Chlorite Group Minerals Research Articles

Mineralogy and geochemistry of altered Emeishan basaltic volcaniclastics with respect to their critical element mineralization

Research on the mineralogical and geochemical characteristics of altered end-Guadalupian basaltic volcanoclastic rocks can increase the understanding of the alteration history of the overlying stratabound Nb(Ta)-Zr(Hf)-REY-Ga mineralization in the Late Permian coal-bearing sequences. In this paper, based on petrographic observations in addition to XRD, XRF, and ICP-MS analyses, we present and discuss in detail the relationships between primary and secondary minerals and outline the distribution of major and trace element chemistry in the middle/Late Permian basaltic volcaniclastics from the ELIP's zone, western Guizhou, southwest China. The primary clastic suite consists of plagioclase-group minerals, clinopyroxenes, feldspathoids, spinels, and basaltic glasses. Fragments of mafic and, less commonly, felsic and alkaline volcanic rocks are minor components of the studied samples. The alteration products are represented by various chlorite-group minerals (including abundant chamosite), quartz, calcite, albite, analcime, barite, and pyrite, along with relatively minor amounts of titanite, sanidine, magnetite, rutile, and copiapite. The mineralogical and geochemical characteristics of the studied volcaniclastics provide strong evidence correlating them with the high-Ti basalt group, widely distributed within the inner Emeishan large igneous province (ELIP) and coeval rift zone of the middle and outer ELIP. After deposition, the volcaniclastics reacted with complex solutions including heated meteoric waters and were periodically infiltrated by seawater and ascending hydrothermal fluids. As a result, the primary volcanic rocks partly lost alkalis, titanium, silica, and most of the trace elements. These elements, especially the incompatible elements, were probably enriched in the overlying tuffaceous and coal-bearing sequences in the middle and outer ELIP.

Mineralogy and enrichment of critical elements (Li and Nb-Ta-Zr-Hf-Ga) in the Pennsylvanian coals from the Antaibao Surface Mine, Shanxi Province, China: derivation of pyroclastics and sediment-source regions

As a critical element, lithium plays an important role in a wide range of modern industries and in particular, battery storage and new energy technologies. Lithium in coal has attracted much attention in recent years because some coals are highly enriched in this element and consequently their corresponding coal combustion products may provide anm alternative source for this element. Previous studies showed that highly enriched Li in coals is generally associated with chlorite group minerals and in most cases attributed to the action of hydrothermal solutions. This paper provides mineralogical and geochemical data on the No. 9 Coal, the major minable coal from the Antaibao Surface Mine, Ningwu Coalfield, Shanxi Province, northern China, and focuses on the modes of occurrence and source of Li in this coal. The No. 9 Coal is a medium ash, medium sulfur, high volatile bituminous coal. The mineralogy of the No. 9 Coal is dominated by kaolinite, calcite, and pyrite, with minor amounts of anatase, rutile, goyazite, quartz, illite, boehmite, and bassanite, and traces of orthoclase, zircon and galena. The studied coal samples are characterized by high contents of Al2O3 (39.80% on average) in comparison with average Chinese coals, and high concentrations of Li, Ga, Se, Zr, Nb, Ta and Th compared with world hard coals. In addition to Li and Al, the critical elements Nb, Ta, Zr, Hf, and Ga in this coal also have a potential economic significance. The geochemical indicators (high Al2O3/TiO2, low Nb/Yb ratios and the specific rare earth element distribution patterns) and the mineral compositions (e.g., very low content of boehmite) indicate that the mineral matter in most coal benches and host rocks is dominantly derived from the Precambrian calc-alkaline granites of the Yinshan and northern Trans North China Orogens, and possibly from the bauxite of the Benxi Formation. Additionally, the geochemical and mineralogical characteristics of the intra-seam partings and some coal benches (quartz-free, kaolinite-dominated mineralogy, high Al2O3/TiO2 and Nb/Yb values) indicate that they were derived from an alkaline intermediate-felsic volcanic source. The highly enriched Li in the studied samples mainly occurs in kaolinite and is attributed to the input of material from sediment-source regions, rather than hydrothermal fluids. In addition, interaction of terrestrial and marine waters may have promoted the Li enrichment process in the partings.

Enrichment of Magnesite and Usage to Obtain Magnesium Fluoride

Magnesium is the sixth most abundant element, constituting 2% of the total mass of the earth's crust. It is a metal that exists only in chemical compounds, and generally exits in carbonate and oxide forms. The most important mineral forms are magnesite (MgCO3), dolomite (MgCO3.CaCO3) and carnallite (KCl.MgCl2-6H2O). Magnesium metal, which is obtained from different sources by various methods, has an important place in the industry. There are approximately 16 billion tons of dolomite and 110 million tons of magnesite reserves in Turkey. The aim of this study is to investigate the use of idle magnesium clay raw material (in Eskişehir) for the production of magnesium fluoride and thus to propose a chemical process for the relevant raw material to the industry. For the experiments, a 10 kg sample was taken and after the whole was ground to 75 µm size, XRF, XRD and DTA analyzes were performed. As a result of XRF analysis, it was determined that it contains 44.28% MgO. As a result of XRD analysis, it was determined that it is magnesite with MgCO3 structure, and also it has dolomite and chlorite group mineral structures. As a result of the experiments, MgF2 was obtained by using HF from the relevant raw material, and it was determined that the efficiency was higher in the experiments performed with raw magnesite.

Solubility product constants for natural dolomite (0–200 °C) through a groundwater-based approach using the USGS produced water database

The calculation of a reliable temperature dependent dolomite solubility product constant (K_sp−dol) has been the subject of much research over the last 70 years. This study evaluates log₁₀(^aCa²⁺/^aMg²⁺) values using PHREEQC (Pitzer approach) for a screened subset (n = 11,480) of formation waters in the U.S. Geological Survey National Produced Waters Geochemical Database V2 (PWGD), an extensive inventory of 165,960 formational waters from a range of sedimentary lithologies in North America up to 6.6 km depth (Blondes and others, 2016). Through extensive ground truthing against datasets sourced from Texas Gulf Coast basin and the Mississippi Salt Dome basin we establish both the geochemical data from the PWGD and a new geothermal model of the US that is used to determine temperatures at-formation-depth to be reliable data sources. The vast majority (90%) of PWGD samples have log₁₀(^aCa²⁺/^aMg²⁺)-temperature values that are interpreted to be indicative of calcite-dolomite equilibrium and buffering by the bulk mineral solubilities. Using statistical models with different parameterisations (different Maier-Kelly formulas, mixed-effects models with various random effects and linear models) log₁₀(^aCa²⁺/^aMg²⁺) values are regressed against the estimated at-formation-depth temperatures to determine K_sp−dol between 0 and 200 °C. This process relies on the well constrained calcite solubility product constant (K_sp−cal). Local effects that modify log₁₀(^aCa²⁺/^aMg²⁺) values are evaluated through the addition of random effects to the mixed model which both improves the statistical reliability of the K_sp−dol model and enables the determination of K_sp−dol values for local dolomite phases. The nature of these local effects is open to interpretation, but we suggest the primary influence on log₁₀(^aCa²⁺/^aMg²⁺) values is the stoichiometry of the dolomite phase systematically modifying log₁₀(^aCa²⁺/^aMg²⁺) values. We discount the influence on log₁₀(^aCa²⁺/^aMg²⁺) values of dolomite order, the solution ionic strength, equilibration with anhydrite and chlorite group minerals, illitization of smectite and albitization of feldspar. For the dolomite solubility equation; the mixed-effects model (model J23) chosen as most representative yields a pK_sp−dol (log₁₀K_sp−dol); We determine pK_sp°−dol to be −17.27 ± 0.35 (25 °C, 1 atm) which is close to prior estimates, including the most recent experimental value reported by Bénézeth and others, 2018 (pKs_p°−dol = −17.19 ± 0.3) validating the groundwater regression analysis approach of this study.

Comparative Study on the Origin and Characteristics of Chinese (Manas) and Russian (East Sayan) Green Nephrites

Green nephrites are widely pursued for their mild texture and vivid color. In recent years, many Russian green nephrites appeared in China (the world’s largest nephrite market) and competed with the Chinese Manas green nephrites, which are traditionally highly valued. In this study, we compared the appearance, mineralogy and geochemical features (with EPMA and LA-ICP-MS) of Chinese (Manas) and Russian (East Sayan) green nephrites to objectively characterize and distinguish between these two nephrites. Chinese (Manas) and Russian (East Sayan) green nephrites are mined from serpentinized ultramafic units in the northern Tian Shan and East Sayan orogen, respectively. In terms of appearance, the Manas green nephrites are slightly bluish or grayish, whilst their East Sayan counterparts are brighter (duck-egg cyan). The Manas nephrites commonly have a caramel color, crumple structure, characteristic white globules and sinuous veins, green stains and yellow–green veins, together with a local fibrous structure. The East Sayan green nephrites are more transparent, with a gentler fine texture, uniform color, many black spots and a few green spots. Some green nephrites from the Arahushun mine of East Sayan have an ice-like appearance. Microscopic petrography and EPMA analysis indicate that both the Manas and East Sayan green nephrites comprise mainly tremolite with minor actinolite. Minor minerals in the Manas samples include chromite, chlorite-group minerals, and uvarovite; whilst those in the East Sayan samples include actinolite, chromite, chlorite-group minerals, and bornite. Bornite is not found in any other sources of green nephrite, and thus is characteristic of Russian (East Sayan) green nephrites. LA-ICP-MS trace element data in their amphiboles and Single-Factor Analysis of Variance (ANOVA) results suggest that the differences in Cr, Zn, Y, Ba, and Sr contents and values of δEu, Eu/Sm, (La/Yb)N, (La/Sm)N, (Gd/Yb)N, ∑HREE, ∑LREE/∑HREE between the two nephrites are present, and can be used as their origin trace.

Marathonite, Pd25Ge9, and palladogermanide, Pd2Ge, two new platinum-group minerals from the Marathon deposit, Coldwell Complex, Ontario, Canada: Descriptions, crystal-chemical considerations, and genetic implications

ABSTRACTMarathonite, Pd25Ge9, and palladogermanide, Pd2Ge, are two new platinum-group minerals discovered in the Marathon deposit, Coldwell Complex, Ontario, Canada. Marathonite is trigonal, space group P3, with a 7.391(1), c 10.477(2) Å, V 495.6(1) Å3, Z = 1. The six strongest lines of the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 2.436(10)(014,104,120,210), 2.374(29)(023,203,121,211), 2.148(100)(114,030), 1.759(10)(025,205,131,311), 1.3605(13)(233,323,036,306), and 1.2395(14)(144,414,330). Associated minerals include: vysotskite, Au-Ag alloy, isoferroplatinum, Ge-bearing keithconnite, majakite, coldwellite, ferhodsite-series minerals (cuprorhodsite-ferhodsite), kotulskite and mertieite-II, the base-metal sulfides, chalcopyrite, bornite, millerite and Rh-bearing pentlandite, oberthürite and torryweiserite, and silicates including a clinoamphibole and a Fe-rich chlorite-group mineral. Rounded, elongated grains of marathonite are up to 33 × 48 μm. Marathonite is white, but pinkish brown compared to palladogermanide and bornite. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths are: 40.8 (470 nm), 44.1 (546 nm), 45.3 (589 nm), and 47.4 (650 nm). The calculated density is 10.933 g/cm3, determined using the empirical formula and the unit-cell parameters from the refined crystal structure. The average result (n = 19) using energy-dispersive spectrometry is: Si 0.11, S 0.39, Cu 2.32, Ge 18.46, Pd 77.83, Pt 1.10, total 100.22 wt.%, corresponding to the empirical formula (based on 34 apfu): (Pd23.82Cu1.19Pt0.18)Σ25.19(Ge8.28S0.40Si0.13)∑8.81 and the simplified formula is Pd25Ge9. The name is for the town of Marathon, Ontario, Canada, after which the Marathon deposit (Coldwell complex) is named.Results from electron backscattered diffraction show that palladogermanide is isostructural with synthetic Pd2Ge. Based on this, palladogermanide is considered to be hexagonal, space group , with a 6.712(1), c 3.408(1) Å, V 133.0(1), Z = 3. The seven strongest lines of the X-ray powder-diffraction pattern calculated for the synthetic analogue [d in Å (I)(hkl)] are: 2.392(100)(111), 2.211(58)(201), 2.197(43)(210), 1.937(34)(300), 1.846(16)(211), 1.7037(16)(002), and 1.2418(18)(321). Associated minerals are the same as for marathonite. Palladogermanide occurs as an angular, anhedral grain measuring 29 × 35 μm. It is white, but grayish-white when compared to marathonite, bornite, and chalcopyrite. Compared to zvyagintsevite, palladogermanide is a dull gray. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths for Ro and Ro' are: 46.8, 53.4 (470 nm), 49.5, 55.4 (546 nm), 50.1, 55.7 (589 nm), and 51.2, 56.5 (650 nm). The calculated density is 10.74 g/cm3, determined using the empirical formula and the unit-cell parameters from synthetic Pd2Ge. The average result (n = 14) using wavelength-dispersive spectrometry is: Si 0.04, Fe 0.14, Cu 0.06, Ge 25.21, Te 0.30, Pd 73.10, Pt 0.95, Pb 0.08, total 99.88 wt.%, corresponding (based on 3 apfu) to: (Pd1.97Pt0.01Fe0.01)Σ1.99(Ge1.00Te0.01)∑1.01 or ideally, Pd2Ge. The name is for its chemistry and relationship to palladosilicide.The crystal structure of marathonite was solved by single-crystal X-ray diffraction methods (R = 7.55, wR2 = 19.96 %). It is based on two basic modules, one ordered and one disordered, that alternate along [001]. The ordered module, ∼7.6 Å in thickness, is based on a simple Pd4Ge3 unit cross-linked by Pd atoms to form a six-membered trigonal ring that in turn gives rise to a layered module containing fully occupied Pd and Ge sites. This alternates along [001] with a highly disordered module, ∼3 Å in thickness, composed of a number of partially occupied Pd and Ge sites. The combination of sites in the ordered and disordered modules give the stoichiometric formula Pd25Ge9.The observed paragenetic sequence is: bornite → marathonite → palladogermanide. Phase equilibria studies in the Pd-Ge system show Pd25Ge9 (marathonite) to be stable over the range of 550–970 °C and that Pd2Ge (palladogermanide) is stable down to 200 °C. Both minerals are observed in an assemblage of clinoamphibole, a Fe-rich, chlorite-group mineral, and fragmented chalcopyrite, suggesting physical or chemical alteration, possibly both. Palladogermanide is also found associated with a magnetite of near end-member composition, potentially indicating a relative increase in fO2. Both minerals are considered to have developed at temperatures of 500–600 °C, under conditions of low fS2 and fO2, given the requirements needed to fractionate, concentrate, and form minerals with Ge-dominant chemistries.

First Report on the Geologic Occurrence of Natural Na–A Zeolite and Associated Minerals in Cretaceous Mudstones of the Paja Formation of Vélez (Santander), Colombia

This study reports for the first time the geologic occurrence of natural zeolite A and associated minerals in mudstones from the Cretaceous Paja Formation in the urban area of the municipality of Vélez (Santander), Colombia. These rocks are mainly composed of quartz, muscovite, pyrophyllite, kaolinite and chlorite group minerals, framboidal and cubic pyrite, as well as marcasite, with minor feldspar, sulphates, and phosphates. Total organic carbon (TOC), total sulfur (TS), and millimeter fragments of algae are high, whereas few centimeters and not biodiverse small ammonite fossils, and other allochemical components are subordinated. Na–A zeolite and associated mineral phases as sodalite occur just beside the interparticle micropores (honeycomb from framboidal, cube molds, and amorphous cavities). It is facilitated by petrophysical properties alterations, due to processes of high diagenesis, temperatures up to 80–100 °C, with weathering contributions, which increase the porosity and permeability, as well as the transmissivity (fluid flow), allowing the geochemistry remobilization and/or recrystallization of pre-existing silica, muscovite, kaolinite minerals group, salts, carbonates, oxides and peroxides. X-ray diffraction analyses reveal the mineral composition of the mudstones and scanning electron micrographs show the typical cubic morphology of Na–A zeolite of approximately 0.45 mμ in particle size. Our data show that the sequence of the transformation of phases is: Poorly crystalline aluminosilicate → sodalite → Na–A zeolite. A literature review shows that this is an unusual example of the occurrence of natural zeolites in sedimentary marine rocks recognized around the world.

EVOLUÇÃO MAGMÁTICA DA INTRUSÃO BÁSICA NO POÇO 1UN30 E SUA INTERAÇÃO COM O ARENITO ENCAIXANTE, NA PORÇÃO NORTE DA BACIA DO PARNAÍBA (N E NE DO BRASIL)

Este trabalho desenvolveu-se através dos resultados das análises petrográficas, químicas e litogeoquímicas do testemunho do poço 1UN30, perfurado na Bacia do Parnaíba. A petrografia aponta: a rocha ígnea como de textura glomeroporfirítica e mineralogia essencial de plagioclásio e piroxênio, com olivina e minerais opacos acessórios; o arenito como quartzo arenito a subarcóseo com arcabouço de quartzo, K-feldspato e minerais opacos, e interstícios preenchidos por tremolita e argilominerais. A rocha ígnea, pela litogeoquímica, é um basalto toleítico intraplaca. Análises em MEV no arenito apontaram os argilominerais como do grupo ilita-esmectita e identificaram minerais do grupo da clorita. Pelas texturas e química dos grãos, identifica-se duas fases de formação de plagioclásio. Uma mais cálcica ocorre como núcleos corroídos, zonados e de textura peneira grossa. A outra consiste nas bordas dos núcleos corroídos ou em cristais isolados, zonados e com textura peneira fina. Conclui-se que a rocha foi formada por quatro eventos evolutivos: primeira fase de cristalização; descompressão rápida, durante a ascensão da câmera magmática; mistura com magma mais quente, rico em cálcio; e segunda fase de cristalização. A interação com o magma formou tremolita e argilominerais no arenito encaixante, com preservação do aspecto sedimentar prévio, em um processo denominado diagênese de contato.

New insights into nanomineralogy and geochemistry of Ni-laterite ores from central Greece (Larymna and Evia deposits)

Nickeliferous laterite ores from two typical central Greece deposits (Larymna and Evia), currently used in the LARCO GMMSA smelting plant to produce ferronickel, were characterized using a combination of diffraction, microscopic, and analytical techniques. X-ray diffraction patterns of various fractions, with emphasis to the clayey material (<2 μm), after glycolation and heating at 550 °C, indicated that both materials contain crystalline Fe3+ oxide (hematite) and chlorite-group phyllosilicates, whereas the Evia sample contains additional illite. Transmission electron microscopy investigations revealed that the LARCO laterite ores consist of complex nanoscale aggregates of the above-mentioned phases. Different Ni-bearing Mg-Fe-phyllosilicates (mainly chlorite-group minerals), occur in mixture with hematite. Nickel is present in all examined phases, and therefore the separation of pure Ni-phases, by physical or chemical methods, is practically unfeasible. Trace element bulk analyses showed that there no significant differences, with regarding to Ni content concentrations (ca. 0.6–0.7 wt.%), between the initial ore and the clay fraction, for both the Larymna and Evia laterites (ca. 30% and 26% wt.% enrichment respectively). However, the Larymna ore contains double quantities of Co and it is enriched in rare earths compared to Evia (ΣREE = 774 ppm and 76 ppm respectively), while Sc concentrations are comparable in both mining areas (64 ppm and 42 ppm respectively). Discrimination diagrams (e.g. Th/Sc vs. Zr/Sc and Ce/Ce* vs. Eu/Eu*) showed that LARCO laterite Ni-ores do not exclusively originate in ultrabasic -ophiolitic- rocks as previously considered.

Radiation Damage Effects in Chlorite Investigated Using Microfocus Synchrotron Techniques

A detailed understanding of the mechanisms and effects of radiation damage in phyllosilicate minerals is a necessary component of the evaluation of the safety case for a deep geological disposal facility (GDF) for radioactive waste. Structural and chemical changes induced by α-particle damage will affect the performance of these minerals as reactive barrier materials (both in the near and far-field) over time scales relevant to GDF integrity. In this study, two examples of chlorite group minerals have been irradiated at α-particle doses comparable to those predicted to be experienced by the clay buffer material surrounding high-level radioactive waste canisters. Crystallographic aberrations induced by the focused 4He2+ ion beam are revealed via high-resolution, microfocus X-ray diffraction mapping. Interlayer collapse by up to 0.5 A is prevalent across both macrocrystalline and microcrystalline samples, with the macrocrystalline specimen displaying a breakdown of the phyllosilicate structure into loosely ...

Natural speciation of nickel at the micrometer scale in serpentine (ultramafic) topsoils using microfocused X-ray fluorescence, diffraction, and absorption

Serpentine soils and ultramafic laterites develop over ultramafic bedrock and are important geological materials from environmental, geochemical, and industrial standpoints. They have naturally elevated concentrations of trace metals, such as Ni, Cr, and Co, and also high levels of Fe and Mg. Minerals host these trace metals and influence metal mobility. Ni in particular is an important trace metal in these soils, and the objective of this research was to use microscale (µ) techniques to identify naturally occurring minerals that contain Ni and Ni correlations with other trace metals, such as Fe, Mn, and Cr. Synchrotron based µ-XRF, µ-XRD, and µ-XAS were used. Ni was often located in the octahedral layer of serpentine minerals, such as lizardite, and in other layered phyllosilicate minerals with similar octahedral structure, such as chlorite group minerals including clinochlore and chamosite. Ni was also present in goethite, hematite, magnetite, and ferrihydrite. Goethite was present with lizardite and antigorite on the micrometer scale. Lizardite integrated both Ni and Mn simultaneously in its octahedral layer. Enstatite, pargasite, chamosite, phlogopite, and forsterite incorporated various amounts of Ni and Fe over the micrometer spatial scale. Ni content increased six to seven times within the same 500 µm µ-XRD transect on chamosite and phlogopite. Data are shown down to an 8 µm spatial scale. Ni was not associated with chromite or zincochromite particles. Ni often correlated with Fe and Mn, and generally did not correlate with Cr, Zn, Ca, or K in µ-XRF maps. A split shoulder feature in the µ-XAS data at 8400 eV (3.7 Å−1 in k-space) is highly correlated (94% of averaged LCF results) to Ni located in the octahedral sheet of layered phyllosilicate minerals, such as serpentine and chlorite-group minerals. A comparison of bulk-XAS LCF to averaged µ-XAS LCF results showed good representation of the bulk soil via the µ-XAS technique for two of the three soils. In the locations analyzed by µ-XAS, average Ni speciation was dominated by layered phyllosilicate and serpentine minerals (76%), iron oxides (18%), and manganese oxides (9%). In the locations analyzed by µ-XRD, average Ni speciation was dominated by layered phyllosilicate, serpentine, and ultramafic-related minerals (71%) and iron oxides (17%), illustrating the complementary nature of these two methods.

Near-Infrared Spectroscopy of Hydrothermal versus Low-Grade Metamorphic Chlorites

Although the composition of chlorite group minerals represents a known proxy for conditions in various geological environments, few comparative studies of chlorites from different geological environments have been carried out. In this study, we compare chlorites from a hydrothermal system with those formed under low-grade metamorphic conditions. Both sets of samples were collected from the Pilbara Craton, Western Australia. Near-infrared (NIR) spectroscopy was used to determine if spectral differences record compositional differences between chlorites from the two geological environments. The spectra showed a significant difference in the Mg-OH absorption wavelength, near 2350 nm, with the hydrothermal group showing longer absorption wavelengths than the metamorphic one. A comparison of the spectral data with geochemical analyses showed a relation between the absorption wavelength and the magnesium-to-iron ratio (magnesium number) of chlorite, as well as the bulk rock composition. Metamorphic rocks have a higher magnesium-to-iron ratio than the hydrothermal ones, predominantly explained by differences in the degree of metasomatism. In the hydrothermal system, mass transfer changes the bulk rock composition while for the metamorphic samples the original bulk chemistry determines the current composition of the rock.

Mineralogical and geochemical characteristics of mudstones in the Jersovec chert deposit

Jersovec chert deposit is a part of the transitional zone between the internal and the external Dinarides. Tethyan cherts are often interlaid with fine-grained material, as is also the case in Jersovec, where chert beds interchange with several thin, up to 10 cm thick layers of fine-grained sedimentary rocks. The source of this material is often questionable and interpreted to be terrigenous, volcanogenic or even combination of both. In order to determine origin and depositional environment of fine-grained material, detailed mineralogical and geochemical analyses were performed. Fine-grained sedimentary rocks were characterised by X-ray diffraction (XRD), scanning electronmicroscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and inductively coupled plasma emission spectroscopy (ICPES) and mass spectroscopy (ICP-MS). All samples are mineralogically very similar but differ in mineral ratios. They contain quartz and clay minerals, predominantly illite/muscovite and chlorite group minerals. SEM/EDS analysis additionally revealed zircon, monazite, Ti-oxide (probably rutile) and iron oxides/hydroxides in all samples, whereas chromite, ilmenite, xenotime, apatite and baryte were found only in some of them. The average sizes of accessory minerals range from 3-20 µm. Two samples differ from the others by their brown colour and higher Fe2O3 and lower SiO2 contents. All other samples are green. Chemical analysis showed that they consist mostly of SiO2 (46.3-69.3 %), Al2O3 (15-24.1 %) and minor contents of K2O (2.8-3.4 %), Fe2O3 (2.1-8.4 %), MgO (1.6-2.3 %), TiO2 (0.5-0.7 %), CaO (0.3-1.4 %), Na2O (0.1 %) and P2O5 (up to 0.5 %). Position of all samples in the Zr/TiO2 vs. (V+Ni+Cr)/ Al2O3 diagram points to terrigenous origin and Sedimentation on the Continental margin. According to the chemical weathering indices (CIA and CIW) material has been subjected to the intense and long weathering, supported also by the index of compositional variability (ICV), which corresponds to the compositionally mature material, and by rounded zircon and ilmenite grains.

Quintinite-1M from the Mariinsky Deposit, Ural Emerald Mines, Central Urals, Russia

The paper describes the first finding of quintinite [Mg4Al2(OH)12][(CO3)(H2O)3] at the Mariinsky deposit in the Central Urals, Russia. The mineral occurs as white tabular crystals in cavities within altered gabbro in association with prehnite, calcite, and a chlorite-group mineral. Quintinite is the probable result of late hydrothermal alteration of primary mafic and ultramafic rocks hosting emerald-bearing glimmerite. According to electron microprobe data, the Mg: Al ratio is ~2: 1. IR spectroscopy has revealed hydroxyl and carbonate groups and H2O molecules in the mineral. According to single crystal XRD data, quintinite is monoclinic, space group C2/m, a =5.233(1), b = 9.051(2), c = 7.711(2) A, β = 103.09(3)°, V = 355.7(2) A3. Based on structure refinement, the polytype of quintinite should be denoted as 1M. This is the third approved occurrence of quintinite-1M in the world after the Kovdor complex and Bazhenovsky chrysotile–asbestos deposit.

Ferromanganese carbonate metasediments of the Sob area, Polar Urals: Bedding conditions, composition, and genesis

The paper presents the results of study of ferromanganese carbonate rocks in the Sob area (Polar Urals), which is located between the Rai-Iz massif and the Seida–Labytnangi Railway branch. These rocks represent low-metamorphosed sedimentary rocks confined to the Devonian carbonaceous siliceous and clayey–siliceous shales. In terms of ratio of the major minerals, ferromanganese rocks can be divided into three varieties composed of the following minerals: (1) siderite, rhodochrosite, chamosite, quartz, ± kutnahorite, ± calcite, ± magnetite, ± pyrite, ± clinochlore, ± stilpnomelane; (2) spessartite, rhodochrosite, and quartz, ± hematite, ± chamosite; (3) rhodochrosite, spessartite, pyroxmanite, quartz ± tephroite, ± fridelite, ± clinochlore, ± pyrophanite, ± pyrite. In all varieties, the major concentrators of Mn and Fe are carbonates (rhodochrosite, siderite, kutnahorite, Mn-calcite) and chlorite group minerals (clinochlore, chamosite). The chemical composition of rocks is dominated by Si, Fe, Mn, carbon dioxide, and water (L.O.I.): total SiO2 + Fe2O 3 tot + MnO + L.O.I. = 85.6−98.4 wt %. The content of Fe and Mn varies from 9.3 to 55.6 wt % (Fe2O 3 tot + MnO). The Mn/Fe ratio varies from 0.2 to 55.3. In terms of the aluminum module AlM = Al/(Al + Mn + Fe), the major portion of studied samples corresponds to metalliferous sediments. The δ13Ccarb range (–30.4 to–11.9‰ PDB) corresponds to authigenic carbonates formed with carbon dioxide released during the microbial oxidation of organic matter in sediments at the dia- and/or catagenetic stage. Ferromanganese sediments were likely deposited in relatively closed seafloor zones (basin-traps) characterized by periodic stagnation. Fe and Mn could be delivered from various sources: input by diverse hydrothermal solutions, silt waters in the course of diagenesis, river discharges, and others. The diagenetic delivery of metals seems to be most plausible. Mn was concentrated during the stagnation of bottom water in basin-traps. Interruption of stagnation promoted the precipitation of Mn. The presence of organic matter fostered a reductive pattern of postsedimentary transformations of metalliferous sediments. Fe and Mn were accumulated initially in the oxide form. During the diagenesis, manganese and iron oxides reacted with organic matter to make up carbonates. Relative to manganese carbonates, iron carbonates were formed under more reductive settings and higher concentrations of carbon dioxide in the interstitial solution. Crystallization of manganese and iron silicates began already at early stages of lithogenesis and ended during the regional metamorphism of metalliferous sediments.

Petrography, Mineralogy, and Origin of the Syenite Pegmatitic Segregation Veins From La Peña Alkaline Complex, Mendoza, Argentina

Abstract The syenite pegmatitic segregation veins (SPSV) of the Early Miocene La Pena alkaline complex (LPC), Mendoza, Argentina, are emplaced in a malignite body. They occur as veins, parallel layers, and small elliptical bodies 1 to 6 cm wide and 0.2 to 1 m in length. The veins with a pegmatitic to micropegmatitic texture have a thin dark border composed of andradite, potassic-hastingsite, and dark micas and a thicker internal zone of poikilitic Ba-Sr-poor K-feldspar (Or 90.3 Ab 8.9 An 0.8 ), nepheline (Ne 74.9 Ks 19.4 Qz 5.7 to Ne 78.7 Ks 20.0 Qz 1.3 ), potassic-hastingsite, dark mica, andradite, scarce clinopyroxene (diopside–hedenbergite), and locally zoned microphenocrysts of Ba-Sr-rich K-feldspar (Or 75.6 Ab 21.7 An 2.7 ). Accessory fluorapatite, titanite, interstitial sodalite, and magnetite and secondary abundant Na- and K-rich zeolites, calcite, chlorite-group minerals, and possibly cancrinite have been identified. The textural and mineralogical characteristics of the SPSV show genetic links with the host malignite that belongs to the potassic alkaline series. The SPSV were formed from a residual syenitic melt (malignite) extracted from a parental tephritic magma. In the residual malignite, the concentration of primary crystals (apatite, clinopyroxene, Ba-Sr-rich K-feldspar, and nepheline) formed a crystal network (mush) with the open spaces occupied by small amounts of residual melt enriched in Al, Na, K, and volatiles and depleted in Ba and Sr. Deformation (by shear movements plus magmatic pressures) produced microfractures and fractures which were occupied by residual interstitial melt. In situ crystallization within these fractures resulted in the formation of the SPSV.

Occurrence of some valuable elements in the unique ‘high-aluminium coals’ from the Jungar coalfield, China

In China, a unique type of coal with extremely high aluminium (Al) content commonly occurs in the southern region of the Yinshan Oldland, Jungar Basin. The typical Al2O3 content in the coal ash is ~45%, and exceeds 60% in some cases. This type of coal forms a league of its own and is named as ‘high-Al coal’. This high-Al coal, not only contains unusually high level of Al but also has high concentrations of Li, Ga, and REY (REE+Y). All these elements (i.e. Al, Li, Ga, REY) with high concentrations in this type of coal are very valuable source to various industries and therefor make perfect economic sense and add extra benefits into coal mines if they can be recovered by beneficiation processes.The mineral compositions in these coals mainly consist of kaolinite, boehmite, chlorite-group minerals, along with minor amounts of quartz, calcite, pyrite, siderite and amorphous clay materials. The Al and rare elements show different patterns of distribution and affinity relationships with organic and inorganic matter. The strong peraluminous granites and moyite from the Yinshan Oldland may be the main source of the Al and rare elements in the coals. Bauxite from the Benxi Formation may also be another source for the Al and rare elements in the coal of the Jungar coalfield.

A Windows program for chlorite calculation and classification

A Microsoft Visual Basic program, WinCcac, has been developed to calculate the structural formulae of chlorite. WinCcac classifies rock-forming chlorite group minerals based on 14 oxygens for complete chlorite analyses. For electron-microprobe-derived chlorite analyses site occupancy can be estimated by using the stoichiometric H2O (wt%) and Fe2O3 (wt%) contents. The program is created to predict cation site-allocations at the different structural positions such as the tetrahedral, octahedral, and interlayer sites. Furthermore, various chlorite geothermometers based on an empirical approach are carried out to specify the condition of formation temperature. WinCcac allows the user to enter and load multiple chlorite analyses in its own data entry window, to edit and load Microsoft Excel files in estimating and classifying chlorite data, and to generate and store all the calculated results in the output of Microsoft Excel file for further data evaluation and graphing purposes.

Concentrations of Valuable Elements of the Coals from the Pingshuo Mining District, Ningwu Coalfield, Northern China

A total of 840 coal samples were taken from the Pingshuo (Pinglu-Shuoxian) Mining District, Ningwu Coalfield, northern China. The samples were analysed by optical microscopy, sequential chemical extraction procedure, SEM–EDX analysis, X-ray powder diffraction and ICP-MS techniques. The results indicate that the Li, Ga and Al contents of the coals have reached an economically valuable level. Total Li reserves reached 100000, 558400 and 382600 tons in the Nos. 4, 9 and 11 seams, respectively. Total Ga reserves reached 28600, 80700 and 40900 tons in the Nos. 4, 9 and 11 seams, respectively. Total Al reserves reached 206000000 tons in the No. 9 seam. The sequential chemical extraction procedure results indicate that the element concentrations are mainly related to inorganic matter. The minerals are kaolinite, boehmite, chlorite-group mineral, quartz, calcite, pyrite, siderite and amorphous clay material. The kaolinite, boehmite and chlorite phase could be the most likely host of the Li, Ga and Al. These elements could be migrated from the Yinshan Oldland or bauxite of the Benxi formation by absorption. The bauxite of the Benxi formation should be the most possible source of Li, Ga and Al of the coal in the Pingshuo district.

Further Information of the Associated Li Deposits in the No.6 Coal Seam at Jungar Coalfield, Inner Mongolia, Northern China

Abstract:Total 138 coal samples and 14 parting samples were taken from the No. 6 Seam of the Jungar Coalfield, Inner Mongolia. These samples were analysed by optical microscopy, sequential chemical extraction procedure (SCEP), inductively coupled plasma mass spectrometry (ICP–MS), X–ray powder diffraction (XRD), and scanning electron microscope in conjunction with an energy–dispersive X–ray spectrometer (SEM–EDX) analysis. The results indicate that the Li contents have reached the industrial grade of the coal associated Li deposit, and the total Li reserves have reached 2406600 tons, that is, 5157000 tons Li2O in the No. 6 seam in the Jungar Coalfield. The sequential chemical extraction procedure results suggest that the Li concentration is mainly related to inorganic matter. The minerals in the coals consist of kaolinite, boehmite, chlorite–group mineral, quartz, calcite, pyrite, siderite and amorphous clay material. Some Li could be absorbed by clay minerals in the Li–bearing coal seam. The chlorite phase could be most likely the host for a part of Li. The Yinshan Oldland should be the most possible source of Li of the coal.