Muscovite Samples Research Articles

Thermoluminescence and Kinetic Parameters of Beta Rays Irradiated Egyptian Muscovite.

The current work was going to study the dosimetric properties of Egyptian muscovite minerals irradiated with β-rays using the thermoluminescence technique (TL). The analysis of the TL glow curves was done using the (Tm - Tstop) and the initial rise methods. The deconvolution of the muscovite glow curves was analyzed to have eight superimposed trapping peaks. These trapes were located at 0.72, 0.80, 0.98, 1.09, 1.19, 1.30, 1.50, and 1.59 eV. Muscovite samples were studied at doses up to 330 Gy and exhibited good linearity in relation to beta radiation. The kinetic parameters, sensitivity, and dosimetric characteristics were evaluated. High accuracy was achieved through the repeatability of TL measurements.

New precise age constraints of the Hatu gold belt, west Junggar, NW China: Implications for a 300 Ma magmatic hydrothermal event in post-collisional setting

Abstract A 300 Ma magmatic hydrothermal ore-forming process is identified in the Hatu gold belt in west Junggar, northwest China, based on precise age constraint by secondary ion mass spectroscopy U-Pb dating of hydrothermal zircon and Ar-Ar dating of muscovite. The gold deposits in the Hatu belt (Hatu, Qi-V, Huilvshan, etc.) are similar in geology, with NE- and NW-trending orebodies composed of gold-bearing quartz veins and auriferous altered tuffaceous wall-rocks. Hydrothermal zircon grains separated from gold-bearing quartz veins in the Qi-V gold deposit provide a concordia age of 299.6 Ma and a nearly identical weighted mean 206Pb/238U age of 300 ± 2 Ma. Muscovite samples also from the gold-bearing quartz veins yield 40Ar/39Ar plateau ages of 299.6 ± 1.7 Ma, 299.9 ± 1.8 Ma, and 300.6 ± 1.9 Ma. By comprehensive compilation of geological and geochemical characteristics, tectonic evolution, and geochronology of the gold deposits in the Hatu gold belt, our new precise age data confirm that the gold deposits in the Hatu belt formed simultaneously at ca. 300 Ma, and likely formed during a post-collisional extensional setting by magmatic hydrothermal fluid from cooling magmatic sources.

Metallogenetic epoch and material source of Be-pegmatite differentiated from biotite granite in Mufushan complex

The Mufushan Complex (MFSC) is a significant rare metal mineralized in the central China district and is renowned for its marked economic value of rare metal deposits. While the main rare metal mineralization (RMM) stage in the MFSC relates to the magmatic event of two-mica monzogranite, the mineralization event related to biotite monzogranite remains unknown. To fill this gap, this study focuses on porphyritic biotite monzogranite and adjacent Be-rich pegmatite samples obtained from Changqing Pegmatite No. 1, which is situated in the southeastern part of the MFSC. We subjected these samples to zircon U–Pb dating and Hf isotope analysis using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) and utilized an electron probe X-ray microanalyzer (EPMA) and LA–ICP–MS to examine the major and trace elements present in the muscovite samples. Our findings revealed precise chronological data for the geological history of Changqing, pinpointing the intrusion age of biotite monzogranite to 145.8 ± 1.1 Ma and the crystallization age of Be-rich pegmatite to 144.9 ± 1.1 Ma, firmly situating these events within the Late Jurassic to Early Cretaceous epoch. Regarding isotopic composition, zircon εHf (t) for granite ranged from −9.29 to −5.09, and their corresponding TDM2 ranged from 1788 to 1520 Ma. Similarly, zircon εHf (t) for pegmatite ranged from −7.89 to −5.47, and their corresponding TDM2 ranged from 1699 to 1544 Ma. These isotopic signatures strongly indicate a shared origin for the initial magma of granite and pegmatite. The partial melting of the thick Lengjiaxi Group tasedimentary strata serves as a material source for RMM. The transition from granite to pegmatite exhibits remarkable constancy in the primary components of muscovite. By examining its geochemical attributes, we observed synchronous decreases in FeO, MgO, SiO2, MnO, Be, Rb, and Cs, coupled with synchronous increases in Nb and Ta contents, along with Ta/Nb values. These findings strongly imply that the Changqing biotite monzogranite and Be-rich pegmatite originate from the continuous differentiation and evolution of a common magmatic source, establishing a clear genetic relationship between them. The MFSC has its origins in three distinct stages of magmatic activity and RMM spanning from 160 Ma to 120 Ma. Considering the distribution patterns of similar pegmatite veins, the metallogenic potential observed during the biotite granite stage may serve as an external indicator of marked mineralization within large batholiths.

The Influence of the Closure of the East Paleo‐Tethys Ocean on Southern South China: Evidences from Kinematics and 40Ar/39Ar Geochronology of the Rongxian Ductile Shear Zone in Southeastern Guangxi

AbstractThe Triassic was a crucial period in the tectonic evolution of the South China Block. Research on tectonic deformation during this period provides information on intracontinental orogenic mechanisms in South China. In this study, alongside thermochronological analyses, we examine the macroscopic and microscopic structural features of the Rongxian ductile shear zone, located south of the Darongshan granite in the southeastern part of Guangxi Province, on the southern margin of South China. Sinistral shear is indicated by the characteristics of rotated σ‐type feldspar porphyroclasts, stretching lineations defined by elongated quartz grains and the orientations of quartz c‐axes. LA‐ICP‐MS U‐Pb dating of zircons from two samples of granitic mylonite and one of granite yielded ages of ca. 256 Ma. Furthermore, two samples of granitic mylonite yield muscovite 40Ar/39Ar plateau ages of 249–246 Ma. These results indicate that the Rongxian ductile shear zone resulted from Early Triassic deformation of the late Permian Darongshan granite. This deformation was likely related to the closure of the eastern Paleo‐Tethys Ocean and the subsequent collision of the South China and Indochina blocks, during the early stage of the Indosinian orogeny.

The effect of muscovite on the microstructural evolution and rheology of quartzite in general shear

We conducted general shear experiments on synthetic mixtures of quartz and muscovite aggregates at 800 °C and 1.5 GPa with 0.1 wt% H2O added in the Griggs apparatus to investigate the role of muscovite content on the microstructural evolution and rheological properties of quartz aggregates. Muscovite content varied between 0, 5, 10 and 25% muscovite. Mechanically, the sample strengths decrease with an increase in muscovite content. At high strains muscovite grains align sub-parallel to the shear plane with C′- bands commonly observed in the muscovite-bearing samples. The presence of muscovite has significant influence on the amount of dynamic recrystallization in quartz; at high strains the pure quartz sample completely recrystallizes while only ∼5% of the quartz in the 25% muscovite sample is dynamically recrystallized at similar strains. The presence of muscovite also has a significant influence on crystallographic preferred orientations (CPO) and grain shape preferred orientations (SPO) of quartz at high strains. At high strains, muscovite is interpretated to deform primarily by basal glide and dissolution-precipitation creep. Finally, our mechanical results fit well with rheological mixing models, where we estimate aggregates with 25% muscovite may deform 1–2 orders of magnitude faster than pure quartz aggregates at conditions near the brittle-ductile transition.

Türkiye'deki Muskovit Ocaklarının Elementel Bileşimlerinin Dağılımı

In this study, the contents of thirty-five elements (nine major-minor oxides, twenty-one heavy metals, and five other elements) in eighty-four muscovite samples collected from three commercially operated quarries in Manisa province of Turkey were determined using an energy dispersive X-ray fluorescence (EDXRF) spectrometer. The mean concentrations of SiO2, Al2O3, K2O, MgO, Na2O, Fe2O3, P2O5, TiO2 and CaO analyzed in mica samples were determined as 57.1, 32.8, 8.7, 2.9, 1.4, 0.8, 0.3, 0.3 and 0.3%, respectively. The mean concentrations of Cr, Zr, Mn, Zn, Ni, Co, Pb, Cu, Cd and Hg analyzed as primary toxic trace heavy metals in mica samples were found as 136.2, 124.6, 58.7, 19.2, 14.8, 6.8, 6.3, 2.6, 2.0 and 1.2 mg kg-1, respectively.

Determination of hydrogen concentration in solids by transmission ERDA under nuclear-elastically enhanced recoiling of H by 8 and 9 MeV He

Hydrogen concentrations in thin self-supporting samples of polyphenylene sulfide (PPS) and muscovite have been determined by nuclear-elastic recoil detection analysis (ERDA) of transmission layout. The analysis procedure is based only on the database of stopping power and recoil cross section for material analysis, without using any reference sample of known H content. For the PPS sample, the determined value of H cm−3 is in good agreement with the calculated value of H cm−3. For the muscovite sample, the H concentration originating each from bound water and absorbed water is uniform over the entire thickness of the sample. The determined concentration H cm−3 of the muscovite agrees excellently with the value of H cm−3 obtained from other quantitative analyses typically applied for minerals. The present results demonstrate the capability of accurate determination of H contents in materials and minerals by transmission ERDA.

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.

Age and genesis of the Jinshan gold deposit in the Chinese North Tianshan: A link to large-scale strike–slip shearing events

Large-scale transcrustal strike–slip shearing, orogenic gold deposits, and magmatic Ni–Cu sulfide deposits are prominent features in the Chinese North Tianshan in the northeastern segment of the Tianshan Orogenic Belt. Therelationshipbetween the shearing events and the different styles of mineralization, however, remains ambiguous. Here, structural data, zircon U–Pb–Hf isotopes, bulk-rock geochemistry, muscovite 40Ar/39Ar age dating, and S–Pb isotopes of pyrite from the Jinshan gold deposit are utilized in conjunction with the Pb isotope composition of mineralized mafic–ultramafic rocks of the Huangshandong Ni–Cu sulfide deposit to characterize thelinkbetweenstrike–slipshearing events, andorogenicAuandmagmaticNi–Cu sulfidemineralization. The new zircon U–Pb age results indicate that the host diorite of the gold orebodies formed at ca. 335 Ma. These diorites are enriched in light rare earth elements and large ion lithophile elements (e.g., Ba, U, K, and Pb), but depleted in high field strength elements (e.g., Nb, Ta, and Ti), and have low MgO (4.45–5.17 wt%) contents, Mg# (0.32–0.36), and (La/Yb)CN ratios (4.81–6.90). Based on the lack of ancient crustal basement rocks in the Qoltag Arc, the depleted Nd–Hf isotope composition (εHf(t) = 10.82–15.38; εNd(t) = 6.17–6.67), the juvenile Hf depleted-mantle model ages (350–530 Ma), and the enrichment in Na2O (4.45–5.17 wt%) relative to K2O (1.05–2.20 wt%) of the diorite, it is inferred that the primary magma from which the diorite crystallized was derived from partial melting of metasomatized mantle wedge in an oceanic arc environment. Two muscovite samples separated from an auriferous quartz lode yield 40Ar/39Ar plateau ages of 248.6 ± 0.8 Ma and 249.6 ± 0.9 Ma, representing the age of the gold mineralization event. The similarity in S–Pb isotope composition of pyrite in the Jinshan gold deposit and pyroxenite in the Huangshandong Ni–Cu sulfide deposit suggests that the auriferous fluids required for the formation of the Jinshan gold deposit could represent a mixture of deuteric fluids with limited upper crustal metamorphic fluids from the Kanggur–Huangshan Shear Zone.

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.

Analysis of Uranium, Thorium and Potassium Radioisotope Content of Muscovite Samples from Turkey

Analysis of Uranium, Thorium and Potassium Radioisotope Content of Muscovite Samples from Turkey

Geology and geochronology of the Tokuzbay gold deposit in the Chinese Altai: A case study of collision-related orogenic gold deposits in Central Asian Orogenic Belt

Orogenic gold deposits are one of the most important gold deposits in the world. However, it is controversial that orogenic gold deposits are only generated at subduction-accretion or both in collisional setting. The Altai Orogen experienced a complex subduction accretion–collision history, including magmatism and metamorphism, and forming giant gold deposits. The Tokuzbay gold deposit consists of quartz vein ores and disseminated ores hosted in dikes. The ore bodies are controlled by secondary shear zone of the NW-, NNW-trending Ma’erkakuli Fault and occurred in meta-sediments, i.e., meta-sandstone and phyllite of Devonian Altai Formation, and diorite dikes and granite porphyritic dikes. Wall rock alteration is represented by silicification, pyritization, and muscovite alteration. The ores are restricted by ductile and brittle deformation in the shear zone. Large amounts of native gold and auriferous tellurium were precipitated during a transition from ductile to brittle regime. These characteristics indicate that the Tokuzbay gold deposit is an orogenic gold deposit in the Altai Orogen. The zircon LA-ICP-MS U-Pb ages of the ore-bearing granite porphyritic dikes and diorite dikes are 390 ± 2.5 Ma (MSWD = 0.87) and 378 ± 4 Ma (MSWD = 0.21), respectively, indicating that the magmatic rocks were emplaced during subduction of the Paleo Asian Ocean beneath Altai Orogen. Muscovite samples associated with gold from the auriferous quartz vein and disseminated ores hosted in diorite dikes returned Ar-Ar ages of 292.7 ± 1 Ma (MSWD = 1.3) and 293.9 ± 1.2 Ma (MSWD = 0.7), indicating that gold mineralization in quartz vein is synchronized with disseminated ores. The gold mineralization is restricted to the Early Permian and overlaps with the collision between Altai Orogen and Junggar Plate. The ore-hosting magmatic rocks related to subduction are more than 100 million years earlier than the ore-forming events. Combined with the regional tectonic evolution and the shear characteristics of the gold district, it is well proved that sinistral shearing trigged by the collision of Junggar Plate and Altai Orogen contributed to gold mineralization of the Tokuzbay deposit. Considering the Altai gold deposits in Kazakhstan, it is revealed that Permian collision between Junggar Plate and Altai Orogen triggered a large number of orogenic gold mineralization.

A new understanding of Demala Group complex in Chayu Area, southeastern Qinghai-Tibet Plateau: Evidence from zircon U-Pb and mica 40Ar/39Ar dating

The Chayu area is located at the southeastern margin of the Qinghai-Tibet Plateau. This region was considered to be in the southeastward extension of the Lhasa Block, bounded by Nujiang suture zone in the north and Yarlung Zangbo suture zone in the south. The Demala Group complex, a set of high-grade metamorphic gneisses widely distributed in the Chayu area, is known as the Precambrian metamorphic basement of the Lhasa Block in the area. According to field-based investigations and microstructure analysis, the Demala Group complex is considered to mainly consist of banded biotite plagiogneisses, biotite quartzofeldspathic gneiss, granitic gneiss, amphibolite, mica schist, and quartz schist, with many leucogranite veins. The zircon U-Pb ages of two granitic gneiss samples are 205 ± 1 Ma and 218 ± 1 Ma, respectively, representing the ages of their protoliths. The zircons from two biotite plagiogneisses samples show core-rim structures. The U-Pb ages of the cores are mainly 644–446 Ma, 1213–865 Ma, and 1780–1400 Ma, reflecting the age characteristics of clastic zircons during sedimentation of the original rocks. The U-Pb ages of the rims are from 203 ± 2 Ma to 190 ± 1 Ma, which represent the age of metamorphism. The zircon U-Pb ages of one sample taken from the leucogranite veins that cut through granitic gneiss foliation range from 24 Ma to 22 Ma, interpreted as the age of the anatexis in the Demala Group complex. Biotite and muscovite separates were selected from the granitic gneiss, banded gneiss, and leucogranite veins for ⁴⁰Ar/³⁹Ar dating. The plateau ages of three muscovite samples are 16.56 ± 0.21 Ma, 16.90 ± 0.21 Ma, and 23.40 ± 0.31 Ma, and the plateau ages of four biotite samples are 16.70 ± 0.24 Ma, 16.14 ± 0.19 Ma, 15.88 ± 0.20 Ma, and 14.39 ± 0.20 Ma. The mica Ar-Ar ages can reveal the exhumation and cooling history of the Demala Group complex. Combined with the previous research results of the Demala Group complex, the authors refer that the Demala Group complex should be a set of metamorphic complex. The complex includes not only Precambrian basement metamorphic rock series, but also Paleozoic sedimentary rock and Mesozoic granitic rock. Based on the deformation characteristics, the authors concluded that two stages of the metamorphism and deformation can be revealed in the Demala Group complex since the Mesozoic, namely Late Triassic-Early Jurassic (203–190 Ma) and Oligocene–Miocene (24–14 Ma). The early stage of metamorphism (ranging from 203–190 Ma) was related to the Late Triassic tectono-magmatism in the area. The anatexis and uplifting-exhumation of the later stage (24–14 Ma) were related to the shearing of the Jiali strike-slip fault zone. The Miocene structures are response to the large-scale southeastward escape of crustal materials and block rotation in Southeast Tibet after India-Eurasia collision.

Ar-Ar chronology of the brittle deformation age for the ore-controlling shear zones in the Jiaodong Peninsula and it's constrains on gold mineralization

胶东地区是典型的剪切带型金矿集中区，精确厘定该地区控矿剪切带的活动时代，可为探讨剪切带与金矿成因关系提供关键的时限约束，并且对矿床成矿模式的建立具有至关重要的意义。大量矿床地质证据显示胶东地区控矿剪切带中脆性变形活动对金矿体的形成具有直接影响，但其脆性变形时代尚不十分清楚。据此，本文在详细研究金矿体赋存特征的基础上，系统选取胶东焦家、玲珑、邓格庄、乳山这四个金矿区控矿剪切带断层泥中白云母进行⁴⁰Ar-³⁹Ar年代学研究。定年结果显示，胶东地区焦家剪切带、招平剪切带以及牟乳剪切带的脆性变形时代分别为110.3±1.5Ma、122.8±1.7Ma、119.6±1.2Ma~115.8±1.4Ma。其中焦家剪切带的脆性变形时代明显晚于招平和牟乳剪切带，可能代表了焦家蚀变岩型矿化形成后易遭受后期的构造叠加。综合胶东各金矿区控矿剪切带变形时代、岩体侵位时代、成矿时代及剪切带活动特征和矿体产出特征，本文认为在多期岩体侵位以及控矿剪切带递进变形过程中，剪切带韧性变形区中由高压流体作用产生的同期脆性破裂可形成脉型矿化，如乳山金矿；而在脆-韧性和脆性变形区中发生的大规模脆性变形可导致脉型和蚀变岩型矿化的形成，如玲珑、邓格庄和焦家金矿。但随着剪切带的递进变形和隆升剥蚀，后期多期次的脆性构造变形叠加，可导致多种矿化类型出现在同一构造部位，如焦家金矿中石英脉型和蚀变岩型矿化。;Jiaodong Peninsula is a typical concentration area for shear zone type gold deposits. Accurate determination of the deformation age of ore-controlling shear zones in this area can provide a key time limit for exploring the relationship between shear zones and the genesis of gold deposits, and is of vital significance to the establishment of metallogenic mechanism. A large number of geological evidences show that the formation of gold orebodies is directly controlled by brittle deformation activities of ore-controlling shear zones in Jiaodong Peninsula, but this deformation age is still unclear. Based on detailed study of the occurrence characteristics of orebodies, we systematically selected muscovite samples from fault gouge in Jiaojia, Linglong, Denggezhuang and Rushan gold mining areas for the Ar-Ar chronology study. ⁴⁰Ar/³⁹Ar dating results show that the brittle deformation ages of Jiaojia, Zhaoping and Muru shear zones in Jiaodong Peninsula are 110.3±1.5Ma, 122.8±1.7Ma and 119.6±1.2Ma~115.8±1.4Ma, respectively. Among them, the brittle deformation age of Jiaojia shear zone is obviously later than those of Zhaopin and Muru shear zones, which may represent that the altered rock type mineralization in Jiaojia deposit is susceptible to structural superposition in the later period. Comprehensively comparing shear zone deformation ages, pluton emplacement ages, metallogenic ages, shear zone activities and orebody occurrence characteristics in Jiaodong gold deposits, it is suggested that: (1) The contemporaneous brittle fractures caused by high-pressure fluids in ductile deformation region of shear zones can lead to the formation of vein type mineralization, e.g. Rushan gold deposits; (2) Large-scale brittle deformation in brittle-ductile and brittle region can lead to the formation of vein type and altered rock type mineralization, e.g. Linglong, Denggezhuang and Jiaojia gold deposits. Both stages take place during the process of multi-stage emplacement and progressive deformation of ore-controlling shear zones. However, with the progressive deformation and uplift denudation of shear zones, the superposition of brittle deformation in the late stage may lead to the occurrence of multiple mineralization types in the same structural site, e.g. quartz vein type and altered rock type mineralization in Jiaojia gold deposit.

Strengthening the inhibition effect of sodium silicate on muscovite by electrochemical modification

The properties of sodium silicate and its influence on the floatability of muscovite before and after electrochemical modification were investigated, and the samples of muscovite were characterized by XPS and FITR. On this basis, the action mechanism of electrochemically modified sodium silicate and muscovite flotation behavior under sodium oleate system was discussed. The results show that the electrochemical modification under certain conditions can increase the degree of hydrolysis and ionization of the sodium silicate solution, increase the content of H+ and the effective inhibitory components H2SiO3, SiO32− and HSiO3− in the regulator solution, so that the decrease of pH value and the increase of electrical conductivity of sodium silicate solution. In addition, electrochemical modification can also enhance the inhibition effect of sodium silicate on. The reason for the enhancement is that the adsorption of modified sodium silicate on the surface of muscovite is strengthened, and the number of Al exposed on the surface of muscovite is reduced. In addition, the SiO32− and HSiO3− plasma produced by hydrolysis and ionization compete with the oleate ion for adsorption, which reduces the proportion of Al-OOCR bonds on the surface of the muscovite, and finally makes the inhibition performance of the sodium silicate on the muscovite improved significantly. The research has some reference significance for improving the separation effect of muscovite.

Thermoluminescence of β-particle induced Bern-4M muscovite

Bern-4M muscovite from Switzerland was investigated via X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and thermoluminescence (TL). Muscovite has the theoretical formula KAl2(AlSi3O10)(FOH)2, or (KF)2(Al2O3)3(SiO2)6(H2O). Chemical analysis of the muscovite sample was carried out using EDS for major oxides. The results indicate that muscovite includes oxygen (59.1%), silicon (18.86%), and aluminum (15.22%) as major elements and contains low concentrations of potassium, magnesium, and sodium. In standard muscovites potassium use to be 10% and oxygen 47%, probably the sample was strongly lixiviated before the analysis. The thermoluminescence spectrum exhibits a wide glow peak located at 250 °C with a shoulder peak at high temperature region. Trap depth and frequency factor were calculated using Hoogenstraaten's method and found to be 1.16 eV and 1.4 × 1010 s−1, respectively. Reproducibility test indicated that the values within ±5% were obtained after 15 cycles. The storage time experiments were performed for different time periods up to 1 week for dark fading.

Nanosized Authigenic Magnetite and Hematite Particles in Mature‐Paleosol Phyllosilicates: New Evidence for a Magnetic Enhancement Mechanism in Loess Sequences of China

AbstractMagnetic enhancement of Chinese loess‐paleosol sequences has been used extensively as a proxy for East Asian summer monsoon variations. However, the pedogenic magnetic particles contributing to this magnetic enhancement are difficult to extract, so it is not clear how they formed. In this study, we reveal pedogenic magnetite and hematite using electron microscopy, synchrotron radiation X‐ray diffraction, and rock magnetic methods. First‐order reversal curves indicate that superparamagnetic/single domain/vortex state magnetic properties dominated both loess and paleosol samples. Samples of muscovite and chlorite, which are paramagnetic, have weak spontaneous magnetization. The 1‐ to 10‐μm‐sized fraction of host silicatesis responsible for most of the magnetic enhancement of paleosols. In the paleosol fraction, we found weathered phyllosilicates (muscovite/chlorite), including many elongated submicron to a few microns authigenic magnetite and hematite particles between layers; however, few such interlayer particles were found in phyllosilicates of the loess fraction. The concentration of magnetite/hematite particles within paleosol muscovite/chlorite grains and in aggregates of phyllosilicate fragments is much higher than that of the submicron iron oxides found on silicate surfaces. Interlayer magnetite particles are dominantly prism‐shaped with aspect ratios >~4. The authigenic magnetite must be mainly responsible for the spontaneous magnetization of the muscovites and chlorites and the paleosol magnetic properties. The protective silicates account for the low extraction efficiency and also the near absence of surface oxidation of pedogenic magnetite. Based on our results, we suggest that magnetite/hematite in weathered phyllosilicates contribute significantly to the magnetic enhancement of mature paleosols.

The rational use of mica as a priority for the mining industry of Irkutsk region

Mica is one of the most widespread minerals. Muscovite and phlogopite whose large reserves are located in Irkutsk region have various industrial applications. Due to the crisis, a large amount of mica remained unclaimed. There are mining dumps of raw materials and production waste. The use of mica and the disposal of industrial waste are urgent problems. One of the ways to solve them is to produce mica-based composite materials. The use of such materials will improve technical and economic indicators of production processes and contribute to the development of low-waste and non-waste technologies, protection of the environment. The article aims to establish fundamental laws of production of mica-based composite materials. The article provides recommendations on production technologies. Samples of muscovite, phlogopite mica, mine scraps and mica waste were studied. The methods of physicochemical analysis were used to study the samples. Thermodynamic and quantum chemical calculations were made. Based on the experimental studies and scientific generalizations, the theoretical foundations of the production technology for temperature-resistant mica-based materials and effective heating elements based on mica composite materials were developed. They are based on the integrated and rational use of mineral raw materials.

Geology and Geochronology of the Maozaishan Sn Deposit, Hunan Province: Constraints from Zircon U–Pb and Muscovite Ar–Ar Dating

The Maozaishan Sn deposit, located south of the Dayishan ore field in the Nanling Range, is a newly explored greisen-type Sn deposit. Two muscovite samples from tin-bearing ores yielded 40Ar/39Ar plateau ages of 154.7 ± 1.1 Ma (Mean standard weighted deviation (MSWD) = 0.48) and 152.6 ± 0.7 Ma (MSWD = 0.25), respectively. Zircon U–Pb dating result of fine-grained biotite monzogranite in the Maozaishan mining area shows that these zircon grains can be subdivided into two populations, with ages of 154.2 ± 2.0 Ma (MSWD = 0.51) and 159.6 ± 1.9 Ma (MSWD = 0.09), respectively, indicating that the monzogranite is formed by a multi-stage magmatic event. It is indicated that formation of the Maozaishan Sn deposit is closely related to the Middle Jurassic granitic magmatism. Based on the trace element compositions of zircon grains, the calculated magma temperatures and oxygen fugacity (log(fO2)) values range from 638 °C to 754 °C (mean = 704 °C) and from −18.9 to −15.8 (mean = −17.1), respectively. In addition, these intrusive rocks in the Dayishan ore field belong to highly fractionated granites and are characterized by low oxygen fugacity and crust–mantle origin, which are consistent to these tin-bearing granites in the Nanling Range and in favor of the Sn mineralization.

Ages and genesis of W-Sn and Ta-Nb-Sn-W mineralization associated with the Limu granite complex, Guangxi, China

The Limu granite complex spans three granitic stages, forming the largest Indosinian Ta–Nb–Sn–W ore field in South China. There includes quartz-vein WSn (type-1) mineralization associated with second-stage granite, as well as Ta–Nb–Sn–W mineralization associated with third-stage granite including quartz–feldspar-vein (type-2), pegmatite dike (type-3), and disseminated (type-4) mineralization. To elucidate the magmatic evolution and genesis of these types of mineralization, we obtained muscovite 40Ar/39Ar ages, zircon LA–ICP–MS UPb ages, and LuHf and Nd isotopic, trace-element, and geochemical compositions of the Limu granite complex. The Limu granites are peraluminous (A/CNK > 1.1) with negative ɛNd(t) values (−8.5 to −9.7) and TDM2 ages of 1780–1685 Ma, suggesting that they were derived mainly from partial melting of Paleoproterozoic basement. Remnants of Caledonian zircons (429.4 ± 5.6 Ma) indicate Caledonian granite melting in the source. Low Zr/Hf (<13) and Nb/Ta (<5) ratios and the tetrad effect in rare-earth-element patterns of the second- and third-stage granites indicate that the magmas were highly evolved and underwent late-stage exsolution of fluids. Muscovite from type-1 ore yielded an 40Ar/39Ar age of 213.7 ± 1.1 Ma. Two hydrothermal zircons and two muscovite samples from third-stage granite containing type-4 mineralization yielded similar UPb ages of ca. 203 Ma and 40Ar/39Ar ages of ca. 208 Ma, respectively. We conclude that type-1 mineralization was formed at ca. 214 Ma and was hydrothermal in origin, whereas Ta–Nb–Sn–W mineralization was formed at ca. 208–203 Ma and was of magmatic-hydrothermal origin. Mantle-derived heat from a long-lived magma chamber was essential for the high-temperature anatexis that formed Ta–Nb–Sn–W-rich melts, with the combined effects of crustal thickening during the Indosinian Orogeny, local delamination, asthenospheric upwelling, and deep faulting facilitating the continuous supply of heat.