Conditions Of Mineral Formation Research Articles

Lattice defects in the disordered quartz structure of gold deposits of the Darasun ore field (Eastern Transbaikalia)

Research subject. The composition, properties, and connection of the lattice defects in the disordered s tructure of quartz with the conditions of its formation. Materials and methods. The quartz of the gold deposits of the Darasun ore field – Darasun, Teremkinskoye, and Talatuy – were studied. For the purpose of comparative analysis, gold-ore quartz from the deposits of Northern Kazakhstan was used. Registration of centers in quartz samples was carried out by the EPR method. When interpreting the obtained results, genetic information consisting in the distribution of substitutional Ge and Ti impurities in quartz was used. Results. Two groups of paramagnetic centers were identified in the quartz under study. One of them is associated with substitutional Al, Ti, and Ge impurities in quartz zones with an ordered crystal structure, while the other is associated with the lattice defects localized in the disordered crystal structure of quartz. The latter group includes several types of E'-centers formed in quartz glass and Al-X-centers caused by Al3+ ions associated with oxygen vacancies. In the case of stable thermodynamic conditions of mineral formation, a linear relationship was established between the concentrations of Al-X-centers (CAl-X) and E'-centers (CEs). Under a change in thermodynamic conditions, a deviation of the points from the CEs(CAl-X) dependence was observed. Conclusions. The type of CEs(CAl-X) dependence is determined by the thermodynamic conditions of mineral formation and can be used to identify cases of non-equilibrium solidification of quartz.

Hydrogen Chloride and Sulfur Dioxide Gas Evolutions from the Reaction between Mg Sulfate and NaCl: Implications for the Sample Analysis at the Mars Instrument in Gale Crater, Mars

The Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA) on the Curiosity rover detected hydrogen chloride (HCl) and sulfur dioxide (SO2) gas evolutions above 600 °C and 700 °C, respectively, from several drilled rock and soil samples collected in Gale crater, which have been attributed to NaCl and Mg sulfates. Although NaCl and Mg sulfates do not evolve HCl or SO2 within the SAM temperature range (<~870 °C) when analyzed individually, they may evolve these gases at <870 °C and become detectable by SAM-EGA when mixed. This work aims to determine how Mg sulfate and NaCl interact during heating and how that affects evolved HCl and SO2 detection temperatures in SAM-EGA. Solid mixtures of NaCl and kieserite were analyzed using a thermogravimeter/differential scanning calorimeter furnace connected to a quadrupole mass spectrometer, configured to operate under similar conditions as SAM, and using X-ray diffraction of heated powders. NaCl analyzed individually did not evolve HCl; however, NaCl/kieserite mixtures evolved HCl releases with peaks above 600 °C. The results suggested that kieserite influenced HCl production from NaCl via two mechanisms: (1) kieserite depressed the melting point of NaCl, making it more reactive with evolved water; and (2) SO2 from kieserite decomposition reacted with NaCl and water (i.e., Hargreaves reaction). Additionally, NaCl catalyzed the thermal decomposition of kieserite, such that the evolved SO2 was within the SAM-EGA temperature range. The results demonstrated that SAM-EGA can detect chlorides and Mg sulfates when mixed due to interactions during heating. These phases can provide information on past climate and mineral formation conditions.

Распространенность и химический состав галотрихита на геотермальных полях Камчатки

Halotrichite has been identified in geothermal fields of the Kambalny-Pauzhetka-Koshelev region, the Bolshoi Semiachik complex, and the Mutnovsky volcano (Kamchatka, Russia). Halotrichite forms efflorescence on soils heated up to 70°C, around steam-gas vents and boiling springs. Tschermigite, rozenite, szomolnokite, gypsum, alunogen, barite, melanterite, hexahydrite, and minerals of the copiapite, alunite and voltaite groups were found in close association with halotrichite. The chemical composition of halotrichite samples from different geothermal fields is similar and characterized by Mg substitution in the Fe2+ position, with Fe2+:Mg ratio ranging from 90:10 to 50:50, and also by Fe3+ substitution in the Al position in some samples, with Al:Fe3+ reaching up to 85:15. Halotrichite is a typical mineral of low-temperature volcanic setting, formed as a result of alteration of parent minerals by hydrothermal fluid and represents an intermediate form of crystallization of leached elements. At the same time, the local conditions of mineral formation — such as variations in Eh, pH, surface temperature, and elemental composition — do not reflect in the chemical composition or other thin typomorphic features of halotrichite. The mechanism of halotrichite formation is probably identical in both geothermal fields and zones of oxidation of sulfide deposits.

Estimation of surface water content at the Tianwen-1 Zhurong landing site

China’s first Mars rover, Zhurong, successfully landed in the south of Utopia Planitia. The surface water content at the landing area can provide constraints on mineral formation conditions and help us better understand the evolution of the Martian aqueous and geological environment. In this work, the surface kinetic temperature of the Zhurong landing area was derived by analyzing data from the Mars Express Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité (OMEGA) spectrometer. Using the Discrete Ordinate Radiative Transfer (DISORT) model, we performed atmospheric correction and thermal correction for the OMEGA data to obtain the surface effective single-particle absorption thickness (ESPAT) parameter to evaluate the surface water content. The surface water content distribution at the landing area was relatively uniform at a lateral scale of ~10 km. At the Zhurong landing site, the surface water content in the topmost layer (a few hundred micrometers) of the regolith was 5−8 weight percent water (wt% H₂O), assuming surface particle sizes of <45 μm, or 1.6−2.5 wt% H₂O, assuming surface particle sizes in the range of 125−250 μm. The Mars Surface Composition Detector (MarSCoDe) onboard Zhurong also observed significant H₂O/OH signals in the landing area. Our results provide an important regional context for the hydration state of the area and can be further verified by the H content derived from the Laser-Induced Breakdown Spectrometer (LIBS) data of MarSCoDe.

PUMPELLYITE FROM METABASALTS OF THE UKRAINIAN CARPATHIANS

In general, the pumpellyite series (hydrous silicates of Ca and Al) includes such mineral species as pumpellyite-(Al), pumpellyite-(Fe2+), pumpellyite-(Fe3+), pumpellyite-(Mg), and pumpellyite-(Mn). We studied pumpellyite from the Mesozoic metabasalts of the Ukrainian Carpathians in order to recreatethe facies conditions of mineral formation. The studied rocks are metabasalts of the Rakhivsko-Chyvchynskyi and Uholskyi magmatic complexes, which were studied using mineralogical, petrographical and petrogeochemical methods. In the rocks of the Rakhivsko-Chyvchynskyi complex, two morphological varieties of pumpellyite-(Fe) were found, while in the Uholskyi complex an intermediate mineral species between pumpellyite-(Al) and pumpellyite-(Fe2+) was found. The temperature of mineralization during the formation of pumpellyite-containing parageneses was determined: according to ternary feldspar geothermometry — 260 and 310 °C and according to chlorite geothermometry — from 170 to 320 °С. On the PT-diagram for metamorphic facies, the mineral paragenesis of both studied magmatic complexes fall into the field of prehnite-pumpellyite facies. The absence of clear pumpellyite-actinolite subfacies associations indicates that the pressure in the mineral formation system did not exceed 300 MPa.

The Gold–Palladium Ozernoe Occurrence (Polar Urals, Russia): Mineralogy, Conditions of Formation, Sources of Ore Matter and Fluid

We studied the mineralization and sulfur isotopic composition of sulfides of gold–palladium ores in olivine clinopyroxenites from the Dzelyatyshor massif made up of a continuous layered series of rocks: olivine-free clinopyroxenite–olivine clinopyroxenite–wehrlite. The primary igneous layering of rocks, manifested as different quantitative ratios of clinopyroxene and olivine in them, controls the local trends of variability in the chemistry of mineral-forming medium and the concentrations of ore components, including noble metals, and sulfur in each separate layer during its cooling. The replacement of primary rock-forming minerals by secondary minerals, when the temperature decreases, is a characteristic trend for pyroxenites: (a) olivine → serpentine, secondary magnetite, and (b) clinopyroxene → amphibole, secondary magnetite → chlorite. The deposition of native gold in parageneses with PGM and sulfides at the Ozernoe occurrence took place during the replacement of earlier rock-forming minerals by chlorite. This process completed mineral formation at the deposit and took place at temperatures 150–250 °C and at the high activity of S, Te, Sb, and As of fluid. The variability of mineral formation conditions during chloritization is reflected in the change of native-sulfide forms of Pd by arsenide-antimonide forms and the sulfur isotopic composition of sulfides. The Pd content in native gold increases in the series—Au-Ag solid solution (<1.5 wt.% Pd)—Au-Cu intermetallides (to 6 wt.% Pd)—Cu-Au-Pd solid solutions (16.2–16.9 wt.% Pd). The sulfur isotopic composition of pyrite, chalcopyrite, and bornite varies from −2.1 to −2.9‰. It is assumed that a deep-seated magmatic basic melt was the source of fluid, ore components, and sulfur.

Gold and silver accessory minerals in ultramafites
 of the Kyzyr-Burlyuksky ultramafic massif (Western Sayan)

The study focuses on gold and silver accessory minerals
 (native silver, cuprous gold, luanheite (Ag3Hg),
 unspecified mineral phase (Cu,Ag,Hg), first diagnosed
 in dunites and apodunite serpentinites of the Kyzyr-Burlyuksky
 ultramafic massif, which is part of the Kurtushibin
 ophiolite belt of Western Sayan. The revealed
 ore minerals are mainly observed in the form of single
 hypidiomorphic, irregular microscopic precipitates (0.5–
 3.0 μm) mainly inside magnetite, much less often in
 grains of avaruite. Typomorphic and chemical features
 of ore minerals, their natural setting in rock-forming
 silicate matrix are characterized. Formation and concentration
 of these accessory minerals is associated with
 superimposed low-temperature transformation (hydration)
 processes affecting original ultramafic rocks. At the
 same time, the presence of luanheite and an unnamed
 phase (Cu,Ag,Hg), along with the previously identified
 potarite (PdHg), is probably evidence of low-temperature
 conditions of mineral formation during the manifestation
 of epigenetic processes of serpentinization (lowgrade
 metamorphism) due to solutions enriched in mercury.
 The source of such solutions could be gabbro intrusions
 that penetrated later into the main ultramafic body.

SOME REGULARITIES OF THE INTERRELATION OF THE GENESIS AND MINERALS DISTRIBUTION IN THE BOWELS

Some regularities of the interrelation of the genesis and minerals distribution in the bowels based on the analysis of information on the temporal and spatial distribution of minerals in geological complexes, primarily in Ukraine, were revealed. The distribution of minerals in magmatic complexes, pegmatites, hydrothermalites and metamorphites was studied. The relationship between tectonics and the distribution of minerals is noted. There is a clear direction of the geological development of the earth's crust: the pacification of tectonic processes — the growth of platforms — the differentiation of mineral matter. The number of formed mineral species increased rapidly from Archean to Phanerozoic complexes, from "basaltic" to "crustal" mineral formation, from ultrabasic rocks to acid ones. The Pre-Greenstone crust of Ukrainian Shield (USh) is predominantly represented by plagioclases and pyroxenes; with the development of granitoids, quartz and alkali feldspars joined them. From early to late stages of USh development, the number of species increased by an order of magnitude. Near-Azov megablock is in the first place. Maximum species formation is associated with alkaline magmatism and processes involving volatile components, in particular pegmatite formation. The number of minerals in pegmatites reaches hundreds of species. Mountain building led to the destruction of igneous rocks and the formation of new minerals. The appearance of free oxygen became a powerful factor in mineral formation. Superimposed processes with the supplying of deep fluids contributed to the transformation and redistribution of minerals and the formation of polygenic ores. The distribution of minerals makes it possible to detect typomorphic species for certain processes, which can be used to determine the criteria of mineralization, its scale, and the erosion section of ore bodies. The distribution of various mineral species, and the same species with identified macro- and microdefects, as a result of the conditions of mineral formation, is of practical importance.

Mineral formation conditions in acid magmatic systems related to the formation of massive sulfide deposits of the Urals and Altai-Sayany area

Studies of melt inclusions in quartz indicate the similarity of acid magmatic systems of massive sulfde deposits in the Urals and Altai-Sayany region. The melts of normal alkalinity corresponding to rhyodacite and rhyolite compositions and related to the tholeiitic series are dominant in all the deposits considered. The magmas are characterized by the same type evolution with a decreasing content of main oxides (TiO2, Al2O3, FeO, MgO, CaO, Na2O, K2O) and an increasing SiO2 content. Our results show the accumulation of Cu in relatively low-H2O acidic melts of ancient (Cambrian) deposits of the Altai-Sayany region and low metal contents in the intermediate (Silurian–Devonian) and H2O-saturated magmas of the Urals. The youngest (Devonian) magmas of Siberia evolve simultaneously along these two directions. The analysis of melt inclusions in quartz suggests that the minimum contents of trace and rare earth elements are characteristic of the Silurian-Devonian acid melts of the Urals, with their maximum contents in the youngest (Devonian) magmas and the intermediate contents of ancient (Cambrian) magmatic systems of the Altai-Sayany region. The features of rare and rare earth element patterns in melt inclusions in quartz indicate the similarity of acid magmatic systems of massive sulfde deposits in the Urals and Altai-Sayany region with present-day suprasubduction melts in the ocean-continent transition zones. Computational modeling using data on melt inclusions in quartz confrms our previous conclusions (Simonov, Maslennikov, 2020) that the occurrence of contrasting (basic and felsic) volcanic complexes with massive sulfde deposits in the Urals and Altai-Sayany region is a result of evolution of basaltoid magmas. Keywords: conditions of mineral crystallization, basaltic-rhyolitic complexes, massive sulfde deposits, melt inclusions, quartz, acidic melts.

Chemical reactions and conditions of mineral formation at tailings storage facilities of the Russian Far East

Cassiterite-sulfide and polymetallic deposits of the Far Eastern Region (FER) were mined by both openpit and underground methods. This resulted in the emerging numerous mine workings and tailings storage facilities (TSFs) (abandoned without reclamation in latest decades) and the formation of mining technogenic mineralogical systems. Sulfide component of minerals in the mining technogenic system is subjected to hypergenic and technogenic processes (oxidation and hydrolysis reactions). As a result, highly concentrated technogenic solutions are formed, from which minerals of various classes precipitate. In this connection the purpose of this study was formulated as follows: to show the possibility of crystallization of technogenic minerals from micropore technogenic solutions. In achieving this goal the following tasks were solved: to demonstrate the possible reactions of oxidation and hydrolysis of technogenic minerals at the tailings storage facilities; to identify Eh-pH parameters of their precipitation from highly concentrated solutions; to determine their possible associations. The studies involved field observations and computations with the use of “Selector” software package. The study findings allow demonstrating possible chemical reactions and physico-chemical conditions of mineral formation for the following elements: Fe, Cu, Pb, Zn, Sb, Mg, Al, and Ca, including the following classes of minerals: oxides and hydroxides, sulfates, carbonates, arsenates and silicates. The paper presented for the first time the crystallization reactions of secondary minerals (37 ones) and their physico-chemical conditions. It was found that secondary minerals: jarosite, pitticite, siderite, tenorite, poznyakite, antlerite and ktenasite crystallize in the interval of positive temperatures, while scorodite, chalcantite, broshantite, cerussite, starkeyite, epsomite and rostite originate in cryogenic conditions (below 0 oC). All other minerals, the possibility of precipitation of which was shown in the paper, crystallized in the whole considered temperature interval, from −25 oС to +45 oС. Field studies and modeling data on formation of technogenic waters (solutions) and crystallization of secondary minerals on the surface of and inside tailings at the tailings storage facilities of the Far East showed high intensity of technogenic processes. Since the tailings storage facilities were not reclaimed, the process of environmental pollution, including the hydrosphere, would last for many decades.

Formation of Diagenetic Minerals in the Carboniferous Rock Complex from the Fore-Sudetic Monocline (SW Poland): Fluid Inclusion, Isotopic and Raman Constraints

The paper presents the latest state of knowledge on clastic sedimentary rocks from the Carboniferous complex in the SW part of the Polish Lowlands, studied to help determine their potential prospectivity for the occurrence of oil and/or gas deposits. Rocks were analyzed with respect to the petrographic-mineralogical characteristics of the Carboniferous deposits, their diagenesis, determinations of pressure-temperature conditions of mineral formation and the hydrocarbon occurrence. Analyses were carried out on samples from four selected boreholes in the Fore-Sudetic Monocline. After microscopic analysis of rocks and minerals in thin sections, the following techniques were used: luminescence analysis (UV, blue light), microthermometric analysis of fluid inclusions in double-sided polished wafers, cathodoluminescence analysis, electron scanning microscope studies, XRD analyses, stable isotopic analyses (carbon, oxygen) on calcite and dolomite-ankerite and Raman spectra of fluid inclusions. Orthochemical components, such as carbonates and authigenic quartz, that form cements or fill the veins cutting the sample material have been studied. Fluid inclusion data in quartz and carbonates result in homogenization temperatures of 74–233 °C. The Raman analysis gives temperature estimations for the organic matter of about 164 °C and 197 °C, depending on the borehole, which points to a low coalification degree. The post-sedimentary processes of compaction, cementation and diagenetic dissolution under eo- and meso-diagenetic conditions to temperatures of over 160 °C influenced the present character of the deposits. P-T conditions of brines and methane trapping have been estimated to be ~850–920 bars and 185–210 °C (vein calcite) and ~1140 bars and 220 °C (Fe-dolomite/ankerite). Therefore, locally, temperatures might have been higher (>200 °C), which may be a symptom of local regional metamorphism of a very low degree.

Crystallomorphological and physical properties of apatite from carbonatites

This paper presents the results of the study of x-ray luminescence of apatite from different genetic types of apatite species in order to study its geochemical characteristics and the possibility of using as a mineral indicator the conditions of ore formation and for search purposes. Apatite Ca2Ca3(F,Cl,OH)2[PO4]3 contains impurities Gd3+, Ce3+, Eu2+, Dy3+, Sm3+, Nd3+ as well as Mn2+ and others. Syngony is hexagonal. Crystals of prismatic habit; usually ending in dipyramide or basopinacoid. Sometimes forms tabular crystals. A hexagonal prism is often preserved. Color greenish, bluish-green; pinkish-purple, gray; often white, colorless or brown. Quite often translucent due to the presence of small internal cracks and inclusions; sometimes the inclusions are arranged oriented, preferably parallel to the main axis of the crystal. Brightly luminesces in cathode, x-ray and ultraviolet rays. The intensity and color of luminescence varies widely depending on the impurities. The presence of three crystal chemical positions in the structure of apatite – two cationic and one anionic makes it possible to be realized in the mineral by a wide heterovalent substitution. The distribution of isomorphic impurities between the crystal chemical positions will depend on the type of cation, its amount, as well as anionic substitutions in apatite. To determine the luminescence intensity values of the characteristic isomorphic impurities of apatite TR3+ (Gd3+, Ce3+, Eu2+, Dy3+, Sm3+, Nd3+) and Mn2+, the X-ray luminescence method was applied. Apatites of different genetic types of the Aldan, Baltic Shields, the Baikal region (Russia), the Sette-Daban Range, and the Maimech-Kotui Province (Yakutia) and the Ukrainian Shield were investigated. The obtained values of luminescence intensity of TR3+ and Mn2+ can be used to diagnose the genetic type of apatite species, the conditions of mineral formation, the type of their mineralization and for search purposes. On the basis of factor analysis, it can be concluded that the intensity of the luminescence centers of rare earth elements in the apatites of each complex depends on the relative age position of the mineral in the groups of successively formed rocks. Analysis of apatite carbonatites from different deposits showed minimal fluctuations in the ratios of radiation intensity of X-ray centers (Ce3+, Sm3+, Mn2+, Eu2+), which may indicate a close geochemical situation and, consequently, the only source of matter in the formation of carbonates. Analysis of apatite carbonatites from different fields showed minimal fluctuations in the radiation intensity ratios of the centers of X-ray luminescence (Ce3+, Sm3+, Mn2+, Eu2+), which, in my opinion, may indicate a close geochemical situation and, as a consequence, the substance or the result.

Пошуково-оцінювальні критерії гідротермального зруденіння рахiвського золоторудного району (Закарпаття)

Complex of the searching-valuation criterions of the Rakhiv ore region gold mineralization have been elaborated. The main amongst them are mineralogy-genetic, geology-structural, thermobarogeochemical and mineralogy-physical ones. The main favorable criteria for gold are: the spread of productive mineral associations and syngeneic fluid inclusions with them; carbon dioxide-water composition of mineral-forming fluids, inclusions in minerals, the density of which does not exceed 0.5 g/cm3; medium temperature conditions of mineral formation (280–120 °С); distribution and sequence (from {100} + {210} to {210}) of crystallization of combined forms of pyrite, which are characterized by: mainly np- and p-conductivity and numerical vectors (in the coordinate system RV – average), oriented towards higher values hole conductivity; the presence of galena, the value of thermoelectric force which is more than 800 μV/deg. Based on the developed criteria, we offered a number of specific recommendations on the prospects of the studied ore occurrences, Saulyak deposit and Rakhiv gold ore district in general.

ЛЮМИНЕСЦЕНЦИЯ КВАРЦ-ХАЛЦЕДОНОВЫХ ОБРАЗОВАНИЙ КУЗБАССА И ЕЁ СВЯЗЬ С ГЕОХИМИЧЕСКИМИ ОСОБЕННОСТЯМИ АГАТОВОЙ МИНЕРАЛИЗАЦИИ

Актуальность. Кварц-халцедоновые образования Кузбасса являются потенциально ювелирно-поделочным материалом, при этом степень их минералогической изученности недостаточна. Кроме того, требуют дальнейшего изучения некоторые аспекты формирования агатов. Цель: изучение люминесцентных характеристик кварц-халцедоновых образований в пределах проявлений Южно-Кузбасского магматического ареала, их изменений по зонам в исследуемых образцах, вариаций в поведении отдельных центров свечения, связанных с собственными и примесными дефектами, выяснение возможного влияния геохимических особенностей исследуемых минералов на их люминесцентные свойства. Объекты: кварц-халцедоновые образования с проявлений Южно-Кузбасского магматического ареала (проявление россыпного типа у д. Ключи (Крапивинский район), миндалекаменные базальты с агатовой минерализацией проявления участка Терсюк (Новокузнецкий район), миндалекаменные базальты с агатовой минерализацией проявлений Салтымаковского хребта (Крапивинский район, Кемеровская область). Методы: рентгеноструктурный анализ, рентгенолюминесцентный анализ, масс-спектрометрия с индуктивно связанной плазмой. Результаты. Методом рентгеноструктурного анализа изучен минеральный состав. Главным образом представлены кварц и халцедон, при этом наибольшее содержание халцедона наблюдается в миндалинах с концентрически-зональным строением. В числе других минералов встречаются кристобалит, доломит, кальцит, цеолиты. Посредством проведения рентгенолюминесцентного анализа получены данные о содержании собственных и примесных дефектов различной природы. Распределение центров люминесценции в слоях агата проявления Терсюк может свидетельствовать о смене окислительного потенциала (во внешней зоне) на восстановительный (во внутренних зонах), что подтверждается геохимическими данными. Для оникса Салтымаковского хребта характерна идентичность спектров РЛ для всех исследуемых слоев, что свидетельствует о постоянстве условий минералообразования. В целом сделан вывод о преобладании в миндалинах участка Терсюк восстановительной среды, а в миндалинах проявлений Салтымаковского хребта и у д. Ключи – окислительной.

Physico-chemical parameters of mineral-forming processes in pegmatites of the ilmenogorsk alkaline complex (South Urals) аnd Altai-Sayany Region (Siberia)

The conditions of mineral formation in non-granite pegmatites of the Urals and Siberia are examined. The physico-chemical parameters of the crystallization of minerals in miaskite-pegmatites of the Ilmenogorsk alkaline complex (South Urals) and pyroxenite-pegmatites from ophiolite associations of the Altai-Sayan region (South Siberia) are determined using inclusions of mineral-forming media in minerals and computational modeling based on data on the composition of melt inclusions in COMAGMAT, PETROLOG and PLUTON programs. The study of multiphase (silicate and salt crystals + vapor and liquid) inclusions showed that nepheline miaskite-pegmatites formed from melts-brines at maximum temperatures of 700–750 °C and pressures of 3100–3600 bar. During further decrease in temperature (up to 500–510 °C) and pressure (up to 1200 bar), cancrinite crystallizes from mostly fuid systems. Sodalite forms at the fnal stages of the pegmatite-forming processes (370–440 °C, up to 1000 bar). The analysis of multiphase fuid inclusions with salt phases indicates the involvement of highly saline fuids with temperatures of 445–455 °C during the formation of pyroxenite-pegmatites in serpentinites. Data on melt inclusions in Cr-spinels from ophiolite ultramafc rocks (including clinopyroxenites) indicate the possible crystallization of pyroxenite-pegmatites (hosted in ordinary pyroxenites) in high-temperature (1315–1245 to 1205–1100 °С) magmatic systems.

Mineral identification of rocks from Pohon Batu hot springs in West Seram using FTIR spectroscopy

This study demonstrates the Fourier Transform Infrared (FTIR) spectroscopy which has been applied to identification of mineral rocks from Pohon Batu hot springs, West Seram regency, Province of Maluku. FTIR spectroscopic interpretation are absorbance or transmittance spectra as a function of wavelength that shows the content of organic compounds found in rocks. From the conditions of mineral formation and presence of various impurity ions and elements also influence the intensity and position of the IR absorption peaks. This study identified the strong peaks of minerals like kaolinite at 3618 cm−1, montmorillonite at 1612 cm−1, organic carbon at 2924 cm−1, quartz at 1874 cm−1, calcite at 1797 cm−1, albite at 1026 cm−1, illite at 756 cm−1 and hematite at 532 cm−1. From the result of FTIR analysis indicates that this area has undergone hydrotermal alteration thus becoming a secondary minerals. Rock-forming minerals in the hydrothermal alteration process are influenced by the presence of temperature, pressure in geothermal fluids and the decomposition of plants and animals.

Gold-Bearing Rodingites of the Agardag Ultramafic Massif (South Tuva, Russia) and Problems of Their Genesis

The limited literature data on gold-bearing albite–pyroxene rodingites are summarized for the Agardag ultramafic massif in southern Tuva. These data are supplemented by new mineralogical, geochemical, thermobarogeochemical, and isotopic–geochemical results in order to reveal the physicochemical mineral formation conditions and sources of ore matter and fluids on gold deposition in rodingites. Rodingites and associated schistose nephritoids are near-fault metasomatites and are confined to a latitudinal tectonic zone in antigorite serpentinites. They formed in two stages. Stage I minerals (pyroxene, albite, etc.) are rodingites and stage II minerals (Na-bearing actinolite, albite, etc.) are nephritoids and veinlets that intersect rodingites. Disseminated sulfides of the Cu–S series (chalcocite, digenite, etc.) and Au minerals (tetra-auricupride and electrum) were deposited during both stages. The temperature regime (500–250°C) and low amount of CO2 in fluid ( $${{{\text{X}}}_{{{\text{C}}{{{\text{O}}}_{{\text{2}}}}}}}$$ = 0.017–0.025) correspond to the formation conditions of typical bimetasomatic rodingites. The degree of oxidation of gas components in fluids CO2/(CO2 + Σreduced gases) increases from rodingites (0.189) to nephritoids (0.299) and antigorite serpentinites (0.738). The O isotopic composition of silicates and calculated O isotopic composition of the fluid during antigorite serpentinization (5.8 to 7.6‰ δ18Оfl and –66 to –69‰ δDfl) correspond to juvenile and magmatic water in contrast to metamorphic water during nephritization and rodingitization (6 to 9.9‰ δ18Оfl and –39 to –46‰ δDfl) with involvement of heavy oxygen that was subjected to the sedimentary cycle. It is suggested that the magmatic ore-bearing fluid (7.3–7.6 wt % NaCl-equiv) separated from gabbroic melts. The oxidized fluid was modified to a reduced fluid during interaction with ultramafic rocks. The mafic and ultramafic rocks were the source of Na, REE, Au, Ag, Cu, and Ni. Deformations with the formation of veins and filling of veinlets are favorable for a high local gold concentration.

Mineral Composition of Manganese Crusts from Belyaevskii Volcano (Sea of Japan)

The polygenic mineral composition of Mn crusts from Belyaevskii Volcano of the Central Basin of the Sea of Japan is determined. The crusts are found for the first time to contain rhodochrosite, manganosite, quenselite, heterolith, manganotantalite, and tungomelane in addition to the previously described todorokite, birnessite, manganite, pyrolusite, and vernadite. Among ore minerals, the breccia crusts include magnetite, titanomagnetite, hematite, pyrite, pyrrhotine, galena, monazite, cerianite, baddeleyite, and pentlandite, while fragments of manganite have silver and numerous particles of copper gold. A significant role in the formation of the mineral composition of the crust was likely played by pore waters involved in the hydrothermal process and organic matter (OM) of the Miocene–Quaternary siliceous–argillaceous strata, which served as the source of many rare and noble metals and affected the redox conditions of mineral formation.

Mineralogical-petrographic Features of Syenitic Migmatites of the Ilmenogorsky Miaskite Block (South Urals)

Syenitic migmatites of the contact of the Ilmenogorsky miaskite block are characterized by high (>500 ppm) contents of REEs, which are mainly hosted in fuorapatite and titanite of the leucosome. Apatite exhibits zoned and sectorial composition with decreasing REE and Si contents and increasing Cа, P, and F contents from central parts to the margins indicating the change in physicochemical conditions of mineral formation. The La/Nd ratios of REE-bearing fuorapatite indicate that apatite-1 formed from a F-bearing fuid in contrast to apatite-2 formed from an alkaline, F–CO2–SO3-rich fuid during albitization. The REEs and F released by alkaline metasomatism accumulated in late generation of REE–F-bearing titanite. Migmatization of rocks was accompanied by involvement of an alkaline F–CO2–SO3-bearing fuid.

Isotopic communication across the water – rock interface: Preservation in solids and signatures in fluids

Water – rock interactions are characteristically associated with isotopic fractionation between phases, yet their remains significant uncertainty in the degree to which these isotope ratios record the conditions of mineral formation or equilibration, and thus their fidelity as proxy records. Here, we present a novel generic modeling framework allowing sub-grid scale tracking of the isotopic signatures recorded in newly formed minerals over the timescale of precipitation and continued isotopic exchange between phases. We demonstrate that the surface area of the solid phase strongly influences the extent to which isotopes reflect the conditions of formation through time.