Study Of Mineral Inclusions Research Articles

Origin of potassium-bearing tourmalines of the Kumdy-Kolsky deposit (Kokchetav massif, Northern Kazakhstan): Study of Mineral inclusions

Research subject. Mineral inclusions in potassium-bearing tourmaline crystals of the Kumdy-Kol microdiamond deposit. Aim. To reconstruct PT conditions for the origin of potassium-bearing tourmalines. Materials and methods. Mineral analysis and element mapping were performed using an X-ray spectral microanalyzer. Raman spectroscopy was used to detect the C and SiO2 polymorphs. Results. For the first time, diamond inclusions were identified in tourmalines with the potassium content ranging from 1.0 to 1.6 wt %. In addition, diamond-bearing zircon was detected in tourmaline crystals, with the K2O content below the detection limit. Previously, diamond inclusions had been exclusively identified only within the most potassium-rich cores of tourmaline crystals, which were approved as a new end member referred to as maruyamaite. Similar to the previous studies, the Kfs inclusions were recognized in both marumaite crystals and tourmaline crystals, with a variable content of potassium. Conclusions. The obtained findings indicate that high-pressure conditions may not be necessary for the formation of potassium-rich tourmaline. The chemical composition of the fluid is most likely to be the main factor controlling the appearance of tourmalines with an unusual composition.

Mantle convection and diamonds

Research subject. The present evolutionary stage of geodynamic theory is associated with the idea of thermochemical convection of various levels in the Earth's mantle, where the centrifugal branches are represented by plumes, and the centripetal - by subduction zones. Aim. The study of diamonds contributes to an understanding of when, at what level in mantle, under what P-T conditions and geochemical environment particular diamonds originated, which were then transported by centrifugal convection flows to the Earth's surface, thereby permitting characterization of this flow. Materials and methods. Generalization of published materials and characterization of mineral inclusions in diamonds allow the general structure of mantle convection to be clarified in different epochs and different regions. Results. The data obtained on mineral inclusions in diamonds, along with the experimental data on the P-T conditions of their mineral parageneses and geophysical data on mantle properties, indicate that the depth of diamond formation varies from the lower lithosphere in the upper part of the upper mantle (≈150-250 km) to the bottom of the lower mantle. At the same time, the diamonds containing mineral inclusions, characteristic of the lower mantle, account for only the first percents of the general number of diamonds. Conclusions. The transport of diamonds from different depths of their origin is a reliable indication of convection processes (as a plume activity) in the mantle. This information provides evidence to the real existence of plumes, which is important in the context of ongoing discussions on the depth of their origin. However, the study of mineral inclusions in diamonds, particularly in superdeep diamonds, is a challenging task due to the retrograde changes, resorption and sometimes complete dissolution on their way to the surface. These circumstances minimize the probability of occurrence of superdeep diamonds and require consideration when making judgements about the reality of existence of superdeep diamonds.

Isotope-Geochemical Features of Apoultrabasic Metasomatites of the Sayan–Baikal Folded Area

Abstract —The paper is concerned with a geochemical study of apoultrabasic metasomatites of the Ospa–Kitoi, Parama, and Ust’-Kelyana ophiolite massifs located in the southern folded framing of the Siberian craton. The isotope (O, C, H, Sr, and Rb) systems of dunites, serpentinites, nephrites, listvenites, and talc–carbonate rocks are studied. The isotopic composition of oxygen in olivines from dunites is characterized by δ18O = 4.6–5.5‰. The δ18O values of serpentinites (4.67–7.35‰) point to the mantle genesis of fluids and might have been inherited from ultrabasic rocks. Nephrites are slightly enriched in heavy oxygen isotope (δ18O = 6.13–9.54‰). This indicates that their fluid phase was transported from serpentinites and captured a small portion of the crustal component. The widest variations in δ18O values, from 8.12 to 17.46‰, are observed in minerals from listvenites. Carbonates from these rocks show a highly heterogeneous isotopic composition of oxygen (δ18O = 12.9–18.8‰) and carbon δ13C = –2.8 to +2.8‰). These rocks formed with the contribution of metamorphogenic fluids. According to the isotopic composition of hydrogen, the examined serpentinites are divided into two groups: with δD values specific to “magmatic water” (δD = –73.50 to –85.00‰) and those typical of meteoric fluids (δD = –151.90 to –167.20‰). The listvenites are characterized by low Rb and high Sr contents. Their 87Sr/86Sr values (0.70702–0.70971) indicate the contribution of a crustal source. The study of fluid inclusions in minerals from listvenites has shown that the rocks formed under relatively low-temperature conditions. The homogenization temperatures of fluid inclusions in quartz and magnesite from listvenites of the Ospa–Kitoi massif are 184–290 ºC and 122–182 ºC, respectively. In the Parama massif, the homogenization temperature of fluid inclusions in quartz is 130–170 ºC. The solutions that formed listvenites of the Ospa–Kitoi massif were slightly saline (TDS = 2.9–8.4 wt.% NaCl eq.), with NaCl and Na2CO3 being the main salt components.

Valuable metals in coals of the Russian Arctic zone

The research results of rare and valuable metals and estimations of resources of these metals in the coal deposits of the Russian Arctic zone are presented. In coal deposits in the Arctic zone of Russia (Pechora, Lensky, Tungusky, Taimyrsky, Zyryansky coal basins, coal deposits of Chukotka, Kamchatka, Franz Josef Land) anomalous concentrations of trace elements (Sc, Ti, V, Ga, Ge, Sr, Y, Zr, Nb. Mo, Pd, REE, etc.) have been established. The metal contents in the coals of the Lensky and Zyryansky basins, the deposits of Kamchatka, and the Franz Josef Land are given. The results of electron microscopic studies of mineral inclusions (with local microanalysis for their diagnosis) of coals of the Russian Arctic are presented. The results of calculating the prognostic resources of TiO2, V2O5, Th, Y2O3, REE 2O3, Sc, Mo, Ga, and other metals in the studied deposits are given. It is shown that coal deposits of the Russian Arctic zone should be considered as an unconventional and promising source of valuable metals. It is necessary to conduct extensive studies of the metal content of coal basins and deposits in the Arctic zone of Russia and assess the geological resources of the valuable metals contained in them.

Micropetrology: Are Inclusions Grains of Truth?

Inclusions in minerals, whether fluids, melts or crystalline phases, are small pieces of the large-scale puzzle of Nature, time-consuming to investigate and often of difficult interpretation. Yet they are windows into the past of their host mineral. Mineral inclusions provide the opportunity to unravel the genesis of their host, and the increasingly refined understanding of their elastic behaviour provides the basis for alternative, equilibrium-independent geobarometry. Fluid and melt inclusions reveal information about material transfer in the Earth system, from shallow mineralization to mantle re-fertilization via subduction. The study of inclusions is thus one of the most intriguing and fertile branches of micropetrology. In this contribution, we focus on two recent developments: the use of elasticity models to extract the formation conditions of the host crystal, and the discovery and investigation of melt inclusions in metamorphic rocks. We also discuss how to evaluate the information provided by inclusions, given that they are no longer at the pressure and temperature conditions of entrapment. We discuss how to understand and quantify the changes undergone during cooling and depressurization, and how metastability-related phenomena in inclusions, such as crystallization of rare polymorphs and preservation of the original content of volatiles in fluid and melt inclusions, provide direct evidence that inclusions represent closed systems. The field of study of inclusions in minerals still has a largely untapped potential. The most fruitful avenues for future research will emerge from continuous technological innovation in analytical and imaging techniques, the application of experimental petrology, and the development and application of new theoretical models for coupled mineral behaviour under changing P-T conditions.

Mineral inclusions in rutile: A novel recorder of HP-UHP metamorphism

The ability to accurately constrain the secular record of high- and ultra-high pressure metamorphism on Earth is potentially hampered as these rocks are metastable and prone to retrogression, particularly during exhumation. Rutile is among the most widespread and best preserved minerals in high- and ultra-high pressure rocks and a hitherto untested approach is to use mineral inclusions within rutile to record such conditions. In this study, rutiles from three different high- and ultrahigh-pressure massifs have been investigated for inclusions. Rutile is shown to contain inclusions of high-pressure minerals such as omphacite, garnet and high silica phengite, as well as diagnostic ultrahigh-pressure minerals, including the first reported occurrence of exceptionally preserved monomineralic coesite in rutile from the Dora–Maira massif. Chemical comparison of inclusion and matrix phases show that inclusions generally represent peak metamorphic assemblages; although rare prograde phases such as titanite, omphacite and corundum have also been identified implying that rutile grows continuously during prograde burial and traps mineralogic evidence of this evolution. Pressure estimates obtained from mineral inclusions, when used in conjunction with Zr-in-rutile thermometry, can provide additional constraints on the metamorphic conditions of the host rock. This study demonstrates that rutile is an excellent repository for high- and ultra-high pressure minerals and that the study of mineral inclusions in rutile may profoundly change the way we investigate and recover evidence of such events in both detrital populations and partially retrogressed samples.

Formation of gold mineralization in ultramafic alkalic magmatic complexes

Study of mineral inclusions within alluvial gold particles of the Guli Complex (East Siberia) and findings of lode gold in rocks of the same intrusion have demonstrated that gold mineralization occurs in interstitions of both early high–magnesium rocks (dunite) and later alkalic and carbonatite rocks. In dunite the native gold occurs in association with Fe–Ni sulfides (monosulfide solid solution, pentlandite, and heazlewoodite). Formation of the gold-bearing alloys took place under a low oxygen potential over a broad range of temperatures: from those close to 600°C down to below 400°C.

PREDICTED SEDIMENTARY SECTION OF SUBGLACIAL LAKE VOSTOK

In early February 2012, the drill hole at the Vostok Station encountered theLakeVostokwater. This step is important to study the lake composition including possible microbial life and to model subglacial environments however, the next ambitious target of the Vostok Drilling Project is sampling of bottom sediments, which contain the unique record of ice sheet evolution and environmental changes in centralAntarcticafor millions of years. In this connection, the forecast of sedimentary succession based on existing geophysical data, study of mineral inclusions in the accretion ice cores and tectonic models is important task. Interpretation of Airborne geophysical data suggests thatLakeVostokis the part of spacious rift system, which exists at least from Cretaceous. Reflection and refraction seismic experiments conducted in the southern part ofLakeVostokshow very thin (200–300 m) stratified sedimentary cover overlying crystalline basement with velocity of 6.0–6.2 km/s. At present, deposition in southernLakeVostokis absent and similar conditions occurred likely at least last3 m.y. when ice sheet aboveLakeVostokchanged insignificantly. It can be also inferred that from the Late Miocene the rate of deposition inLakeVostokwas extremely low and so the most of sedimentary section is older being possibly of Oligocene to early to middle Miocene age when ice sheet oscillated and deposition was more vigorous. If so, the sampling of upper few meters of this condensed section is very informative in terms of history of Antarctic glaciation. Small thickness of sedimentary cover raises a question about existence of lake (rift) depression during preglacial and early glacial times.

First information about the geology of central antarctica based on study of mineral inclusions in ice cores of the Vostok station borehole

Study of mineral inclusions in the basal part of the central Antarctic ice sheet from the borehole at the Vostok station was carried out. Mineral inclusions were trapped during freezing of the subglacial Lake Vostok water on the base of the glacier, when it crossed a shallow coastal area. It is established that the mineral inclusions are aggregates consisting mainly of clay minerals and quartz up to 150 microns. Crystals of aragonite and sulfides detected in the inclusions may indicate the presence of modern hydrothermal activity beneath the ice. Small (up to 4.5 mm) fragments of siltstone and aleuropelite in some aggregates suggest that lithified clastic sediments are exposed on the western coast of Lake Vostok, where removal of debris material occurred at the expense of exaration. Detrital zircon and monazite, found in siltstones and aleuropelite, suggest the chronology of geological complexes of the provenance area, which is, as is assumed, located in the Gamburtsev mountains in the central Antarctic. The age of the provenance area is 0.8–1.2 to 1.6–2.0 billion years.

A 3‐D study of mineral inclusions in chromite from ordinary chondrites using synchrotron radiation X‐ray tomographic microscopy—Method and applications

Abstract– A method is described for imaging in 3‐D the interiors of meteoritic chromite grains and their inclusions using synchrotron radiation X‐ray tomographic microscopy. In ordinary chondrites, chromite is the only common mineral that survives long‐term weathering on Earth. Information about the silicate matrix of the original meteorite, however, can be derived from mineral inclusions preserved in the protecting chromite. The inclusions are crucial in the classification of fossil meteorites as well as sediment‐dispersed chromite grains from decomposed meteorites and larger impacts, as these are used for characterizing the past influx of material to Earth, but have previously been difficult to locate. The method is non‐destructive and time efficient for locating inclusions. The method allowed quantitative and morphological studies of both host chromite grains and inclusions in three dimensions. The study of 385 chromite grains from eight chondrites (H4–6, L4–6, LL4, LL6) reveals that inclusions are abundant and equally common in all samples. Almost two‐thirds of all chromite grains contain inclusions, regardless of group and type. The study also shows that the size of the inclusions and the host chromite grains, as well as the number of inclusions, within the host chromite grains vary with petrographic type. Thus, the petrographic type of the host of a suite of chromite grains can be determined based solely on inclusion content. The study also revealed that the amount of fractures in the host chromite can be correlated to previously assigned shock stages for the various chondrites. The study has thus shown that the features and inclusions of fossil chromite grains can give similar information about a former host meteorite as do studies of an unweathered whole meteorite, meaning that this technique is essential in the studies of ancient meteorite flux to Earth.

Experimental study of diamond crystallization in carbonate-peridotite melts at 8.5 GPa

The composition of the parental melt for the predominant mass of natural diamonds may be determined from concerted mineralogical and experimental data [1]. The study of mineral inclusions in diamonds demonstrates their affiliation to peridotite and eclogite parageneses [2]; i.e., the composition of the diamond crystallization medium is strongly variable. Its component composition may be estimated from inclusions of minerals, quenched melts, and fluids in diamonds. It has become evident that the multicomponent and multiphase parental medium consists of chemically different compounds and phases: oxides, silicates, aluminosilicates, sulfides, phosphates, carbonates, chlorides, metals, water, carbon dioxide, and others. However, the main problem of dominating compound in parental media during the diamond formation is still unclear. The reason is that efficiency of diamond formation for

Zircons and clay from morainal Permian siltstone at Mt Rymill (73°S, 66°E), Prince Charles Mountains, Antarctica, reflect the ancestral Gamburtsev Subglacial Mountains–Vostok Subglacial Highlands complex

Clasts of red siltstone with Glossopteris from moraine around Mt Rymill in the southern Prince Charles Mountains, East Antarctica, can be traced upslope in the Lambert Graben system to the nearby Gamburtsev Subglacial Mountains (GSM). The clasts contain zircons with SHRIMP U–Pb ages of 620–460 Ma and 1300–970 Ma from host rocks of intermediate to mafic rocks, and a clay fraction with a T DM Nd model age of 2.72 Ga and εNd of − 18.3, derived from upper continental crust. East of the GSM, at Lake Vostok, clasts of siltstone in accreted ice can be traced to the Vostok Subglacial Highlands (VSH). The clasts contain zircons and monazites with SHRIMP U–Pb ages [Leitchenkov, G.L., Belyatsky, B.V., Rodionov, N.V., Sergeev, S.A., 2007. Insight into the geology of the East Antarctic hinterland: a study of mineral inclusions from ice cores of the Lake Vostok borehole. In: Cooper, A.K., Raymond, C.R. (Eds.), Online Proceedings of the 10th ISAES, USGS Open-file Report 2007-1047, Short research Paper 014, 4 pages.] broadly similar to those from Mt Rymill, and a T DM Nd model age of 1.88 Ga and εNd of − 15 [Delmonte, B., Petit, J.R., Basile-Doelsch, I., Lipenkov, V., Maggi, V., 2004. First characterization and dating of East Antarctic bedrock inclusions from subglacial Lake Vostok accreted ice. Environmental Chemistry 1, 90–94.]. Other Mesozoic and Paleozoic sediments deposited in a radial pattern about central Antarctica contain detrital zircons dominated by populations aged 700–500 Ma and 1300–1000 Ma, which we interpret as reflecting a GSM-VSH provenance dominated by rocks generated during the Pan-Gondwanaland and Grenville events of supercontinental assembly.

Birefringence analysis of diamond utilising the MetriPol system

Birefringence has long been recognised in diamond as an anomalous optical property for a cubic mineral (Lang, 1967). Various causes have been postulated for this phenomenon but they all identify birefringence as being the result of the photoelastic effect (change of refractive index with stress) (Poindexter, 1955). Until now birefringence studies (a non-destructive analytical technique) has not been utilised because of the time-consuming and inaccurate nature of the analysis. The MetriPol is a new automated birefringence analysis system that can produce very accurate data in a matter of seconds (Glazer et al., 1996). The MetriPol system is being utilised in an experimental investigation to re-evaluate the photoelastic constants for diamond. These constants are fundamental in relating stress and strain to the resultant birefringence. Data generated from this birefringence analysis can easily be manipulated to calculate the stress and strain within a diamond. Optical studies of mineral inclusions have often reported the occurrence of strain birefringence in the surrounding diamond, and X-ray and Raman investigations of such inclusions have shown that some can remain under relatively high residual pressures after their transportation to the surface (e.g. Izraeli et al., 1999). We report quantitative birefringence analysis of such strain features and their implication concerning the P & T conditions of entrapment, assuming no subsequent strain release has occurred. This birefringence data is being compared with analyses using the above techniques, as well as finite element analysis modelling, to test the validity of the results.

Stable Isotopes and the Origin of Diamond

Most diamonds form in a relatively narrow depth interval of Earth's subcontinental mantle between 150 and 250 km. From carbon isotope analyses of diamond obtained in the 1970s, it was first proposed that eclogitic diamonds form from crustal carbon recycled into the mantle by subduction and that the more abundant peridotitic diamonds formed from mantle carbon. More recent stable isotope studies using nitrogen, oxygen, and sulfur, as well as carbon, combined with studies of mineral inclusions within diamonds, have strengthened arguments supporting and opposing the early proposal. The conflicting evidence is reconciled if mantle carbon is introduced via fluid into mantle eclogites and peridotites, some of which represent subducted oceanic crust.

Ion beam excited optical spectroscopy of inorganic compounds

Abstract

Association between rare-metal mineralization and acid magmatism based on a study of mineral inclusions

Association between rare-metal mineralization and acid magmatism based on a study of mineral inclusions

Conditions of origin of natural diamonds of peridotite affinity

Studies of mineral inclusions in natural diamonds and rare diamondiferous xenoliths from kimberlites show that most diamonds are associated with a dunite or harzburgite paragenesis. The diamondiferous peridotites and dunites have predominantly coarse or tabular textures that suggest low‐temperature (<1100°C) equilibration. Application of the KD Fe/Mg(Ga/Ol) geothermometer of O'Neill and Wood to analytical data for the minerals in these rocks shows that most have equilibrated below 1100°C. Application of this thermometer to pairs of olivine and garnet crystals included in individual diamonds indicates that the diamonds have crystallized in the range 900°–1300°C, with a majority of estimated equilibration temperatures falling in the range below 1150°C. Comparison of these estimates of equilibration temperature with the zone of invariant vapor composition solidus for kimberlite and garnet lherzolite determined by Eggler and Wendlandt suggests that many diamonds may have formed in subsolidus events.

DISTINCTIVE FEATURES OF THE HEALING OF A CRACK IN A CRYSTAL UNDER CONDITIONS OF DECLINING TEMPERATURE

The concentrations of aqueous solution from which quartz, feldspar, topaz, tourmaline and other minerals crystallize during the hydrothermal stage, is important to an understanding of pegmatite formation. Two opposing theories have been advanced on solution concentration: 1) Pegmatitic minerals separate from highly concentrated solution, without marked change in concentration, by gradual cooling. 2) Pegmatitic minerals separate as a result of flow and of renovation of the exhausted contents of solutions; this need is based on low solubility of silica in pure water. Study of liquid inclusions in minerals reveals that separation of hydrothermal minerals is known to occur from aqueous solutions heavily saturated with alkaline-halide salts, carbonates, borates, and free carbonic acid. From observations made on secondary liquid inclusions in topaz samples from pegmatites, it was found that one-third of the inclusion-cavity volume was occupied by the gas bubble and the remainder of the volume, largely, by small...