European Journal of Mineralogy最新文献

{"title":"An Unusual Presentation of Angiolymphoid Hyperplasia with Eosinophilia as Postauricular Mass: A case Report.","authors":"Rubina Galib, Nainsi Gupta, Abdur Rahman, Mohd Aftab, Shagufta Qadri, Kiran Alam","doi":"10.1007/s12070-023-04178-2","DOIUrl":"10.1007/s12070-023-04178-2","url":null,"abstract":"<p><p>Angiolymphoid hyperplasia with eosinophilia (ALHE) is a rare, benign, reactive vaso-proliferative condition in the dermal and subcutaneous tissues of the head and neck. A 28-year-old female presented with slow-growing painless swelling behind her left ear. FNAC revealed benign soft tissue neoplasm and histopathological examination after surgical excision revealed angiolymphoid hyperplasia with eosinophilia. ALHE origin has been variously attributed to prior trauma, hyperestrogenemia, infectious agents, atopy, reactive hyperplasia, and benign neoplasia. Retroauricular ALHE has been rarely reported. However, on the basis of our case report, it should be a viable differential diagnosis when large subcutaneous tumors of the head and neck are encountered. When big subcutaneous tumors of the head and neck are present, especially in females, a valid differential diagnosis for angiolymphoid hyperplasia with eosinophilia, a rare condition marked by dermal or subcutaneous endothelial cell proliferation, should also be considered.</p>","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"10 1","pages":"1138-1142"},"PeriodicalIF":0.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10908713/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86140986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atomic-scale environment of niobium in ore minerals as revealed by XANES and EXAFS at the Nb K-edge","authors":"Quentin Bollaert, Mathieu Chassé, Guillaume Morin, Benoît Baptiste, Alexandra Courtin, L. Galoisy, Gautier Landrot, Cécile Quantin, Georges Calas","doi":"10.5194/ejm-36-55-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-55-2024","url":null,"abstract":"Abstract. The mineralogy of niobium (Nb) is characterized by multicomponent oxides such as AB2O6, A2B2O7, ABO4, and ABO3 in which Nb is incorporated in the B site. Such complex crystal-chemistry prevents their unambiguous identification in ore deposits such as hydrothermal rocks and laterites which exhibit complex and fine-grained textures. The understanding of the processes controlling Nb ore deposit formation in various geological settings is therefore limited, although Nb is a critical element. In this study, we use X-ray absorption spectroscopy (XAS) at the Nb K-edge to investigate the local atomic-scale structure around Nb in a large set of natural and synthetic minerals of geological and technological importance. Our X-ray absorption near-edge structure (XANES) data at the Nb K-edge show three major features of variable position and intensity and then can be related to the local distortion and coordination number of the Nb site. Shell-by-shell fits of the extended X-ray absorption fine structure (EXAFS) data reveal that the NbO6 octahedra are distorted in a variety of pyrochlore species. At least two distinct first shells of O atoms are present while reported crystallographic data yield regular octahedra in the same minerals. Next-nearest Nb–Nb distances in pyrochlore and Nb-bearing perovskite mirror a corner-sharing NbO6 network, whereas the two Nb–Nb distances in columbite are typical of edge- and corner-sharing NbO6 octahedra. Such a resolution on the Nb site geometry and the intersite relationships between the next-nearest NbO6 octahedra is made possible by collecting EXAFS data under optimal conditions at 20 K and up to 16 Å−1. The local structure around substituted Nb5+ in Fe3+, Ti4+, and Ce4+ oxides suffers major changes relative to the unsubstituted structures. The substitution of Nb5+ for Ti4+ in anatase leads to the increase in the interatomic distances between Nb and its first and second Ti4+ neighbors. The substitution of Nb5+ for Ce4+ in cerianite reduces the coordination number of the cation from eight to four, and the Nb–O bonds are shortened compared to Ce–O ones. In hematite, Nb5+ occupies a regular site, whereas the Fe3+ site is strongly distorted suggesting major site relaxation due to charge mismatch. The sensitivity of XANES and EXAFS spectroscopies at the Nb K-edge to the local site geometry and next-nearest neighbors demonstrated in this study would help decipher Nb speciation and investigate mineralogical reactions of Nb minerals in deposit-related contexts such as hydrothermal and lateritic deposits.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"10 13","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermodynamics of vivianite-group arsenates M3(AsO4)2 ⋅  8H2O (M is Ni, Co, Mg, Zn, Cu) and chemical variability in the natural arsenates of this group","authors":"J. Majzlan, Anna Reichstein, Patrick Haase, M. Števko, Jiří Sejkora, Edgar Dachs","doi":"10.5194/ejm-36-31-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-31-2024","url":null,"abstract":"Abstract. In this work, we investigated the M3(AsO4)2⋅ 8H2O end members annabergite (M is Ni), erythrite (M is Co), and hörnesite (M is Mg) and their solid solutions. Acid-solution calorimetry and relaxation calorimetry were used to determine the solubility products (log Ksp) for annabergite (−33.7), erythrite (−32.1), and hörnesite (−22.3). Solubility products for other end members of this group were extracted from the literature and critically evaluated. The enthalpies of mixing are complex, related to subsystems M(1)3(AsO4)2⋅ 8H2O–M(1)M(2)2(AsO4)2⋅ 8H2O and M(1)M(2)2(AsO4)2⋅ 8H2O–M(2)3(AsO4)2⋅ 8H2O. They are small and positive for the annabergite–erythrite solid solution and small and negative for the annabergite–hörnesite solid solution. Autocorrelation analysis of Fourier-transform infrared (FTIR) spectra shows correlation of strain decrease in the structure with the negative enthalpies of mixing in the annabergite–hörnesite solid solution. A set of more than 600 electron microprobe analyses of the M3(AsO4)2⋅ 8H2O minerals documents the variability and complexity in this group. Most common compositions are those dominated by Ni, Co, or Ni–Co. The analytical results were used to calculate the maximal configurational entropies which could be a factor that compensates for the small enthalpies of mixing in the annabergite–erythrite solid solution. The data presented here can be used to model sites polluted with metals and arsenic and to enhance our understanding of complex solid solutions.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"42 5","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139447529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple growth of zirconolite in marble (Mogok metamorphic belt, Myanmar): evidence for episodes of fluid metasomatism and Zr–Ti–U mineralization in metacarbonate systems","authors":"Qian Guo, Shun Guo, Yueheng Yang, Qian Mao, Jiangyan Yuan, Shitou Wu, Xiaochi Liu, K. Sein","doi":"10.5194/ejm-36-11-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-11-2024","url":null,"abstract":"Abstract. Fluid infiltration into (meta-)carbonate rocks is an important petrologic process that induces metamorphic decarbonation and potential mineralization of metals or nonmetals. The determination of the infiltration time and the compositional features of reactive fluids is essential to understand the mechanism and process of fluid–rock interactions. Zirconolite (ideal formula: CaZrTi2O7) is an important U-bearing accessory mineral that can develop in metasomatized metacarbonate rocks. In this study, we investigate the occurrence, texture, composition, and chronology of various types of zirconolite from fluid-infiltrated reaction zones in dolomite marbles from the Mogok metamorphic belt, Myanmar. Three types of zirconolite are recognized: (1) the first type (Zrl-I) coexists with metasomatic silicate and oxide minerals (forsterite, spinel, phlogopite) and has a homogeneous composition with high contents of UO2 (21.37 wt %–22.82 wt %) and ThO2 (0.84 wt %–1.99 wt %). (2) The second type (Zrl-II) has textural characteristics similar to those of Zrl-I. However, Zrl-II shows a core–rim zonation with a slightly higher UO2 content in the rims (average of 23.5 ± 0.4 wt % (n=8)) than the cores (average of 22.1 ± 0.3 wt % (n=8)). (3) The third type (Zrl-III) typically occurs as coronas around baddeleyite and coexists with polycrystalline quartz. Zrl-III has obviously lower contents of UO2 (0.88 wt %–5.3 wt %) than those of Zrl-I and Zrl-II. All types of zirconolite have relatively low rare earth element (REE) contents (&lt; 480 µg g−1 for ΣREE). Microtextures and compositions of the three zirconolite types, in combination with in situ zirconolite U–Pb dating using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), reveal episodic fluid infiltration and element mobilization in the dolomite marbles. The first-stage infiltration occurred at ∼ 35 Ma, leading to the formation of Mg-rich silicates and oxides and accessory minerals (Zrl-I, baddeleyite, and geikielite). The reactive fluid was characterized by high contents of Zr, Ti, U, and Th. After that, some Zrl-I grains underwent a local fluid-assisted dissolution–precipitation process, which produced a core–rim zonation (i.e., the Zrl-II type). The final stage of fluid infiltration, recorded by the growth of Zrl-III after baddeleyite, took place at ∼ 19 Ma. The infiltrating fluid of this stage had relatively lower U contents and higher SiO2 activities than the first-stage infiltrating fluid. This study illustrates that zirconolite is a powerful mineral that can record repeated episodes (ranging from 35 to 19 Ma) of fluid influx, metasomatic reactions, and Zr–Ti–U mineralization in (meta-)carbonates. This mineral not only provides key information about the timing of fluid flow but also documents the chemical variation in reactive fluids. Thus, zirconolite is expected to play a more important role in characterizing the fluid–carbonate interaction, orogenic CO2 release, and the transfer an","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"14 3","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural and compositional data for childrenite from the Homolka granite, Czech Republic","authors":"Jonas Toupal, D. Mauro, C. Biagioni, Federica Zaccarini, R. Gieré","doi":"10.5194/ejm-36-1-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-1-2024","url":null,"abstract":"Abstract. Members of the childrenite–eosphorite series, ideally (Fe1−xMnx)AlPO4(OH)2⋅H2O, from the highly evolved Homolka granite, in the southern Czech Republic, were characterized using a multi-analytical approach. They occur as anhedral grains, up to ∼0.2 mm in size, associated with quartz, muscovite, albite, and K-feldspar. Tiny inclusions of probable uraninite have been observed. Backscattered electron images reveal a patchy zoning of these members of the childrenite–eosphorite series, related to an uneven distribution of Fe and Mn. On the basis of electron microprobe analysis, the average composition of the studied material is (Fe0.68Mn0.28Ca0.03)Σ0.99Al0.96(P1.04Si0.01)Σ1.05O4.00(OH)2.09⋅0.91H2O, thus corresponding to childrenite. Unit-cell parameters of this species are a=6.9226(9), b=10.4081(13), c=13.3957(17) Å. Its crystal structure was refined in the space group Cmca down to R1=0.0295 on the basis of 602 unique reflections with Fo>4σ(Fo) and 66 refined parameters. The crystal structure analysis agrees with the results of electron microprobe analysis and suggests that, in the studied material, Fe occurs in the divalent oxidation state only. Crystal structure data are also consistent with the Raman spectrum collected on the same grain that was structurally characterized, confirming the occurrence of PO4 groups only in childrenite.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"53 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139386141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In situ study of the reaction phase A plus high-P clinoenstatite to forsterite plus water at reduced water activity","authors":"Christian Lathe, M. Koch‐Müller, Bernd Wunder, Oona Appelt, Melanie Sieber, S. Bhat, R. Farla","doi":"10.5194/ejm-35-1149-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-1149-2023","url":null,"abstract":"Abstract. We examined the reaction phase A plus high-P clinoenstatite to forsterite plus water (Reaction R1) by means of in situ X-ray diffraction measurements with the large volume press at the synchrotron PETRA III, Hamburg. Contrary to the study of Lathe et al. (2022), in which all experiments on Reaction (R1) were performed at a water activity of 1, the reversed experiments presented in this study were performed at reduced water activity with mole fractions of about XH2O= XCO2=0.5. The intention of this investigation was to test the observation made by Perrillat et al. (2005), which was that dehydration reactions are kinetically faster at reduced than under water-saturated conditions. The position of Reaction (R1) at the reduced conditions was determined by reversal brackets at 9.1 and 9.5 GPa (630 and 700 ∘C), at 9.7 and 10.0 GPa (725 and 700 ∘C), at 9.8 and 10.2 GPa (675 and 750 ∘C), and at 10.5 GPa (675 and 740 ∘C). Additionally, we performed two offline experiments with brackets at 10.0 and 10.6 GPa (750 and 700 ∘C, respectively) that are in agreement with the results of the in situ experiments. We do not observe any “intermediate” precursor phase in our experiments. The equilibrium of Reaction (R1) is shifted by about 100 ∘C to lower temperature compared to the results under water-saturated conditions. Thus, at a water activity (aH2O) below 1 the phase A plus clinoenstatite dehydration reaction can only occur in extremely cold subduction slabs. The kinetics of Reaction (R1) dehydration at reduced water activity is slower than that determined previously by Lathe et al. (2022) under water-saturated conditions. Thus, the above-mentioned hypothesis of Perrillat et al. (2005) could not be confirmed. However, in both of our studies on Reaction (R1), the newly formed dehydration product forsterite was of nanometer size, which supports earlier experimental observations, which is that product phases of dehydration reactions are generally very fine-grained and might promote the concept that intermediate-depth earthquakes in subduction zones are initiated by mechanical instabilities from extremely fine-grained materials formed during dehydration reactions.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"27 23","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138947141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Retrogression of ultrahigh-pressure eclogite, Western Gneiss Region, Norway","authors":"Dirk Spengler, Adam Włodek, Xin Zhong, A. Loges, Simon J. Cuthbert","doi":"10.5194/ejm-35-1125-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-1125-2023","url":null,"abstract":"Abstract. The Western Gneiss Region (WGR) in western Norway exposes ultrahigh-pressure (UHP) eclogites that occur repeatedly, within an area of high-pressure (HP) eclogites, without evidence of being separated by tectonic shear or ductile flow structures. We studied 10 eclogites from two northern UHP areas and the interjacent HP area to evaluate the significance of this pattern. The orthopyroxene in orthopyroxene-bearing samples has low Al2O3 contents (0.17 wt %–0.37 wt %), provided its grain boundaries were unaffected by partial recrystallisation or replacement. Classical geothermobarometry based on element partitioning between coexisting mineral phases suggests metamorphic conditions within the diamond stability field for the samples from both the HP and UHP areas. The primary clinopyroxene in the associated orthopyroxene-free eclogites contains aligned inclusions of either needle-shaped quartz ± pargasite or lamellar albite, which are absent from the secondary (symplectic) clinopyroxene. Reconstructed mineral compositions of the primary clinopyroxene obtained from grain cross-section surfaces using a scanning electron beam or image processing are non-stoichiometric, and they have higher Ca-Eskola and lower Ca-Tschermak components than the inclusion-bearing host clinopyroxene. The molar ratios of these endmembers are consistent with the needles in the primary clinopyroxene being formed from vacancy-bearing precursor clinopyroxene by the exsolution reaction 2 Ca-Eskola = Ca-Tschermak + 3 quartz during early eclogite-facies retrogression. Further retrogression partially transformed the needle-shaped quartz to irregularly shaped albite within the clinopyroxene and partially transformed both clinopyroxene generations to amphibole that occasionally preserves the needles. The similarity of both the maximum metamorphic conditions and the mineral exsolution microstructures in the eclogites from UHP and HP areas indicates a shared metamorphic history within the stability field of diamond, but a history that diverged during retrogression. Consequently, the alternations of UHP and HP areas in the WGR may have formed by a process that allowed for spatial variations in retrogression efficiency, such as the localisation of strain (recrystallisation) or fluid flow (diffusion) or both, rather than by tectonic stacking of UHP and HP units. Evidence for the UHP metamorphism of WGR crustal rocks is now found from NE to SW along the entire coastal section that covers previously recognised UHP and interjacent areas.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"73 3","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139002258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An experimental study of the effect of water and chlorine on plagioclase nucleation and growth in mafic magmas: application to mafic pegmatites","authors":"Paul Heckmann, G. Iacono-Marziano, Sabina Strmić Palinkaš","doi":"10.5194/ejm-35-1111-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-1111-2023","url":null,"abstract":"Abstract. In this study, the effects of H2O and Cl on the grain size and nucleation delay of plagioclase in basaltic magma were investigated using dynamic and equilibrium experiments at 1150 ∘C, 300 MPa, and oxygen fugacity between FMQ − 1.65 and FMQ + 0.05 (fayalite–magnetite–quartz). Each experiment consisted of five samples of basaltic composition (from the Hamn intrusion in Northern Norway) containing varying amounts of H2O (up to 2 wt %) and Cl (up to 1 wt %). The equilibrium experiments were used as a reference frame for the phase assemblage, geochemical composition, and liquidus temperatures and were compared to thermodynamic models using MELTS software. Experimental phase abundances and plagioclase compositions are in good agreement with the predictions of MELTS. The dynamic experiments were initially heated above the liquidus temperature to destroy crystal nuclei and then kept at 1150 ∘C for 100, 250, or 1800 min. These experiments show that as the concentration of H2O in the melt increases, plagioclase nucleation is delayed, plagioclase abundance decreases, but its size increases. Therefore, the addition of H2O seems to favor plagioclase growth at the expense of nucleation. Thermodynamic and kinetic calculations corroborate an increase in the nucleation delay of plagioclase with increasing H2O content dissolved in the melt, suggesting that H2O decreases the undercooling of the silicate melt. The addition of Cl also seems to delay plagioclase nucleation, although this is not supported by kinetic calculations. Increasing the Cl content decreases plagioclase abundance but does not significantly affect its size. The homogeneous pegmatitic pockets of the mafic–ultramafic Hamn intrusion exhibit several petrological and geochemical features, suggesting that H2O and Cl enrichment in the silicate melt was the origin of the pegmatitic texture. The experimental results presented here indicate that H2O, rather than Cl, may have played an important role in the formation of the pegmatitic texture.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"60 5","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139003186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trace and ultratrace elements in spinel subgroup minerals of ultramafic rocks from the Voltri Massif (NW Italy): the influence of microstructure and texture","authors":"S. Fornasaro, Paola Comodi, L. Crispini, Sandro Zappatore, A. Zucchini, Pietro Marescotti","doi":"10.5194/ejm-35-1091-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-1091-2023","url":null,"abstract":"Abstract. An innovative multi-analytical approach comprising mineralogical, minero-chemical, and microstructural analyses as well as an indirect machine learning-based statistical method was applied to investigate the mineralogy and the mineral chemistry of spinel subgroup minerals (SSMs) of different ultramafic rocks from the high-pressure metaophiolites of the Voltri Massif (Central Liguria, NW Italy). The study was focused on the correlation between the compositional variations of SSMs and their texture, microstructure, and the degree of serpentinization of the host rock. The SSM occurs with three main textures and microstructures linked to the progressive serpentinization and deformation of ultramafic rocks during the Alpine orogenic events: (i) Cr-spinel porphyroclasts with various degrees of recrystallization (up to magnetite porphyroblasts) within partially serpentinized peridotite and massive serpentinite; (ii) magnetite crystals associated with pseudomorphic and non-pseudomorphic serpentine textures (e.g., mesh, hourglass, ribbon, and interpenetrating textures) in partially serpentinized peridotite and massive serpentinites; and (iii) magnetite crystals re-oriented along the foliations developed in serpentine schist. The chemical composition of SSMs varies systematically within the textures and microstructures. These processes also affected the chemical composition of SSMs, the availability of Mn, Zn, Ni, and Co in solution, and their consequent incorporation in the lattice of chromian spinel due to olivine breakdown, the major repository of these elements in ultramafic rocks. At a general scale, the trace and ultratrace variability is primarily related to the petrologic and tectonic evolution but, at a local scale, also the mineralogical, lithological, structural, and textural features correlated to the degree of serpentinization and/or deformation. These significantly influence the distribution and concentration of trace and ultratrace elements in SSMs. The results of the present work were also confirmed by an innovative indirect statistical method performed through the Weka Machine Learning Workbench.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"27 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139008357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan","authors":"H. Rehman, T. Kagoshima, N. Takahata, Yuji Sano, F. Barou, D. Mainprice, Hiroshi Yamamoto","doi":"10.5194/ejm-35-1079-2023","DOIUrl":"https://doi.org/10.5194/ejm-35-1079-2023","url":null,"abstract":"Abstract. Zircon grains preserve records of crystallization, growth, and/or deformation that can be envisaged from their internal structures and through the U–Pb isotope analysis. Electron backscatter diffraction (EBSD) is a non-destructive method for visualizing undeformed domains to differentiate them from those that are plastically deformed. In this study, we report EBSD analyses conducted on zircon grains, in thin sections with available textural information, from Himalayan eclogites. The studied eclogite samples show no petrographic evidence of shearing or mylonitization. However, several zircon grains preserve plastically deformed domains. These deformed domains display several degrees of misorientation relative to the undeformed domain and yielded geologically reset ages when analysed for U–Pb isotope ratios using nanoscale secondary ion mass spectrometry (NanoSIMS), in contrast to most undeformed domains which retained the protolith age. The degree of resetting is positively correlated with the extent of misorientation. These pieces of evidence indicate that plastic deformation in zircon grains, equilibrated at higher pressure–temperature conditions, affected the primary geochemical and geochronological records. Based on these observations, we assume that not only regional shearing/mylonitization in metamorphic rocks affects the geochemical records, but also that zircon grains in apparently unsheared high-grade metamorphic rocks behave plastically. The micro-scale intra-grain plastically deformed domains can easily be identified through EBSD analysis in the form of crystallographic misorientations. To extract meaningful geochronological results, it is necessary to identify undisturbed domains in zircon grains before applying any destructive analytical method.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":"12 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138598418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}