The study of kimberlite rocks is important as they provide critical information regarding the composition and dynamics of the continental mantle and are the principal source of diamonds. Despite many ...decades of research, the original compositions of kimberlite melts, which are thought to be derived from depths > 150 km, remain highly debatable due to processes that can significantly modify their composition during ascent and emplacement. Snapshots of the kimberlite‐related melts were entrapped as secondary melt inclusions hosted in olivine from sheared peridotite xenoliths from the Udachnaya‐East pipe (Siberian craton). These xenoliths originated from 180‐ to 220‐km depth and are among the deepest derived samples of mantle rocks exposed at the surface. The crystallised melt inclusions contain diverse daughter mineral assemblages (>30 mineral species), which are dominated by alkali‐rich carbonates, sulfates, and chlorides. The presence of aragonite as a daughter mineral suggests a high‐pressure origin for these inclusions. Raman‐mapping studies of unexposed inclusions show that they are dominated by carbonates (>65 vol.%), whereas silicates are subordinate (<13 vol.%). This indicates that the parental melt for the inclusions was carbonatitic. The key chemical features of this melt are very high contents of alkalis, carbon dioxide, chlorine, and sulfur and extremely low silica and water. Alkali‐carbonate melts entrapped in xenolith minerals likely represent snapshots of the primitive kimberlite melt. This composition is in contrast with the generally accepted notion that kimberlites originated as ultramafic silicate water‐rich melts. Experimental studies revealed that alkali‐carbonate melts are a very suitable diamond‐forming media. Therefore, our findings support the idea that some diamonds and kimberlite magmatism may be genetically related.
Olivine‐hosted secondary melt inclusions from deepest mantle xenoliths from the Udachnaya kimberlite pipe (Siberian craton, Russia) were studied. Raman‐mapping studies of unexposed inclusions show that they are dominated by carbonates (>65 vol.%, especially alkali‐rich varieties), whereas silicates are subordinate (<13 vol.%), i.e. the melt parental for these inclusions was alkali‐carbonatitic. The presence of aragonite, a high‐pressure polymorph of CaCO3, among carbonates suggests deep mantle origin for these inclusions and they likely represent snapshots of the primitive kimberlite melt.
Abstract
Trace amounts of water dissolved in minerals affect density, viscosity and melting behaviour of the Earth’s mantle and play an important role in global tectonics, magmatism and volatile ...cycle. Water concentrations and the ratios of hydrogen isotopes in the mantle give insight into these processes, as well as into the origin of terrestrial water. Here we show the presence of molecular H
2
in minerals (omphacites) from eclogites from the Kaapvaal and Siberian cratons. These omphacites contain both high amounts of H
2
(70 to 460 wt. ppm) and OH. Furthermore, their ∂D values increase with dehydration, suggesting a positive H isotope fractionation factor between minerals and H
2
–bearing fluid, contrary to what is expected in case of isotopic exchange between minerals and H
2
O-fluids. The possibility of incorporation of large quantities of H as H
2
in nominally anhydrous minerals implies that the storage capacity of H in the mantle may have been underestimated, and sheds new light on H isotope variations in mantle magmas and minerals.
One of the problems of public administration is the need to select the best criteria for assessing the quality of life of the population. The aim of the study is to provide a critical analysis of ...current approaches to measuring and monitoring the quality of life of the population. The object of the study is the quality of life of the population. The subject of the research is approaches to measuring and monitoring the quality of life of the population.The article provides a comparative characteristic of the prevailing classes of measures used in economics. The advantages and disadvantages of natural, monetary, physical, power, temporal, dimensionless units of quality of life have been analysed. The main foreign and domestic approaches to such monitoring have been considered and the positions of the Russian Federation in foreign ratings of the quality of life have been indicated. Using the methods of content analysis, comparison, systems analysis, expert assessment, etc., the features of contemporary quality of life assessment tools have been highlighted. Global, subnational and national quality of life assessment methods in relation to measurement tools have been compared and a comparative analysis has been presented in a summary graph.The author’s classification of quality of life management approaches has been presented. Historical and economic analysis allows us to distinguish between the monetarist approach, the social justice approach, and the physico-economic approach. Monetary methods of managing the quality of life of the population are based on financial and economic factors and monetary measurement tools, the social justice approach is based on the study of socio-psychological factors and life satisfaction indicators, the physical and economic approach reconciles the needs of the socio-economic system with the capabilities of the natural environment and uses power units of measurement. Foreign research in recent years has been dominated by subjective (socio-psychological) measurement methods, whereas in Russian research objective measurement indicators still play a major role in monitoring quality of life.The article offers recommendations for developing an improved methodology for assessing the quality of life of the population using social time.
The paper presents a comprehensive review of currently available data on melt inclusions entrapped in minerals of kimberlites of different age and different provenance in ancient cratons. The ...crystallized melt inclusions represent snapshots of kimberlite melts at different stages of their evolution. All of the inclusions are completely crystallized and consist of daughter minerals and shrinkage bubbles, which sometimes contain low-density CO
2
, but no aqueous fluids and quenched silicate glasses have been found so far. Although more than 60 mineral species have been identified among the daughter phases in the inclusions, all inclusions hosted in various minerals from different kimberlites have closely similar or even identical composition. The daughter minerals are various Na–K–Ca, Na–Ca, Na–Mg, K–Ca, Ca–Mg, Ca, Mg, and Na carbonates; Na–Mg and Na carbonates with additional anions Cl
–
,
, and
; and alkali sulfates, chlorides, phosphates, sulfides, oxides, and silicates. Alkali carbonates, sulfates, and chlorides are usually absent from among the groundmass phases of most kimberlites sampled worldwide, except the Udachnaya-East kimberlite in Siberia. However, this mineral assemblage, in association with such widespread kimberlite minerals as olivine, micas, monticellite, spinel-group minerals, perovskite, rutile, ilmenite, calcite, and dolomite, is common in the crystallized melt inclusions in all studied kimberlites. Carbonates (~30 to 85 vol %) always dominate over silicates (no more than 18 vol %) in all inclusions. All inclusions also contain variable (2 to 55 vol %.) amounts of chlorides (halite and sylvite). In cases where the abundance of carbonates is relatively low (30–50 vol %), the other major phases within inclusions are chlorides (18–55 vol %) rather than daughter silicates, as could be expected based on the traditional paradigm of the silicate composition of kimberlite melts. Published data on melt inclusions in the kimberlite minerals strongly imply that parental kimberlite melts were generated and further evolved within the Na
2
O–K
2
O–CaO–MgO–CO
2
–Cl system, that is, they were alkali-rich carbonate/carbonate–chloride liquids. According to various estimates, SiO
2
content in kimberlite melts could have varied during different stages of their evolution from a few to 19 wt %. Clearly, kimberlite bodies are altered in the crust via interaction with meteoric and/or connate waters, resulting in serpentinization of kimberlite olivine and dissolution of many bona fide magmatic minerals, such as alkali carbonates, sulfates, and chlorides. In the traditional approach to studying kimberlites, the role of such components as Na
2
O, CO
2
, Cl, and to a lesser extent K
2
O, S, and F in the petrogenesis of kimberlite magmas and rocks have been largely underestimated, while the roles of olivine- and serpentine-forming components, such as of SiO
2
, MgO, and H
2
O are still exaggerated.
In chronic experiments on calves, the effect of the left-ventricular assist device (LVAD) technique by using a disc pump on the indicators of ionic and acid-base homeostasis. At blood velocity of 20% ...from the total volume, a trend towards an increase in K
+
concentration and a slight decrease in the concentration of Na
+
, pH, and standard base excess in animal plasma were observed. If the blood velocity increased up to 90%, the indicators of ionic and acid-base homeostasis returned to their baseline values. In parallel, stroke volume and cardiac output as well as BP at the outlet of the heart and inside it and HR increased simultaneously with a blood pressure decrease in the input cannula site. There were no differences in plasma concentrations of Ca
2+
and Cl
-
at different blood flow volumes.
Cratons represent the oldest preserved lithospheric domains. Their lithosphere (lithospheric mantle welded to overlying Precambrian crystalline basement) is considered to be particularly robust and ...long-lived due to the protecting presence of buoyant and rigid “keels” made up of residual harzburgites. Although the cratons are mostly assumed to form in the Archaean, the timing of their formation remains poorly constrained. In particular, there are very few datasets describing concurrently the age of both the crustal and mantle portions of the lithosphere. In this study, we report new U–Pb ages and Hf isotope compositions for zircons in crustal xenoliths from the Udachnaya kimberlite in the central Siberian craton; this dataset includes samples from both the upper and lower portions of the crust. The zircon ages agree well with model melt-extraction Re–Os ages on refractory peridotite xenoliths from the same pipe; taken together they allow an integrated view of lithosphere formation. Our data reveal that the present day upper crust is Archaean, whereas both the lower crust and the lithospheric mantle yield Paleoproterozoic ages. We infer that the deep lithosphere beneath the Siberian craton was not formed in a single Archaean event, but grew in at least two distinct events, one in the late Archaean and the other in the Paleoproterozoic. Importantly, a complete or large-scale delamination and rejuvenation of the Archaean lower lithosphere (lower crust and lithospheric mantle) took place in the Paleoproterozoic. This further demonstrates that craton formation can be a protracted, multi-stage process, and that the present day crust and mantle may not represent complementary reservoirs formed through the same tectono-magmatic event. Further, deep cratonic lithosphere may be less robust and long living than often assumed, with rejuvenation and replacement events throughout its history.
•Crustal xenoliths at Udachnaya pipe include both granulitic lower crust and gneissic upper crust.•Lower crustal samples have a Paleoproterozoic U–Pb zircon age.•Upper crustal samples are Neoarchaean (ca. 2.7 Ga).•The Proterozoic lower crust does not correspond to reworking of the Archaean crust.•The Archaean lithosphere was removed and replaced in the Paleoproterozoic.
We examine major and trace element compositions of whole-rocks and minerals of 18 spinel harzburgite xenoliths from the Udachnaya kimberlite in the central Siberian craton. The samples are fresh, ...modally homogeneous and large enough to provide representative whole-rock samples (>100g); all residual spinel peridotites in our collections that satisfied these criteria were selected for this study. Their Mg# ranges from 0.92 to 0.93. Thirteen xenoliths have 6–22% orthopyroxene (opx) and 0–3% clinopyroxene (cpx); five are opx-rich (31–43%) and contain 3–5% cpx. The low-opx Udachnaya harzburgites define regular co-variation trends on major and minor oxide plots and appear to be pristine melt extraction residues. Their Al–Fe and Al–Mg# trends, in combination with experimental results on melting of fertile peridotites, indicate an origin by ∼40% of polybaric decompression fractional melting between 7−4GPa and ≤1–2GPa. In line with Cr and HREE abundances, garnet was stable in the residues at early melting stages. Thus, the spinel facies cratonic peridotites situated at >40 to 130km (1–4GPa), are residues of melting that took place over a broader depth range; the residues probably underwent density-driven segregation from the denser ambient mantle to form the base of cratonic nuclei. The opx-rich Udachnaya harzbrugites cannot be produced by dry or hydrous melting at 1–7GPa and might be related to fractionation or metamorphic segregation of initial high-P melting residues and their interaction with interstitial liquids retained in the residues during gravity-driven upwelling. Our results, in comparison with published data on arc and fore-arc peridotites, show no evidence that significant enrichments in silica (opx) could be produced during melting or metasomatism in subduction settings, or that initial melting residues were dunites, which were later transformed to harzburgites by melt-rock reactions.
► Low-opx harzburgites are most common and are pristine melt extraction residues. ► They are formed by 40% decompression melting between 7−4GPa and ≤1–3GPa. ► Garnet was stable in the residues at early melting stages. ► Opx-rich harzburgites cannot be residues of dry or hydrous melting.
This paper reports the first discovery of zoned aragonite, a high-pressure CaCO
3
polymorph, in a mantle xenolith from kimberlite. Aragonite is the most common epigenetic mineral in the studied ...xenolith and is located in the interstitial space, where it can occupy up to 80 vol %. According to the
P‒T
parameters of the last equilibrium (6.9 GPa and 1350°C), the studied sheared lherzolite belongs to the deepest mantle xenoliths from kimberlites. Based on the stability of aragonite, it could have formed in sheared lherzolite both
in situ
in the lithospheric mantle and during ascent of the kimberlite magma to a depth of ~80 km. The studied aragonite has high contents of SrO (from ~0.7 to 8.3 wt %) and Na
2
O (up to ~1.1 wt %). Diffusion modeling at mantle temperatures of 1100–1350°C shows that the aragonite grains lose zonation in SrO over ~1–7 years. Thus, the zonation pattern indicates a link between the formation of aragonite in the sheared lherzolite and magmatism, which formed the eastern body of the Udachnaya pipe. In general, such high contents of aragonite in the interstitial space of the studied xenolith are direct evidence of the existence of carbonatite melts in the lithospheric mantle of ancient cratons at depths below ~230 km shortly before the formation of kimberlites on the surface. The results in the present study again raise the question regarding the compositions of primitive kimberlite melts and true concentrations of alkalis (in particular, Na
2
O) in them.
Aptamers are widely used as molecular recognition elements for detecting and blocking functional biological molecules. Since the common “alphabet” of DNA and RNA consists of only four letters, the ...chemical diversity of aptamers is less than the diversity of protein recognition elements built of 20 amino acids. Chemical modification of nucleotides enlarges the potential of DNA/RNA aptamers. This review describes the latest achievements in a variety of approaches to aptamers selection with an extended genetic alphabet.
PDF
