Journal articles: 'Modal mineralogy'

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Mena Silva, Camilo, Bjørn Sørensen, Kurt Aasly, and Steinar Ellefmo. "Geometallurgical Approach to the Element-to-Mineral Conversion for the Nabbaren Nepheline Syenite Deposit." Minerals 8, no. 8 (July 29, 2018): 325. http://dx.doi.org/10.3390/min8080325.

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Nabbaren nepheline syenite, a silica-deficient intrusive rock with low Fe content, was the industrial mineral deposit study case in this study. The quality of industrial mineral products are generally based on their bulk chemistry, which are directly related to their modal mineralogy and mineral chemistry; however, these are costly and time-consuming to determine. A geometallurgical-based methodology, known as element-to-mineral conversion (EMC), was applied to estimate its modal mineralogy based on its given bulk and mineral chemistry. EMC is a convenient and cost-effective technique, which can be used to quickly estimate modal mineralogy. Two EMC methodologies were applied: one least square based, LS-XRD, and one regression based, R-XRD. Additionally, average and specific mineral chemistries were used during estimations. The R-XRD method, a method not yet used for EMC purposes, gave better modal mineralogy estimations than LS-XRD. Considering the restrictions in the method, R-XRD shows potential for improvement and implementation at operational scale, making it a valuable geometallurgical tool for increasing resource performance, easing decision-taking processes, and reducing risks. The use of different mineral chemistries did not influence the modal mineralogy estimation, unlike the method used for it.

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Jennings, S., D. Hasterok, and J. Payne. "A new compositionally based thermal conductivity model for plutonic rocks." Geophysical Journal International 219, no. 2 (August 16, 2019): 1377–94. http://dx.doi.org/10.1093/gji/ggz376.

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SUMMARY Thermal conductivity is a physical parameter crucial to accurately estimating temperature and modelling thermally related processes within the lithosphere. Direct measurements are often impractical due to the high cost of comprehensive sampling or inaccessibility and thereby require indirect estimates. In this study, we report 340 new thermal conductivity measurements on igneous rocks spanning a wide range of compositions using an optical thermal conductivity scanning device. These are supplemented by a further 122 measurements from the literature. Using major element geochemistry and modal mineralogy, we produce broadly applicable empirical relationships between composition and thermal conductivity. Predictive models for thermal conductivity are developed using (in order of decreasing accuracy) major oxide composition, CIPW normative mineralogy and estimated modal mineralogy. Four common mixing relationships (arithmetic, geometric, square-root and harmonic) are tested and, while results are similar, the geometric model consistently produces the best fit. For our preferred model, $k_{\text{eff}} = \exp ( 1.72 \, C_{\text{SiO}_2} + 1.018 \, C_{\text{MgO}} - 3.652 \, C_{\text{Na}_2\text{O}} - 1.791 \, C_{\text{K}_2\text{O}})$, we find that SiO2 is the primary control on thermal conductivity with an RMS of 0.28 W m−1 K−1or ∼10 per cent. Estimates from normative mineralogy work to a similar degree but require a greater number of parameters, while forward and inverse modelling using estimated modal mineralogy produces less than satisfactory results owing to a number of complications. Using our model, we relate thermal conductivity to both P-wave velocity and density, revealing systematic trends across the compositional range. We determine that thermal conductivity can be calculated from P-wave velocity in the range 6–8 km s−1 to within 0.31 W m−1 K−1 using $k({V_p}) = 0.5822 \, V_p^2 - 8.263 \, V_p + 31.62$. This empirical model can be used to estimate thermal conductivity within the crust where direct sampling is impractical or simply not possible (e.g. at great depths). Our model represents an improved method for estimating lithospheric conductivity than present formulas which exist only for a limited range of compositions or are limited by infrequently measured parameters.

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Luth, Robert W. "Possible implications of modal mineralogy for melting in mantle lherzolites." Geochimica et Cosmochimica Acta 66, no. 12 (June 2002): 2091–98. http://dx.doi.org/10.1016/s0016-7037(02)00906-7.

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Tolosana-Delgado, R., H. von Eynatten, and V. Karius. "Constructing modal mineralogy from geochemical composition: A geometric-Bayesian approach." Computers & Geosciences 37, no. 5 (May 2011): 677–91. http://dx.doi.org/10.1016/j.cageo.2010.08.005.

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Metzner, Christian, and Wolfgang Grimmeisen. "MONA: a user-friendly computer-program for calculating the modal mineralogy of rocks from chemical analyses." European Journal of Mineralogy 2, no. 5 (October 4, 1990): 735–38. http://dx.doi.org/10.1127/ejm/2/5/0735.

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Howard, K. T., G. K. Benedix, P. A. Bland, and G. Cressey. "Modal mineralogy of CV3 chondrites by X-ray diffraction (PSD-XRD)." Geochimica et Cosmochimica Acta 74, no. 17 (September 2010): 5084–97. http://dx.doi.org/10.1016/j.gca.2010.06.014.

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Usdansky, Steven I. "GRCHEM: a BASIC program to calculate granite chemistry from modal mineralogy." Computers & Geosciences 11, no. 2 (January 1985): 229–33. http://dx.doi.org/10.1016/0098-3004(85)90008-1.

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Scanza, R. A., N. Mahowald, S. Ghan, C. S. Zender, J. F. Kok, X. Liu, and Y. Zhang. "Modeling dust as component minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing." Atmospheric Chemistry and Physics Discussions 14, no. 12 (July 2, 2014): 17749–816. http://dx.doi.org/10.5194/acpd-14-17749-2014.

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Abstract. The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral components in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as +0.05 W m−2 for both CAM4 and CAM5 simulations with mineralogy and compare this both with simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 W m−2) and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, −0.05 and −0.17 W m−2, respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in-situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.

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Scanza, R. A., N. Mahowald, S. Ghan, C. S. Zender, J. F. Kok, X. Liu, Y. Zhang, and S. Albani. "Modeling dust as component minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing." Atmospheric Chemistry and Physics 15, no. 1 (January 15, 2015): 537–61. http://dx.doi.org/10.5194/acp-15-537-2015.

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Abstract. The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale, using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral components in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as + 0.05 Wm−2 for both CAM4 and CAM5 simulations with mineralogy. We compare this to the radiative forcing from simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 Wm−2) and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, −0.05 and −0.17 Wm−2, respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.

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BLAND, Philip A., Gordon CRESSEY, and Olwyn N. MENZIES. "Modal mineralogy of carbonaceous chondrites by X-ray diffraction and Mössbauer spectroscopy." Meteoritics & Planetary Science 39, no. 1 (January 2004): 3–16. http://dx.doi.org/10.1111/j.1945-5100.2004.tb00046.x.

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King, A. J., P. F. Schofield, K. T. Howard, and S. S. Russell. "Modal mineralogy of CI and CI-like chondrites by X-ray diffraction." Geochimica et Cosmochimica Acta 165 (September 2015): 148–60. http://dx.doi.org/10.1016/j.gca.2015.05.038.

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Dehaine, Quentin, Laurens T. Tijsseling, Gavyn K. Rollinson, Mike W. N. Buxton, and Hylke J. Glass. "Geometallurgical Characterisation with Portable FTIR: Application to Sediment-Hosted Cu-Co Ores." Minerals 12, no. 1 (December 22, 2021): 15. http://dx.doi.org/10.3390/min12010015.

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Cobalt (Co) mine production primarily originates from the sediment-hosted copper (Cu) deposits of the Democratic Republic of Congo (DRC). These deposits usually consist of three ore zones with a supergene oxide ore blanket overlying a transition zone which grades into a sulphide zone at depth. Each of these zones display a mineral assemblage with varying gangue mineralogy and, most importantly, a distinct state of oxidation of the mineralisation. This has direct implications for Cu and Co extraction during mineral processing as it dictates which processing method is to be used (i.e., leaching vs. flotation) and affects the performance of these. To optimise resource efficiency, reduce technical risks and environmental impacts, comprehensive understanding of variation of ore mineralogy and texture in the deposit is essential. By defining geometallurgical ore types according to their inferred metallurgical behaviour, this information can serve to classify the resources and improve resource management. To obtain insight into the spatial distribution of mineral grades, it is necessary to develop techniques that have the potential to measure rapidly and, preferably, within the mine at relatively low-cost. In this study, the application of portable Fourier transformed infrared (FTIR) spectroscopy is investigated to measure the mineralogy of drill core samples. A set of samples from a sediment-hosted Cu-Co deposit in DRC was selected to test this approach. Results were validated using automated mineralogy (QEMSCAN). Prediction of gangue and target mineral grades from the FTIR spectra was achieved through partial least squares regression (PLS-R) combined with competitive adaptive reweighted sampling (CARS). It is shown that the modal mineralogy obtained from FTIR can be used to classify the ore according to type of mineralisation and gangue mineralogy into geometallurgical ore types. This classification supports selection of a suitable processing route and is likely to affect the overall process performance.

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Schofield, P. F., K. S. Knight, S. J. Covey-Crump, G. Cressey, and I. C. Stretton. "Accurate quantification of the modal mineralogy of rocks when image analysis is difficult." Mineralogical Magazine 66, no. 1 (February 2002): 189–200. http://dx.doi.org/10.1180/0026461026610022.

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AbstractThe volume proportions of the mineral phases in two strongly deformed olivine-orthopyroxene rocks have been quantified by whole-pattern stripping of fixed geometry X-ray powder diffraction data. The results were compared with the phase proportions as determined by Rietveld refinement of time-of-flight neutron powder diffraction data, and were shown to be in excellent agreement. The X-ray technique not only provides a very rapid and cost-effective method of determining phase proportions, but it also circumvents several of the problems associated with obtaining this information by image analysis. Moreover, the technique is particularly advantageous in strongly textured rocks or in rocks that contain significant residual strains. As such it offers a powerful technique for analysing the mineralogical composition of fine-grained and/or deformed experimental run products, which makes it of considerable potential for monitoringin situthe progress of mineral reactions during laboratory experiments.

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Harvey, P. K., T. S. Brewer, M. A. Lovell, and S. A. Kerr. "The estimation of modal mineralogy: a problem of accuracy in core-log calibration." Geological Society, London, Special Publications 136, no. 1 (1998): 25–38. http://dx.doi.org/10.1144/gsl.sp.1998.136.01.04.

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15

Hamilton, Victoria E., and Philip R. Christensen. "Determining the modal mineralogy of mafic and ultramafic igneous rocks using thermal emission spectroscopy." Journal of Geophysical Research: Planets 105, E4 (April 1, 2000): 9717–33. http://dx.doi.org/10.1029/1999je001113.

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Maloy, A. K., and A. H. Treiman. "Evaluation of image classification routines for determining modal mineralogy of rocks from X-ray maps." American Mineralogist 92, no. 11-12 (November 1, 2007): 1781–88. http://dx.doi.org/10.2138/am.2007.2477.

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Li, Shuai, and Ralph E. Milliken. "Estimating the modal mineralogy of eucrite and diogenite meteorites using visible-near infrared reflectance spectroscopy." Meteoritics & Planetary Science 50, no. 11 (October 13, 2015): 1821–50. http://dx.doi.org/10.1111/maps.12513.

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Brown, D. "Modal mineralogy and chemical composition of the Uralide lower crust determined from physical properties data." Tectonophysics 433, no. 1-4 (April 2007): 39–51. http://dx.doi.org/10.1016/j.tecto.2007.01.001.

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Koch, Pierre-Henri, Cecilia Lund, and Jan Rosenkranz. "Automated drill core mineralogical characterization method for texture classification and modal mineralogy estimation for geometallurgy." Minerals Engineering 136 (June 2019): 99–109. http://dx.doi.org/10.1016/j.mineng.2019.03.008.

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20

Nikonow, Wilhelm, and Dieter Rammlmair. "Automated mineralogy based on micro-energy-dispersive X-ray fluorescence microscopy (µ-EDXRF) applied to plutonic rock thin sections in comparison to a mineral liberation analyzer." Geoscientific Instrumentation, Methods and Data Systems 6, no. 2 (October 18, 2017): 429–37. http://dx.doi.org/10.5194/gi-6-429-2017.

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Abstract. Recent developments in the application of micro-energy-dispersive X-ray fluorescence spectrometry mapping (µ-EDXRF) have opened up new opportunities for fast geoscientific analyses. Acquiring spatially resolved spectral and chemical information non-destructively for large samples of up to 20 cm length provides valuable information for geoscientific interpretation. Using supervised classification of the spectral information, mineral distribution maps can be obtained. In this work, thin sections of plutonic rocks are analyzed by µ-EDXRF and classified using the supervised classification algorithm spectral angle mapper (SAM). Based on the mineral distribution maps, it is possible to obtain quantitative mineral information, i.e., to calculate the modal mineralogy, search and locate minerals of interest, and perform image analysis. The results are compared to automated mineralogy obtained from the mineral liberation analyzer (MLA) of a scanning electron microscope (SEM) and show good accordance, revealing variation resulting mostly from the limit of spatial resolution of the µ-EDXRF instrument. Taking into account the little time needed for sample preparation and measurement, this method seems suitable for fast sample overviews with valuable chemical, mineralogical and textural information. Additionally, it enables the researcher to make better and more targeted decisions for subsequent analyses.

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Koh, Edwin J. Y., Eiman Amini, Geoffrey J. McLachlan, and Nick Beaton. "Utilising convolutional neural networks to perform fast automated modal mineralogy analysis for thin-section optical microscopy." Minerals Engineering 173 (November 2021): 107230. http://dx.doi.org/10.1016/j.mineng.2021.107230.

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Ebel, Denton S., Ellen J. Crapster-Pregont, and Jon M. Friedrich. "Image Analysis of 2D X-ray Intensity Maps: Element Abundances, Mineralogy, and Modal Analysis of Meteorites." Microscopy and Microanalysis 20, S3 (August 2014): 752–53. http://dx.doi.org/10.1017/s1431927614005480.

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Poulet, F., O. Ruesch, Y. Langevin, and H. Hiesinger. "Modal mineralogy of the surface of Vesta: Evidence for ubiquitous olivine and identification of meteorite analogue." Icarus 253 (June 2015): 364–77. http://dx.doi.org/10.1016/j.icarus.2014.06.002.

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Demattê, José Alexandre Melo, Fabrício da Silva Terra, and Carlos Fernando Quartaroli. "Spectral behavior of some modal soil profiles from São Paulo State, Brazil." Bragantia 71, no. 3 (November 6, 2012): 413–23. http://dx.doi.org/10.1590/s0006-87052012005000038.

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Remote sensing has a high potential for environmental evaluation. However, a necessity exists for a better understanding of the relations between the soil attributes and spectral data. The objective of this work was to analyze the spectral behavior of some soil profiles from the region of Piracicaba, São Paulo State, using a laboratory spectroradiometer (400 to 2500 nm). The relations between the reflected electromagnetic energy and the soil physical, chemical and mineralogical attributes were analyzed, verifying the spectral variations of soil samples in depth along the profiles with their classification and discrimination. Sandy soil reflected more, presenting a spectral curve with an ascendant form, opposite to clayey soils. The 1900 nm band discriminated soil with 2:1 mineralogy from the 1:1 and oxidic soils. It was possible to detect the presence of kaolinite, gibbsite, hematite and goethite in the soils through the descriptive aspects of curves, absorption features and reflectance intensity. A relation exists between the weathering stage and spectral data. The evaluation of the superficial and subsuperficial horizon samples allowed characterizing and discriminating the analytical variability of the profile, helping to soil distinguishing and classification.

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Burns, Roger G. "Spectral mineralogy of terrestrial planets: scanning their surfaces remotely." Mineralogical Magazine 53, no. 370 (April 1989): 135–51. http://dx.doi.org/10.1180/minmag.1989.053.370.02.

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AbstractSpectral measurements of sunlight reflected from planetary surfaces, when correlated with experimental visible-near-infrared spectra of rock-forming minerals, are being used to detect transition metal cations, to identify constituent minerals, and to determine modal mineralogies of regoliths on terrestrial planets. Such remote-sensed reflectance spectra measured through earth-based telescopes may have absorption bands in the one micron and two micron wavelength regions which originate from crystal field transitions within Fe2+ ions. Pyroxenes with Fe2+ in M2 positions dominate the spectra, and the resulting 1 μm versus 2 µm spectral determinative curve is used to identify compositions and structure-types of pyroxenes on surfaces of the Moon, Mercury, and asteroids, after correcting for experimentally-determined temperature-shifts of peak positions. Olivines and Fe2+-bearing plagioclase feldspars also give diagnostic peaks in the 1 µm region, while tetrahedral Fe2+ in glasses absorb in the 2 µm region as well. Opaque ilmenite, spinel and metallic iron phases mask all of these Fe2+ spectral features. Laboratory studies of mixed-mineral assemblages enable coexisting Fe2+ phases to be identified in remote-sensed reflectance spectra of regoliths. Thus, noritic rocks in the lunar highlands, troctolites in central peaks of impact craters such as Copernicus, and high-Ti and low-Ti mare basalts have been mapped on the Moon's surface by telescopic reflectance spectroscopy. The Venusian atmosphere prevents remote-sensed spectral measurements of its surface mineralogy, while atmospheric CO2 and ferric-bearing materials in the regolith on Mars interfere with pyroxene characterization in bright- and dark-region spectra. Reflectance spectral measurements of several meteorite types, including specimens from Antarctica, are consistent with a lunar highland origin for achondrite ALHA 81005 and a martian origin for shergottite EETA 79001, although source regions may not be outermost surfaces of the Moon and Mars. Correlations with asteroid reflectance spectra suggest that Vesta is the source of basaltic achondrites, while wide ranges of olivine/pyroxene ratios are inconsistent with an ordinary-chondrite surface composition of many asteroids. Visible-near-infrared spectrometers are destined for instrument payloads in future spacecraft missions to neighbouring solar system bodies.

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Aarestrup, Emil, Taus R. C. Jørgensen, Paul E. B. Armitage, Allen P. Nutman, Ole Christiansen, and Kristoffer Szilas. "The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 1. Constraints on the P–T evolution from igneous, metasomatic and metamorphic amphiboles." Mineralogical Magazine 84, no. 5 (September 10, 2020): 662–90. http://dx.doi.org/10.1180/mgm.2020.68.

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AbstractThe metamorphic history of the Mesoarchean Amikoq Layered Complex within the Akia terrane of SW Greenland was characterised by electron microprobe mineral data and detailed petrography on 12 representative samples, integrated with zircon U–Pb geochronology and petrology. The complex intruded into a >3004 Ma supracrustal association now consisting of granoblastic metabasites with subordinate quartz-rich gneiss. Supracrustal host rocks contain a relict high-temperature assemblage of orthopyroxene–clinopyroxene (± pigeonite exsolution lamellae, exsolved at ~975–1010°C), which is interpreted to pre-date the Amikoq intrusion. Cumulate to granoblastic-textured rocks of the main Amikoq Layered Complex range modally from leuconorite to melanorite, orthopyroxenite to harzburgite/dunite and rare hornblende melagabbro. Observed mineralogy of main complex noritic lithologies is essentially relict igneous with orthopyroxene–biotite and hornblende–plagioclase thermometers yielding temperatures of ~800–1070°C. An anatectic zircon megacryst from a patchy quartzo–feldspathic leucosome hosted in an orthopyroxene-dominated Amikoq rock reflects local anatexis at peak metamorphic P–T conditions and yields an intrusion minimum age of 3004 ± 9 Ma. Field observations indicate local anatexis of orthopyroxene-dominated lithologies, possibly indicating a post-intrusion peak temperature of >900°C. The last preserved stages of retrogression are recorded in paragneiss plagioclase–garnet, biotite–garnet and host rock ilmenite–magnetite pairs (≤3 kbar and ~380–560°C).The Amikoq Complex intruded a MORB-like crustal section and the former remained relatively undisturbed in terms of modal mineralogy. Preservation of igneous textures and mineralogy are related to an anhydrous, high-grade metamorphic history that essentially mimics igneous crystallisation conditions, whereas local high-strain zones acted as fluid pathways resulting in hydrous breakdown of igneous minerals. There is no evidence of equilibration of the intrusion at sub-amphibolite-facies conditions.

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Kruk, Mikhail Nikolaevich, Anna Gennadievna Doroshkevich, Ilya Romanovich Prokopyev, and Ivan Aleksandrovich Izbrodin. "Mineralogy of Phoscorites of the Arbarastakh Complex (Republic of Sakha, Yakutia, Russia)." Minerals 11, no. 6 (May 24, 2021): 556. http://dx.doi.org/10.3390/min11060556.

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The Arbarastakh ultramafic carbonatite complex is located in the southwestern part of the Siberian Craton and contains ore-bearing carbonatites and phoscorites with Zr-Nb-REE mineralization. Based on the modal composition, textural features, and chemical compositions of minerals, the phoscorites from Arbarastakh can be subdivided into two groups: FOS 1 and FOS 2. FOS 1 contains the primary minerals olivine, magnetite with isomorphic Ti impurities, phlogopite replaced by tetraferriphlogopite along the rims, and apatite poorly enriched in REE. Baddeleyite predominates among the accessory minerals in FOS 1. Zirconolite enriched with REE and Nb and pyrochlore are found in smaller quantities. FOS 2 has a similar mineral composition but contains much less olivine, magnetite is enriched in Mg, and the phlogopite is enriched in Ba and Al. Of the accessory minerals, pyrochlore predominates and is enriched in Ta, Th, and U; baddeleyite is subordinate and enriched in Nb. Chemical and textural differences suggest that the phoscorites were formed by the sequential introduction of different portions of the melt. The melt that formed the FOS 1 was enriched in Zr and REE relative to the FOS 2 melt; the melt that formed the FOS 2 was enriched in Al, Ba, Nb, Ta, Th, U, and, to a lesser extent, Sr.

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Acevedo Zamora, Marco Andres, and Balz S. Kamber. "Petrographic Microscopy with Ray Tracing and Segmentation from Multi-Angle Polarisation Whole-Slide Images." Minerals 13, no. 2 (January 20, 2023): 156. http://dx.doi.org/10.3390/min13020156.

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‘Slide scanners’ are rapid optical microscopes equipped with automated and accurate x-y travel stages with virtual z-motion that cannot be rotated. In biomedical microscopic imaging, they are widely deployed to generate whole-slide images (WSI) of tissue samples in various modes of illumination. The availability of WSI has motivated the development of instrument-agnostic advanced image analysis software, helping drug development, pathology, and many other areas of research. Slide scanners are now being modified to enable polarised petrographic microscopy by simulating stage rotation with the acquisition of multiple rotation angles of the polariser–analyser pair for observing randomly oriented anisotropic materials. Here we report on the calibration strategy of one repurposed slide scanner and describe a pilot image analysis pipeline designed to introduce the wider audience to the complexity of performing computer-assisted feature recognition on mineral groups. The repurposed biological scanner produces transmitted light plane- and cross-polarised (TL-PPL and XPL) and unpolarised reflected light (RL) WSI from polished thin sections or slim epoxy mounts at various magnifications, yielding pixel dimensions from ca. 2.7 × 2.7 to 0.14 × 0.14 µm. A data tree of 14 WSI is regularly obtained, containing two RL and six of each PPL and XPL WSI (at 18° rotation increments). This pyramidal image stack is stitched and built into a local server database simultaneously with acquisition. The pyramids (multi-resolution ‘cubes’) can be viewed with freeware locally deployed for teaching petrography and collaborative research. The main progress reported here concerns image analysis with a pilot open-source software pipeline enabling semantic segmentation on petrographic imagery. For this purpose, all WSI are post-processed and aligned to a ‘fixed’ reflective surface (RL), and the PPL and XPL stacks are then summarised in one image, each with ray tracing that describes visible light reflection, absorption, and O- and E-wave interference phenomena. The maximum red-green-blue values were found to best overcome the limitation of refractive index anisotropy for segmentation based on pixel-neighbouring feature maps. This strongly reduces the variation in dichroism in PPL and interference colour in XPL. The synthetic ray trace WSI is then combined with one RL to estimate modal mineralogy with multi-scale algorithms originally designed for object-based cell segmentation in pathological tissues. This requires generating a small number of polygonal expert annotations that inform a training dataset, enabling on-the-fly machine learning classification into mineral classes. The accuracy of the approach was tested by comparison with modal mineralogy obtained by energy-dispersive spectroscopy scanning electron microscopy (SEM-EDX) for a suite of rocks of simple mineralogy (granulites and peridotite). The strengths and limitations of the pixel-based classification approach are described, and phenomena from sample preparation imperfections to semantic segmentation artefacts around fine-grained minerals and/or of indiscriminate optical properties are discussed. Finally, we provide an outlook on image analysis strategies that will improve the status quo by using the first-pass mineralogy identification from optical WSI to generate a location grid to obtain targeted chemical data (e.g., by SEM-EDX) and by considering the rock texture.

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Can, İlkay B., Seda Özçelik, and Zafir Ekmekçi. "Effects of Pyrite Texture on Flotation Performance of Copper Sulfide Ores." Minerals 11, no. 11 (November 1, 2021): 1218. http://dx.doi.org/10.3390/min11111218.

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Pyrite particles, having framboidal/altered texture, are known to significantly affect pulp chemistry and adversely affect flotation performance. Therefore, the main objectives of this study were to demonstrate influence of pyrite mineralogy on the flotation of copper (sulphidic) ores and develop alternative conditions to improve the performance. Two copper ore samples (Ore A and Ore B) having different textural/modal mineralogy and flotation characteristics were taken from different zones of the same ore deposit. Ore B contained framboidal pyrite and altered pyrite/marcasite, which is considered the main reason for the low flotation performance in both copper and pyrite flotation sections of the process plant. Flotation tests were conducted under different conditions using the two ore samples and a 50:50 blend. The results showed that Ore A could be concentrated under the base conditions, as applied in the existing flotation plant. On the other hand, Ore B did not respond to the base conditions and a copper recovery of only 5% could be obtained. Besides, blending Ore B with Ore A negatively affected the flotation behavior of Ore A. An alternative flotation chemistry was applied on Ore B using Na2S for surface cleaning and Na-Metabisulfite (MBS) for pyrite depression in the copper flotation stage. The surface cleaning reduced the rate of oxidation of the framboidal pyrite in Ore B. As a result, the copper recovery could be increased to 52% Cu for Ore B, and 65% for the mixed ore sample.

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van der Merwe, Gertruida M. E., Michiel C. Laker, and Christl Bühmann. "Clay mineral associations in melanic soils of South Africa." Soil Research 40, no. 1 (2002): 115. http://dx.doi.org/10.1071/sr00097.

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The melanic horizon is 1 of 5 diagnostic topsoil horizons distinguished in the South African soil classification system. Melanic soils span a wide spectrum, ranging from those that intergrade with a vertic to those that intergrade with a humic horizon. Melanic soils are therefore expected to vary considerably with respect to a variety of physical, chemical, and clay mineralogical properties. The objective of the present study was to determine the clay mineral compositions of melanic horizons from 58 modal profiles and to establish to what extent melanic soil properties are related to clay mineralogy. Special emphasis was placed on the characterisation of the clay fraction in terms of group and species identification. X-ray diffractometry was employed almost exclusively as the investigative technique in mineral identification and quantification. Melanic A horizons showed a large degree of variation with regard to their clay mineral associations. More than half of the soils were dominated by smectite, 30&percnt; by kaolinite, and the rest by an association of about equal proportions of mica, kaolinite, and smectite. Talc and hydroxy-interlayered vermiculite occurred in a number of soils while one horizon was dominated by an illite/smectite interstratification. The smectite component was identified as belonging to either beidellite or vermiculite species, depending on the method employed. About a quarter of the smectitic soils contained montmorillonite as well but not as the dominant swelling phase. mollisols, clay mineralogy, layer charge.

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YING, Zi, Yu-jun Cui, Nadia Benahmed, and Myriam Duc. "Changes in mineralogy and microstructure of a lime-treated silty soil during curing time." E3S Web of Conferences 195 (2020): 03044. http://dx.doi.org/10.1051/e3sconf/202019503044.

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Lime treatment is widely applied to improve the workability and long-term durability of soils. In this study, the curing time effect on the mineralogy and microstructure of lime-treated soil was investigated. The soil samples were prepared with 2 % lime and statically compacted at dry (w = 17 %) and wet (w = 20%) sides of optimum. X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) were performed on lime-treated soil at various curing times. The presence of XRD peaks attributed to portlandite even after 150 days curing time indicated that it was not totally converted in cementitious compounds after reaction with silica and alumina from clay minerals. By contrast, no obvious XRD reflections of well-crystallized cementitious compounds were identified. Furthermore, all samples compacted at dry and wet side of optimum exhibited bi-modal pore size distribution, with a decrease of macro-pore frequency with increasing water content. The microstructure changes with increasing curing time did not follow monotonic tendency. On the whole, the quantities of pores less than 0.006 μm and micro-pores increased and the quantity of macro-pores decreased with increasing curing time due to the possible creation of poorly crystallized or amorphous cementitious compounds.

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Schulz, Bernhard, Dirk Sandmann, and Sabine Gilbricht. "SEM-Based Automated Mineralogy and Its Application in Geo- and Material Sciences." Minerals 10, no. 11 (November 11, 2020): 1004. http://dx.doi.org/10.3390/min10111004.

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Scanning electron microscopy based automated mineralogy (SEM-AM) is a combined analytical tool initially designed for the characterisation of ores and mineral processing products. Measurements begin with the collection of backscattered electron (BSE) images and their handling with image analysis software routines. Subsequently, energy dispersive X-ray spectra (EDS) are gained at selected points according to the BSE image adjustments. Classification of the sample EDS spectra against a list of approved reference EDS spectra completes the measurement. Different classification algorithms and four principal SEM-AM measurement routines for point counting modal analysis, particle analysis, sparse phase search and EDS spectral mapping are offered by the relevant software providers. Application of SEM-AM requires a high-quality preparation of samples. Suitable non-evaporating and electron-beam stable epoxy resin mixtures and polishing of relief-free surfaces in particles and materials with very different hardness are the main challenges. As demonstrated by case examples in this contribution, the EDS spectral mapping methods appear to have the most promising potential for novel applications in metamorphic, igneous and sedimentary petrology, ore fingerprinting, ash particle analysis, characterisation of slags, forensic sciences, archaeometry and investigations of stoneware and ceramics. SEM-AM allows the quantification of the sizes, geometries and liberation of particles with different chemical compositions within a bulk sample and without previous phase separations. In addition, a virtual filtering of bulk particle samples by application of numerous filter criteria is possible. For a complete mineral phase identification, X-ray diffraction data should accompany the EDS chemical analysis. Many of the materials which potentially could be characterised by SEM-AM consist of amorphous and glassy phases. In such cases, the generic labelling of reference EDS spectra and their subsequent target component grouping allow SEM-AM for interesting and novel studies on many kinds of solid and particulate matter which are not feasible by other analytical methods.

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Esbensen, Kim H., and Agnete Steenfelt. "Geochemical prospecting in complex sample media-multivariate data analysis of indirect observations (PLS-regression between modal mineralogy and geochemistry)." Journal of Geochemical Exploration 32, no. 1-3 (April 1989): 345–47. http://dx.doi.org/10.1016/0375-6742(89)90073-3.

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Howard, K. T., C. M. O’D Alexander, D. L. Schrader, and K. A. Dyl. "Classification of hydrous meteorites (CR, CM and C2 ungrouped) by phyllosilicate fraction: PSD-XRD modal mineralogy and planetesimal environments." Geochimica et Cosmochimica Acta 149 (January 2015): 206–22. http://dx.doi.org/10.1016/j.gca.2014.10.025.

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Puchalski, Raya C., Sandra M. Barr, and Chris E. White. "Field relations and petrology of the Trafalgar Plutonic Suite and comparisons with other Devonian granitoid plutons in the Meguma terrane, Nova Scotia, Canada." Atlantic Geology 56 (April 18, 2020): 001–17. http://dx.doi.org/10.4138/atlgeol.2020.001.

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The Trafalgar Plutonic Suite intruded metasedimentary rocks of the Goldenville and Halifax groups in the northeastern part of the Meguma terrane of southern Nova Scotia at about 374 Ma, based on previously published U–Pb and 40Ar/39Ar mineral ages. Using field and petrographic observations, the suite is divided into 20 different plutons on the combined basis of variations in grain size (fine, medium, or coarse), texture (equigranular or porphyritic) and modal mineralogy (quartz diorite/tonalite, granodiorite, monzogranite, and syenogranite). The granodiorite, monzogranite, and syenogranite plutons are relatively uniform in composition with little variation in mineralogy or chemistry within each pluton or between plutons of the same lithology. In contrast the quartz diorite/tonalite plutons show mineralogical and chemical variation, both within and between plutons. The granodiorite, monzogranite, and syenogranite plutons closely resemble other peraluminous granitoid plutons characteristic of the Meguma terrane. The quartz diorite/tonalite plutons are varied but chemically resemble minor Devonian mafic intrusions elsewhere in the Meguma terrane. Like other plutons of the Meguma terrane, the Trafalgar Plutonic Suite has chemical characteristics of volcanic-arc to syn-collisional granitoid rocks and likely has experienced extensive contamination by metasedimentary material as documented by previous studies of plutons in the Meguma terrane. The minor quartz diorite/tonalite plutons are additional examples of the mafic rocks that have been proposed in tectonic models of the Meguma terrane to have facilitated melting of the lower crust to generate granodioritic parent magmas, followed by crystal fractionation and extensive contamination by metasedimentary material.

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Herd, Christopher D. K., Jon M. Friedrich, Richard C. Greenwood, and Ian A. Franchi. "An igneous-textured clast in the Peace River meteorite: insights into accretion and metamorphism of asteroids in the early solar system." Canadian Journal of Earth Sciences 50, no. 1 (January 2013): 14–25. http://dx.doi.org/10.1139/e2012-078.

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The mineralogy, petrology, and geochemistry of an igneous-textured clast in the Peace River L6 chondrite meteorite was examined to determine the roles of nebular processes, accretion, and parent-body metamorphism in its origin. The centimetre-scale clast is grey and fine grained and is in sharp contact with the host chondrite. Two sub-millimetre veins cut across both the clast and host, indicating that the clast formed prior to the impact (shock) event(s) that produced the numerous veins present in the Peace River meteorite. The clast and host are indistinguishable in terms of mineral compositions. In contrast, there are differences in modal mineralogy, texture, as well as trace element and oxygen isotope composition between the clast and host. These differences strongly suggest that the clast was formed by impact melting of LL-group chondritic material involving loss of Fe–FeS and phosphate components, followed by relatively rapid cooling and incorporation into the Peace River host meteorite. Subsequent metamorphism on the Peace River parent body caused recrystallization of the clast and homogenization of mineral compositions and thermally labile element abundances between the clast and host. Shock metamorphism, including formation of shock melt veins, occurred post-metamorphism, during fragmentation of the L chondrite parent body. The results suggest that the formation of the Peace River parent asteroid included the incorporation of material from other asteroids and that the pre-metamorphic protolith was a breccia. Accordingly, we propose that the Peace River meteorite be reclassified as a polymict breccia.

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Howard, K. T., G. K. Benedix, P. A. Bland, and G. Cressey. "Modal mineralogy of CM chondrites by X-ray diffraction (PSD-XRD): Part 2. Degree, nature and settings of aqueous alteration." Geochimica et Cosmochimica Acta 75, no. 10 (May 2011): 2735–51. http://dx.doi.org/10.1016/j.gca.2011.02.021.

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Stoppa, F., A. R. Woolley, and A. Cundari. "Extension of the melilite-carbonatite province in the Apennines of Italy: the kamafugite of Grotta del Cervo, Abruzzo." Mineralogical Magazine 66, no. 4 (August 2002): 555–74. http://dx.doi.org/10.1180/0026461026640049.

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AbstractA new occurrence of a rare kamafugite near L'Aquila, Abruzzo, is described in detail to characterize its paragenesis and to establish possible genetic links with similar alkaline mafic igneous rocks from the Oricola-Camerata Nuova (OC) volcanic field, ˜20 km to the west. Both occurrences belong to the Umbria-Latium-Ultralkaline-District (ULUD), an igneous district represented by rare kamafugites and carbonatites and distinct from the much more voluminous Roman Region (RR) rocks. The new kamafugite was found in a cave known as Grotta del Cervo (GC), associated with epiclastic and pyroclastic rocks. In the latter, lapilli ash tuff, welded lapilli, ultramafic xenoliths, cognate lithics and pelletal lapilli have been identified. The mineralogy of the welded lapilli comprises, in order of decreasing abundance, diopside, leucite, haüyne, Mg-mica, andraditic garnet, apatite, magnetite, kalsilite and olivine. The rock is carbonate-free. Based on bulk-rock chemistry it is classified as a kamafugite, closely approaching the composition of ULUD kamafugites, according to Sahama's (1974) criteria. Separate lapilli ash tuff, characterized by the same silicate mineralogy as that of the welded lapilli, plus modal carbonate exceeding 10 wt.%, is classified as a carbonatitic kamafugite. Bulk-rock and trace-element compositions confirm that the Grotta del Cervo rocks closely approach the ULUD analogues.The Grotta del Cervo occurrence partially fills the geographical and compositional gap between ULUD rocks and the rocks from the Vulture Complex, also a carbonatite and melilitite locality ˜200 km south of GC, and adds considerably to the bulk of kamafugitic and related rocks lying along the Italian Apennines. The petrogenesis of these kamafugites rocks is discussed and possible mineralogical similarities with the Roman Region rocks are highlighted.

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Schlegel, Tobias U., Renee Birchall, Tina D. Shelton, and James R. Austin. "MAPPING THE MINERAL ZONATION AT THE ERNEST HENRY IRON OXIDE COPPER-GOLD DEPOSIT: VECTORING TO Cu-Au MINERALIZATION USING MODAL MINERALOGY." Economic Geology 117, no. 2 (March 1, 2022): 485–94. http://dx.doi.org/10.5382/econgeo.4915.

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Abstract Iron oxide copper-gold (IOCG) deposits form in spatial and genetic relation to hydrothermal iron oxide-alkali-calcic-hydrolytic alteration and thus show a mappable zonation of mineral assemblages toward the orebody. The mineral zonation of a breccia matrix-hosted orebody is efficiently mapped by regularly spaced samples analyzed by the scanning electron microscopy-integrated mineral analyzer technique. The method results in quantitative estimates of the mineralogy and allows the reliable recognition of characteristic alteration as well as mineralization-related mineral assemblages from detailed mineral maps. The Ernest Henry deposit is located in the Cloncurry district of Queensland and is one of Australia’s significant IOCG deposits. It is known for its association of K-feldspar altered clasts with iron oxides and chalcopyrite in the breccia matrix. Our mineral mapping approach shows that the hydrothermal alteration resulted in a characteristic zonation of minerals radiating outward from the pipe-shaped orebody. The mineral zonation is the result of a sequence of sodic alteration followed by potassic alteration, brecciation, and, finally, by hydrolytic (acid) alteration. The hydrolytic alteration primarily affected the breccia matrix and was related to economic mineralization. Alteration halos of individual minerals such as pyrite and apatite extend dozens to hundreds of meters beyond the limits of the orebody into the host rocks. Likewise, the Fe-Mg ratio in hydrothermal chlorites changes systematically with respect to their distance from the orebody. Geochemical data obtained from portable X-ray fluorescence (p-XRF) and petrophysical data acquired from a magnetic susceptibility meter and a gamma-ray spectrometer support the mineralogical data and help to accurately identify mineral halos in rocks surrounding the ore zone. Specifically, the combination of mineralogical data with multielement data such as P, Mn, As, P, and U obtained from p-XRF and positive U anomalies from radiometric measurements has potential to direct an exploration program toward higher Cu-Au grades.

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Crapster-Pregont, Ellen J., and Denton S. Ebel. "Reducing Supervision of Quantitative Image Analysis of Meteorite Samples." Microscopy and Microanalysis 26, no. 1 (December 20, 2019): 63–75. http://dx.doi.org/10.1017/s1431927619015216.

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AbstractWhen selecting a method for determining modal mineralogy and elemental composition of geological samples (e.g., meteorites), a number of factors should be considered, includingthe number of objects or the area to be analyzed; the scale of expected chemical variation; instrument time restrictions; and post-processing time. This study presents a method that minimizes acquisition time while maintaining the ability to distinguish minerals based on combinations of intensities of electron probe micro-analyzer-generated X-ray element maps. While some other methods yield similar outcomes, this method's post-processing utilizes standard parameterized, X-ray intensity “map math” in an algorithm that is adaptable and requires minimal supervision once implemented. This study's minimized supervision in the post-processing of X-ray intensity maps decreases analysis time and its adaptability increases the number of potential applications. The method also facilitates calibration of the exact locations of analysis using laser ablation methods. While the method described here has advantages, the choice of method always depends on the question being asked.

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MENZIES, O. N., P. A. BLAND, F. J. BERRY, and G. CRESSEY. "A Mössbauer spectroscopy and X-ray diffraction study of ordinary chondrites: Quantification of modal mineralogy and implications for redox conditions during metamorphism." Meteoritics & Planetary Science 40, no. 7 (July 2005): 1023–42. http://dx.doi.org/10.1111/j.1945-5100.2005.tb00171.x.

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Howard, K. T., G. K. Benedix, P. A. Bland, and G. Cressey. "Modal mineralogy of CM2 chondrites by X-ray diffraction (PSD-XRD). Part 1: Total phyllosilicate abundance and the degree of aqueous alteration." Geochimica et Cosmochimica Acta 73, no. 15 (August 2009): 4576–89. http://dx.doi.org/10.1016/j.gca.2009.04.038.

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43

Dasgupta, Somnath, P. K. Bhattacharya, G. Chattopadhyay, H. Banerjee, N. Majumdar, M. Fukuoka, and Supriya Roy. "Petrology of Mg-Mn amphibole-bearing assemblages in manganese silicate rocks of the Sausar Group, India." Mineralogical Magazine 52, no. 364 (March 1988): 105–11. http://dx.doi.org/10.1180/minmag.1988.052.364.09.

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AbstractMg-Mn amphibole (tirodite), with or without pyroxmangite in the total absence of pyroxenes and high-calcic pyroxenoids, occurs in the Mn silicate rocks of the Sausar Group, India. The rocks were metamorphosed to amphibolite facies condition (T ∼ 650°C, P ∼ 6 kbar). Tirodite-pyroxmangite pairs developed in both carbonate-free and rhodochrosite-bearing assemblages. Also tirodite coexists with either kutnahorite or manganoan calcite in the absence of pyroxmangite. Mineral reactions inferred from modal abundances and compositions of the phases indicate stabilization of the amphibole alone from a bivalent cation-bearing residual unbuffered XCO2 system with XMn < 0.3. On the other hand, tirodite-pyroxmangite pairs appeared in unbuffered low to intermediate XCO2 assemblages with XMn > 0.35. Pyroxenes and high-calcic pyroxenoids did not appear in the present situation, though they occur elsewhere in rocks with broadly similar contents of immobile components. Closely associated assemblages of diverse mineralogy suggest that the XMn and XCO2, rather than the physical conditions of metamorphism, are the decisive factors in promoting the observed phase assemblages.

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44

Hedley, C. B., I. J. Payton, I. H. Lynn, S. T. Carrick, T. H. Webb, and S. McNeill. "Random sampling of stony and non-stony soils for testing a national soil carbon monitoring system." Soil Research 50, no. 1 (2012): 18. http://dx.doi.org/10.1071/sr11171.

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The New Zealand Soil Carbon Monitoring System (Soil CMS) was designed, and has been used, to account for soil organic carbon change under land-use change, during New Zealand’s first Commitment Period (2008–2012) to the Kyoto Protocol. The efficacy of the Soil CMS model has been tested for assessing soil organic carbon stocks in a selected climate–land-use–soil grouping (cell). The cell selected for this test represents an area of 709 683 ha and contains soils with a high-activity clay mineralogy promoting long-term stabilisation of organic matter, and is under low-producing grassland in a dry temperate New Zealand climate. These soils have been sampled at randomly selected positions to assess total soil organic carbon stocks to 0.3 m, and to compare with the modelled value. Results show no significant difference between the field estimation (67 ± 30 Mg C/ha), the mean value of the model calibration dataset (79 ± 28 Mg C/ha), and the value predicted by the model (101 ± 41 Mg C/ha), although all estimates have large uncertainties associated with them. The model predicts national soil organic carbon stocks as a function of soil texture, clay mineralogy, land use, climate class, and a slope–rainfall erosivity product. Components of uncertainty within the model include the size and distribution of the calibration dataset, and lack of representativeness of the calibration soil samples, which were sampled for other reasons, e.g. soil survey and forest mensuration. Our study has shown that major components of uncertainty in our field estimation of soil organic carbon stocks (investigated using the indices reproducibility, RP; and coefficient of variation, CV) are short-range (within-plot) and regional (between-sites) spatial variability. Soil organic carbon stocks vary within our selected climate–land-use–soil cell due to varying stoniness (stony soils RP 44%, CV 21%; non-stony soils RP 27%, CV 13%), soil depth, slope position, and climatic effects. When one outlier soil was removed from the model calibration dataset, and the three very stony sites were removed from the randomly selected field validation set, the model calibration dataset and the field dataset means agreed well (78 ± 26 and 78 ± 21 Mg C/ha, respectively). The higher modelled value, before removal of the outlier, is likely to reflect a bias in the model dataset towards conventionally selected modal profiles containing less stony soils than those encountered by the random sampling strategy of our field campaign. Therefore, our results indicate (1) that the Soil CMS provides an adequate estimation of soil organic carbon for the selected cell, and (2) ongoing refinements are required to reduce the uncertainty of prediction.

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Kern, H., K. Mengel, K. W. Strauss, T. I. Ivankina, A. N. Nikitin, and I. T. Kukkonen. "Elastic wave velocities, chemistry and modal mineralogy of crustal rocks sampled by the Outokumpu scientific drill hole: Evidence from lab measurements and modeling." Physics of the Earth and Planetary Interiors 175, no. 3-4 (July 2009): 151–66. http://dx.doi.org/10.1016/j.pepi.2009.03.009.

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46

Borghini, Giulio, Patrizia Fumagalli, and Elisabetta Rampone. "Melt–rock interactions in a veined mantle: pyroxenite–peridotite reaction experiments at 2 GPa." European Journal of Mineralogy 34, no. 1 (February 16, 2022): 109–29. http://dx.doi.org/10.5194/ejm-34-109-2022.

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Abstract. Interaction between peridotite and pyroxenite-derived melts can significantly modify the mineralogy and chemistry of the upper mantle, enhancing its heterogeneity, by creating re-fertilized peridotites and secondary-type pyroxenites. We experimentally investigated the reaction between a fertile lherzolite and MgO-rich basaltic andesite produced by partial melting of an olivine-free pyroxenite at 2 GPa and 1300–1450 ∘C. The aim was to constrain the rate and style of melt–peridotite reaction mostly as a function of temperature, i.e. assuming variable physical status of the host peridotite. Experiments juxtaposed pyroxenite on a synthesized fertile lherzolite to evaluate the modal and mineral compositional changes in the fertile lherzolite resulting from the reaction with pyroxenite-derived melt. At 1300 and 1350 ∘C, the reaction produces a thin orthopyroxene-rich reaction zone confined between partially molten pyroxenite and modally unmodified subsolidus lherzolite. Chemical changes in minerals of the pyroxenite crystal mush suggest that element diffusion across the pyroxenite–peridotite interface, coupled with orthopyroxene precipitation, plays a role in the reactive crystallization of mantle pyroxenite veins. At 1380 and 1400 ∘C, infiltration of pyroxenite-derived melt significantly modifies the mineralogy and chemistry of the host peridotite by creating orthopyroxene-rich websterites and pyroxene-rich lherzolite. At 1450 ∘C, pyroxenitic melt fluxes into molten peridotite, enhancing peridotite melting and creating a melt-bearing dunite associated with a refractory harzburgite. At a given pressure, bulk compositions of hybrid rocks originating through melt–peridotite interaction are mostly controlled by the chemistry of the reacting melt. Interaction between pyroxenitic melt and peridotite causes XMg[XMg=Mg/(Mg+Fetot)] and XCr[XCr=Cr/(Cr+Al)] decrease and TiO2 increase in pyroxenes and spinel across the pyroxenite–peridotite boundary. Similar chemical gradients in minerals are observed in pyroxenite–peridotite associations from natural mantle sequences. The comparison with mineral chemistry variations derived by reaction experiments potentially represents a petrologic tool to discriminate between low- versus high-temperature melt–peridotite reactions.

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Omotunde, V. B. "Mineralogy and Geochemistry of Hydrothermally altered Talcose rocks from Ila Orangun-Oyan areas, part of Southwestern Nigeria." Indian Journal of Science and Technology 13, no. 40 (October 31, 2020): 4244–61. http://dx.doi.org/10.17485/ijst/v13i40.1686.

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Background/Objectives: Talcose rocks within Precambrian Basement Complex serve as relics of Archean greenstones. alterations associated with polycyclic-orogenies that affected this complex is studied to understand mineralogical and geochemical alterations. Methods: Five fresh samples of talcose rocks were collected during field mapping. These samples were cut into thin sections to reveal modal mineralogy, altered minerals and degree of alteration of such minerals. Mineral phase identification of the talcose rocks was conducted using X-ray Broker D8 ADVANCE diffractometer while whole rock analysis was carried out using Inductively Coupled Plasma Mass Spectrometry. Findings: Lithological relationship revealed from field evidence showed that the talc bodies occurred in close association with micaceous schist. The mineral assemblage of talc, tremolite, actinolite, chlorite and calcite suggest low grade greenschist metamorphic facies from possible hydrothermal alteration. Geochemical results revealed the following range of concentrations; SiO2 42.19-59.03%; Al2O3 1.1 - 11.8%; Fe2O3 7.64-9.56%; MgO 24.47-26.639%; Ni 594-1207ppm; Co 43.2-113.9ppm; Sn 6-41ppm; V 32-75ppm and Zr 1.3-58.7ppm, and these are typical of talcose rocks. Petrogenetic studies suggest a komatiitic origin with a peridotitic komatiite precursor for the talc-chlorite-tremolite schist. Enrichment in LREE, depletion in HREE and a negative Eu anomaly suggest alteration of the parent magma for the talcose rock and plagioclase fractionation. The trends observed for the LILE, HFSE and REE suggest possible contamination or mixing of crustal and mantle materials during the formation of the protolith. Ni and Co concentrations are higher than average crustal values with implication for ultrabasic to basic magma composition for the komatiitic progenitor and also suggestive of possible mineralisation. Conclusion: Mineralogical examination has revealed a talc-chlorite-tremolite composition for the talcose rocks with peridotitic komatiite precursory while geochemical composition supported ultrabasic magmatism similar to those with the Ilesha schist belt.

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Cui, Yao, and J. K. Russell. "Magmatic origins of calc-alkaline intrusions from the Coast Plutonic Complex, southwestern British Columbia." Canadian Journal of Earth Sciences 32, no. 10 (October 1, 1995): 1643–67. http://dx.doi.org/10.1139/e95-131.

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Major element, trace element, and rare earth element data are presented for Permian to Tertiary calc-alkaline plutonic and volcanic rocks along a transect across the southern Coast Plutonic Complex from Vancouver to Anderson Lake. Late Jurassic to Late Cretaceous plutons are divided into two compositional suites based on mineralogy: (1) the hornblende intrusive suite (tonalite, quartz diorite, diorite, and gabbro) characterized by abundant modal hornblende and little or no K-feldspar, and (2) the K-feldspar intrusive suite (mainly granite and granodiorite) containing significant modal K-feldspar and less hornblende. Compositions of hornblende intrusive suite rocks are effectively portrayed on Pearce element-ratio diagrams utilizing axes X1 = [0.8571 Si−0.1429(Fe + Mg) + 1.2857 Ca + 1.8574 K]/Zr and Y1 = 1.1428 Ti + Al + Fe + Mg + Ca + 1.5714 Na + 0.4762 P]/Zr, because the diagram accounts for the stoichiometry of PI ± Hbl ± Bt ± Ep ± Ttn + Ap. Rocks from the K-feldspar intrusive suite are studied on diagrams using the element-ratio pair X2 = [2 Ti + Al + 3.3333 P]/Zr and Y2 = [2 Ca + Na + K]/Zr, which creates a linear trend of compositional variations controlled by the phases PI ± Kfs ± Bt ± Ttn + Ap. Mean intercepts of model trends on the element-ratio diagrams suggest differences among plutons that relate to source-region processes. For example, samples belonging to the hornblende intrusive suite represent a minimum of six batches of magma. Mean intercept values for plutons west of the Owl Lake–Harrison fault zone are significantly higher than those situated east of this structural break. These systematic differences allude to fundamental differences in the nature of Mesozoic magmatism in Wrangellia (and Harrison) terrane compared with that in Cadwallader, Bridge River, and Methow terranes, and probably in the Intermontane superterrane east of the structural break.

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Subandrio, Joko, and Ronaldo Irzon. "Trace and Rare Earth Elements Compositional Change on Andesite Alteration in Kaligesing, Purworejo." Jurnal Geologi dan Sumberdaya Mineral 21, no. 1 (February 24, 2020): 17. http://dx.doi.org/10.33332/jgsm.geologi.v21i1.452.

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The change of chemical composition because of hydrothermal alteration process is related to the modification on mineralogy and elements mobility. Different alteration conditions could lead to dissimilar geochemical character. This study aims to discuss the alteration effect on trace and rare earth elements composition of an andesite outcrop with hydrothermal alteration in Kaligesing, Purworejo, Central Java Province. Microscopic analysis at Central for Geological Survey was applied to determine the modal mineral composition of the selected samples whilst trace and rare earth elements abundances was measured using Inductively Coupled Plasma – Mass Spectrometry. Plagioclase is the major phenocryst embedded in the fine-grained feldspar and glass groundmass of relatively fresh andesite. On the other hand, sericite, chlorite, epidote, and iron oxide are detected in the altered rock. The more Sr and Rb compositions on unaltered sample exhibit their common existence in plagioclase. The bigger Rb/Sr and the lower Ba/Sr ratios inward to the center of alteration might indicate the more degree of K-bearing mineral formation than Ca-rich mineral alteration. The Ba/Zr escalation and Zr/Y reduction from relatively fresh rock through to the vein of the studied samples are parallel to the previous investigation about andesite alteration. Chondrite-normalized rare-earth elements (REE) pattern of unaltered, altered, and vein samples depicts similar patterns: strong enrichment of Low REE, positive Eu anomaly, and relatively flat high REE. The decrease of Eu anomaly may reflect the reduction of plagioclase modal composition because of alteration and might indicate a reductive alteration state.Keywords: Alteration, andesite, geochemistry, trace and rare earth elements.

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Farkašovský, Roman, Katarína Bónová, and Marián Košuth. "Microstructural, modal and geochemical changes as a result of granodiorite mylonitisation – a case study from the Rolovská shear zone (Čierna hora Mts, Western Carpathians, Slovakia)." Geologos 22, no. 3 (September 1, 2016): 171–90. http://dx.doi.org/10.1515/logos-2016-0019.

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Abstract Strong tectonic remobilisation and shear zone development are typical features of the easternmost part of the Veporicum tectonic unit in the Western Carpathians. The granodiorite mylonites in the area of the Rolovská shear zone (Čierna hora Mts) underwent a complex polystage evolution during the Hercynian and Alpine orogenies. Deformation during the latter reached greenschist facies under metamorphic conditions. Mylonites are macroscopically foliated rocks with a stretching lineation and shear bands. Structurally different mylonite types, ranging from protomylonites to ulramylonites with typical grainsize reduction from the margins towards the shear zone centre, have been assessed. The modal mineralogy of the different mylonite types changes considerably. Typical is a progressive decrease in feldspar content and simultaneously the quartz and white mica content increases from protomylonites towards the most strongly deformed ultramylonites. The deformation had a brittle character in less deformed rocks and a ductile one in more deformed tectonites. Obvious chemical changes occur in mesomylonites and ultramylonites. During mylonitisation, the original biotite granodiorite was depleted of Mg, Fe, Na, Ca and Ba, while K, Rb and mainly Si increased considerably. Other (major and trace) elements reflect erratic behaviour due to lateral mobility. Chemical changes indicate the breakdown and subsequent recrystallisation of biotite and feldspars and, in turn, the crystallisation of albite and sericite. REE decrease in ultramylonites due to the breakup of accessory minerals during deformation and alteration.

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Journal articles on the topic 'Modal mineralogy'

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