), 828; https://0-doi-org.brum.beds.ac.uk/10.3390/min10090828 - 20 Sep 2020

Cited by 4 | Viewed by 3467

Abstract

In this contribution, we report the metasomatic characteristics of a lamprophyre dyke–marble contact zone from the Hongseong–Imjingang belt along the western Gyeonggi Massif, South Korea. The lamprophyre dyke intruded into the dolomitic marble, forming a serpentinized contact zone. The zone consists of olivine, serpentine, calcite, dolomite, biotite, spinel, and hematite. Minor F and Cl contents in the serpentine and biotite indicate the composition of the infiltrating H₂O-CO₂ fluid. SiO₂ (12.42 wt %), FeO (1.83 wt %), K₂O (0.03 wt %), Sr (89 ppm), U (0.7 ppm), Th (1.44 ppm), and rare earth elements (REEs) are highly mobile, while Zr, Cr, and Ba are moderately mobile in the fluid. Phase equilibria modelling suggests that the olivine, spinel, biotite, and calcite assemblage might be formed by the dissolution of dolomite at ~700 °C, 130 MPa. Such modelling requires stable diopside in the observed conditions in the presence of silica-saturated fluid. The lack of diopside in the metasomatized region is due to the high K activity of the fluid. Our log activity K₂O (a_K2O)–temperature pseudosection shows that at a_K2O~−40, the olivine, spinel, biotite, and calcite assemblage is stable without diopside. Subsequently, at ~450 °C, 130 MPa, serpentine is formed due to the infiltration of H₂O during the cooling of the lamprophyre dyke. This suggests that hot H₂O-CO₂ fluids with dissolved major and trace elements infiltrated through fractures, grain boundaries, and micron-scale porosity, which dissolved dolomite in the marble and precipitated the observed olivine-bearing peak metasomatic assemblage. During cooling, exsolved CO₂ could increase the water activity to stabilize the serpentine. Our example implies that dissolution-reprecipitation is an important process, locally and regionally, that could impart important textural and geochemical variations in metasomatized rocks. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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25 pages, 11204 KiB

Open AccessFeature PaperArticle

Comparison of the Calcareous Shells of Belemnitida and Sepiida: Is the Cuttlebone Prong an Analogue of the Belemnite Rostrum Solidum?

by M. Isabel Benito and Matías Reolid

Minerals 2020, 10(8), 713; https://0-doi-org.brum.beds.ac.uk/10.3390/min10080713 - 12 Aug 2020

Cited by 4 | Viewed by 3950

Abstract

The microstructure of the rostrum solidum of Jurassic belemnites is compared with that of Sepia cuttlebones, in order to examine possible convergences in their style of growth. For this study, transmitted and polarized light, cathodoluminescence, epifluorescence, scanning electron and backscattered electron microscopy have been employed. Despite differences in the primary mineralogy of the studied belemnites and sepiids, calcite and aragonite, respectively, many similarities have been observed between the microstructure of the belemnite rostra and the prong of Sepia cuttlebone: (1) In both, crystals start growing from successive spherulites, from which crystals emerge radially towards the apex and the external walls, displaying internally micro-fibrous texture. (2) Both display concentric growth layering, comprising an alternation of organic-rich and organic-poor layers, which, in turn, is traverse by the radially-arranged micro-fibrous crystals. (3) The highest organic matter content and porosity have been observed along the apical area of the Sepia prong, similarly to that interpreted for belemnite rostra. The strong convergences observed suggest that the growth of belemnites occurred similarly to that of the prong of sepiids and that the Sepia prong is the analog of the belemnite rostrum. Additionally, non-classical crystallization processes are proposed to be involved in the formation Sepia endoskeleton. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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18 pages, 21814 KiB

Open AccessArticle

Microstructure Investigation of Oil-Bearing Rhyolites: A Case Study from the Hailar Basin, NE China

by Anqi Mao, Han Zheng and Xiaomeng Sun

Minerals 2020, 10(8), 699; https://0-doi-org.brum.beds.ac.uk/10.3390/min10080699 - 06 Aug 2020

Cited by 3 | Viewed by 3007

Abstract

Understanding the microstructure of rhyolites may greatly promote exploration efforts on rhyolitic hydrocarbon reservoirs; however, related studies are sparse. In this contribution, the microstructure and related porosity of oil-bearing rhyolitic lavas from the Hailar Basin (NE China) were investigated using a combination of optical microscopy, fluorescence image analysis, and scanning electron microscopy. The direct visual and quantitative analyses show that the rhyolites are heterogeneous and porous rocks and have complex microstructures. Phenocryst-rich rhyolitic lava, perlitic lava, and spherulitic rhyolite may be favorable targets for rhyolitic hydrocarbon exploration. For the phenocryst-rich rhyolitic lavas, embayment pores, cleavages, cavitational and shear fractures, and intracrystalline sieve pores are commonly observed in the phenocrysts; while flow-parallel laminar and micropores are ubiquitous in the groundmass. Perlitic lavas are characterized by the occurrence of numerous perlitic fractures which can also be produced in the glassy groundmass of other lavas. Spherulitic rhyolites mainly consist of small-sized (<1 mm) clustered or large-sized (>1 mm) isolated spherulites. Clustered spherulites are characterized by the development of interspherulite pores. Isolated spherulites contain numerous radiating micropores. Both types of spherulites may have water expulsion pores formed in the spherulite–glass border. The formation of the microstructure and related porosity of rhyolites is controlled by pre-, syn- (e.g., deuteric crystal dissolution, cavitation, ductile–brittle deformation, and high-T devitrification), and post-volcanic (e.g., hydration and low-T devitrification) processes. Although pores with diameters > 50 μm are often observed, small pores dominate in pore-size distribution. Small (<15 μm) and large (>300 μm) pores give the most volumetric contribution in most cases. Medium-sized pores with diameters ranging from ~150–300 μm are the least developed and contribute the least to the total volume. The results of this paper can be beneficial to further the understanding of the microstructure and pore system of rhyolites and may be applied to rhyolitic lava hydrocarbon reservoirs elsewhere. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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27 pages, 19581 KiB

Open AccessArticle

Sequential Scheelite Mineralization of Quartz–Scheelite Veins at the Sangdong W-Deposit: Microtextural and Geochemical Approach

by Woohyun Choi, Changyun Park, Yungoo Song, Chaewon Park, Ha Kim and Chulgyoo Lee

Minerals 2020, 10(8), 678; https://0-doi-org.brum.beds.ac.uk/10.3390/min10080678 - 30 Jul 2020

Cited by 7 | Viewed by 4307

Abstract

The Sangdong W (tungsten)-deposit is known as one of the world’s largest W-deposits, a magmatic–hydrothermal ore deposit including both skarn and hydrothermal alteration zones. The strata-bound characteristic of the deposit resulted in three major orebodies (hanging wall, main, footwall). The main ore mineral is a scheelite (CaWO₄)–powellite (CaMoO₄) solid solution. We examined the fluid evolution and scheelite formation process of the quartz–scheelite veins of the ore deposit, based on the microtextures and geochemical characteristics of the scheelite. After the initial magmatic–hydrothermal fluid release from the granitic body, prograde skarn is formed. In the later prograde stage, secondary fluid rises and precipitates stage I scheelite. Well-developed oscillatory zoning with the highest Mo content indicates continuous fluid infiltration under an open system. Pressure rises as mineralization occurs, generating the pressure release of the retrograde fluid. Fluid migrates downward by the gravitational backflow mechanism, forming stage II to IV scheelites. Dented oscillatory zoning of stage II scheelite is strong evidence of this pressure release. Stage III and IV scheelite do not show specific internal structures with pure scheelite composition. Retrograde scheelites are formed by fractional crystallization under a closed system. The observation of systematical fractional crystallization in the quartz–scheelite vein system is a meaningful result of our research. The geochemical characteristics and microtextural evidence imprinted in scheelites from each stage provide crucial evidence for the understanding of sequential scheelite mineralization of the quartz–scheelite vein system of the Sangdong W-deposit. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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15 pages, 6080 KiB

Open AccessArticle

Mg-Phengite in Carbonate Rock Syngenetically Formed from Hydrothermal Fluid: Micro-Textural Evidence and Mineral Chemistry

by Chaewon Park, Namsoo Kim, Sung-Ja Choi and Yungoo Song

Minerals 2020, 10(8), 668; https://0-doi-org.brum.beds.ac.uk/10.3390/min10080668 - 27 Jul 2020

Cited by 9 | Viewed by 5059

Abstract

Phengite series is a dioctahedral solid solution between two end-members of muscovite [K₁[Al₂]^VI[Al₁,Si₃]^IVO₁₀(OH)₂] and celadonite [K₁[(Fe³⁺,Al)₁,(Mg,Fe²⁺)₁]^VI [...] Read more.

Phengite series is a dioctahedral solid solution between two end-members of muscovite [K₁[Al₂]^VI[Al₁,Si₃]^IVO₁₀(OH)₂] and celadonite [K₁[(Fe³⁺,Al)₁,(Mg,Fe²⁺)₁]^VI[Si₄]^IVO₁₀(OH)₂], which have a hetero-valent substitution of Al^VIAl^IV ↔ (Mg, Fe)^VISi^IV. In this study, we report a hydrothermal-originated authigenic Mg-phengite-series mineral, which occurred as polycrystalline aggregates (Type 1), pore-fillings (Type 2) and well-crystallized lath form (Type 3) from the Haengmae Formation, a dolomite–pebble-bearing fine sand-sized dolostone, in South Korea. Based on micro-textural observation, three types of Mg-phengite are associated with crystalline dolomite, and are followed by calcite precipitation as pore-filling, indicating that these should be formed by the influx of a Mg-rich hydrothermal fluid after the deposition of some clastic sediments and before calcite-filling. The structural formula based on O₁₀(OH)₂ shows that the number of Mg atoms per formula unit (apfu) of Mg-phengite ranges from 0.00 to 0.70 with no Fe, which is relatively high, compared with the previously reported metamorphic phengites. In REEs mineral chemistry, the Mg-phengites are characterized by the enrichment of REEs and by the particular enrichment of LREEs in the polycrystalline aggregates of Mg-phengite. It strongly suggests that the Mg-phengite should be formed by the infiltration of the highly evolved Mg- and REEs-enriched hydrothermal fluid into the clastic sedimentary rock (Haengmae Formation) as a strata-bound form, syngenetically or during early diagenesis. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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14 pages, 4712 KiB

Open AccessEditor’s ChoiceArticle

Measurement of 3D-Shape Preferred Orientation (SPO) Using Synchrotron μ-CT: Applications for Estimation of Fault Motion Sense in a Fault Gouge

by Ho Sim, Yungoo Song, Jaehun Kim, Eomzi Yang, Tae Sup Yun and Jae-Hong Lim

Minerals 2020, 10(6), 528; https://0-doi-org.brum.beds.ac.uk/10.3390/min10060528 - 09 Jun 2020

Cited by 4 | Viewed by 3129

Abstract

We propose a 3D-shape preferred orientation (SPO) measurement method of rigid grains using synchrotron micro-computational tomography (μ-CT). The method includes oriented sampling, 3D μ-CT imaging, image filtering, ellipsoid fitting, and SPO measurement. After CT imaging, all processes are computerized, and the directions of thousands of rigid grains in 3D-space can be automatically measured. This method is optimized for estimating the orientation of the silt-sized rigid grains in fault gouge, which indicates P-shear direction in a fault system. This allows us to successfully deduce fault motion sense and quantify fault movement. Because this method requires a small amount of sample, it can be applied as an alternative to study fault systems, where the shear sense indicators are not distinct in the outcrop and the fault gouge is poorly developed. We applied the newly developed 3D-SPO method for a fault system in the Yangsan fault, one of the major faults in the southeastern Korean Peninsula, and observed the P-shear direction successfully. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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18 pages, 4847 KiB

Open AccessEditor’s ChoiceArticle

Strain-Induced Fabric Transition of Chlorite and Implications for Seismic Anisotropy in Subduction Zones

by Dohyun Kim, Haemyeong Jung and Jungjin Lee

Minerals 2020, 10(6), 503; https://0-doi-org.brum.beds.ac.uk/10.3390/min10060503 - 31 May 2020

Cited by 4 | Viewed by 2698

Abstract

Seismic anisotropy of S-wave, trench-parallel or trench-normal polarization direction of fast S-wave, has been observed in the fore-arc and back-arc regions of subduction zones. Lattice preferred orientation (LPO) of elastically anisotropic chlorite has been suggested as one of the major causes of seismic anisotropy in subduction zones. However, there are two different LPOs of chlorite reported based on the previous studies of natural chlorite peridotites, which can produce different expression of seismic anisotropy. The mechanism for causing the two different LPOs of chlorite is not known. Therefore, we conducted deformation experiments of chlorite peridotite under high pressure–temperature conditions (P = 0.5–2.5 GPa, T = 540–720 °C). We found that two different chlorite LPOs were developed depending on the magnitude of shear strain. The type-1 chlorite LPO is characterized by the [001] axes aligned subnormal to the shear plane, and the type-2 chlorite LPO is characterized by a girdle distribution of the [001] axes subnormal to the shear direction. The type-1 chlorite LPO developed under low shear strain (γ ≤ 3.1 ± 0.3), producing trench-parallel seismic anisotropy. The type-2 chlorite LPO developed under high shear strain (γ ≥ 5.1 ± 1.5), producing trench-normal seismic anisotropy. The anisotropy of S-wave velocity (AVs) of chlorite was very strong up to AVs = 48.7% so that anomalous seismic anisotropy in subduction zones can be influenced by the chlorite LPOs. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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28 pages, 33604 KiB

Open AccessArticle

Effect of Mineral Processes and Deformation on the Petrophysical Properties of Soft Rocks during Active Faulting

by Anita Torabi, Juan Jiménez-Millán, Rosario Jiménez-Espinosa, Francisco Juan García-Tortosa, Isabel Abad and Tor S. S. Ellingsen

Minerals 2020, 10(5), 444; https://0-doi-org.brum.beds.ac.uk/10.3390/min10050444 - 15 May 2020

Cited by 9 | Viewed by 3375

Abstract

We have studied damage zones of two active faults, Baza and Padul faults in Guadix-Baza and Granada basins, respectively, in South Spain. Mineral and microstructural characterization by X-ray diffraction and field emission electron microscopy studies have been combined with structural fieldwork and in situ measurements of rock properties (permeability and Young’s modulus) to find out the relation between deformation behavior, mineral processes, and changes in the soft rock and sediment properties produced by fluid flow during seismic cycles. Our results show that microsealing produced by precipitation of dolomite and aragonite along fractures in the damage zone of Baza Fault reduces the permeability and increases the Young’s modulus. In addition, deformation bands formed in sediments richer in detrital silicates involved cataclasis as deformation mechanism, which hamper permeability of the sediments. In the Granada Basin, the calcarenitic rocks rich in calcite and clays in the damage zone of faults associated to the Padul Fault are characterized by the presence of stylolites without any carbonate cement. On the other hand, marly lithofacies affected by faults are characterized by the presence of disaggregation bands that involve cracking and granular flow, as well as clay smear. The presence of stylolites and deformation bands in these rocks reduces permeability. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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17 pages, 6064 KiB

Open AccessArticle

Microstructural and Geochronological Analyses of Mesozoic Ductile Shear Zones in the Western Gyeonggi Massif, Korea: Implications for an Orogenic Cycle in the East Asian Continental Margin

by Jeong-Yeong Park, Seung-Ik Park and Taejin Choi

Minerals 2020, 10(4), 362; https://0-doi-org.brum.beds.ac.uk/10.3390/min10040362 - 17 Apr 2020

Cited by 9 | Viewed by 3242

Abstract

In response to orogenic cycles, the ductile shear zone records a complex crustal deformation history. In this study, we conducted a microstructural analysis of two NW–SE trending ductile shear zones (Deokjeok Shear Zone (DSZ) and Soya Shear Zone (SSZ)) in the Late Triassic post-collisional granites along the western Gyeonggi Massif in the Korean Peninsula. The DSZ, overlain by the Late Triassic to the Early Jurassic post-collisional basin fill (Deokjeok Formation), has asymmetric microstructures indicative of a top-down-to-the-northeast shear. Depending on the structural position, the SSZ, which structurally overlies the Deokjeok Formation, exhibits two contrasting styles of deformation. The lower portion of the SSZ preserves evidence of top-up-to-the-southwest shearing after top-down-to-the-northeast shearing; on the other hand, the upper portion only indicates a top-up movement. Given the primary deformation mechanisms of both quartz and feldspar, the deformation temperatures of DSZ and SSZ were estimated at ~300–350 °C and ~350–400 °C, respectively, indicative of the mid-crustal condition. New zircon U-Pb isotopic ages from mylonitic granite in the SSZ and volcanic rocks in the Deokjeok Formation, combined with previously published geochronological data, indicate that the post-collisional granites and volcano-sedimentary sequence were nearly contemporaneous (ca. 223–217 Ma) and juxtaposed because of the Late Triassic orogenic collapse and subsequent new orogenic event. In this study, we highlight the role of the extensional DSZ as a detachment propagated into the middle crust during the Late Triassic orogenic collapse. Our results report a deformational response to a transition from the collisional Songrim Orogeny to the subduction-related Daebo Orogeny in the western Gyeonggi Massif. This, in turn, provides essential insight into cyclic mountain building/collapse in the East Asian continental margin during the Mesozoic time. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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21 pages, 6659 KiB

Open AccessArticle

Representativity of 2D Shape Parameters for Mineral Particles in Quantitative Petrography

by Edgar Berrezueta, José Cuervas-Mons, Ángel Rodríguez-Rey and Berta Ordóñez-Casado

Minerals 2019, 9(12), 768; https://0-doi-org.brum.beds.ac.uk/10.3390/min9120768 - 11 Dec 2019

Cited by 35 | Viewed by 4613

Abstract

This paper introduces an assessment of the representation of shape parameter measurements on theoretical particles. The aim of the study was to establish a numerical method for estimating sphericity, roundness, and roughness on artificially designed particles and to evaluate their interdependence. The parameters studied included a fractal dimension (FD), solidity (So), Wadell’s roundness (Rw), a perimeter-area normalized ratio (¥), and sphericity (S). The methods of the work included: (a) the design of theoretical particles with different shapes, (b) the definition of optimal analysis conditions for automated measurements, (c) the quantification of particle parameters by computer vision-based image processing, and (d) the evaluation of interdependence between the parameters. The study established the minimum sizes required for analysis of the particle shape. These varied depending on the method used (150 pixels or 50 pixels). Evaluating the relationships between the parameters showed that FD and So are independent of S. Nevertheless, Rw and ¥ are clearly dependent on S and, thus, must be numerically corrected to Rwc and ¥c. FD, So, Rwc, and ¥c were used to establish, mathematically, a new regularity parameter (RBC) that reflects the degree of roundness of a particle. The process was applied to a case study and the evaluation of all parameters corroborated previous petrographic characterizations. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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