Muscovite Research Articles

A middle Permian ophiolite fragment in Late Triassic greenschist- to blueschist-facies rocks in NW Turkey: An earlier pulse of suprasubduction-zone ophiolite formation in the Tethyan belt

The Eastern Mediterranean region within the Tethyan belt is characterised by two main pulses of suprasubduction-zone ophiolite formation during the Early–Middle Jurassic and Late Cretaceous. Despite vast exposures of the Permo-Triassic accretionary complexes, related suprasubduction-zone ophiolites and the timing of subduction initiation leading to the formation of Permo-Triassic accretionary complexes are unknown so far. Here we report on a ~40km long and 0.3 to 1.8km wide metaophiolite fragment within transitional greenschist- to blueschist-facies oceanic rocks from NW Turkey. The metaophiolite fragment is made up mainly of serpentinite and minor dykes or stocks of strongly sheared metagabbro with mineral assemblages involving actinolite/winchite, chlorite, epidote, albite, titanite and phengite. The metagabbro displays (i) variable CaO and MgO contents, (ii) anomalously high Mg# (=100∗molar MgO/(MgO+FeOtot)) of 75–88, and (iii) positive Eu anomalies, together with low contents of incompatible elements such as Ti, P and Zr, suggesting derivation from former plagioclase cumulates. The serpentinites comprise serpentine, ±chlorite, ±talc, ±calcite and relict Cr-Al spinel surrounded by ferrichromite to magnetite. Relict Cr-Al spinels are characterised by (i) Cr/(Cr+Al) ratios of 0.45–0.56 and Mg/(Mg+Fe2+) ratio of 0.76–0.22, (ii) variable contents of ZnO and MnO, and (iii) extremely low TiO2 contents. Zn and Mn contents are probably introduced into Cr-Al spinels during greenschist- to blueschist metamorphism. Compositional features of the serpentinite such as (i) Ca- and Al-depleted bulk compositions, (ii) concave U-shaped, chondrite-normalised rare earth element patterns (REE) with enrichment of light and heavy REEs, imply that serpentinites were probably derived from depleted peridotites which were refertilised by light rare earth element enriched melts in a suprasubduction-zone mantle wedge. U-Pb dating on igneous zircons from three metagabbro samples indicates igneous crystallisation at 262Ma (middle Permian). Timing of the metamorphism is constrained by incremental 40Ar/39Ar dating on phengitic white mica at 201Ma (latest Triassic). We conclude that the metaophiolite represents a fragment of middle Permian suprasubduction-zone oceanic lithosphere, involved in a latest Triassic subduction zone. These data, together with several reports in literature, indicate that the middle Permian was a time of suprasubduction-zone ophiolite formation in the Tethyan belt.

Mineralogical Composition of Particle-Size Fractions of Solonetzes from the North Crimean Lowland

Data on the mineralogical composition of clay ( 10 μm) fractions of meadow solonchakous solonetzes (Calcic Gypsic Salic Stagnic Solonetz (Albic, Siltic, Columnic, Cutanic, Differentic)) developing from loesslike loam and clay in the North Crimean Lowland are presented. Fractions >5 μm constitute nearly 50% of the soil mass and are characterized by the same mineralogical composition in the entire profile; they consist of quartz, plagioclases, potassium feldspars, and micas (biotite and muscovite). The eluvial-illuvial redistribution of clay in the course of solonetzic process is accompanied by changes in the portion of mixed-layer minerals and hydromicas in the upper part of the profile; a larger part of the smectitic phase is transformed into the superdisperse state. In the eluvial SEL horizon and in the illuvial BSN horizon, the clay fraction is impoverished in smectitic phase and enriched in trioctahedral hydromicas. Upon calculation of the content of clay minerals per bulk soil mass, the distribution of mixed-layer minerals is either eluvial, or eluvial-illuvial, whereas the distribution of hydromicas has an illuvial pattern without distinct eluvial minimum in the SEL horizons. The eluvial-illuvial distribution pattern of clay minerals in solonetzes of the North Crimean Lowland is compared with the distribution pattern of clay minerals in solonetzes of the West Siberian Lowland. Coefficients characterizing differentiation of solonetzes by the contents of particular mineral components are suggested.

Chlorite, white mica and clay minerals as proximity indicators to ore in the shallow porphyry environment of Quebrada de la Mina deposit, Argentina

The mineralogy and chemical composition of mica-like phyllosilicates (>2 µm) and clay fraction (<2 µm) of the shallow hydrothermal alteration zones of the Quebrada de la Mina Cu-Au deposit (San Juan Province, Argentina) were constrained by petrography, XRD, electronic microprobe and IR. The results allow us to identify: (1) relict patches of quartz + K-feldspar ± rutile (potassic) alteration, (2) a peripheral clinochlore-rich propylitic halo, and (3) a central white mica (>2 µm) and illite halo associated with phyllic and tourmaline-rich phyllic assemblages.The subhorizontal, shallow level Au-rich (>0.5 ppm Au) zone at the Quebrada de la Mina deposit coincides with the phyllic halo. The distribution of Au, Ag, Zn, Pb and As forms partially overlapping haloes toward shallower levels. Weak Cu (Mo) anomalies were found in potassic patches below the Au-rich zone. High Mn and Fe contents in clinochlore from the peripheral propylitic halo suggest a distance of ∼1 km to a porphyry Cu-(Au) mineralized core at deeper levels.White micas (>2 µm) in Quebrada de la Mina show a range of compositions between muscovite and illite. In the propylitic halo and in the patches of potassic alteration, white micas (>2 µm) show the highest values of Fe + Mg + Mn (0.40–0.55 apfu) and the lowest of Al (2.40–2.55 apfu). In the phyllic alteration zone of Quebrada de la Mina, white micas (>2 µm) with Al contents between 2.45 and 2.70 apfu and Fe + Mg + Mn between 0.35 and 0.15 apfu match the areas with high gold content (>0.5 ppm Au). The lowest values of Fe + Mg + Mn (0.11–0.05 apfu) and the highest Al contents (2.80–2.85 apfu) occur in white micas from the tourmaline-rich phyllic zone.Values of the Kübler index of illite of 0.19–0.1 2θ in the clay fraction of deep samples are indicative of higher temperature and/or higher fluid/rock ratios during illite formation, compared to values of the Kübler index > 0.2 2θ recognized in shallow samples. Thus, both the compositional variations in chlorite and white micas and the illite crystallinity could be used as a guide for exploration of copper-gold mineralization in shallow levels of porphyry systems.

Pressure-Induced Melting of Confined Ice.

The classic regelation experiment of Thomson in the 1850s deals with cutting an ice cube, followed by refreezing. The cutting was attributed to pressure-induced melting but has been challenged continuously, and only lately consensus emerged by understanding that compression shortens the O:H nonbond and lengthens the H–O bond simultaneously. This H–O elongation leads to energy loss and lowers the melting point. The hot debate survived well over 150 years, mainly due to a poorly defined heat exchange with the environment in the experiment. In our current experiment, we achieved thermal isolation from the environment and studied the fully reversible ice–liquid water transition for water confined between graphene and muscovite mica. We observe a transition from two-dimensional (2D) ice into a quasi-liquid phase by applying a pressure exerted by an atomic force microscopy tip. At room temperature, the critical pressure amounts to about 6 GPa. The transition is completely reversible: refreezing occurs when the applied pressure is lifted. The critical pressure to melt the 2D ice decreases with temperature, and we measured the phase coexistence line between 293 and 333 K. From a Clausius–Clapeyron analysis, we determine the latent heat of fusion of two-dimensional ice at 0.15 eV/molecule, being twice as large as that of bulk ice.

Infinite charge mobility in muscovite at 300 K

Evidence is presented for infinite charge mobility in natural crystals of muscovite mica at room temperature. Muscovite has a basic layered structure containing a flat monatomic sheet of potassium sandwiched between mirror silicate layers. It is an excellent electrical insulator. Studies of defects in muscovite crystals indicated that positive charge could propagate over great distances along atomic chains in the potassium sheets in the absence of an applied electric potential. The charge moved in association with anharmonic lattice excitations that moved at about sonic speed and created by nuclear recoil of the radioactive isotope 40K. This was verified by measuring currents passing through crystals when irradiated with energetic alpha particles at room temperature. The charge propagated more than 1000 times the range of the alpha particles of average energy and 250 times the range of channelling particles of maximum energy. The range is limited only by size of the crystal.

Vapour Diffusion Route to Mineralize Graphene and Polymer Surfaces with Calcium Phosphate Intended for Biomedical Applications

After successful application of the sitting drop vapour diffusion route to deposit calcium phosphate layers on mica muscovite sheets, in this work we have extended the method to mineralize polymer surfaces (OSTE+) and bidimensional materials (graphene), aimed to prepare implants or scaffolds for nonload bearing applications in the medical sector. Thin octacalcium phosphate/apatite layers have been deposited on mica muscovite sheets. Thin apatite/octacalcium phosphate layers deposited on OSTE+ polymer lames. When graphene nanoflakes where used as support, this technique yielded apatite/graphene nanocomposites.

High‐P tectono‐metamorphic evolution of mylonites from the Variscan basement of the Northern Apennines, Italy

AbstractStrain localization within shear zones may partially erase the rock fabric and the metamorphic assemblage(s) that had developed before the mylonitic event. In poly‐deformed basements, the loss of information on pre‐kinematic phases of mylonites hinders large‐scale correlations based on tectono‐metamorphic data. In this study, devoted to a relict unit of Variscan basement reworked within the nappe stack of the Northern Apennines (Italy), we investigate the possibility to reconstruct a complete pressure (P)–temperature (T)–deformation (D) path of mylonitic micaschist and amphibolite by integrating microstructural analysis, mineral chemistry and thermodynamic modelling. The micaschist is characterized by a mylonitic fabric with fine‐grained K‐white mica and chlorite enveloping mica‐fishes, quartz, and garnet pseudomorphs. Potassic white mica shows Mg‐rich cores and Mg‐poor rims. The amphibolite contains green amphibole+plagioclase+garnet+quartz+ilmenite defining S1 with a superposed mylonitic fabric localized in decimetre‐ to centimetre‐scale shear zones. Garnet is surrounded by an amphibole+plagioclase corona. Phase diagram calculations provide P–T constraints that are linked to the reconstructed metamorphic‐deformational stages. For the first time an early high‐P stage at &gt;11 kbar and 510°C was constrained, followed by a temperature peak at 550–590°C and 9–10 kbar and a retrograde stage (&lt;475°C, &lt;7 kbar), during which ductile shear zones developed. The inferred clockwise P–T–D path was most likely related to crustal thickening by continent‐continent collision during the Variscan orogeny. A comparison of this P–T–D path with those of other Variscan basement occurrences in the Northern Apennines revealed significant differences. Conversely, a correlation between the tectono‐metamorphic evolution of the Variscan basement at Cerreto pass, NE Sardinia and Ligurian Alps was established.

Application of CASI/SASI and fieldspec4 hyperspectral data in exploration of the Baiyanghe uranium deposit, Hebukesaier, Xinjiang, NW China

ABSTRACTHyperspectral technology can quickly identify hydrothermal altered minerals and can locate the possible hydrothermal/mineralization centres through the variations of the spectral characteristic parameters of some specific altered minerals. In this study, airborne sensors Compact Airborne Spectrographic Imager (CASI)/ Shortwave infrared Airborne Spectrographic Imager (SASI) and visible-shortwave infrared spectrometer FieldSpec4 hyperspectral data were used to study the alteration characteristics to locate the possible hydrothermal/mineralization centres for the Baiyanghe uranium deposit, Xinjiang, NW China. The results showed that the hydrothermal altered minerals mainly included white mica (it is a general term for aqueous silicoaluminate mineral group, and mainly includes muscovite and illite in the text) (Al-rich, Al-median, and Al-poor white mica), montmorillonite, kaolinite, chlorite, carbonate, and ferric iron (Fe2O3, and the ferric iron alteration usually presents red, mainly hematite in the text); and that the alteration had obvious zoning characteristics. The variations in the absorption-peak wavelength of white mica at 2200 nm, SWIR-IC (short-wavelength infrared illite crystallinity, a dimensionless quantity, and it is defined as the absorption-peak depth of illite at 2200 nm divided by the absorption-peak depth of illite at 1900 nm on a hull quotient spectrum) of white mica, and acid–base properties revealed that the possible hydrothermal/mineralization centres were located in the northern contact zone between the Yangzhuang rock body and the northern volcanic rocks of the Devonian and in the acidic alteration zone to north of the deposit about 3.0–4.0 km, where there appeared a certain number of uranium mineralization occurrences. These results pointed to the existence of multiple hydrothermal activities and could provide references for periphery uranium exploration and geological origin of this uranium area.

Substrate-induced strain and charge doping in CVD-grown monolayer MoS2

Due to its electronic-grade quality and potential for scalability, two-dimensional (2D) MoS2 synthesized by chemical vapor deposition (CVD) has been widely explored for electronic/optoelectronic applications. As 2D MoS2 can be considered a 100% surface, its unique intrinsic properties are inevitably altered by the substrate upon which it is grown. However, systematic studies of substrate-layer interactions in CVD-grown MoS2 are lacking. In this study, we have analyzed built-in strain and charge doping using Raman and photoluminescence spectroscopy in 2D MoS2 grown by CVD on four unique substrates: SiO2/Si, sapphire, Muscovite mica, and hexagonal boron nitride. We observed decreasing strain and charge doping in grown MoS2 as the substrates become less rough and more chemically inert. The possible origin of strain was investigated through atomic force microscopy roughness measurements of the as-grown layer and substrate. Our results provide direction for device optimization through careful selection of the growth substrate and pave the way for further investigations to unravel the complex nature of the 2D monolayer-substrate interface.

Magmatic–hydrothermal processes in Sangdong W–Mo deposit, Korea: Study of fluid inclusions and 39Ar–40Ar geochronology

The Sangdong scheelite–molybdenite deposit in northeast South Korea consists of strata-bound orebodies in intercalated carbonate-rich layers in the Cambrian Myobong slate formation. Among them, the M1 layer hosts the main orebody below which lie layers of F1–F4 host footwall orebodies. Each layer was first skarnized with the formation of a wollastonite + garnet + pyroxene assemblage hosting minor disseminated scheelite. The central parts of the layers were subsequently crosscut by two series of quartz veining events hosting minor scheelite and major scheelite–molybdenite ores, respectively. The former veins associate amphibole–magnetite (amphibole) alteration, whereas the latter veins host quartz–biotite–muscovite (mica) alteration. Deep quartz veins with molybdenite mineralization are hosted in the Cambrian Jangsan quartzite formation beneath the Myobong formation. In the Sunbawi area, which is in close proximity to the Sangdong deposit, quartz veins with scheelite mineralization are hosted in Precambrian metamorphic basement. Three muscovite 39Ar–40Ar ages between 86.6 ± 0.2 and 87.2 ± 0.3 Ma were obtained from M1 and F2 orebodies from the Sangdong deposit and Sunbawi quartz veins. The Upper Cretaceous age of the orebodies is concordant with the published ages of the hidden Sangdong granite, 87.5 ± 4.5 Ma. This strongly suggests that the intrusion is causative for the Sangdong W–Mo ores and Sunbawi veins.Fluid inclusions in the quartz veins from the M1 and F2 orebodies, the deep quartz-molybdenite veins, and the Sunbawi veins are commonly liquid-rich aqueous inclusions having bubble sizes of 10–30 vol%, apparent salinities of 2–8 wt% NaCl eqv., and homogenization temperatures of 180–350 °C. The densities of the aqueous inclusions are 0.70–0.94 g/cm3. No indication of fluid phase separation was observed in the vein. To constrain the formation depth in the Sangdong deposit, fluid isochores are combined with Ti–in–quartz geothermometry, which suggests that the M1 and F2 orebodies were formed at depths of 1–3 km and 5–6 km below the paleosurface, respectively. The similarity of the Cs (cesium) concentrations and Rb/Sr ratios in the fluid inclusions of the respective orebodies indicate an origin from source magmas having similar degrees of fractionation and enrichment of incompatible elements such as W and Mo. High S concentrations in the fluids and possibly organic C in the sedimentary source likely promoted molybdenite precipitation in the Sangdong orebodies, whereas the scheelite deposition in the deep quartz–molybdenite veins hosted in the quartzite is limited by a lack of Ca and Fe in the hydrothermal fluids. The molybdenite deposition in the Sunbawi quartz–molybdenite veins hosted in the Precambrian metamorphic basement rocks was possibly limited by a lack of reducing agents such as organic C.

Microstructures, mineral chemistry and geochronology of white micas along a retrograde evolution: An example from the Aar massif (Central Alps, Switzerland)

This study investigates gneissic tectonites of different mechanical origins, and aims at unravelling the link between microstructures, white mica chemistry and K-Ar data. The highest temperature mylonitic deformation, which is investigated, is dominated by dislocation creep in monomineralic quartz, and viscous granular flow in polymineralic domains. These mylonites show homogenous mineral chemistry, resulting in robust and consistent K-Ar age data. The lowest temperature deformation investigated, is that of a retrograde brittle deformation, producing cohesionless fault gouges. Within the cohesionless fault gouges, frictional granular flow is considered as the main deformation mechanism. The K-bearing phases inside the fault gouges record no chemical resetting during this brittle overprint, but contain mechanically fragmented K-bearing micas and significant amounts of newly produced smectite. This yields K-Ar ages inside of a gouge that are in the range of adjacent mylonite ages, and may not represent the timing of gouge formation. In an effort to understand these uncertainties in K-Ar ages, detailed observations of the microstructural context of K-bearing white mica were made. Microstructural criteria in combination with quantitative element mapping allowed for the discrimination of five important mica-related processes: (1) fracturing/recrystallization of white mica; (2) (re)-precipitation of new fine-grained white mica inside the deforming rock matrix; (3) pseudomorphic replacement of precursor minerals by white mica and chlorite; (4) pseudomorphic replacement of pre-existing white mica without grain size reduction; and (5) remnant grains. The combination of these different processes led to a high variability in mineral chemistry and isotope data for tectonites, which relates directly to variations in the size of the equilibrium volumes. Despite the samples being highly deformed in the presence of fluids, inherited sheet silicates may survive. If inherited sheet silicates are present they contribute to an increase in both the chemical heterogeneity and the apparent K-Ar ages of a sample.

Enhanced adsorption of 2,4-dichlorophenol from aqueous solution using modified low cost Algerian geomaterial

Abstract Natural geological material (GM) (CEC = 21 meq/100 g, SBET = 3.39 m²/g), available in large amount in Timimoun (South Algeria), was modified with an ammonium quaternary dodecyl- and cetyl-trimethyl ammonium bromide (DTAB and CTAB, respectively). The X-ray diffraction (XRD) revealed that the natural geomaterial represents mainly muscovite mica; and organic molecules salts were not intercalated in the interlayers; the modification process was thus limited to the surface. Adsorption of 2,4-dichlorophenol (2,4-DCP) from aqueous solution via batch sorption experiments onto GM, GM-DTAB, and GM-CTAB was investigated. The results show increased 2,4-DCP adsorption on the GM composites compared to natural GM. The maximum uptake occurred at pH = 6, a contact time of 60 min, and an adsorbent dose of 4 g/L. The surface modification of muscovite by quaternary ammonium bromide and sequential adsorption of 2,4-DCP were also evaluated by XRD and FTIR. The kinetic adsorption data were in good agreement with a pseudo-second-order model. Freundlich adsorption model was best to describe adsorption equilibrium data for 2,4-DCP onto GM-DTAB and in the case of GM-CTAB, experimental data agree well with the Langmuir isotherm model. The monolayer adsorption capacity (qm) was 110.75 mg/g for GM-DTAB, 239.8 mg/g for GM-CTAB, and 354.6 mg/g for activated carbon.

Monitoring Ion Track Formation Using In Situ RBS/c, ToF-ERDA, and HR-PIXE.

The aim of this work is to investigate the feasibility of ion beam analysis techniques for monitoring swift heavy ion track formation. First, the use of the in situ Rutherford backscattering spectrometry in channeling mode to observe damage build-up in quartz SiO2 after MeV heavy ion irradiation is demonstrated. Second, new results of the in situ grazing incidence time-of-flight elastic recoil detection analysis used for monitoring the surface elemental composition during ion tracks formation in various materials are presented. Ion tracks were found on SrTiO3, quartz SiO2, a-SiO2, and muscovite mica surfaces by atomic force microscopy, but in contrast to our previous studies on GaN and TiO2, surface stoichiometry remained unchanged. Third, the usability of high resolution particle induced X-ray spectroscopy for observation of electronic dynamics during early stages of ion track formation is shown.

Effect of Surface Binding on Individual Bacterial Cells: Raman and AFM Approaches

Bacterial cell polarity is an internal cell asymmetry that correlates with the cell ability to sense energy and metabolite sources, chemical signals, quorum signals, toxins, and movement in the desired directions. This ability also plays central role in cell attachment to various surfaces and biofilm formation. Biochemical analysis and molecular imaging demonstrate that sensing of energy and nutrients by the cell correlates with asymmetric protein, lipid and other molecule distributions within the cell. In the present work, we develop an experimental approach and analyze how attachment to inorganic mineral, mica affects Cyt redox state inside individual G. sulfurreducens cells. The approach is based on confocal Raman microscopy allowing for simultaneous detection of Raman spectra of individual bacterial cell and the substrate and allowing for precise estimation of the border between them. Applying Gaussian deconvolution and principal component analysis we are able to identify spectral signatures of cytochrome redox states and their intracellular location. Our results demonstrate that attachment of G. sulfurreducens cells to a muscovite (mica) selectively changes Cyt redox state at the cell side facing the mineral. This leads to the formation of a gradient of redox potential needed for directed electron transfer within the cell. Our results open the possibility for analyzing electrochemical potentials inside individual bacterial cells. They indicate that Cyt redox state might be a driving force switching cell metabolic activity that leads to irreversible cell attachment to electrode, cell-to-cell association, and biofilm formation.

Petrology, geochemistry and zirconology of impure calcite marbles from the Precambrian metamorphic basement at the southeastern margin of the North China Craton

Impure calcite marbles from the Precambrian metamorphic basement of the Wuhe Complex, southeastern margin of the North China Craton, provide an exceptional opportunity to understand the depositional processes during the Late Archean and the subsequent Palaeoproterozoic metamorphic evolution of one of the oldest cratons in the world. The studied marbles are characterized by the assemblage calcite+clinopyroxene+plagioclase+K-feldspar+quartz+rutile±biotite±white mica. Based on petrography and geochemistry, the marbles can be broadly divided into two main types. The first type (type 1) is rich in REE with a negative Eu anomaly, whereas the second type (type 2) is relatively poor in REE with a positive Eu anomaly. Notably, all marbles exhibit remarkably uniform REE patterns with moderate LREE/HREE fractionation, suggesting a close genetic relationship.Cathodoluminescence imaging, trace elements and mineral inclusions reveal that most zircons from two dated samples display distinct core-rim structures. Zircon cores show typical igneous features with oscillatory growth zoning and high Th/U ratios (mostly in the range 0.3–0.7) and give ages of 2.53−2.48Ga, thus dating the maximum age of deposition of the protolith. Zircon rims overgrew during granulite-facies metamorphism, as evidenced by calcite+clinopyroxene+rutile+plagioclase+quartz inclusions, by Ti-in-zircon temperatures in the range 660–743°C and by the low Th/U (mostly <0.1) and Lu/Hf (<0.001) ratios. Zircon rims from two dated samples yield ages of 1839±7Ma and 1848±23Ma, respectively, suggesting a Palaeoproterozoic age for the granulite-facies metamorphic event. These ages are consistent with those found in other Precambrian basement rocks and lower-crustal xenoliths in the region, and are critical for the understanding of the tectonic history of the Wuhe Complex.Positive Eu anomalies and high Sr and Ba contents in type 2 marbles are ascribed to syn-depositional felsic hydrothermal activity which occurred at 2.53−2.48Ga. Our results, together with other published data and the inferred tectonic setting, suggest that the marbles' protolith is an impure limestone, rich in detrital silicates of igneous origin, deposited in a back-arc basin within an active continental margin during the late Archean and affected by synchronous high-T hydrothermalism at the southeastern margin of the North China Craton.

Structural modification in swift heavy ion irradiated muscovite mica**Project supported by the National Natural Science Foundation of China (Grant Nos. 11675233 and 11505243).

Two-layer monoclinic (2M) muscovite mica sheets with a thickness of 12 μm are irradiated with Sn ions at room temperature with electronic energy loss (dE/dx)e of 14.7 keV/nm. The ion fluence is varied between 1×1011 and 1×1013 ions/cm2. Structural transition in irradiated mica is investigated by x-ray diffraction (XRD). The main diffraction peaks shift to the high angles, and the inter-planar distance decreases due to swift heavy ion (SHI) irradiation. Dehydration takes place in mica during SHI irradiation and mica with one-layer monoclinic (1M) structure is thought to be generated in 2M mica after SHI irradiation. In addition, micro stress and damage cross section in irradiated mica are analyzed according to XRD data. High resolution transmission electron microscopy (HRTEM) is used on the irradiated mica to obtain the detailed information about the latent tracks and structural modifications directly. The latent track in mica presents an amorphous zone surrounded by strain contrast shell, which is associated with the residual stress in irradiated mica.

Mapping white mica alteration associated with the Jiama porphyry-skarn Cu deposit, central Tibet using field SWIR spectrometry

Field measurement of the short-wave infrared (SWIR) reflectance from drill hole samples proved to be an effective method to map variations in white mica composition (Tschermak substitution) associated with hydrothermal alteration zonation of the Jiama porphyry-skarn Cu deposit, Tibetan Plateau, China. This SWIR mineral spectral information provides geological insights into: (a) the possible nature of the related magmatic intrusions. (b) the physicochemistry of the associated hydrothermal fluids; (c) the interactions between these fluids and country rocks; and (d) potential vectors to economic mineralization. The results suggest that the Al-OH band wavelength of white mica can used as an indicator in the subsequent steps of prospecting.

Metal ion-exchange on the muscovite mica surface

The surface potassium ions of muscovite mica were exchanged for several different metal ions from aqueous solution (Ag, Ca, V, Mn, Fe, Ni, Cu, Zn, Co, and Cd). The surfaces were rinsed in water, dried under nitrogen atmosphere, and subsequently analysed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and, for half the systems, surface X-ray diffraction (SXRD). XPS and SXRD confirmed the presence of the different metal ions at the muscovite mica surface, with a partial monolayer of the monovalent and divalent ions present on the surface. No counter ions from the used salts were detected. AFM revealed that Ni-, and Fe-terminated muscovite mica surfaces were partially covered by nanoparticles, most likely consisting of metal (hydr)oxide. The exchanged ions remained on the surface after rinsing with ultra pure water three times. SXRD showed that Cd and Ag have a lower affinity for the muscovite mica surface than Cu, Ca, and Mn.

Synthesis, structure, and thermal properties of new polypropylene nanocomposites prepared by using MgCl2‐mica/TiCl4 based catalyst

ABSTRACTPreparation of polypropylene/mica nanocomposites via in situ polymerization is investigated. The nanocomposites were successfully synthesized using a Ziegler‐Natta catalyst based on MgCl2/modified mica/TiCl4. Muscovite mica was organically modified with quaternary ammonium salt, and with triethylaluminum. The treatment with triethylaluminum increased the disorder in the stacking of clay layers, producing a more active catalyst for propylene polymerization, although the mica containing catalysts had lower activity than the standard one prepared without clay. The nanostructure of the composites was characterized by X‐ray diffraction. The results showed that part of the mica layers were exfoliated in the polymer matrix, although tactoids were still present. Small‐angle X‐ray scattering analysis was used to determine how mica and its concentration influence the size of the polymer nanocrystals. Differential scanning calorimetry was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the nanocomposite samples. Thermogravimetric analysis showed that polypropylene/mica nanocomposites presented much higher thermal stability than the polypropylene without mica, which means that mica had a barrier effect against heat. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45587.

P-T evolution of metapelites from the Bajgan complex in the Makran accretionary prism, south eastern Iran

The Bajgan Complex, one of the basement constituents of the arc massif in Iranian Makran forms a rugged, deeply incised terrain. The complex consists of pelitic schists with minor psammitic and basic schists, calc silicate rocks, amphibolites, marbles, metavolcanosediments, mafic and felsic intrusives as well as ultramafic rocks. Metapelitic rocks show an amphibolite facies regional metamorphism and contain garnet, biotite, white mica, quartz, albite±rutile±apatite. Thermobarometry of garnet schist yields pressure of more than 9kbar and temperatures between 560 and 675°C. The geothermal gradient obtained for the peak of regional metamorphism is 19°C/km, corresponding to a depth of ca. 31km. Replacement of garnet by chlorite and epidote suggest greenschist facies metamorphism due to a decrease in temperature and pressure through exhumation and retrograde metamorphism (370–450°C and 3–6kbar). The metapelitic rocks followed a ‘clockwise’ P–T path during metamorphism, consistent with thermal decline following tectonic thickening. The formation of medium-pressure metamorphic rocks is related to presence of active subduction of the Neotethys Oceanic lithosphere beneath Eurasia in the Makran.