Phlogopite Samples Research Articles

Middle Triassic Cu–Pb–Zn Skarn mineralization in the Wulonggou gold ore field, Eastern Kunlun Orogen, NW China: Insights from phlogopite Ar–Ar and zircon U–Pb dating and Sr–Nd–Pb–Hf isotopes

The skarn is one of the most significant Cu–Pb–Zn mineralization worldwide. The timing of the magmatic-hydrothermal activity is of importance for understanding the Cu–Pb–Zn mineralization process. The Cu–Pb–Zn skarn mineralization has been recognized in the northwestern section of the Wulonggou gold ore field, Eastern Kunlun Orogen (EKLO), NW China. However, no precise geochronological data has been measured for the Cu–Pb–Zn mineralization, and the source of ore-forming materials is also not well studied. In this study, we present new LA-ICPMS U–Pb ages and Sr–Nd–Hf isotopic compositions for granodiorite and diorite in the northern section of the Wulonggou gold ore field, as well as an Ar–Ar age for phlogopite and Pb isotopic compositions for sulfides and intrusions, further to constrain the ages of mineralization and magmatism, and the source of ore-forming materials. Two granodiorite samples yield mean ages of 245 ± 2 to 243 ± 2 Ma and a diorite has a mean age of 245 ± 2 Ma. A phlogopite sample, which is associated with Cu–Pb–Zn mineralization, has been chosen to precisely date the formation of Cu–Pb–Zn ores by Ar–Ar method and yields a well–defined plateau age of 240.4 ± 1.2 Ma. These results indicate that the Cu–Pb–Zn skarn mineralization formed in the Middle Triassic and is closely related to the coeval magmatism. The εHf(t) values of the ore-related granodioritic and dioritic rocks range from −2.8 to +2.5, whereas an un-mineralized granodiorite sample (WHFG–1) shows lower εHf(t) values of –9.3 to –3.4, indicating that these magmatic rocks are derived from the mixing of magma with different proportions of mantle- and crust-components. A mixing model with ∼40–70 % mantle contribution involved in the formation of ore-related granodiorite and diorite was revealed by Sr–Nd–Hf isotopic compositions. Combined with Pb isotopic compositions for sulfides, feldspar, and bulk rocks, we consider a common source for the ore-forming materials and magmatism. In addition, higher εHf(t) and εNd(t) values for ore-related magmatism implicate that mantle-derived melts show a vital role in the Cu–Pb–Zn skarn mineralization process.

SYNERGETIC EFFECTS OF PALLADIUM(II) AND COPPER(II) COMPOUNDS FIXED ON MODIFIED PHLOGOPITE IN THE REACTION WITH SULFUR DIOXIDE

Palladium(II) and cuprum(II) compounds are the basic components of the Wacker-type heterogeneous catalyst for the low-temperature oxidation of carbon monoxide with oxygen. Al2O3, activated carbon and carbon fiber materials are most commonly used as a carrier. In search of new potential natural media, layered aluminosilicate – phlogopite as part of natural phlogopite concentrate was investigated and it was proved that copper-palladium catalysts are formed on acid-modified samples of phlogopite, which provide a high degree of conversion of carbon monoxide, which meets the sanitary and chemical norm of CO in the working area, namely CKCO ≤ 20 mg/m3. Regardless of the nature of the carrier, it was found that the catalytic effect is achieved due to the synergism of palladium(II) and copper(II). A typical situation is when carbon monoxide and sulfur dioxide are simultaneously present in the waste gases of industrial enterprises. In this regard, research on the polyfunctionality of the Pd(II)-Cu(II)/S̅ nanocatalyst is relevant. The kinetics of the interaction of sulfur dioxide with mono- and bimetallic compositions based on compounds of palladium(II), copper(II) and acid-modified natural (Phl) and thermally swollen (TS-Phl) phlogopite were studied. It was established that monometallic compositions М(ІІ)-KBr/X̅Н-TC-Phl-1, М(ІІ) = Cu(ІІ), Pd(ІІ) fixed on acid-modified samples of swollen phlogopite, except for 6Н-TS-Phl-1, do not show protective properties against sulfur dioxide. It has been proven that the bimetallic compositions Pd(II)-Cu(II)-KBr/S̅ (S̅ = 6H-Phl-1; X̅H-TS-Phl-1, X̅ = 1, 2, 3, 6 M HNO3) in the reaction with SO2 reveal a synergistic effect with a coefficient of КS >> 1, which leads to an increase in the time of the protective action of the samples and the amount of absorbed sulfur dioxide. The synergism constant depends on the conditions of acid modification of the carrier and has a maximum value in the case of the bimetallic composition fixed on the carrier 2Н-ТS-Phl-1.

Studying Breakdown and Electrical Hardening of Crystal Materials with Proton Conductivity

The breakdown mechanism of a number of crystal materials with hydrogen bonds is investigated. The contribution of the proton component is considered and it is shown that the formation of an avalanche-streamer discharge is characteristic of multilayer electrical insulation materials. As a result of the breakdown, a discharge channel is formed, along which the protons that form the reverse proton conductivity will move in the opposite direction. In the process of directed translational diffusion of protons, the formation and decay of H3O+ and OH-ions occur, which move in opposite directions, resulting in the formation of a reverse positive streamer from the anode to the cathode. For layered samples of phlogopite, muscovite, and magnesium hydrosilicate, it is shown that for thin samples, a volume charge is formed as a result of a multi-avalanche-streamer discharge that significantly exceeds the volume charge that occurs in thick samples, which is determined by the value of high temperature maximum of the spectrum of thermally stimulated depolarization currents. The field of the volume charge reduces the external electric field, as a result of which the breakdown field strength in thin samples increases. That is, the material is electrically strengthened. Based on the results of the research, a non-destructive method of electrical hardening of electrical insulation materials was developed, which was confirmed by the patent.

Development of Kinetic Parameters for Nitric Acid Leaching of Phlogopite and the Characterization of Solid Products

AbstractSouth Africa is a net importer of fertilizer products, importing all of its potassium, as well as 60–70% of its nitrogen requirements. Thus, domestic prices are impacted significantly by international prices, shipping costs, and exchange rates. Producing these fertilizers locally would be far more economical. Phlogopite, a rich source of potassium, is discarded in large quantities during mining operations; the objective of the present study, therefore, was to determine the acid-leaching characteristics and behavior of phlogopite as a means of releasing potassium. Phlogopite samples were leached with nitric acid (source of nitrogen for fertilizers) at various concentrations, temperatures, and reaction times. The feed phlogopite and leached residue samples corresponding to conversions of 14% (LP1), 44% (LP2), and 100% (LP3) were collected and analyzed using X-ray fluorescence spectroscopy (XRF), X-ray diffractometry (XRD), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer–Emmett–Teller surface area and porosity analysis (BET), thermogravimetric analysis (TGA), and field emission gun-scanning electron microscopy (FEG-SEM). The feed phlogopite was highly crystalline. The absence of defects in the lattice meant that the motion of H+ atoms penetrating into the lattice was restricted, suggesting internal diffusion-controlled leaching. Furthermore, results obtained from the various analytical techniques corroborated each other in terms of the release of cations during leaching. All leaching experiments were conducted batchwise, in a closed system. The gravimetric data from the experiments were used to identify a suitable model which predicts accurately the leaching behavior. The reaction was found to be internal diffusion-controlled, and the D1 model, which represents one-dimensional diffusion through a flat plate, predicts the leaching behavior most accurately. The observed activation energies (Ea) and pre-exponential constants (k0) varied with initial nitric acid concentration ([H+]0).

P59 - Topic: AS08-Treatment/AS08j-Supportive care - Iron overload: MDS IRON ROAD: AN INTERNET-BASED ALGORITHM FOR THE DIAGNOSIS, WORKUP AND MANAGEMENT OF IRON OVERLOAD IN MDS FROM THE CANADIAN CONSORTIUM ON MDS (CCMDS)

Phyllosilicates, such as micas and chlorite, are common rock-forming minerals and often show preferred orientation in deformed rocks. In combination with single-crystal anisotropy, this leads to anisotropy of physical properties in the rock, such as magnetic susceptibility. In order to effectively use the magnetic anisotropy to understand a rock fabric, it is necessary to identify the minerals responsible for the magnetic anisotropy. Techniques have been developed to separate contributions of the ferrimagnetic, antiferromagnetic, paramagnetic, and diamagnetic susceptibilities to the anisotropy of magnetic susceptibility. Because diamagnetic and paramagnetic susceptibility are both linearly dependent on field, separation of the anisotropic contributions requires understanding how the degree of anisotropy of the paramagnetic susceptibility changes as a function of temperature. Note that diamagnetic susceptibility is not dependent on temperature. The increase in paramagnetic anisotropy at low temperature is used to separate the paramagnetic and diamagnetic subfabrics, and can be expressed by the p77 factor. In this study, we determined p77, which is the change in the degree of anisotropy (δk) between room temperature (298 K) and liquid nitrogen temperature (77 K), for a series of micas and chlorite. The paramagnetic susceptibility ellipsoid is highly oblate with the minimum principal susceptibility normal to the silicate layers at both 77 K and RT. The degree of anisotropy δk increases by a factor of approximately 6.3–8.7 for individual samples of muscovite, phlogopite and chlorite on cooling from RT to 77 K and between 11.2 and 12.4 for biotite. A decrease in temperature enhances the paramagnetic anisotropy in a mineral. Biotite exhibits a relatively stronger enhancement due to the onset of magnetic ordering below ~ 100 K. This can have important implications for interpreting low temperature anisotropy in mudstones, mica schists and gneisses.

Mineralogical characteristics of phlogopite from Dupen kamen, Republic of Macedonia

Abstract: In this paper are presented mineralogicalcharacteristicsof phlogopite from Dupen kamen, Republic of Macedonia. Several samples of phlogopite from Dupen kamenwere analysed by XRD, scanning electron microscope (SEM) and Infrared spectroscopy (IR).The use of these three methods showed that they are very useful methods for rapid mineral analysis contributing important analytical information. The results of the X-ray powder pattern, SEM analysis and Infrared spectroscopyenabled straightforward identification of the studied mineral sample as phlogopite.Phlogopite is located in a series ofmarblesthat are part ofthePelagonianmetamorphic complex. It occurs in yellow and gold yellow monoclinic-prismatic crystals. Transparent to translucent with vitreous lustre.Streak is white. Hardnessis 2-2½ while density is 2.7 - 2.9 g/cm3. Cleavage is perfect on {001}.Concentration of Mg is 16.50-17.98%, Al 6.16-7.31%, Si 20.86-26.84% while K from 8.59 to 9.93%. Phlogpite in marble form Dupen kamen is considered that was formed probably by reaction between dolomite and earlier formed potassium feldspar or muscovite. Keywords: phlogopite, (SEM)-scanning electron microscope, (X-ray)-powder diffraction(IR) infrared spectroscopy

Low-temperature magnetic anisotropy in micas and chlorite

Phyllosilicates, such as micas and chlorite, are common rock-forming minerals and often show preferred orientation in deformed rocks. In combination with single-crystal anisotropy, this leads to anisotropy of physical properties in the rock, such as magnetic susceptibility. In order to effectively use the magnetic anisotropy to understand a rock fabric, it is necessary to identify the minerals responsible for the magnetic anisotropy. Techniques have been developed to separate contributions of the ferrimagnetic, antiferromagnetic, paramagnetic, and diamagnetic susceptibilities to the anisotropy of magnetic susceptibility. Because diamagnetic and paramagnetic susceptibility are both linearly dependent on field, separation of the anisotropic contributions requires understanding how the degree of anisotropy of the paramagnetic susceptibility changes as a function of temperature. Note that diamagnetic susceptibility is not dependent on temperature. The increase in paramagnetic anisotropy at low temperature is used to separate the paramagnetic and diamagnetic subfabrics, and can be expressed by the p77 factor. In this study, we determined p77, which is the change in the degree of anisotropy (δk) between room temperature (298K) and liquid nitrogen temperature (77K), for a series of micas and chlorite. The paramagnetic susceptibility ellipsoid is highly oblate with the minimum principal susceptibility normal to the silicate layers at both 77K and RT. The degree of anisotropy δk increases by a factor of approximately 6.3–8.7 for individual samples of muscovite, phlogopite and chlorite on cooling from RT to 77K and between 11.2 and 12.4 for biotite. A decrease in temperature enhances the paramagnetic anisotropy in a mineral. Biotite exhibits a relatively stronger enhancement due to the onset of magnetic ordering below ~100K. This can have important implications for interpreting low temperature anisotropy in mudstones, mica schists and gneisses.

The high-pressure behavior of micas: Vibrational spectra of muscovite, biotite, and phlogopite to 30 GPa

The infrared spectra of natural samples of muscovite, biotite, and phlogopite are characterized to pressures of ~30 GPa, as is the Raman spectrum of muscovite to ~8 GPa. Both far-infrared and mid-infrared data are collected for muscovite, and mid-infrared data for biotite and phlogopite. The response of the hydroxyl vibrations to compression differs markedly between the dioctahedral and trioctahedral micas: the hydrogen bonding in dioctahedral environments increases with pressure, as manifested by shifts to lower frequency of the hydroxyl-stretching vibrations, whereas cation-hydrogen repulsion likely produces shifts to higher frequency of the hydroxyl vibrations within trioctahedral environments. An abrupt decrease in frequency and increase in band width of the hydroxyl-stretching vibration in muscovite is observed at pressures above ~18–20 GPa, implying that the previously documented pressure-induced disordering is associated with the local environment and shifts in location of the hydroxyl unit in this material. The far-infrared vibrations of muscovite indicate that its compressional mechanism changes above 5–8 GPa, as the K-O stretching vibration with a zero-pressure frequency near 112 cm−1 shifts in its pressure dependence from 6.9 cm−1/GPa below this pressure range to 0.78 cm−1/GPa above it. Thus, it appears that the magnitude of interlayer compression is decreased above this pressure, and hence that the compression of muscovite may become less strongly anisotropic. The mid-infrared bands that are primarily produced by vibrations of the tetrahedral layer broaden under pressure in both muscovite and biotite: within biotite, a spectral region that may be associated with higher coordination of tetrahedral cations increases in amplitude above about 25 GPa. The corresponding bands in phlogopite undergo less broadening, and their behavior is fully reversible on decompression.

Substitution mechanisms and implications for the estimate of water fugacity for Ti-rich phlogopite from Mt. Vulture, Potenza, Italy

The crystal chemistry of Ti-rich phlogopite from deposits of the oldest activity (~740 ka) of Mt. Vulture, Potenza, Italy, was investigated to identify the substitution mechanisms in Ti-rich phlogopite and to determine its potential as a geohygrometer. Substitution mechanisms were determined by electron probe microanalysis (EPMA), single-crystal X‑ray diffraction (SCXRD), Mössbauer spectroscopy, and micro-Fourier transform infrared (FTIR) spectroscopy. Magnetite and sanidine from the mica-rich host rocks were also analyzed. Use of the biotite-magnetite-sanidine geohygrometer in these volcanics (essentially trachytic-phonolitic ignimbrites) is exploited. All investigated phlogopite samples consist of the 1M polytype, with 5.3275(2) ≤ a ≤ 5.3635(4) Å, 9.2211(4) ≤ b ≤ 9.2958(8) Å, 10.1211(5) ≤ c ≤ 10.281(1) Å, and 99.980(3) ≤ β ≤ 100.097(2)°. Structure refinements in space group C2/m converged to 2.42 ≤ R 1 ≤ 4.00% and 2.04 ≤ wR 2 ≤ 4.50%. VI Fe 3+ /Fe tot from Mössbauer analyses ranged from 34(1)-89(1)%. The main bands in the OH-stretching region are 3709, 3682, and 3658 cm -1 , and were assigned to 3Mg-OH - -K-OH - , 3Mg-OH - -K-O 2- , and 2MgFe 3+ - OH - -K-O 2- local configurations, respectively. The overall crystal chemical features are compatible with the M3 + -Tschermak substitutions ( VI M 2+ + IV Si 4+ ↔ VI M 3+ + IV Al, with M 3+ = Al,Fe 3+ ), M 3+ -oxy [ VI M 2+ + (OH)- ↔ M 3+ + (O) 2- + ½H 2 ↑] and Ti-oxy substitutions [ VI M 2+ + 2(OH) - → VI Ti 4+ + 2(O) 2- + H 2 ↑]. The magnetite composition varies between Mt 82 Uv 18 and Mt 93 Uv 07 , whereas the proportion of orthoclase with respect to albite plus anorthite is 0.77 ≤ X Or ≤ 0.82. A partly ionic model was used to estimate annite activity, starting from experimentally determined substitutions in phlogopite. The resulting water fugacity was an order of magnitude lower than that calculated using stoichiometry to determine the phlogopite formula. The results are consistent with the occurrence of a well-developed hydrothermal system that altered the magmatic oxygen fugacity conditions at Mt. Vulture.

Zircon U–Pb and phlogopite 40Ar–39Ar age of the Chengchao and Jinshandian skarn Fe deposits, southeast Hubei Province, Middle–Lower Yangtze River Valley metallogenic belt, China

The Chengchao and Jinshandian deposits in the southeast Hubei Province are the two largest skarn Fe deposits in the Middle–Lower Yangtze River Valley metallogenic belt (MLYRVMB), China. They are characterized by NW-striking orebodies that are developed along the contacts between the Late Mesozoic granitoid and Triassic carbonate and clastic rocks. New sensitive high-resolution ion microprobe and laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating of the mineralization-related quartz diorite and granite at Chengchao yield ages of 129 ± 2 and 127 ± 2 Ma, respectively, and those at Jinshandian of 127 ± 2 and 133 ± 1 Ma, respectively. These results are interpreted as the crystallization age of these intrusions. Hydrothermal phlogopite samples from the skarn ores at Chengchao and Jinshandian have the plateau 40Ar–39Ar ages of 132.6 ± 1.4 and 131.6 ± 1.2 Ma, respectively. These results confirm that both intrusions and associated skarn Fe mineralization were formed contemporaneously in the middle Early Cretaceous time. New zircon U–Pb and phlogopite 40Ar–39Ar ages in this study, when combined with available precise geochronological data, demonstrate that there were two discontinuous igneous events, corresponding to two episodes of skarn Fe-bearing mineralization in the southeast Hubei Province: (1) 140–136 Ma diorites and quartz diorites and 141–137 Ma skarn Cu–Fe or Fe–Cu deposits and (2) 133–127 Ma quartz diorites and granites and 133–132 Ma skarn Fe deposits. This scenario is similar to that proposed for the entire MLYRVMB. The intrusions related to skarn Fe deposits show obviously petrological and geochemical differences from those related to skarn Cu–Fe or Fe–Cu deposits. The former are quartz diorite and diorite in petrology and have similar adakitic geochemical signatures and in equilibrium with a garnet-rich residue, whereas the latter are petrologically granite and quartz diorite that are distinguishable from adakitic rocks and in equilibrium with a plagioclase residue. These features indicated that two episodes of magmatism and the formation of skarn Fe-bearing deposits in the southeast Hubei Province, MLYRVMB, might be associated lithosphere thinning induced by asthenosphere upwelling during the Late Mesozoic.

Al-Saturated Phlogopite: Charge Considerations and Crystal Chemistry

AbstractFactors controlling the crystal structure of phlogopite have been widely investigated; but the role of electrostatic interactions, for example, has received much less attention than other factors. The purpose of the present study was to peform a single-crystal refinement of an Al-saturated phlogopite and to use that refinement to supplement crystal-chemical analyses. The phlogopite investigated was from the Rumford quadrangle, Maine, and has the following chemistry: (K0.81Na0.03)Σ=0.84(Mg1.84Fe0.522+Al0.45Mn0.02Ti0.074+)Σ=2.90(Si2.78Al1.22)Σ=4O10(OH1.81,F0.05)Σ=1.86\$\end{document}. The sample is a 1M polytype with C2/m symmetry and cell dimensions of a = 5.3220(4), b = 9.2170(7), c = 10.2511(8) Å, and β = 100.081(1)°. Hydrogen atoms were located and the crystal structure was refined to give parameters R1 = 0.0301 and weighted R2 = 0.0887. The octahedral M1 site was larger than the M2 (average M1—O: 2.079 Å, average M2—O: 2.062 Å) and the electron counts were equal (M1 = M2 = 14.8 e−); based on bond distances, which are more accurate than electron counts in determining occupancy; this result is consistent with a slight preference of Mg for M2 and Fe2+ for M1.Thirty-five Al-rich, natural phlogopite-1M samples that are of (1) high metamorphic grade, and that have (2) total Al contents ⩾ 1.27 atoms per formula unit (a.p.f.u.), (3) Fe3+ contents ⩽ 0.11 a.p.f.u., and (4) Mn contents ⩽0.10 a.p.f.u. along with the newly described phlogopite, exhibited crystal chemical trends related to increasing Al content. Octahedral substitutions of smaller, high-charge cations (i.e. Al) apparently decrease distortions in the octahedral sites and produce longer M2—O4 distances. In addition, VIFe-F avoidance apparently occurs in high Al-content samples, which are generally high in VIFe. The data set also shows that these samples have limited ordering among M sites (Fe2+ in M1 and Al in M2), an increase in β (99.96° to 100.32°) possibly caused by cation ordering and therefore size differences of M1 and M2, and interlayer (A) sites with A—Oouter distances that increase and A—Oinner distances that decrease with increasing Ti content.Computer models were used to simulate electrostatic interactions in phlogopite structures with variable Al concentrations utilizing Pauling’s electrostatic valency principle, which considers first-coordination electrostatic interactions. The model results were compared to the maximum Al concentrations in natural and synthetic phlogopite samples. Model results revealed no indications (e.g. a limit reached or a sudden change occurred) that charge saturation/undersaturation of the apical oxygen atoms at Al contents equal to the maximum in natural and/or synthetic samples causes instability that could not be balanced by bond-length variation. However, a cation of higher charge substituting at M1 (or M2) may result in higher electrostatic repulsions between the other octahedral sites. Thus, the Al3+ content in the octahedral sites may reach a maximum, with Fe2+ for Mg substitutions favored.

57Fe Mössbauer spectroscopy study of phlogopite megacrysts from an evolved carbonatitic kimberlite in the northeastern Oman Mountains

The Fe oxidation degree determined by 57Fe Mossbauer spectroscopy and microprobe was used to characterize fresh and altered phlogopite megacrysts from an evolved carbonatitic kimberlite from northeastern Oman. The Quadrupole splitting (QS) varies between 2.19 and 2.48 mm/s (Fe2 + ) in the fresh phlogopite samples and between 2.40 and 2.47 mm/s in the altered phlogopite samples. The quadrupole splitting of the Fe3 + doublets varies between 0.66 and 0.85 mm/s in the fresh samples. The altered phlogopite samples show three Fe3 + doublets; the first show a quadrupole splitting between 0.97 and 1.13, the second quadrupole splitting varies between 0.24 and 0.46 mm/s and the third varies between − 0.23 and − 0.35 mm/s. The phlogopite was observed to have an average Fe3 + /Fetotal of 35% to 37%, and corresponds to fresh phlogopite. The second one results from the alteration of the first type, and the Fe3 + /Fetotal ranges between 40% and 57%. Tetrahedral Fe3 + ions were confirmed in the altered phlogopite samples. Quantitative Fe site distributions can be obtained from room-temperature Mossbauer data if the different recoilless factors for octahedral Fe2 + and tetrahedral Fe3 + are considered. The observed isomer shifts are consistent with Mossbauer temperatures of 330 K, reported in the literature for tetrahedral and octahedral Fe3 + and Fe2 + in phlogopite. The results are compared to those obtained for natural and synthetic phlogopite from worldwide.

The etching of alpha-recoil tracks in phlogopite

This work uses three phlogopite samples to investigate the etching behavior of alpha-recoil tracks ( α -recoil tracks), which is a key problem in dating procedures. At the initial stage of the etching process, the number of alpha-recoil tracks increased linearly with etching time, then the linearity was interrupted due to the overlapping of alpha-recoil tracks. The slope of the etching line could be similar and also could be different both in the same sample and in different samples. It is shown that the etching time could vary with different contents of U and Th and could not exceed 200 min in 4% HF acid at 25 ± 1 ∘ C in order to get a satisfactory etching line and to calculate the exact density. We propose two valid methods that can accurately determine the position of the sample's surface and may reduce the alpha-recoil track dating errors.

Origin of the Tongshankou porphyry–skarn Cu–Mo deposit, eastern Yangtze craton, Eastern China: geochronological, geochemical, and Sr–Nd–Hf isotopic constraints

The Tongshankou Cu–Mo deposit, located in the westernmost Daye district of the Late Mesozoic Metallogenic Belt along the Middle-Lower reaches of the Yangtze River, eastern China, consists mainly of porphyry and skarn ores hosted in the Tongshankou granodiorite and along the contact with the Lower Triassic marine carbonates, respectively. Sensitive high-resolution ion microprobe zircon U–Pb dating constrains the crystallization of the granodiorite at 140.6 ± 2.4 Ma (1σ). Six molybdenite samples from the porphyry ores yield Re–Os isochron age of 143.8 ± 2.6 Ma (2σ), while a phlogopite sample from the skarn ores yields an 40Ar/39Ar plateau age of 143.0 ± 0.3 Ma and an isochron age of 143.8 ± 0.8 Ma (2σ), indicating an earliest Cretaceous mineralization event. The Tongshankou granodiorite has geochemical features resembling slab-derived adakites, such as high Sr (740–1,300 ppm) and enrichment in light rare earth elements (REE), low Sc (<10 ppm), Y (<13.3 ppm), and depletion in heavy REE (<1.2 ppm Yb), and resultant high Sr/Y (60–92) and La/Yb (26–75) ratios. However, they differ from typical subduction-related adakites by high K, low MgO and Mg#, and radiogenic Sr–Nd–Hf isotopic compositions, with (87Sr/86Sr)t = 0.7062–0.7067, ɛNd(t) = −4.37 to −4.63, (176Hf/177Hf)t = 0.282469–0.282590, and ɛHf(t) = −3.3 to −7.6. The geochemical and isotopic data, coupled with geological analysis, indicate that the Tongshankou granodiorite was most likely generated by partial melting of enriched lithospheric mantle that was previously metasomitized by slab melts related to an ancient subduction system. Magmas derived from such a source could have acquired a high oxidation state, as indicated by the assemblage of quartz–magnetite–titanite–amphibole–Mg-rich biotite in the Tongshankou granodiorite and the compositions of magmatic biotite that fall in the field between the NiNiO and magnetite–hematite buffers in the Fe3+–Fe2+–Mg diagram. Sulfur would have been present as sulfates in such highly oxidized magmas, so that chalcophile elements Cu and Mo were retained as incompatible elements in the melt, contributing to subsequent mineralization. A compilation of existing data reveals that porphyry and porphyry-related Cu–Fe–Au–Mo mineralization from Daye and other districts of the Metallogenic Belt along the Middle-Lower reaches of the Yangtze River took place coevally in the Early Cretaceous and was related to an intracontinental extensional environment, distinctly different from the arc-compressive setting of the Cenozoic age that has been responsible for the emplacement of most porphyry Cu deposits of the Pacific Rim.

UNUSUAL FIBROUS SODIAN TAINIOLITE EPITACTIC ON PHLOGOPITE FROM MARBLE XENOLITHS OF MONT SAINT-HILAIRE, QUEBEC, CANADA

Samples of marble xenoliths, thermally metamorphosed by the igneous rocks of Mont Saint-Hilaire, Quebec, contain idiomorphic plates of phlogopite. These plates were later overgrown and to some extent topotactically replaced by sodian tainiolite, tapering in fragile fibers extending parallel to [100]. The fibers only protrude parallel to [100] of the phlogopite host. Unit-cell parameters of phlogopite and tainiolite, both 1 M polytypes (space group C 2/ m ), are so similar that the phases in the phlogopite –tainiolite intergrowth could not be distinguished by single-crystal X-ray methods. Phlogopite of composition K1.01(Mg1.96Fe0.66Li0.20Mn0.03Ti0.03Al0.04)∑2.92(Si3.28Al0.72)∑4O10[(OH)1.14F0.86]∑2 has the highest Si/Al value of natural samples of phlogopite known to us. The epitactic fibers of tainiolite, of composition K1.01(Mg2.00Fe0.01Li0.59Na0.38)∑2.98(Si3.99Al0.01)∑4O10[F1.79Cl0.01 (OH)0.20]∑2, represent to our knowledge the first example of an extended solid-solution, established by combined electron-microprobe and laser-ablation mass-spectrometry analyses, between tainiolite, K(LiMg2)Si4O10F2, and the recently described mineral shirokshinite, K(NaMg2)Si4O10F2. The latest mineral formed in the observed paragenesis is the zeolite mesolite, accompanied by an unidentified aluminosilicate with Ca/K ≈ 1.

40Ar/39Ar dating for Cenozoic kamafugite from western Qinling in Gansu Province

40Ar/39Ar ages were determined for 6 phlogopite samples from a kamafugite pipe occurring in western Qinling, yielding a time span of 22 to 23 Ma for kamafugite eruption. Together with known geochronological data for the Qinghai-Tibet Plateau (QTP) and its peripheral regions, it is concluded that these Cenozoic potassic-ultrapotassic volcanic rocks are products of post-collisional volcanism. The age of the Cenozoic volcanic rocks in western Qinling partly overlaps that of potassic volcanics from the Gandise belt, reflecting the northward migration of the post-collisional volcanism in QTP. The age data not only confirm the temporal and spatial migration of post-collisional volcanism in QTP, but also provide geochronological constraints on the geodynamic setting at depth and the regimes of the tectonic evolution since Neogene in western Qinling regions.

Development of high precision Rb–Sr phlogopite and biotite geochronology; an alternative to 40Ar/ 39Ar tri-octahedral mica dating

Potassium–Ar and Rb–Sr dating of minerals was fundamental in early efforts to date magmatic and metamorphic processes and paved the way for geochronology to become an important discipline within the earth sciences. Although K–Ar and, in particular, 40Ar/ 39Ar dating of micas is still widely applied, Rb–Sr dating of micas has declined in use, even though numerous studies demonstrated that tri-octahedral mica yields geologically realistic, and more reliable and reproducible Rb–Sr ages than the K–Ar or 40Ar/ 39Ar system. Moreover, a reduction of uncertainties typically reported for Rb–Sr ages (ca. 1%) can now be achieved by application of multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) rubidium isotope dilution measurements (<0.3%). Replicate Rb–Sr biotite ages from the Oslo rift, Norway, yield an external reproducibility of ±0.3% ( n=4) and an analytical error of ±0.8 Ma for individual ages that vary between 276.9 and 275.5 Ma. Conventional thermal ionisation mass spectrometry (TIMS) Rb analysis on the same mineral separates yields ages between 276.1 and 271.7 Ma, three times the spread compared to Rb MC-ICPMS data. Biotite and phlogopite from the central Nagssugtoqidian orogen, West Greenland, yield 40Ar/ 39Ar plateau ages (ca. 1700 Ma) with a spread of ±150 Ma, while Rb–Sr ages on either biotite or phlogopite separates have a much narrower range of ±10 Ma. This comparison of Rb–Sr and 40Ar/ 39Ar ages demonstrates the robustness of the Rb–Sr system in tri-octahedral micas and cautions against the sole use of 40Ar/ 39Ar tri-octahedral mica ages to date geological events. Analytical errors of 16 Ma for these Rb–Sr mica ages determined by TIMS are reduced to <±5 Ma when the Rb concentration is determined by MC-ICPMS. All the TIMS and MC-ICPMS data from the Nagssugtoqidian orogen agree within assigned analytical uncertainties. However, high precision Rb–Sr dating by MC-ICPMS can resolve geological information obscured by TIMS age determinations. TIMS data for seven phlogopite samples form an isochron age of 1645±6 Ma, and thus, no differentiation in age between the different samples can be made. In contrast, MC-ICPMS Rb measurements on the same samples reveal two distinct populations with ages of 1633±3 or 1652±5 Ma. Combining the mica Rb–Sr geochronological data with the well-constrained thermal history of this ancient orogen, we estimate the closure temperature of the Rb–Sr system in 1–2 mm slowly cooled phlogopite crystals, occurring in a matrix of calcite and plagioclase to be ∼435 °C, and at least 50 °C above that of biotite.

Weathering of phlogopite by Bacillus cereus and Acidithiobacillus ferrooxidans.

The purpose of this study was to assess the weathering of finely ground phlogopite, a trioctahedral mica, by placing it in contact with heterotrophic (Bacillus cereus) and acidophilic (Acidithiobacillus ferrooxidans) cultures. X-ray diffraction analyses of the phlogopite sample before and after 24 weeks of contact in B. cereus cultures revealed a decrease in the characteristic peak intensities of phlogopite, indicating destruction of individual structural planes of the mica. No new solid phase products or interlayer structures were detected in B. cereus cultures. Acidithiobacillus ferrooxidans cultures enhanced the chemical dissolution of the mineral and formed partially weathered interlayer structures, where interlayer K was expelled and coupled with the precipitation of K-jarosite [KFe3(SO4)2(OH)6].

Microwave Exfoliation of Vermiculite and Phlogopite

AbstractVermiculites and phlogopites can be exfoliated by chemical and thermal treatment methods to obtain chemically inert, adsorbent, fire-resistant, low-density materials with excellent thermal and acoustic insulation properties. The water content of the clay generally determines the extent of exfoliation and the presence of interstratification is claimed to increase the rate of exfoliation. Considering the strong interaction between water and microwaves, the effect of microwave power on exfoliation characteristics of vermiculites and phlogopites after treatment with water and hydrogen peroxide solution were studied at 600, 950 and 1300 W for microwave exposure times of 10, 20, 30, 60, 120 and 300 s. It was observed that the water molecules in the interlayers of the individual flakes were driven off quickly by microwave treatment causing layer separation in the samples. The vermiculite sample showed 2.8 and 5.6 times, respectively, the exfoliation ratio of the phlogopite samples, in accord with their water contents.

Influence of F content on the composition of Al-rich synthetic phlogopite: Part II. Probing the structural arrangement of aluminum in tetrahedral and octahedral layers by27Al MQMAS and1H/19F-27Al HETCOR and REDOR experiments

The influence of F substitution on the local structure of Al in the tetrahedral and octahedral sheets of synthetic Al-rich phlogopite samples with nominal gel compositions of K(Mg 3-x Al x )[Al 1+x Si 3-x O 10 ] (OH) y (F) 2-y between 0.0 ≤ x ≤ 0.8 and 0.5 ≤ y ≤ 1.8, was studied by 27 Al MAS, MQMAS, { 1 H/ 19 F} → 27 Al 2 D CPMAS (HETCOR) and { 1 H/ 19 F} 27 Al REDOR solid-state NMR and by IR spectroscopy. Changes in intensity of the absorption bands in the OH-stretching region of the IR spectra clearly indicate the incorporation of octahedral Al. Signals from the different phases can be separated in the 27 Al MQMAS NMR spectra by generation of an isotropic dimension in F1. The 27 Al quadrupolar parameters of the four phases were estimated from 27 Al MAS NMR spectra obtained at 104.26 and 208.42 MHz. The quadrupolar coupling constant and isotropic chemical shift increases with increasing Al content for the IV Al site in phlogopite. The VI Al site shows a clear increase of the asymmetry parameter and C Q with increasing F content. The estimated 27 Al signal areas show the lowest amount of impurity phases at high OH contents and a stabilization of VI Al sites by hydroxyl groups. The {1H} → 27 Al 2D CPMAS (HETCOR) NMR experiment at short contact times provides information about site neighborhoods of tetrahedral Al sites and Mg 3 OH as well as Mg 2 AlOH sites, whereas magnetization is only transferred to the octahedral Al sites from hydroxyl groups in Mg 2 AlOH sites. The { 19 F} → 27 Al 2D CPMAS (HETCOR) NMR spectrum is dominated by IV Al sites coupled to the Mg 3 F complex in phlogopite. Resonances from Mg 2 AlF complexes are not observed. Finally, the { 1 H/ 19 F} 27 Al REDOR experiments support the results of the 2D CPMAS (HETCOR) experiments.