Biotite Mica Research Articles

The role of biotite in the deterioration of pyrrhotite within concrete aggregates: Trois-Rivières case study

In Trois-Rivières, Canada, numerous commercial and residential structures suffered severe concrete degradation due to internal sulfate attack (ISA). The deterioration was attributed to the use of sulfide-bearing aggregates obtained from nearby quarries. The objective of this study was to investigate the mechanisms involving pyrrhotite oxidation and the role of biotite in this process. Detailed analysis, including reflected light optical characterization, mineral chemistry, and EPMA chemical mapping, revealed significant oxidation of pyrrhotite within damaged concrete, resulting in the formation of iron oxyhydroxides as secondary phases. Furthermore, a textural association between biotite mica and pyrrhotite was observed in fresh and damaged aggregate samples. While the chemical composition of biotite remains unchanged, it accelerates the deleterious reactions when in direct contact with pyrrhotite. As oxidation proceeds, naturally occurring biotite crystals near pyrrhotite act as pathways, facilitating the ingress of oxygen and water while simultaneously channeling the release of iron and sulfur compounds.

Ignimbrites Related to Neogene Volcanism in the Southeast of the Iberian Peninsula: An Experimental Study to Establish Their Pozzolanic Character

The speed at which climate change is happening is leading to a demand for new pozzolanic materials that improve the quality of cements and, at the same time, limit the emission of greenhouse gases into the atmosphere. The main objective of this work is the detailed characterization of an ignimbrite sample (IGNS) to demonstrate its effectiveness as a natural pozzolan. To meet this objective, a series of tests were carried out. In the first stage, mineral and chemical analyses were performed, such as petrographic analysis by thin section (TSP), X-ray diffraction (XRD), oriented aggregate (OA), scanning electron microscopy (SEM) and X-ray fluorescence (XRF). In the second stage, the following technical tests were carried out: chemical quality analysis (QCA), pozzolanicity test (PT) and mechanical compressive strength (MS) at 7, 28 and 90 days, using mortar specimens with ignimbrite/cement formulation (IGNS/PC): 10, 25 and 40% to establish the pozzolanic nature of the ignimbrite. The results of the mineral and chemical analyses showed that the sample has a complex mineralogical constitution, consisting of biotite mica, potassium feldspar, plagioclase, smectite (montmorillonite), quartz, volcanic glass, iron, titanium and manganese oxides, chlorite and chlorapatite. On the other hand, the technological tests revealed the pozzolanic nature of the sample, as well as visible increases in the mechanical compressive strengths in the three proportions, the most effective being IGNS/PC:10% and IGNS/PC:25% at 7, 28 and 90 days of setting. The results obtained could be applied in the formulation of new pozzolanic cements with ignimbrite as a natural pozzolanic aggregate.

Brillouin light scattering spectroscopy as a versatile probe of hypersound in diverse materials systems

An overview of the inelastic laser light scattering technique of Brillouin spectroscopy and its application to the study of hypersound in a diverse set of materials systems will be presented. In particular, results obtained from recent Brillouin scattering experiments on natural gastropod mucus, layered high temperature superconductor Bi2Sr2CaCu2O8+δ, biotite micas, and satellite tobacco mosaic virus crystals will be highlighted. Collectively, these results demonstrate the utility of Brillouin light scattering spectroscopy as a sensitive non-destructive probe of hypersound velocity and attenuation in the vicinity of structural phase transitions, the influence of chemical composition and incommensurate structure on material elasticity, and of phonon dynamics in challenging materials classes.

Crystallographic preferred orientation of quartz deformed at granulite conditions: the Kalinjala Shear Zone, Port Neill, South Australia

Crystallographic preferred orientations of quartz aggregates in mylonitic orthogneisses from the highest strained central region of the Kalinjala Shear Zone, Port Neill South Australia, are products of a combination of constrictional and flattening strains. These rocks were deformed under granulite facies peak metamorphic conditions, reaching pressures of ∼1.0 GPa and temperatures of ∼800 ± 50 °C. Neutron diffraction textural and fabric analysis methods reveal a dominant single c-axis maximum parallel to the Y-strain axis. This is accompanied by a symmetric orthorhombic pattern, where the c-axis fabrics and corresponding pole figure densities of {a}, {m}, {r} and {z} planes are arranged around the XY foliation plane. These fabrics from coexisting adjacent layers suggest that the activation of prism-<a> slip is characteristic for these high-temperature deformation conditions. A small asymmetry in the [c], {a} and {m} pole figures suggests a minor component of dextral shearing. The c-axis pattern is weakened where the foliation is dominated by secondary phases, such as concentrations of biotite mica. The opening angles obtained from cross-girdle c-axis patterns produce temperature estimates that are ∼100 °C lower than the peak metamorphic temperature of ∼800 ± 50 °C, but closer to temperatures related to a component of flattening strain. These c-axis patterns are consistent with other structural characteristics and can be related to the late-stage flattening strains during the Kimban Orogeny. KEY POINTS Mylonitic orthogneisses are deformed under granulite facies conditions. Quartz fabrics were measured by bulk neutron diffraction and optical methods. Mylonite c-axis fabrics can be related to the high-temperature deformation and activation of the prism-< a > slip system. Crystal preferred orientations indicate a large component of flattening strain superimposed on the dextral shearing observed in the Kalinjala Shear Zone.

Antimicrobial potential of four mica drugs and their chemical and mineralogical properties

BackgroundMica drugs, a group of herbo-metallic traditional preparations comprising biotite mica as the major mineral ingredient, are prescribed for skin disorders and respiratory ailments and other chronic conditions in South Asian countries, particularly India and Sri Lanka. Mica-based drugs (Abhrak drugs) are subjected to unique and varied preparation procedures and the bioactivity of the drugs can be affected by drug-processing conditions, the ingredients used and the mica composition. The current study aimed to evaluate and compare, on the basis of their physical and chemical characteristics, the antimicrobial potential of two commercial mica drugs AbBb (Abhrak bhashma) and AbCh (Abhrak Chenhuram) and two mica drugs ABL1 (Abhrak Bhasma Laboratory Prepared 1) and ABL2 (Abhrak Bhasma Laboratory Prepared 2) prepared in the laboratory under different conditions.MethodsAntimicrobial activity of all four drugs was assessed at 10 mg/ml concentration against Pseudomonas aeruginosa, Escherischia coli, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and Candida albicans using well diffusion assay, agar dilution assay and Miles and Misra method. Major and trace metal constituents of the drug samples were measured using atomic absorption spectrometry. Mineralogical properties, bacteria-mineral interactions, morphological changes in microbes and the surface characteristics of the drugs were determined using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM).ResultsThe drugs ABL1, ABL2 and AbBh exhibited antimicrobial activity against only Gram-positive organisms (S. aureus and MRSA) when tested with Miles and Misra method (broth method). Mineralogical studies (XRD) revealed that biotite mica was altered into secondary clay minerals and iron oxides in the commercial drug AbCh while the other three drugs had altered mica and iron oxide phases. The essential elements (Na, K, Ca and Mg) required for microbial functions were present in varying extents in all four drugs while they were present in exceedingly high amounts in AbCh having comparatively high cation-exchange capacity, consistent with the observation that AbCh was inactive against all the microbes tested. The three drugs (ABL1, ABL2 and AbBh) showing antimicrobial activity contained comparatively high amounts of Fe, Zn and Cu that are known to display antimicrobial properties at high concentrations. SEM studies revealed that the drug particles adhered and entrapped the bacterial species, presumably modifying the physiochemical characteristics of the bacteria and eventually causing lethality.ConclusionThree of the four mica drugs inhibited the tested Gram-negative bacteria and the antibacterial activity of the mica drugs depends on their constituents and the methods of preparation.

Biotite as a geoindicator of rare earth element contamination in Gomati River Basin, Ganga Alluvial Plain, northern India.

Rare earth elements (REE) are emerging as modern high-technology-related novel micro-contaminants in freshwater aquatic systems and are therefore attracting global attention due to their potential human health risks. The Gomati River (a tributary of the Ganga River) sediments were analyzed for REE concentrations to establish REE contamination and to identify biotite mica mineral as a geoindicator. Chondrite-normalized REE pattern of the river sediments and biotite mica mineral were similar and depict a strong light REE (LREE) enrichment and relatively flatter heavy REE (HREE). The maximum total REE (∑REE) concentration increased from 323µg/g in 2012 to 673µg/g in 2019. In the ∑REE, LREE contribution was > 80%, because of anthropogenic inputs, mainly petroleum-cracking catalysts and other high-technology-based products. The XRD analysis and the geochemical signature of the Gomati River sediments reveal the meaningful existence of biotite mica mineral. A distinct downstream REE enrichment pattern was identified in biotite from the mica-rich bedload sediments. The scanning electron microscopy-energy dispersive X-ray (SEM-EDX) mapping images of biotite also revealed the precipitation of Lanthanum, at the weathered edges, during the early stage of mineral weathering. Biotite mica was identified as a geoindicator for the assessment of REE contamination in the Gomati River and the Hindon River Basin of the Ganga Alluvial Plain. Future research is needed for the application of biotite mica mineral as a geoindicator that can help the environmental scientists to contribute more effectively to the interdisciplinary efforts in River Science.

Comparison between Mineralogical Properties of Oak Forest and Un-Cultivated Soils in Iraqi Kurdistan Region

This study was conducted to identify the mineralogical properties of oak forest and uncultivated soils at 12 locations in the Iraqi Kurdistan region, which included (Brifca, Gara, and Matin) in Duhok governorate, (Awagrd, Bilah, and Malakan) in Erbil governorate, (Badawan, Bardanga, and Chwarta) in Sulaimani Governorate and (Bakhakon, Hawar, and Sartak) in Halabja governorate. Clay minerals were identified from X-ray diffraction data and peaks. Peak height is used as a rough indicator of the relative abundance of minerals. In general, the expansion of 14°A to 17°A in the ethylene glycol treatment was not detected because measuring started at 5? so that’s why we cannot differentiate between Chlorite and Smectite in that treatment. Swelling chlorite was the dominant mineral in these soils. While the miner clay minerals at those locations were Kaolinite. Mica was identified at all locations, while the dominant type of mica in forest soils was Muscovite, which was obtained from 6 sites, and Mica Biotite was obtained from 4 sites. In uncultivated sites, both types of mica were recorded at 5 sites.

Peritectic Melting of Mica in Fault‐Related Pseudotachylite Melts and Potassium Mass Balance as an Indicator of Fluid‐Absent Source Conditions.

AbstractPseudotachylites are generally considered to be produced by flash melting of the most fusible minerals, with compositions often dominated by biotite mica. We present phase fraction calculations for 237 pseudotachylite analyses from 28 localities spanning a range of host rock compositions from granites to peridotites. Pseudotachylite matrix compositions cannot be reproduced by a simple linear mixture of the minerals in their host rocks and commonly show a potassium deficit in pseudotachylites which contain significant contributions from biotite or muscovite. This is strongly indicative of peritectic melting of mica under fluid‐absent conditions. Occasionally, a negative contribution from an aluminosilicate phase is required but with a positive contribution from potassium feldspar. This is most consistent with peritectic melting of micas under fluid present conditions. The present data therefore suggest that, while fluid absent flash melting might be the most common mode of formation of pseudotachylite, in some instances pseudotachylites can be produced in the presence of a free fluid. Potassium mass balance of pseudotachylites might therefore be a diagnostic indicator of fluid‐absent conditions in their source regions during seismogenic rupture. We give some examples of observational evidence of peritectic liquidus phases in pseudotachylites and suggest that the significance of these phases might have been overlooked in previous studies.

Nanoparticles of biotite mica as KrishnaVajraAbhraka Bhasma: synthesis and characterization

BackgroundBio-inorganic nanoparticles or metal nanoparticles are used in medicine for diagnostic and treatment purposes. The nanomedicines from traditional Ayurvedic system are termed as bhasma. Rasashastra, the branch of inorganic medicines of Ayurveda, has documented monographs of metal-mineral bhasmas as potent drugs. However there is lack of scientific analytical data of the end products. ObjectivesPresent study was aimed at finding out the morphological, structural, elemental and chemical composition of the Krishna vajra abhraka bhasma (KVB). Materials and methodsBhasma of KVB (Biotite Mica) was prepared in our laboratory using biotite mica sheets befitting selection criteria and carrying out further processes with strict SOPs as per AFI. ResultsThe bhasma complied with the confirmatory tests from Rasashastra. The physical and physicochemical tests correlate with the results obtained by instrumental analytical methods. SEM revealed square shaped nanoparticles of mean size of 92.3 nm. EDAX showed presence of Si, Mg, O, Fe, Ca, Na, C, K and Al. XRD revealed the crystalline nature of bhasma with mixture of various individual oxides and spinel shape of the crystal. DLS showed that the nanoparticles are unimodal in nature. FTIR and NMR showed the organic functional groups obtained from cow milk and selected herbs, indicating unique bio-inorganic nature of the KVB. ConclusionThe therapeutic potential imparted to the formulation could be due to the cow milk and specific herbs utilized during the manufacturing process.

Comparison between Mineralogical Properties of Oak Forest and Un-Cultivated Soils in Iraqi Kurdistan Region

This study was conducted to identify the mineralogical properties of oak forest and un-cultivated soils at 12 locations in the Iraqi Kurdistan region, which included (Brifca, Gara, and Matin) in Duhok governorate, (Awagrd, Bilah, and Malakan) in Erbil governorate, (Badawan, Bardanga, and Chwarta) in Sulaimani Governorate and (Bakhakon, Hawar, and Sartak) in Halabja governorate. Clay minerals were identified from X-ray diffraction data and peaks. Peak height is used as a rough indicator of the relative abundance of minerals. In general, the expansion of 14A to 17A in ethylene glycol treatment was not detected because measuring started from 5 so thats why we cannot be differentiated between Chlorite and Smectite in that treatment. Swelling chlorite was the dominant mineral in these soils. While the miner clay mineral at that locations were Kaolinite. Mica was identified at all locations, while the dominant type of Mica at forest soils was Muscovite which was obtained from 6 sites, while Mica Biotite was obtained from 4 sites, but in un-cultivated sites, both types of mica recorded at 5 sites.

Complex Electrical Conductivity of Biotite and Muscovite Micas at Elevated Temperatures: A Comparative Study.

The unique physicochemical, electrical, mechanical, and thermal properties of micas make them suitable for a wide range of industrial applications, and thus, the interest for these kind of hydrous aluminosilicate minerals is still persistent, not only from a practical but also from a scientific point of view. In the present work, complex impedance spectroscopy measurements were carried out in muscovite and biotite micas, perpendicular to their cleavage planes, over a broad range of frequencies (10−2 Hz to 106 Hz) and temperatures (473–1173 K) that have not been measured so far. Different formalisms of data representation were used, namely, Cole-Cole plots of complex impedance, complex electrical conductivity and electric modulus to analyze the electrical behavior of micas and the electrical signatures of the dehydration/dehydroxylation processes. Our results suggest that ac-conductivity is affected by the structural hydroxyls and the different concentrations of transition metals (Fe, Ti and Mg) in biotite and muscovite micas. The estimated activation energies, i.e., 0.33–0.83 eV for biotite and 0.69–1.92 eV for muscovite, were attributed to proton and small polaron conduction, due to the bound water and different oxidation states of Fe.

Trace element mobility, regional significance and global implication of Gomati river basin, northern India

We studied trace element mobility in the Gomati River (an alluvial tributary of the Ganga River in northern India) Basin by analyzing thirty-six time series water samples for their dissolved concentration of trace elements. Sodium-normalised elemental mobility indices vary over a wide range of the six orders of magnitude from 102 (Cd) to 10–4 (Zr). The highly mobile elements are B, As, Se, Sr, Mo and Cd. The moderately mobile elements are Al, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb and Pb. Titanium, Fe and Al, commonly assumed to be immobile at global level, are identified as moderately mobile elements. High trace element mobility in the Gomati River Basin had the geogenic factor associated with the chemical weathering of biotite mica mineral. For the river water quality assessment, the concentration of B, Cr, Cu, Zn, As and Pb lies below the desirable limits; while the concentration of Al, Fe and Se are above the WHO permissible limits of drinking water. At global scale, the Gomati River Basin contributes dissolved flux in significant proportions, namely Al (5.8%), Ti (4.4%), Fe (1.1%), Ni (1.2%), Se (21.5%) and Pb (1.7%) of total riverine flux. The proposed system model may provide means of qualify and quantify the environmental effects of trace elements mobility.

COMPARISON BETWEEN CHEMICAL AND MINERALOGICAL PROPERTIES OF OAK FOREST AND BARE CULTIVATED SOILS IN IRAQI KURDISTAN REGION

This study was conducted during 1/7/2016 to 20/12/2018, which aimed to determine chemical and mineralogical properties of oak forest and bare cultivated soils at 6 locations in Iraqi Kurdistan region, the samples were collected from two depths (0 – 30) and (30 – 60) cm. The study included some chemical and physical properties and identification of clay minerals from X-ray diffraction data. Peak height is used as a rough indicator of relative abundance of minerals. In general, the expansion of 14°A to ≈ 17°A in ethylene glycol treatment was not detected because measuring started from 5θ so that’s why we cannot differentiated between Chlorite and Semectite in that treatment. The main results indicated that the organic matter, clay content and CEC values in forest soils were higher than their values in bare cultivated soils, swelling chlorite being the dominant mineral in these soils. While the miner clay mineral at that locations were Kaolinite. Mica was identified at all location, while the dominant type of Mica at forest soils was Muscovite which was obtained from 4 Locations, while Mica Biotite was dominant in bare cultivated soils which was obtained from 4 sites.

Fractionation of Li, Be, Ga, Nb, Ta, In, Sn, Sb, W and Bi in the peraluminous Early Permian Variscan granites of the Cornubian Batholith: Precursor processes to magmatic-hydrothermal mineralisation

The Early Permian Variscan Cornubian Batholith is a peraluminous, composite pluton intruded into Devonian and Carboniferous metamorphosed sedimentary and volcanic rocks. Within the batholith there are: G1 (two-mica), G2 (muscovite), G3 (biotite), G4 (tourmaline) and G5 (topaz) granites. G1–G2 and G3–G4 are derived from greywacke sources and linked through fractionation of assemblages dominated by feldspars and biotite, with minor mantle involvement in G3. G5 formed though flux-induced biotite-dominate melting in the lower crust during granulite facies metamorphism. Fractionation enriched G2 granites in Li (average 315ppm), Be (12ppm), Ta (4.4ppm), In (74ppb), Sn (18ppm) and W (12ppm) relative to crustal abundances and G1 granites. Gallium (24ppm), Nb (16ppm) and Bi (0.46ppm) are not significantly enriched during fractionation, implying they are more compatible in the fractionating assemblage. Sb (0.16ppm) is depleted in G1-G2 relative to the average upper and lower continental crust. Muscovite, a late-stage magmatic/subsolidus mineral, is the major host of Li, Nb, In, Sn and W in G2 granites. G2 granites are spatially associated with W-Sn greisen mineralisation.Fractionation within the younger G3–G4 granite system enriched Li (average 364ppm), Ga (28ppm), In (80ppb), Sn (14ppm), Nb (27ppm), Ta (4.6ppm), W (6.3ppm) and Bi (0.61ppm) in the G4 granites with retention of Be in G3 granites due to partitioning of Be into cordierite during fractionation. The distribution of Nb and Ta is controlled by accessory phases such as rutile within the G4 granites, facilitated by high F and lowering the melt temperature, leading to disseminated Nb and Ta mineralisation. Lithium, In, Sn and W are hosted in biotite micas which may prove favourable for breakdown on ingress of hydrothermal fluids. Higher degrees of scattering on trace element plots may be attributable to fluid–rock interactions or variability within the magma chamber. The G3-G4 system is more boron-rich, evidenced by a higher modal abundance of tourmaline. In this system, there is a stronger increase of Sn compared to G1-G2 granites, implying Sn in tourmaline-dominated mineral lodes may represent exsolution from G4 granites.G1–G4 granite abundances can be accounted for by 20–30% partial melting and 10–40% fractionation of a greywacke source. G5 granites are analogues of Rare Metal Granites described in France and Germany. These granites are enriched in Li (average 1363ppm), Ga (38ppm), Sn (21ppm), W (24ppm), Nb (52ppm) and Ta (15ppm). Within G5 granites, the metals partition into accessory minerals such as rutile, columbite-tantalite and cassiterite, forming disseminated magmatic mineralisation. High observed concentrations of Li, In, Sn, W, Nb and Ta in G4 and G5 granites are likely facilitated by high F, Li and P, which lower melt temperature and promote retention of these elements in the melt, prior to crystallisation of disseminated magmatic mineralisation.

Effect of STAC on Structure of Biotite when Biotite Transform to Hydrated Ba-Mica

After Ba2+/K+ ion exchange, hydrated Ba2+ replaced K+ from interlayer spacing of biotite. original biotite transformed to vermiculite-type hydrated Ba-mica. in order to study the effect of long-chain alkylammonium on biotite after structure changes, biotite, hydrated Ba-mica and mixing mica (A mixture of biotite and hydrated Ba-mica) were used to be modified by STAC (octadecyl trimethylammonium chloride). Fourier transform infrared spectroscopy and powder X-ray diffraction spectroscopywere were used to characterize the obtained samples to reveal the changes of interlayer spacing and basal spacing. The results showed that STA+ could not enter into the interlayer spacing of biotite but enter into that of hydrated Ba-mica and mixing mica. Almost all basal spacing of Ba-mica and mixing mica were increased to 2.8nm.

Radiation damage in biotite mica by accelerated α-particles: A synchrotron microfocus X-ray diffraction and X-ray absorption spectroscopy studyk

A critical radiation damage assessment of the materials that will be present in a Geological Disposal Facility (GDF) for radioactive waste is a priority for building a safety case. Detailed analysis of the effects of high-energy α-particle damage in phyllosilicates such as mica is a necessity, as these are model structures for both the clay-based backfill material and the highly sorbent components of a crystalline host rock. The α-radiation stability of biotite mica [general formula: K(Mg, Fe)3(Al, Si3O10)(F, OH)2] has been investigated using the 5 MV tandem pelletron at the University of Manchester’s Dalton Cumbrian Facility (DCF) and both the microfocus spectroscopy (I18) and core X-ray absorption spectroscopy (B18) beamlines at Diamond Light Source (U.K.). Microfocus X-ray diffraction mapping has demonstrated extensive structural aberrations in the mica resulting from controlled exposure to the focused 4He2+ ion (α-particle) beam. Delivered doses were comparable to α-particle fluences expected in the highly active, near-field of a GDF. At doses up to 6.77 displacements per atom (dpa) in the region of highest particle fluence, biotite mica displays a heterogeneous structural response to irradiation on a micrometer scale, with sequential dilation and contraction of regions of the structure perpendicular to the sheets, as well as a general overall contraction of the phyllosilicate layer spacing. At the peak of ion fluence, the structure collapses under a high point defect density and amorphous areas are pervasive among altered domains of the original lattice. Such structural alterations are likely to affect the material’s capacity to sorb and retain escaped radionuclides over long timescales; increased edge site availability may favor increased sorption while interlayer uptake will likely be reduced due to collapse. Radiation-induced reduction of structural iron at the region of highest structural damage across an α-particle’s track has been demonstrated by Fe K-edge X-ray absorption near edge spectroscopy (XANES) and local structural disorder has been confirmed by analysis of both potassium K-edge XANES and Fe K-edge extended X-ray absorption fine structure analysis. An infrared absorption study of deformations in the OH– stretching region, along with electron probe microanalysis complements the synchrotron data presented here.

Geochemistry of Schists of Northwest Obudu Plateau, Southeastern Nigeria

Precambrian, highly foliated, fine – medium grained schists, which comprise migmatitic schist (MS), quartz mica schist (QMS), biotite mica schist (BMS) and hornblende biotite schist (HBS) constitute important lithological unit in Northwest Obudu Plateau. The schists are associated with gneisses, amphibolites and metaquartzites, and variously intruded by granites, pegmatites and quartzo-feldspathic veins. Sedimentary rocks, which are mostly Cretaceous sandstones, flank the western margin of the study area. Modal analysis shows that all the schists are enriched in quartz, plagioclase (An32), biotite and garnet, except the HBS which is relatively depleted in quartz but highly enriched in biotite (25 vol. %) and hornblende (55 vol. %). Sillimanite and epidote occur in accessory amounts. The co-existence of quartz- plagioclase (An32)- garnet-biotite- muscovite- sillimanite in the MS assemblage indicates that the Schists are derivatives of metamorphism of pelitic and mafic rocks, which had attained the uppermost amphibolite facies grade. Geochemically, the schists are enriched in Si02, which ranges from 60.11 wt % in the HBS, rising to 62.94 wt % in the BMS and 66.58 wt % in the QMS, with average of 64.56 wt %. The high SiO2 content points to a probable effect of an intruding granitic magma on the Pan – African schists. The Al2O3, Fe2O3, MgO, CaO and alkalies are relatively moderate to high. The samples are quartz normative, have high molecular value of Al2O3 &gt; {CaO + Na2O + K2O}. Plots in chemical discrimination diagrams confirm the peraluminous characteristics of the schist and suggest pelitic rock protolith except for the HBS.Keywords: Petrochemistry, Obudu Plateau, Protolith, Metapelite, Precambrian, Uppermost Amphibolite Facies

Late Cretaceous and Cenozoic tectonics of the Malay Peninsula constrained by thermochronology

New thermochronological analyses of granites from the Malay Peninsula record the region’s thermal history during the Late Mesozoic and Cenozoic. 40Ar/39Ar and (U–Th–Sm)/He analyses are combined with existing fission track data to provide a comprehensive set of temperature and time data. Fully and partially reset K-feldspar and biotite mica 40Ar/39Ar analyses indicate a significant period of thermal perturbation between ∼100 and ∼90Ma, and a second lesser perturbation between ∼51 and ∼43Ma. Zircon (U–Th–Sm)/He analyses and existing fission track data indicate exhumation of the Malay Peninsula in the Cretaceous, and renewed, localised exhumation in the early Paleogene. Apatite (U–Th–Sm)/He and fission track data indicate rapid exhumation of the region in the Late Eocene and Oligocene. Late Cretaceous tectonism is linked to the reversal of a regional dynamic topographic low following the cessation of subduction along the Sundaland margin in the Late Cretaceous, causing regional uplift and exhumation and the addition of significant heat into the crust via mantle upwelling. Early Paleogene exhumation may reflect the continuation of Cretaceous tectonism or a discrete phase of Paleocene exhumation linked to localised transpressional tectonics. Eocene tectonism is coincident with major subsidence offshore of the Malay Peninsula, interpreted to reflect regional block faulting in response to north–south compression driven by the resumption of subduction along the southern margin of Sundaland in the Eocene.

Molecular beam growth of micrometer-size graphene on mica

We demonstrate molecular beam growth of graphene on biotite mica substrates at temperatures below 1000°C. As indicated by optical and atomic force microscopy, evaporation of carbon from a high purity solid-state source onto biotite surface results in the formation of single-, bi-, and multilayer graphene with size in the micrometer regime. It is shown that the graphene grown directly on mica surface is of very high crystalline quality with the defect density below the threshold detectable by Raman spectroscopy. The interaction between graphene and the mica substrate is studied by comparison of the Raman spectroscopy and atomic force microscopy data with the corresponding results obtained for graphene flakes mechanically exfoliated onto biotite substrates. Experimental insights are combined with density functional theory calculations to propose a model for the initial stage of the van der Waals growth of graphene on mica surfaces. This work provides hints on how the direct growth of high quality graphene on insulators can be realized in general without exceeding the thermal budget limitations of Si technologies.

Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin, Sonbhadra district, Uttar Pradesh, India

Around 9000 inhabitants in the Panda River basin, Sonbhadhra District, Uttar Pradesh, India, are vulnerable to a “silent” dental and skeletal fluorosis from groundwater consumption. The fluoride source and seasonal groundwater quality variation were studied by collecting 65 groundwater samples in the Upper Panda River basin. Major rock types are phyllites and granite gneissic rocks. Fluoride concentrations are in the range 0.4–5.6 mg/L in the pre-monsoon season and 0.1–6.7 mg/L in the post-monsoon season. Fluor-apatite and biotite mica in the granite gneissic rock were identified as the main provenance of fluoride in the groundwater through water–rock interactions. Due to precipitation of calcium, soils become alkaline with high contents of sodium; these conditions allow fluoride to accumulate in water. According to risk index calculations, the fluoride-affected villages were shown to fall in the fluoride risk zone (with a risk index of around 1.7). On the basis of mineral stability diagrams, groundwater from the weathered and fractured aquifers appears to be stable within the kaolinite field, suggesting weathering of silicate minerals. The groundwater is chemically potable and suitable for domestic and agricultural purposes, except for a few wells in the southern region that are contaminated with high amounts of fluoride. Editor D. Koutsoyiannis Citation Raju, N.J., Dey, S., Gossel, W., and Wycisk, P., 2012. Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin, Sonbhadra District, Uttar Pradesh, India. Hydrological Sciences Journal, 57 (7), 1433–1452.