Group Minerals Research Articles

Minerals explained 62

Eudialyte is a mineral unfamiliar to most people. This is likely to change in the near future, as this mineral is of increasing economic importance. Eudialyte is now known to be one of a group that has grown in number to a remarkable extent in recent years, and eudialytes are index minerals for a specific category of igneous rocks and are repositories for elements, such as the rare earths, which have become increasingly critical to modern technology. The eudialyte group now comprises about 50 members of which about 29 members are fully recognized, and exploitation of eudialyte group minerals will soon be a reality. The mineral's name comes from Greek: Eu διάλυτος, meaning ‘well decomposable’—a reference to the fact that, unlike the highly refractory zircon (the common source of zirconium), eudialyte is soluble in common acids, making it relatively cheap to work.

A review of flotation and selective separation of pyrrhotite: A perspective from crystal structures

Pyrrhotite is an associated mineral that exists widely in sulfide ore. The presence of pyrrhotite will affect the recovery of platinum group minerals. Therefore, researchers have paid increasing attention to the flotation separation of pyrrhotite. Pyrrhotite superstructures owning different Fe/S ratios results in various crystal structures, corresponding to different physical, chemical and electronic properties, and consequently different flotation behavior. In the present paper, a comprehensive review is conducted to discuss the influence of crystal structures on the natural floatability, mineral-reagent interaction, surface oxidation and flotation electrochemistry of pyrrhotite. The selective flotation process of pyrrhotite from its associated minerals is also reviewed in this paper. It is hoped that this review can summarize the newly published research results combined with some representative results from the past, to provide a theoretical basis for the study of the flotation mechanism of pyrrhotite and provide a new direction for future research on pyrrhotite.

Ecandrewsite (ZnTiO3) in Amphibolites, Sierras de Córdoba, Argentina: Mineral Chemistry and Comparison with Different Worldwide Paragenetic Occurrences

ABSTRACT Ecandrewsite (ZnTiO3) and other ilmenite-group minerals have been found in amphibolites of the Sierras de Córdoba basement, Argentina, in an area where zinc is a relatively widespread element in the associated metasedimentary and metaigneous sequences. Ilmenite group minerals occur as anhedral to subhedral, tens to a hundred micrometer-sized relic inclusions in titanite. Electron microprobe analyses reveal compositions along a discontinuous solid-solution trend ranging from manganoan ferroan ecandrewsite toward ilmenite s.s., passing through intermediate members such as ferroan manganoan ecandrewsite, zincian manganoan ilmenite, and manganoan ilmenite. Considering that thermodynamic constraints do exist for the solubility of ZnTiO3 in ilmenite under mid- to high-grade regional metamorphic conditions, we believe that ecandrewsite and Zn-rich ilmenite compositions were attained by metasomatic fluid–mineral reactions during retrograde regional metamorphism, i.e., after the centripetal replacement of protolithic Zn-bearing ilmenite group species by titanite. The original composition of the ilmenite group species might have been Zn-poor ilmenite; however, the attainment of ecandrewsite compositions possibly needed an external supply of zinc provided by the fluid. The variations of the zinc contents were controlled by the substitution of Fe by Zn + Mn in the absence of any type of regular zonation. This is the first worldwide report of ecandrewsite in amphibolites, which has so far been described in quartz-rich metasediments, quartz-gahnite exhalites, kyanitic schists, nepheline syenites, metamorphosed volcanic hosted massive sulfide (VHMS) mineralizations, and albitites. The presence of ecandrewsite in amphibolite, as has been proved for zincian ilmenite and gahnite in other metasedimentary sequences elsewhere in the world, could become another pathfinder or indicator mineral for Zn-enriched portions of the crust.

Overview about Raman spectroscopy of types of olivine group minerals: A brief review

AbstractThe main idea of this work is to develop a brief synthesized review of the spectra of the members of the olivine group (forsterite, fayalite, Co‐olivine, and Ni‐olivine). In particular, the objective is to descriptively evaluate the different κ1 and κ2 values from the spectral bands of each mineral. The results gathered from the documentary survey of several published articles, it was possible to notice a substantial difference between the κ1 and κ2 values of forsterite and the other members. On the other hand, the difference between the values of κ1 and κ2 among the other members is almost imperceptible (fayalite, Ni‐olivine, and Co‐olivine). Thus, the probable main difference between all fayalite and other members (Co‐ and Ni‐olivine) can be seen in lower wavenumbers between 200 and 300 cm−1. In conclusion, if the objective is just to distinguish olivine, the doublet band is a good parameter to be used, but if you want to detail about which mineral of the olivine group was analyzed, the lower wavenumbers probably are the best choices.

The Paleo-Mesoarchaean Gondpipri Mafic-Ultramafic Intrusions, Western Bastar Archaean Craton, Central India: Insights from Bulk-Rock Geochemistry and Sm-Nd and S Isotope Studies on the Formation of Ni-Cu-PGE Mineralization

Abstract Magmatic Ni-Cu-platinum group element (PGE)-Te mineralization in the Gondpipri mafic-ultramafic layered intrusion of ca. 3323 ± 74 Ma age, western Bastar craton, central India, is one of the most prospective exploration targets for magmatic sulfides in India. The Gondpipri layered intrusion is divided into two distinct groups of rocks based on their mineralization potential, which include (1) mineralized layered gabbro and pyroxenite and (2) a barren olivine gabbro intrusion. The host rocks show Cu + Ni concentrations up to 5,000 ppm with a Cu/Ni ratio <1 and all PGE values between 0.1 and 1.1 ppm. Mineralization occurs in two modes: type I mineralization occurring as blebs, specks, and dissemination and type II mineralization occurring as stringers and minor veins. The geochemical data suggest that the parental magma of the host rock was generated at depths between spinel and garnet peridotite mantle source regions and subsequently modified by assimilation fractional crystallization (AFC) of the continental crust. High large ion lithophile elements, Th/Yb ratios of the studied rocks, and Sm-Nd isotope studies are consistent with a depleted mantle source. The geochemical proxies such as Th versus Ba/Th and (Ta/La)PM versus (Hf/Sm)PM and higher Sr/Nd (2.21–82.58) ratios indicate involvement of fluid-related subduction metasomatism and enrichment processes in an island-arc tectonic setting. Mineral assemblages and textural relationships between platinum group minerals (PGMs) and base metal sulfides suggest that sulfide-silicate liquid immiscibility was brought about by the precipitation of magnetite/Cr magnetite resulting in sulfide saturation in the melt by decreasing S solubility. Sulfur isotope compositions (δ34S: 1.61–3.30‰) and Sm-Nd geochemistry suggest that the sulfur was added in the tholeiitic magma by magmatic process. Crustal contamination played a significant role in sulfide saturation and in bringing about PGE and Te, As, Bi, Sb, Se (TABS) mineralization. PGM-NiTeBi developed at relatively low temperatures, whereas moncheite (PtPd)Te2 and merenskyite (PdTe) were formed at 650°C. The identification of Ni-Cu-PGM-Te in the margin of the western Bastar craton boosts deeper subsurface exploration.

Oxidation behaviour of sperrylite and platarsite (100) surfaces: A DFT study

The density functional theory (DFT) was employed to investigate the oxidation mechanism and electronic structures of sperrylite (PtAs2) and platarsite (PtAsS) (100) surface. The cluster expansion (CE) and virtual crystal approximation (VCA) methods were used to construct the PtAsS models. The PtAsS constructed model by CE possessed symmetry of P213, while the VCA maintained the Pa-3 symmetry. The computed surface energies and morphologies for all surface models, depicted the (100) plane the preferred cleavage. The oxidation mechanisms of the (100) surfaces of sperrylite and platarsite favoured the mono atomic oxygen bonding, which resulted from the dissociation of the O2 molecule on the surfaces. The adsorption energies were more exothermic for PtAs2 (100) surface oxidation (–315.82 kJ.mol–1), suggesting that sperrylite highly oxidises than the platarsite mineral. The PtAsS (CE) (100) surface oxidises stronger than the PtAsS (VCA) (100) surface, which is owed to the less (100) surface stability of the PtAsS (CE) than for PtAsS (VCA). The partial density of states (PDOS) and Bader charges indicated that the adsorbed As, S and As/S atoms donate electrons to the O2 atoms. These finding clearly illustrated that the arsenide PGMs primarily oxidises through the As sites for sperrylite and As and S sites for platarsite. Therefore the study has demonstrated the oxidation behaviour of the sperrylite and platarsite platinum group minerals (PGMs) and unravelled the surface hindrance for collector interaction during floatation which results in poor floatability of arsenide PGMs.

Linkages of Various Calcium Sources on Immune Performance, Diarrhea Rate, Intestinal Barrier, and Post-gut Microbial Structure and Function in Piglets.

The purpose of this experiment was to investigate the effects of different sources of calcium on immune performance, diarrhea rate, intestinal barrier, and post-intestinal flora structure and function in weaned piglets. A total of 1,000 weaned piglets were randomly assigned to five groups 10 replicate pens per treatment, 20 piglets per pen and fed calcium carbonate, calcium citrate, multiple calcium, and organic trace minerals of different concentrations of acidifier diets. The results of the study showed that the replacement of calcium carbonate with calcium citrate and multiple calcium had almost no significant effect on immune indexes (IL-1β, IL-6, IL-10, TNF-α) of piglets compared with the control group (p > 0.05). The five groups did not show a change in the diarrhea rate and diarrhea index (p > 0.05). The diet containing multiple calcium dramatically decreased the TP compared to the C and L diet (p < 0.05). No significant difference in HDL was noted in the five groups (p > 0.05). However, the concentration of LDL in blood in the multiple calcium group was significantly higher than that in groups L and D (p < 0.05). Moreover, the concentration of Glu in blood in the multiple calcium group was significantly higher than that in group C (p < 0.05). Compared with the control group, calcium citrate plus organic trace minerals diet markedly increased UCG-005 abundance in the colon (p < 0.05). In addition, the relative abundance of Prevotellaceae_NK3B31_group had an upward trend in the colon of the M group compared to the D group (p = 0.070). Meanwhile, calcium citrate plus organic trace minerals diet markedly increased Clostridium_sensu_stricto_1 abundance in the colon (p < 0.05). Metagenomic predictions by PICRUSt suggested that the colonic and fecal microbiota was mainly involved in carbohydrate metabolism, amino acid metabolism, energy metabolism, and metabolism of cofactors and vitamins.

Mechanism and Control of Saponite Synthesis from a Self-Assembling Nanocrystalline Precursor.

Saponite is a clay mineral of the smectite group that finds applications in the chemical industry as a catalyst or catalyst precursor as well as in nanocomposites used for structural or catalytic applications. Saponite of controlled composition, crystallinity, particle size, and morphology would be highly beneficial to industry; however, such materials are not found in a sufficiently pure form in nature. Synthetic methods to produce saponite with specific properties are currently lacking as the understanding of the mechanisms controlling its formation, crystalline properties and particle morphology, is limited. Understanding the saponite formation mechanism is crucial for the development of a highly tuned and controlled synthesis leading to materials with specific properties. Here, we report a new chemical reaction mechanism explaining the nucleation and kinetics of saponite growth at different pHs, at 95-100 °C, and under the influence of pH-modifying additives explored via a combination of X-ray scattering methods and infrared spectroscopy. Our results show that the main factor affecting the nucleation and growth kinetics of saponite is the pH, which has a particularly significant impact on the rate of initial nucleation. Non-uniform reactivity of the aluminosilicate gel also significantly affects saponite growth kinetics and causes a change in the rate-determining step as seen in graphical abstract. The most crystalline saponite is obtained when the nucleation is suppressed by a low initial pH (<7), but the reaction is performed at a higher pH of about 9. The stacking of the saponite sheets can be further improved by a separate postsynthesis treatment with an alkali (NaOH) solution. A simple, ambient pressure method for synthesizing a highly crystalline saponite is proposed that could be easily upscaled for industrial purposes.

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.

Effect of Blunging/Dispersion Parameters on Separation of Halloysite Nanotubes from Gangue Minerals

Clay minerals need to be dispersed with blungers before their utilization in the related industries due to their plastic properties, and size reduction is carried out in a wet medium. Clay minerals also contain impurities such as nonplastic materials in their structure. Mechanical dispersion parameters are important in the separation of clay group minerals (halloysite and kaolinite) from their typical non-clayey gangue minerals (quartz and goethite). In this study, the removal of impurities from halloysite ore obtained from Kızıldam, Turkey, was examined in terms of mechanical dispersion parameters, namely, feed size, blunging time and speed, pulp concentration, pulp temperature, and the aging process. The effect of these parameters on halloysite dispersion was determined by particle size, chemical, and mineralogical analysis, and optical and scanning electron microscope images. The results obtained from the studies of the mechanical dispersing and particle size distribution of the products indicated that the optimum dispersion parameters were determined as −10 mm feed size, 8 h, and 1000 rpm blunging time, and speed, 35% pulp concentration at 25 °C pulp temperature. Under these optimum conditions, a 72.3% amount of −38 μm clay product containing 35.6% of halloysite, 46.5% of kaolinite, 12.0% quartz, 1.9% goethite, 0.9% gibbsite, and 3.2% other minerals were obtained from the halloysite ore, having 30.5% of halloysite, 43.4% of kaolinite, 19.1% quartz, 2.9% goethite, 1.4% gibbsite, and 2.7% other minerals. In this study, it was understood that feed size, pulp concentration, blunging time, and speed were important parameters, while pulp temperature and the aging process had no significant effect on the mechanical dispersion of Kızıldam halloysite. In addition, impurities such as quartz and iron-bearing minerals were separated from the ore by blunging and sieving.

Application of per-pixel and sub-pixel unmixing methods on ASTER images to map hydrothermal alterations in a highly metamorphosed terrain: a case of the Musina copper deposit field

This study focuses on mapping hydrothermal alterations in Musina Copper Deposit Field which is characterized by unique concentric zonation of hydrothermal alterations from an outer zone of sericitization (phyllic) followed by inward zones of chloritization and epidotization (propylitic). Per-pixel and mixture tuned matched filtering (MTMF) sub-pixel unmixing methods were applied on ASTER data to map hydrothermal alterations. False colour composite (FCC) generated from combination of propylitic, phyllic and host rock index was effective in delineating alteration zones. The spatial distribution of alteration group minerals: chlorite–epidote and sericite–muscovite from MTMF classification correspond with their associated alteration zones. Correlation coefficient (R 2) was utilized to assess accuracy of the results by comparing MF scores of alteration minerals with copper concentrations. R 2 was 0.78 for chlorite–epidote and 0.69 for sericite– muscovite. Copper concentration levels increase towards chlorite–epidote region which represents the inward propylitic zone. Following the geometry and alteration zonation, follow-up targets were generated.

The Mushiston Sn deposit in Tajik Tien Shan as the type locality for stannite-cassiterite-hydrostannate mineralization: New mineral chemistry data and genetic constraints

The Mushiston Sn deposit is located in Hercynian South Tien Shan fold and thrust belt on the territory of Tajikistan. Unique features of the deposit include sulphide-dominated composition of the primary ore with stannite being the main ore mineral, and a thick oxidation zone where stannite is replaced by various hydrostannate minerals. Therefore, the Mushiston deposit is a rare example of stannite-cassiterite-hydrostannate mineralization and the type locality where several new hydrostannate minerals such as mushistonite, natanite and vismirnovite were first described. The structure of the deposit is characterized by a series of subvertical, generally NE-trending mineralized veins crosscutting the limbs of the large submeridional anticline composed of Paleozoic sedimentary strata. The primary ore mainly consists of a quartz-stannite group minerals – cassiterite mineral assemblage with other subordinate sulfides and minor sulfosalts. A 200–400 m thick zone of supergene oxidation is developed in the upper part of the deposit. New mineral chemistry data reveal compositional variations of the stannite group minerals, sphalerite and sulfosalts. The chemical compositions of co-existing stannite group minerals and sphalerite indicate extensive mutual substitution between Fe and Zn. The use of stannite-sphalerite geothermometry constrains the temperature for the main stage of the primary ore formation in the range of 257–308 °C. The tetrahedrite geothermometry yields temperatures in the range of 170–200 °C, which is in agreement with geological evidence for the late crystallization of sulfosalts at lower temperatures. The geological and mineralogical features of the Mushiston Sn deposit correspond to the mesothermal hydrothermal vein system mainly developed under intermediate sulfidation conditions. The proposed genetic model for the Mushiston deposit suggests formation of brittle fractures in the thermal aureole above the concealed causative granitoid intrusion, by regional analogue of Permo-Carboniferous age, where magmatic fluids mixed with meteoric water to form the hydrothermal system responsible for deposition of cassiterite-sulfide ore.

Preliminary Study on the Mechanical Activation and High-Temperature Treatment of Saponite-Containing Tailings Generated during Kimberlite Ore Dressing

This study investigates transformations of a pre-mechanically activated saponite-containing material with subsequent high-temperature treatment. The thermogravimetric analysis confirmed that the mechanical activation of saponite leads to the destruction of its layered structure, accompanied by the release of silicon dioxide and magnesium oxide in free form. The values of surface activity for mechanically activated saponite-containing material are also calculated. It is shown that when mechanically activated saponite-containing material is mixed with water, minerals of the serpentine group are formed, and further high-temperature treatment leads to the formation of minerals of the olivine group. It is experimentally shown that high-temperature treatment leads to the creation of a more durable structure of the saponite-containing material. This is due to decreased porosity and pore size, and sorption of moisture from the environment is also reduced. The study showed that saponite-containing waste materials can be effectively treated to create composite materials based on magnesia binders. Thus, with this method, the waste is effectively recycled into various green building material and can be used as supplementary cementitious material or fine aggregate replacement in concrete.

Assessment of the fracture stress of clay-carbonate rocks of the Vereiskian reservoir for oil fields in the Perm region

Currently, one of the most effective stimulating oil production methods from the Vereiskian production zones of oil fields in Perm Krai is proppant hydraulic fracturing (PHF). The effectiveness of the method largely depends on the geometric dimensions of the fracture and the optimal distribution of the proppant in it. The mudstones of the Vereiskian stage limit the growth of the fracture in height, but in certain cases its can be broken in the course of hydraulic fracturing. In this regard, the determination of the conditions for their fracturing is an urgent and important task. In the absence of rock samples of proper quality, the chemical composition of mudstones was determined during the study. The obtained results are compared with the existing data on the minerals of the montmorillonite group of clays. To determine the parameters of the ultimate stress state of the formation, a Mohr’s circle of stress is constructed using the known values of the compressive stress and the angle of internal friction of the clays. As a result, the fracture stress of mudstones is obtained, which is in the range of bottom-hole pressures during hydraulic fracturing, that is, there is a possibility of fracture growth outside the target interval.

Potential use of Indonesian basil (Ocimum basilicum) maceration to increase estradiol and progesterone synthesis and secretion to improve prenatal growth of offspring using female albino rats as an animal model.

Background and Aim:Basil is well known as a medicinal plant that contains high essential oils and antioxidant compounds that have the potential to improve ovarian development. Thus, basil may have the potential to improve the growth and development of the uterus and placenta for optimal prenatal growth of offspring. This study aimed to evaluate the effect of Indonesian basil maceration on gonad development of mature female albino rats.Materials and Methods:Fifteen 8-week-old female Sprague-Dawley rats, at the diestrus stage of the estrus cycle, were divided into three different treatment groups: Control group (mineral water), bas-low group (1% of basil maceration), and bas-high group (5% of basil maceration). Basil maceration was dissolved and administered in mineral drinking water, and the treatments were given for 20 days (4 estrus cycles). At the end of the treatment period, serum follicle-stimulating hormone (FSH), estradiol, and progesterone (Pg) were measured using enzyme-linked immunosorbent assay. The relative weight of the ovary and uterus; diameter and length of uterine cornual; vascularization of uterus; the diameter of uterine glands; the number of primary, secondary, and tertiary de Graaf follicles; the number of corpora luteum; as well as the expression of vascular endothelial growth factor (VEGF) in the ovary were determined.Results:There was no significant difference (p>0.05) in the serum FSH level of rats treated with basil maceration drinking water doses of 1% and 5% compared to the control group. However, serum estradiol and Pg concentrations in the 1% and 5% basil maceration groups were significantly higher (p<0.05) than those of the control group. Furthermore, 1% and 5% basil maceration significantly increased the uterus’s relative weight, diameter, and vascularization. Serum estradiol concentrations contributed to the elevated expression of VEGF compared to Pg.Conclusion:Administration of basil maceration for 20 days before mating could improve follicle growth and development, eventually increasing estradiol synthesis and secretion, thus improving the uterus’s preparation for implantation. This makes basil maceration an attractive candidate in clinical research to enhance the growth and development of the uterus and placenta, which will better support the optimum prenatal growth and development of embryos and fetuses, resulting in superior offspring.

Zero-Valent-Dominant Pyrochlores: Endmember Formula Calculation and Petrogenetic Significance

ABSTRACT The existing classification of pyrochlore group minerals is essentially based on the dominant valence rule. However, coupled heterovalent-homovalent substitutions at the A-, B-, and Y-sites commonly result in charge-imbalanced endmember formulae. The application of the site total charge (STC) method permits the determination of a charge-balanced endmember. Species names are assigned by using the dominant constituent rule. According to the current IMA nomenclature scheme, some previously established pyrochlore species, such as kalipyrochlore, strontiopyrochlore, bariopyrochlore, plumbopyrochlore, ceriopyrochlore, yttropyrochlore, bismutopyrochlore, and uranpyrochlore, are all grouped as zero-valent-dominant pyrochlores, resulting in the loss of petrogenetic information. In this work, the zero-valent-dominant pyrochlores of the pyrochlore group (sensu stricto) are classified into R+-, R2+-, R3+-, and R4+-pyrochlores where the respective cations (R) are the dominant valencies at the A- and Y-sites (for R+-pyrochlores) after vacancies (□) and H2O. The endmember charge arrangements are determined by the STC method to obtain charge-balanced endmember formulae for all possible zero-valent pyrochlore species. It is recommended that suitable adjectival modifiers be used along with the species name to emphasize the abundance of certain cations, which may or may not be reflected in the endmember formula. This approach would facilitate the usage of pyrochlore group minerals for all practical petrological and exploration purposes. It is considered that pyrochlores with significant A-site vacancies do not necessarily reflect formation in a supergene environment, as such pyrochlores can also form in hydrothermal parageneses.

Geology, mineralogy, geochemistry and conditions of forming the Tukan gold-quartz deposit (Khudolaz trough, South Urals)

Research subject. Detailed mineralogical and geochemical studies of rocks of the Tukan gold-quartz deposit (quartz veins, dolerites, gabbro-diorites) were carried out. The deposit is one of numerous small gold-quartz occurrences in the Khudolaz trough of the West Magnitogorsk zone.Methods. The morphology and composition of native gold was studied using an Axios kop 40 A optical microscope and Tescan Vega 3 and JEOL-6390LV scanning electron microscopes. The chemical composition of rocks was determined by X-ray fluorescence (Carl Zeiss VRA-30) and atomic emission (Shimadzu ICPE-9000) analyzes. Fluid inclusions were analyzed using Linkam TMS-600 thermostage equipped with Link-System 32 DV-NC software and an Olympus BX51 optical microscope. The gas composition of fluid inclusions was examined by Raman spectroscopy (Horiba LabRam HR800 Evolution).Results. Gold-bearing quartz veins and dolerites intersect ing the gabbrodiorite intrusion of the Khudolaz complex are associated with submeridional strike-slip faults. Native gold has a various morphology and is confined to cracks in quartz veins and altered dolerites. The composition of gold is stable, with the average fineness of 871 ± 8.3‰. An analysis of fluid inclusions in a gold-bearing quartz vein showed that gold was formed at temperatures of no less than 186–230°С from a fluid with a salinity of 4–8 wt % NaCl-eq. The presence of gases СО2, N2 and CH4 was found in fluid inclusions. Dolerites and gabbrodiorites hosting gold-bearing veins contain sulfides (pyrite, pyrrhotite, chalcopyrite, pentlandite, violarite), sulfoarsenides (cobaltite and its analogs), as well as mine rals of Ag (hessite) and Pb (kuranakhite and phases similar in composition to minerals of the dugganite group and burckhardtite). Conclusions. The sustained composition of native gold and a narrow range of salinity and homogenization temperatures of fluid inclusions indicate the formation of gold during a single stage of mineralization. The main source of gold could have been the dolerite dikes of the Ulugurtau complex. The presence of CO2, N2 and CH4 gases in fluid inclusions from goldbearing quartz indicates that not only magmatic fluid, but also fluid from the host rocks took part in mineral formation. The low value of the ratio X(CO2)/X(CH4) ≤ 0.7 indicates a moderately reduced ore-forming fluid. Low Au concentrations (0.1– 0.4 ppm) in quartz veins, dolerites, and gabbro-diorites, including those containing visible gold, indicate a weak commercial potential of the deposit

Sedimentological and environmental aspects of subsurface Basrah sediments-south Iraq

Twelve core samples were collected from 8, 10, 15, 21, 24.5 and 30 m depth from two holes in Basrah city. Textural analysis showed that the sediments of the first hole (Al-Ashar area) were siltyclay in nature at depth 8m , followed by clayeysilt at 10-21m (Saad square), whereas sand sediments were found at depths 24.5 to 30m. The statistical parameters of grain size analysis of the sediments of each hole indicated that the sediments at depth 8-21m were deposited under low energy environment. On the other hand the sediments at depth 24.5-30m were deposited under high-energy environments. The identified heavy minerals in the present study could be categorized into four groups; mica group, un-stable, ultra stable and meta-stable group minerals.&#x0D;

Минералы группы атакамита из рудопроявлений на дне Атлантического океана

The study of samples with minerals of the atacamite group from the ore fields of the Atlantic Ocean made it possible to reveal their genetic features and hydrothermal nature. The objects were observed with the help of underwater television directly on the ocean floor. The lifted samples were initially studied under binoculars aboard the R/V Professor Logachev. Due to their characteristic rich bluish-green color, atacamites were easily recognized among other minerals, and their diagnosis was further confirmed by the results of studying optical properties in transparent polished sections, under an electron microscope, and during X-ray diffraction analysis.

Mineralogical, Textural and Chemical Characteristics of Ophiolitic Chromitite and Platinum Group Minerals from Kabaena Island (Indonesia): Their Petrogenetic Nature and Geodynamic Setting

This contribution presents the first systematic mineralogical study of chromite composition, silicates and PGM (platinum group minerals) by electron microprobes in the podiform chromitite of Kabaena Island (Indonesia) mined in the past. The main target of this study is to understand the petrogenetic nature of the parental melt from which the chromitites of Kabaena Island precipitated and, indirectly, define the geodynamic tectonic setting of their emplacement. The evolution of PGM, from the magmatic stage to low-temperature processes, is also discussed. The variation of the Cr# = Cr/(Cr + Al), being comprised between 0.65 and 0.75, is similar to the podiform-type chromitite and indicates the absence of Al-rich chromitite. The calculated composition of the parental melt varies from arc to MORB (mid-ocean ridge basalts). Several grains of olivine and clinopyroxene have been found in the silicate matrix or included in fresh chromite. Olivine shows a composition typical of a hosted mantle, and clinopyroxene is similar to those analyzed in the forearc of an SSZ (supra-subduction zone). Small PGM, varying in size from 1 to 10 μm, occur in the chromitites. The most abundant PGM is laurite, which has been found included in fresh chromite or in contact with ferrian chromite along the cracks in the chromite. Laurite forms polygonal crystals, and it occurs as a single phase or in association with clinopyroxene and amphibole. Tiny blebs of Ir-Os alloy (less than 2 μm across) have been found associated with grains of awaruite in the serpentine gangue of the chromitites. The composition of the investigated chromitites suggests that they formed in the mantle of a forearc ophiolite. All the discovered grains of laurite are considered to be magmatic in origin, i.e., entrapped as solid phases during the crystallization of chromite at temperatures above 1000 °C and a sulfur fugacity below sulfur saturation. Iridium–osmium alloys are secondary in origin and represent a low-temperature, around 400 °C, exsolution product.