Phlogopite Mica Research Articles

Volume self-diffusion of oxygen in biotite, muscovite, and phlogopite micas

The kinetics of oxygen self-diffusion have been measured in natural samples of biotite, muscovite, and phlogopite micas under hydrothermal conditions using both bulk exchange and profiling analyses. All experiments were run at 1000 bars (100 MPa) water pressure except those designed to measure water pressure dependence, which ranged from 200 to 2000 bars. The Arrhenius relations obtained for layer-parallel diffusive transport in the three micas by bulk exchange experiments, fit to an infinite cylinder model, are Mineral biotite muscovite phlogopite Q (kcal mol) 34 ±2 39 ± 5 42 +- 3 D 0 (cm 2 s) 9.1 × 10 −6 7.7 × 10 −5 1.4 × 10 −4 T(°C) 500–800 512–700 600–900. The results of ion microprobe (SIMS) depth profiling perpendicular to the layers (parallel to c-axis) yield diffusion coefficients 3 to 4 orders of magnitude lower than for transport parallel to the layers. A single layer-parallel step profiling experiment yields a diffusion coefficient identical, within uncertainty, to those obtained from bulk exchange experiments. A slight dependence of diffusion rate on water pressure may obtain in phlogopite; however, the difference is approximately within the uncertainty of the measurement. Diffusion rates are similar, within about a half an order of magnitude, for a range of biotite composition from annite 4 to annite 63, as well as for muscovite. Comparison of oxygen diffusion rates in biotite from this study with Ar, K, and Rb diffusion from published data supports the idea that water is the oxygen-bearing species in hydrothermal diffusion experiments. The implication of these results for natural systems is that the micas, especially biotite, will continue to exchange oxygen isotopes via volume diffusion down to temperatures as low as 300 °C. The rapid diffusion kinetics may explain biotite oxygen isotope disequilibrium, which is commonly observed even in rocks where other mineral phases preserve equilibrium compositions.

Improved precision of RbSr dating of kimberlitic micas: An assessment of a leaching technique

RbSr isotopic analysis of phlogopite micas has commonly been used to determine the emplacement ages of kimberlite and other alkaline intrusives. Leaching of fresh as well as partially altered phlogopite samples in dilute (∼ 2 N) HCl, prior to isotopic analysis, increases the precision of the calculated ages significantly without disturbing the RbSr isotope systematics of the micas. The leaching step removes trace amounts of carbonate, which typically has a high Sr concentration (2000–9000 ppm), from the mica separates and thus increases the 87Rb/ 86Sr and 87Sr/ 86Sr ratios of the analysed samples. Leaching for a period of 10 min. had no affect on the Rb concentrations of the analysed phlogopite samples. However, leaching for a period of 12 hr. lowered the Rb contents of the phlogopites by a few per cent. All but one of the phlogopite samples leached for 12 hr. plot on an isochron. The slight loss in Rb content of these samples was thus complemented by loss of radiogenic Sr, which occurred along with the Rb in the large interlayer cation sites of the mica lattice. The emplacement age of the Makganyene kimberlite pipe is 121.2 ± 1.2 Ma, given by a RbSr isochron, including 19 phlogopite samples and one whole-rock sample. The initial 87Sr/ 86Sr ratio of 0.7100 ± 0.0002, in conjunction with the phlogopite mineralogy, indicates that the kimberlite is a Group-II kimberlite.

Dielectric response of humid phlogopite

The dielectric response of phlogopite mica has been measured for frequency lying between 10 mHz and 10 kHz with humidity as a parameter. The measured complex capacitance shows a low frequency dispersion (LFD) at high humidities. A weak loss peak is also present at high frequencies and low humidity levels.

The Petrography and composition of phlogopite micas from the Blue Ball Kimberlite, Arkansas: A record of chemical evolution during crystallization

The Blue Ball kimberlite, Scott County, Arkansas, contains between 23 and 36 modal % phlogopite. Phlogopite is present as phenocrysts, a groundmass phase, and as coronas around serpentinized olivine phenocrysts. Intermediate and reverse pleochroism, seen in phenocryst cores and the majority of groundmass phlogopites, can be correlated with the mineral chemistry. Reverse pleochroism, exhibited by phenocryst rims, rare groundmass grains, and phlogopites forming coronas around olivine, is generally accompanied by an increase in total Fe (as FeO) and a decrease in Al2 O3. Analyses of those phlogopites whoch exhibit reverse pleochroism have high cation totals, indicative of the presence of Fe3+. We suggest that these pleochroic schemes are a function of Fe3+ in the tetrahedral site, which is expressed in terms of ΔT = [8 - (Si + Al)]. All Blue Ball phlogopites have positive values for ΔT, but reverse pleochroism is found only when ΔT > 0.6, indicative of increased Fe3+ in the residual magma. It is concluded that phlogopite was on the liquidus throughout practically all of the kimberlite crystallization, because of the wide range in phlogopite compositions and the general decrease in Ba from micas exhibiting intermediate to reverse pleochroism. Variations of MG #, Ti, Ba, Si, and Al within the phlogopites have been used to trace the crystallization of other phases present in the kimberlite, namely olivine and spinel (chromite and titanomagnetite). Olivine was an early crystallizing phase, causing a decrease in MG # and Si, and an increase in Ti and Al in the phlogopites, a reflection of residual magma composition. Minor chromite also crystallized at this time, but was not of sufficient quantity to override the effect of olivine fractionation on the residual magma. Widespread Titano-magnetite crystallization occurred as olivine fractionation ceased, causing an increase in MG # and Si, and a decrease in Ti and Al. By examining these chemical variations with ΔT, the evolution of the Blue Ball kimberlite has been determined.

Geology and geochronology of the Arnea, Sithonia and Ouranopolis intrusions, Chalkidiki peninsula, northern Greece

The Chalkidiki Peninsula comprises the Greek geotectonic units of the Vardar-Axios Zone and the Serbo-Macedonian Massif. Several granitic bodies of various ages intrude this area and many of them are of unknown or disputed age. The ages of the Arnea, Sithonia and Ouranopolis granitoids are investigated using 40Ar− 39Ar stepheated mineral and Rb-Sr whole rock analyses. The Arnea granite has experienced intense but variable deformation, recrystallization and retrogression. In general it lacks easily datable minerals because of it's highly evolved silica rich composition. However coarse-grained phlogopitic mica separated from a minor less evolved porphyritic part of the intrusion yields an excellent 40Ar- 39Ar plateau age of 136 ± 1 Ma. Rb-Sr whole rock samples give a regression line of age 155 ± 11Ma and an initial 87Sr/ 86Sr ratio of 0.7174 ± 0.0017 (MSWD 280). The scatter may reflect the widespread recrystallization and deformation of the Arnea granite. The Arnea granite is at least Late Jurassic in age and has undergone regional greenschist metamorphism during the Early Cretaceous. Biotite from the Sithonia granitoid yields a plateau age of 43 ± 0.6 Ma. Muscovites from crosscutting pegmatites within the granitoid give slightly saddle-shaped age spectra with minimum ages of 49 Ma and 50 Ma, suggesting Argon-40 excess. Biotite and muscovite from the Ouranopolis granitoid yield plateau ages of 44 ±1.1 Ma and 47 ± 0.7 Ma respectively. It is suggested that this granitoid is coeval and cogenetic with the Sithonia granitoid. Both intrusions are Eocene in age. Rb-Sr whole rock samples from the Sithonia and Ouranopolis granitoids failed to provide any isochrons. This is interpreted to be due to inhomogeneities in these young intrusions. The age data strongly suggest that the Sithonia and Ouranopolis granitoids are unrelated to the Arnea granite. Coupled with geochemical and petrographic data these results clarify the relationships between some of the granitic intrusions and have important regional implications.

The role of transition element adsorption on growth kinetics of the phlogopite mica

The role of transition element adsorption on growth kinetics of the phlogopite mica

A Mossbauer study of the effects of heat treatment on phlogopite micas

Phlogopite samples from different regions were studied by a Mossbauer spectroscopic technique after heat treating them in air at different temperatures. All the samples show a loss of micaceous tetrahedral-octahedral-tetrahedral structure above 1000 degrees C. The oxidation and dehydroxylation processes occurring prior to decomposition were explained with the help of Vedder and Wilkin's propositions. The relaxation patterns observed were the consequence of the superparamagnetic phenomenon due to the presence of fine particles. An attempt was made to calculate particle sizes with the help of Mossbauer parameters.

A Cesium-Selective Ion Sieve Made by Topotactic Leaching of Phlogopite Mica

Ahydrated, sodium phlogopite mica with a c-axis spacing [d(001)] of 12.23 A made by careful low-temperature leaching, showed extremely high selectivity for cesium. This newly discovered cesium ion sieve is useful in the decontamination as well as immobilization of cesium at room temperature through chemical bonding and may find applications in nuclear waste disposal and in decontamination of the environment after accidental releases of nuclear materials.

Atomic force profiling by utilizing contact forces

Atomic force microscopy (AFM) is a new technology currently being developed. Stylus profilometry (SP) was developed earlier. A procedure is reported here which combines features of both SP and AFM. In this approach a stylus scans a sample surface and responds to contact forces. Force values are maintained within the elastic range of the sample, and high resolution is achieved by means of a sensitive tunnel gap feedback circuit control. Initial tests of performance have been conducted over a range of applied loads with tungsten styluses on phlogopite mica samples to image lamellar steps with subnanometer resolution.

The effect of gamma irradiations on etching characteristics of some solid state track recorders

Abstract Solid state nuclear track recorders viz. CR-39 plastic, glass and phlogopite mica pre-exposed to 252Cf fission fragments are irradiated with gamma doses varying from 50 K rad to 50 M rad in order to study the effect of gamma irradiation on etching characteristics of these detectors. It is found that all these detectors are dose rate dependent. CR-39 is found to be more sensitive to gamma rays then any other solid state track recorder.

The reaction between phlogopite and calcium chloride at elevated temperatures

AbstractThe reaction of phlogopite mica and CaCl2·2H2O has been studied within the temperature range 600–1000°C. The reaction products have been studied by chemical analysis, electron microscopy combined with a micro‐analyser, X‐ray diffraction (XRD), thermoanalytical methods and IR spectrometry. The reaction products were milled and the elemental distribution in different particle size fractions was investigated.Potassium can be converted into a water‐soluble form almost completely above the melting point of CaCl2 in this reaction. Iron, Mg and Al do not change into a soluble form. On grinding, Fe and K concentrate in smaller particles while Al prefers larger ones. The formation of several new phases in the reaction can be confirmed by XRD. The mica dehydroxylates above 700°C, which can be detected in the IR spectra, and this may affect the reaction.

Stratigraphic setting and mineralogy of the Arctic volcanogenic massive sulfide prospect, Ambler District, Alaska

The Arctic prospect is the largest (>36 million metric tons) volcanogenic massive sulfide deposit known within the Ambler district in northwestern Alaska. These deposits are hosted by the low-greenschist-grade, Devonian-Mississippian Ambler sequence (informal name) of bimodal, basaltic, and rhyolitic volcanic and volcaniclastic rocks, pelitic, graphitic, and calcareous metasediments. Detailed field mapping, core logging, petrography, X-ray diffractometry, and electron microprobe and whole-rock analyses of hydrothermally altered rocks were used to determine the emplacement history and setting of sulfide deposition. The Arctic prospect contains mineralization at three separate stratigraphic intervals. The largest and most economically important of these three intervals, termed the Main horizon, contains 90 to 95 percent of the known ore reserves. Main horizon minera]ization consists of one to possibly as many as 14 semimassive sulfide lenses within a well-developed, horizontally stratified sequence of alteration types, including pyritic (pyrite-phengite-calcite) and chloritic (chlorite-quartz) alteration, dolomite, phlogopite, albite, talc, and white mica. These alteration types together form a pervasively altered zone ( 3 which is asymmetric to the vent area for the ore fluids.The deposit is high in Cu and barite, has moderate amounts of Zn and Ag, and is low in pyrite, Fe, Pb, and Au. Ternary plots of Cu, Pb, and Zn abundances are very similar to those of massive sulfides formed at divergent plate boundaries, with total metal content at Arctic in the top 1 percent (Cu), 3 percent (Zn), and 4 percent (Pb and Ag) of volcanogenic massive sulfides worldwide. Strong lateral zonation of metals (Cu overlying the vent area, Zn intermediate, and Pb and Ag distal) parallels, but is offset from, an asymmetric distribution of alteration. Most sulfides were deposited not over the vent but on a relatively fiat area and in topographic channels between an elongate vent area pa]eohigh and a carbonaceous mudbearing basin to the northwest.No single volcanic unit can be genetically tied to mineralization. The onset of hydrothermal activity was apparently related to fault activity in the vent area and continued during emplacement of subsequent (postore) rhyolites. Mineralization at Arctic took place along a synvolcanic fault in a tectonically and volcanically active basin within a rifting continental margin, possibly related to an active oceanic rift. Jurassic(?) to Cretaceous, low-greenschist-grade (chlorite-muscovite subfacies) regional metamorphism was essentially isochemical on a macroscopic scale and preserved many primary features of the deposit and its host rocks.

Application of 36/40Ar Versus 39Ar/40Ar Correlation diagrams to the 40Ar/39Ar spectra of phlogopites from Southern African kimberlites

40Ar/39Ar incremental heating analyses were performed on phlogopite mica from the DK‐7 kimberlite pipe in southern Botswana. No age plateau was obtained, as the spectrum yielded a step‐wise increase in age with increasing temperature. The ages appear to be anomalously high, suggesting the presence of excess radiogenic argon components that have been partially released by diffusion during cooling of the kimberlite.The pattern of data points on an 39Ar/40Ar vs. 39Ar/40Ar correlation plot, however, delineates two types of excess argon, one which is radiogenic‐rich, and one with a 40Ar/36Ar ratio of 366. The latter component may reflect the contamination of the kimberlite xenocrysts by fluid originating from an undegassed mantle source.

Volatile contents of phlogopite micas from South African kimberlite

Phlogopite micas from nodules in South African kimberlites were analyzed for major elements with the electron microprobe and for volatile contents by high temperature mass spectrometry. The micas are from primary- (deformed) and secondary- (undeformed) textured grains in perodotite xenoliths, glimmerites, MARID (mica-amphibole-rutile-ilmenite-diopside) suite nodules and a mica megacryst. The major element and volatile contents of micas exhibiting these modes of occurrence overlap to a greater extent than indicated in previous studies. Concentrations of volatile species occupying structurally defined crystallographic sites (H2O, F, Cl) are greater for many of the micas than predicted on the basis of the mica formula, particularly for the glimmerite and MARID suite samples. A correlation exists between micas with tetrahedral and octahedral cation deficiencies and those with excess H2O, F and Cl. Substitution of H+ for tetrahedral and possibly octahedral cations may be responsible for the excess H2O in these micas. Except for one sample, the major element and volatile data for the peridotite, glimmerite and MARID suite micas indicate that they crystallized at oxygen fugacities below the quartz-fayalite-magnetite buffer. F and K2O are in the correct proportion in the micas to provide the source for these elements in alkali basalts, but not in mid-ocean ridge basalts. Kaersutite amphibole is a more likely source of potassium and fluorine in mid-ocean ridge basalts.

Topotactic route to synthesis of novel hydroxylated phases: I. Trioctahedral Micas

AbstractK-depleted phlogopite mica was used as a topotactic precursor and treated with alkali (Li+, K+, , Rb+, Cs+), alkaline-earth (Mg2+, Ca2+, Sr2+, Ba2+) and trivalent (Al3+) cations under hydrothermal conditions of 200°C and 30 MPa pressure. K-, NH4-, Rb- and Cs-aluminosilicate micas were synthesised at 200°C in one day. The synthesis of Cs-aluminosilicate mica, with potential applications in the management of nuclear wastes, has been achieved for the first time by this approach. Ion exchange by Li+, Na+ and alkaline-earth cations under hydrothermal conditions did not produce anhydrous mica phases but resulted in hydrous phases with one or two layers of water molecules between the clay layers. The formation of hydrous phases may be attributed to the high hydration energy of the above cations compared to K+, , RB+ and Cs+. Ion exchange with Al3+ produced a chlorite-like phase because of the hydrolysis of Al3+ under these hydrothermal conditions. These studies are of relevance in the immobilization of wastes where hazardous ions can be fixed in highly stable insoluble phases like mica or chlorite.

Development of machineable bioactive glass ceramics for medical uses

Following a controlled, two-stage phase separation in glasses of the system Na 2O/K 2OMgOAl 2O 3SiO 2CaOP 2O 5F, annealing results in both fluorophlogopite and apetite crystallization. The phlogopite mica crystals make the material machineable, whereas the apatite crystals provide for its bioactivity. Animal tests show direct intergrowth with the bone. Bone cells and blood vessels can be found in the immediate neighbourhood of the implant.

Mechanical degradation of mica during processing with polypropylene

AbstractMechanical degradation of reinforcing fillers during processing is a problem that has been seldom studied due to a lack of particle size determination techniques. Using phlogopite mica as an example, a method allowing a rapid and accurate characterization of flake size and aspect ratio will be described. The influence of several parameters on the mechanical degradation of mica flakes in a mica/polypropylene system has been studied using a laboratory roller blade mixer. The degradation was found to occur in two stages. The first stage takes place immediately after the addition of mica, where the average flake size decreases very rapidly by as much as 20 percent. In the second stage, the particle size remains essentially constant with the time of mixing at low concentrations (2 percent wt); at higher concentrations (40 percent wt) there is a slow reduction in the flake size. The influence of other parameters such as system viscosity, mode of mica addition, silane treatment, and the initial particle size is also discussed.

Dynamic and steady state flow of polypropylene/mica systems

AbstractSix compositions containing commercial polypropylene, PP, and monodispersed, untreated phlogopite mica were prepared. Their rheological properties were determined at 180°C in dynamic and capillary flows. The results are discussed in terms of strain‐induced orientation of mica flakes. Two critical volume fractions were found to affect the flow: ψc defined as a concentration of flakes overlap and ψm as a concentration of maximum packing of freely sedimenting particles. At ψ > ψc yield stress and at ψ > ψm non‐linearity in dynamic response were observed.

The properties of mica‐filled polypropylenes

AbstractWater‐ground Phlogopite micas were classified into narrow particle‐size distributions containing flakes with well‐defined diameters and thicknesses in order to evaluate the influence of particle size and flake aspect ratio on the mechanical properties of mica‐filled polypropylenes, For the purposes of comparison, most of the injection‐molded specimens contained 40 percent (by weight) mica. As expected, the flexural and tensile modulus values increased in proportion to the aspect ratio over the range from 30 to 60 to a maximum of 8 GPa. The measured tensile strengths of the mica‐filled polypropylenes increased substantially as the flake diameter became smaller, but did not correlate with the flake aspect ratio. The attainable properties were frequently dependent upon the method of mixing, and considerable care was necessary to ensure proper dispersion and adequate coupling. Intensive mixing, as in a Gelimat Mixer, may cause in situ delamination and particle‐size reduction of the mica filler particles, leading to a marked increase in tensile strength of the resulting composite. The mica‐filled compounds could be reprocessed many times without significant loss of properties, particularly compounds having mica particles less than 40 μm in diameter. The fracture energies (notched Izod) and the heat‐distortion temperatures were not appreciably influenced by the size or aspect ratios of the mica within this range. Increased fracture toughness could be achieved by reducing the mica concentration or employing a polypropylene copolymer. Guidelines are presented to indicate the preferred characteristics of mica fillers and the influence of mixing conditions on performance.

Phyllosilicates and associated minerals in some Paleozoic stratiform sulfide deposits of southeastern Australia

The Pb-Zn ores of eight of the nine deposits are characterized by one or the other of the phyllosilicate assemblages chlorite + talc + phlogopite-biotite or chlorite + muscovite. The other contains chlorite + phlogopitic trioctahedral mica but no talc. Phyllosilicate mineral chemistry is highly systematic and is related to ore type and ore stratigraphy. In all cases chemical equilibrium between the phyllosilicates has been approached on a small scale. Equilibria were established substantially at the sedimentary-early diagenetic stage. The phyllosilicates were deposited as chemical precipitates in the hydrothermal aprons at the time of sea-floor exhalative activity. Subsequent metamorphism has done little more than perfect crystal structures and coarsen grain size.--Modified journal abstract.