Multiple-mineral inclusions in diamonds from the Snap Lake/King Lake kimberlite dike, Slave craton, Canada: a trace-element perspective     

Prinya Promprated  Lawrence A. Taylor  Mahesh Anand  Christine Floss  Nikolai V. Sobolev  Nikolai P. Pokhilenko 《Lithos》2004,77(1-4):69-81

Multiple inclusions of minerals in diamonds from the Snap Lake/King Lake kimberlites of the southeastern Slave craton in Canada have been analyzed for trace elements to elucidate the petrogenetic history of these inclusions, and of their host diamonds. As observed worldwide, the harzburgitic-garnet diamond inclusions (DIs) possess sinusoidal REE patterns that indicate an early depletion event, followed by metasomatism by LREE-enriched, HREE-depleted fluids. Furthermore, these fluids appear to contain appreciable concentrations of LILE and HFSE, based on the increasing abundances of these elements in the olivine inclusion that occurs at the outer portion of a diamond compared to that near the core. The compositions of these fluids are probably a mixture of hydrous-silicic melt, carbonatitic melt, and brine, similar to the compositions of micro-inclusions in diamonds reported by Navon et al. (2003). Comparison between the compositions of majoritic and normal harzburgitic garnets shows that the former are more depleted in terms of major/minor elements (higher Cr#) but significantly more enriched in the REE (up to 10×). This characteristic may indicate the higher susceptibility for metasomatic enrichment of previously more depleted garnets. Garnets of eclogitic paragenesis show strong LREE-depleted patterns, whereas the coexisting omphacite inclusion has relatively flat light- and middle-REE but depleted HREE. Whole-rock reconstruction from coexisting garnet and omphacite inclusions indicates that the protolith of these inclusions was probably the extrusive section of an oceanic crust, subducted beneath the Slave craton.  相似文献   

Nature of diamonds in Yakutian eclogites: views from eclogite tomography and mineral inclusions in diamonds   总被引：1，自引：0，他引：1  

Mahesh Anand  Lawrence A. Taylor  Kula C. Misra  William D. Carlson  Nikolai V. Sobolev 《Lithos》2004,77(1-4):333-348

We have performed dissections of two diamondiferous eclogites (UX-1 and U33/1) from the Udachnaya kimberlite, Yakutia in order to understand the nature of diamond formation and the relationship between the diamonds, their mineral inclusions, and host eclogite minerals. Diamonds were carefully recovered from each xenolith, based upon high-resolution X-ray tomography images and three-dimensional models. The nature and physical properties of minerals, in direct contact with diamonds, were investigated at the time of diamond extraction. Polished sections of the eclogites were made, containing the mould areas of the diamonds, to further investigate the chemical compositions of the host minerals and the phases that were in contact with diamonds. Major- and minor-element compositions of silicate and sulfide mineral inclusions in diamonds show variations among each other, and from those in the host eclogites. Oxygen isotope compositions of one garnet and five clinopyroxene inclusions in diamonds from another Udachnaya eclogite (U51) span the entire range recorded for eclogite xenoliths from Udachnaya. In addition, the reported compositions of almost all clinopyroxene inclusions in U51 diamonds exhibit positive Eu anomaly. This feature, together with the oxygen isotopic characteristics, is consistent with the well-established hypothesis of subduction origin for Udachnaya eclogite xenoliths. It is intuitive to expect that all eclogite xenoliths in a particular kimberlite should have common heritage, at least with respect to their included diamonds. However, the variation in the composition of multiple inclusions within diamonds, and among diamonds, from the same eclogite indicates the involvement of complex processes in diamond genesis, at least in the eclogite xenoliths from Yakutia that we have studied.  相似文献   

Surface wave tomography of the Barents Sea and surrounding regions   总被引：1，自引：0，他引：1  

Anatoli L. Levshin  Johannes Schweitzer  Christian Weidle  Nikolai M. Shapiro  Michael H. Ritzwoller 《Geophysical Journal International》2007,170(1):441-459

The goal of this study is to refine knowledge of the structure and tectonic history of the European Arctic using the combination of all available seismological surface wave data, including historical data that were not used before for this purpose. We demonstrate how the improved data coverage leads to better depth and spatial resolution of the seismological model and discovery of intriguing features of upper-mantle structure. To improve the surface wave data set in the European Arctic, we extensively searched for broad-band data from stations in the area from the beginning of the 1970s until 2005. We were able to retrieve surface wave observations from regional data archives in Norway, Finland, Denmark and Russia in addition to data from the data centres of IRIS and GEOFON. Rayleigh and Love wave group velocity measurements between 10 and 150 s period were combined with existing data provided by the University of Colorado at Boulder. This new data set was inverted for maps showing the 2-D group-velocity distribution of Love and Rayleigh waves for specific periods. Using Monte Carlo inversion, we constructed a new 3-D shear velocity model of the crust and upper mantle beneath the European Arctic which provides higher resolution and accuracy than previous models. A new crustal model of the Barents Sea and surrounding areas, published recently by a collaboration between the University of Oslo, NORSAR and the USGS, constrains the 3-D inversion of the surface wave data in the shallow lithosphere. The new 3-D model, BARMOD, reveals substantial variations in shear wave speeds in the upper mantle across the region with a nominal resolution of 1°× 1°. Of particular note are clarified images of the mantle expression of the continent-ocean transition in the Norwegian Sea and a deep, high wave speed lithospheric root beneath the Eastern Barents Sea, which presumably is the remnant of several Palaeozoic collisions.  相似文献   

The protolith nature of diamondiferous metamorphic rocks of the Kokchetav Massif     

Vladislav Shatsky  Emil Jagoutz  Olga Kozmenko  Alexey Ragozin  Sergei Skuzovatov  Nikolai Sobolev 《《地质学报》英文版》2018,92(Z1):173-173

  相似文献   

Sicilian serpentinite xenoliths containing abiotic organics with nanodiamond clusters as key model for prebiotic processes     

Sergei K.Simakov  Vittorio Scribano  Nikolai N.Mel’Nik  Germana Barone 《地学前缘(英文版)》2021,12(1):255-263

Rock fragments from the deepest parts of a buried hydrothermal system belonging to the Mesozoic Tethys Ocean entered as xenoliths in a Miocenic diatreme,hence brought to the surface,in the Hyblean Plateau(Sicily).Some xenoliths consist of strongly serpentinized ultramafic rocks bearing blebs of abiotic organic matter,where clusters of amorphous carbon nanoparticles,including nanodiamonds,are immersed.Such an occurrence conjures up established hypotheses that diamond surfaces are suitable catalytic platforms stimulating the assemblage of complex bio-organic molecules relevant to the emergence of life on Earth.The appearance of bio-organic molecules under primitive Earth conditions is one of the major unsolved questions on the origin of life.Here we report new micro-Raman spectra on blebs of abiotic organic matter from a selected xenolith.Diamond bands were related to hydrogenated nanocrystalline diamonds,with size of nearly 1-1.6 nm,formed from organics at low pressures and temperatures.In particular,diamond surfaces can give rise to crystalline interfacial water layers that may have played a fundamental role in the early biosphere evolution as a good medium for rapidly transporting positive charges in the form of hydrated protons.Nowadays,proton gradients in alkaline hydrothermal vents along oceanic ridges are generally viewed as key pre-biotic factors.In general,serpentinites span the entire geological record,including prebiotic times.These hydrous ultramafic rocks often display evidence of abiotic carbon species,both organic and inorganic,including nanodiamonds,being also capable to give rise to chemiosmotic processes and proton gradients necessary to the organisms,such as the"Last Universal Common Ancestor"(LUCA),in the prebiotic Earth.  相似文献   

A novel probe for point injections in groundwater monitoring wells     

Fahrmeier  Nikolai  Goeppert  Nadine  Goldscheider  Nico 《Hydrogeology Journal》2022,30(3):1021-1029

Hydrogeology Journal - Groundwater monitoring wells or boreholes often show complex flow behaviors that are essential to understand for the characterization of aquifer systems. In karst or...  相似文献   

Multi-stage metasomatism of diamondiferous eclogite xenoliths from the Udachnaya kimberlite pipe,Yakutia, Siberia   总被引：1，自引：1，他引：0  

Kula?C.?MisraEmail author  Mahesh?Anand  Lawrence?A.?Taylor  Nikolai?V.?Sobolev 《Contributions to Mineralogy and Petrology》2004,146(6):696-714

The primary garnet (pyrope-almandine)-omphacite (Cpx 1, 6.5–7 wt% Na₂O)-sulfide (Fe-Ni-Co mss) assemblage of the two diamondiferous eclogite xenoliths studied (U33/1 and UX/1) experienced two mantle metasomatic events. The metasomatic event I is recorded by the formation of platy phlogopite (~ 10 wt% K₂O), prior to incorporation of the xenoliths in the kimberlite. The bulk of the metasomatic alteration, consisting of spongy-textured clinopyroxene (Cpx 2A, 1–3 wt% Na₂O), coarser-grained clinopyroxene (Cpx 2B, 2–5 wt% Na₂O), pargasitic amphibole (~ 0.8 wt% K₂O; 3–3.5 wt% Na₂O), kelyphite (Cpx 3, mostly <1 wt% Na₂O; and zoned Mg-Fe-Al spinel), sodalite, calcite, K-feldspar, djerfisherite (K_5.95Na_0.02Fe_18.72Ni_2.36Co_0.01Cu_4.08S₂₆Cl ) and a small amount of K-Ca-Fe-Mg glass, is ascribed to the metasomatic event II that occurred also in the upper mantle, but after the xenoliths were incorporated in the kimberlite. A pervasive chloritic alteration (mainly clinochlore + magnetite) that overprints earlier assemblages probably took place in the upper crustal environment. The diamonds are invariably associated with secondary clinopyroxene and chlorite, but the diamonds formed before the entrainment of the xenoliths in the Udachnaya kimberlite.Editorial Responsibility: T.L. Grove  相似文献   

Palaeoclimatic record from a loess–soil profile in northeastern Bulgaria—II. Correlation with global climatic events during the Pleistocene     

Diana Jordanova  & Nikolai Petersen 《Geophysical Journal International》1999,138(2):533-540

Magnetic susceptibility ( χ ) variations and the behaviour of the ratio of susceptibility to saturation magnetization ( χ/J _s ) along the loess/palaeosol section at Koriten (NE Bulgaria) are used to deduce climatic changes during the Pleistocene in southeastern Europe. A good correlation of susceptibility variations with the astronomically tuned oxygen isotope record from ODP site 677 enables us to propose a more precise dating of the upper part of the Bulgarian loess complex. Close correspondence between susceptibility and δ ^{1 8} O records demonstrates the global significance of the palaeoclimatic signal recorded, although differences in relative amplitudes of χ and χ/J _s and δ ^{1 8} O create difficulties in making quantitative estimates of the climatic humidity in the past. The role of local factors affecting the palaeoclimatic mineral magnetic record deduced from the profile studied in Bulgaria is discussed.  相似文献   

Influence of the Solar Activity Cycle on the Gasdynamic Structureof the Heliospheric Interface     

Nikolai Zaitsev 《Astrophysics and Space Science》2000,274(1-2):149-156

The effects of the 11 year solar activity cycle on the heliospheric plasma interface in the presence of neutral H-atoms have been investigated. Our calculations show that nonstationary processes of such kind lead to1) a decrease of the mean interstellar plasma density in the interface;2) a sequence of shocks and rarefaction waves moving from the heliopause (HP)to the bow shock (BS); 3) an expansion of the region between the BS and HP;4) the TS excursion along the upwind direction is within 30%of the mean solar distance. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Long-Term Temperature Trends and Tree Growth in the Taymir Region of Northern Siberia   总被引：2，自引：0，他引：2  

Gordon C. Jacoby  Nikolai V. Lovelius  Oleg I. Shumilov  Oleg M. Raspopov  Juri M. Karbainov  David C. Frank 《Quaternary Research》2000,53(3):312

The northernmost conifers in the world are located well above the Arctic Circle in the Taymir region of northern Siberia and have been recording the thermal environment for centuries to millennia. The trees respond to temperatures beyond the narrow season of actual cambial cell division by means of root growth, photosynthesis, lignification of cell walls, and other biochemical processes. Data from annual tree-ring widths are used to reconstruct May–September mean temperatures for the past four centuries. These warm-season temperatures correlate with annual temperatures and indicate unusual warming in the 20th century. However, there is a loss of thermal response in ring widths since about 1970. Previously the warmer temperatures induced wider rings. Most major warming and cooling trends are in agreement with other high-latitude temperature reconstructions based on tree-ring analyses with some regional differences in timing of cooling in the late 18th century and of warming in the late 19th century.  相似文献