Distribution and changes of active layer thickness (ALT) and soil temperature (TTOP) in the source area of the Yellow River using the GIPL model   总被引：2，自引：0，他引：2  

DongLiang Luo  Jin HuiJun  Sergei Marchenko  Vladimir Romanovsky 《中国科学:地球科学(英文版)》2014,57(8):1834-1845

Active layer thickness (ALT) is critical to the understanding of the surface energy balance, hydrological cycles, plant growth, and cold region engineering projects in permafrost regions. The temperature at the bottom of the active layer, a boundary layer between the equilibrium thermal state (in permafrost below) and transient thermal state (in the atmosphere and surface canopies above), is an important parameter to reflect the existence and thermal stability of permafrost. In this study, the Geophysical Institute Permafrost Model (GIPL) was used to model the spatial distribution of and changes in ALT and soil temperature in the Source Area of the Yellow River (SAYR), where continuous, discontinuous, and sporadic permafrost coexists with seasonally frozen ground. Monthly air temperatures downscaled from the CRU TS3.0 datasets, monthly snow depth derived from the passive microwave remote-sensing data SMMR and SSM/I, and vegetation patterns and soil properties at scale of 1:1000000 were used as input data after modified with GIS techniques. The model validation was carried out carefully with ALT in the SAYR has significantly increased from 1.8 m in 1980 to 2.4 m in 2006 at an average rate of 2.2 cm yr^?1. The mean annual temperature at the bottom of the active layer, or temperature at the top of permafrost (TTOP) rose substantially from ?1.1°C in 1980 to ?0.6°C in 2006 at an average rate of 0.018°C yr^?1. The increasing rate of the ALT and TTOP has accelerated since 2000. Regional warming and degradation of permafrost has also occurred, and the changes in the areal extent of regions with a sub-zero TTOP shrank from 2.4×10⁴ to 2.2×10⁴ km² at an average rate of 74 km² yr^?1. Changes of ALT and temperature have adversely affected the environmental stability in the SAYR.  相似文献   

Observations of the Deeply Eclipsing Dwarf Nova Gy Cnc     

Nataly A. Katysheva  Sergei Yu. Shugarov 《Astrophysics and Space Science》2005,296(1-4):469-472

We present photometric measurements of the eclipsing dwarf nova and X-ray source GY Cnc. The observations were collected during outbursts and in quiescence. The investigation of plates from the Sonneberg archive showed that the mean outburst interval is about 210–270 days, that the outburst is very fast, and lasts for about 5 days.  相似文献   

Petrological constraints on the origin of arc picrites,New Georgia Group,Solomon Islands   总被引：7，自引：0，他引：7  

A.?RohrbachEmail author  S.?Schuth  C.?Ballhaus  C.?Münker  S.?Matveev  C.?Qopoto 《Contributions to Mineralogy and Petrology》2005,149(6):685-698

Subduction related picrites from the New Georgia archipelago (Solomon Islands) range in bulk MgO from 13 to 30 wt%. Two generations of olivine are identified based on CaO contents: High-CaO olivine phenocrysts from the picritic parental melt and low-CaO olivine xenocrysts incorporated from either lithospheric or asthenospheric upper mantle. There is also evidence that some of the low-CaO olivines are boninitic in origin. The bulk MgO range in the picrites is largely controlled by assimilation of low-CaO olivine xenocrysts. Oxidation states of the melt (FMQ+2.2), calculated from magnetite activities in liquidus chromites, constrain the MgO content of the parental melt to 13 wt%, assuming Fe–Mg exchange equilibrium between melt and liquidus olivine composition. The dry liquidus temperature of the parent melt based on this MgO content is 1340°C, about 80°C above the temperature obtained with the olivine–clinopyroxene Ca-exchange thermobarometer. The residence time of the low-CaO olivine xenocrysts in the magma, estimated from Ca- and Fe–Mg interdiffusion profiles, did not exceed 1 year.  相似文献   

On the calculation of low-frequency oscillations of the Earth's core     

Sergei Diakonov 《Geophysical Journal International》1991,107(2):291-296

  相似文献   

Post-collisional melting of crustal sources: constraints from geochronology,petrology and Sr,Nd isotope geochemistry of the Variscan Sichevita and Poniasca granitoid plutons (South Carpathians,Romania)   总被引：1，自引：1，他引：0  

Jean-Clair Duchesne  Jean-Paul Liègeois  Viorica Iancu  Tudor Berza  Dmitry I. Matukov  Mihai Tatu  Sergei A. Sergeev 《International Journal of Earth Sciences》2008,97(4):705-723

The Sichevita and Poniasca plutons belong to an alignment of granites cutting across the metamorphic basement of the Getic Nappe in the South Carpathians. The present work provides SHRIMP age data for the zircon population from a Poniasca biotite diorite and geochemical analyses (major and trace elements, Sr–Nd isotopes) of representative rock types from the two intrusions grading from biotite diorite to biotite K-feldspar porphyritic monzogranite. U–Pb zircon data yielded 311 ± 2 Ma for the intrusion of the biotite diorite. Granites are mostly high-K leucogranites, and biotite diorites are magnesian, and calcic to calc-alkaline. Sr, and Nd isotope and trace element data (REE, Th, Ta, Cr, Ba and Rb) permit distinguishing five different groups of rocks corresponding to several magma batches: the Poniasca biotite diorite (P₁) shows a clear crustal character while the Poniasca granite (P₂) is more juvenile. Conversely, Sichevita biotite diorite (S₁), and a granite (S₂*) are more juvenile than the other Sichevita granites (S₂). Geochemical modelling of major elements and REE suggests that fractional crystallization can account for variations within P₁ and S₁ groups. Dehydration melting of a number of protoliths may be the source of these magma batches. The Variscan basement, a subduction accretion wedge, could correspond to such a heterogeneous source. The intrusion of the Sichevita–Poniasca plutons took place in the final stages of the Variscan orogeny, as is the case for a series of European granites around 310 Ma ago, especially in Bulgaria and in Iberia, no Alleghenian granitoids (late Carboniferous—early Permian times) being known in the Getic nappe. The geodynamical environment of Sichevita–Poniasca was typically post-collisional of the Variscan orogenic phase.  相似文献   

Temperature regime of mountain permafrost in the Russian Altai Mountains     

Robert SYSOLYATIN  Sergei SERIKOV  Mikhail ZHELEZNYAK  Mark SHATZ  Yana TIKHONRAVOVA 《山地科学学报》2022,(1):33-45

This study presents the long-term temperature monitoring in the Russian Altai Mountains.In contrast to the Mongolian and Chinese parts,the modem temperature reg...  相似文献   

A mineral and cumulate perspective to magma differentiation at Nisyros volcano,Aegean arc     

Martijn?KlaverEmail authorView author&#;s OrcID profile  Sergei?Matveev  Jasper?Berndt  C.?Johan?Lissenberg  Pieter?Z.?Vroon 《Contributions to Mineralogy and Petrology》2017,172(11-12):95

Lavas and pyroclastic products of Nisyros volcano (Aegean arc, Greece) host a wide variety of phenocryst and cumulate assemblages that offer a unique window into the earliest stages of magma differentiation. This study presents a detailed petrographic study of lavas, enclaves and cumulates spanning the entire volcanic history of Nisyros to elucidate at which levels in the crust magmas stall and differentiate. We present a new division for the volcanic products into two suites based on field occurrence and petrographic features: a low-porphyricity andesite and a high-porphyricity (rhyo)dacite (HPRD) suite. Cumulate fragments are exclusively found in the HPRD suite and are predominantly derived from upper crustal reservoirs where they crystallised under hydrous conditions from melts that underwent prior differentiation. Rarer cumulate fragments range from (amphibole-)wehrlites to plagioclase-hornblendites and these appear to be derived from the lower crust (0.5–0.8 GPa). The suppressed stability of plagioclase and early saturation of amphibole in these cumulates are indicative of high-pressure crystallisation from primitive hydrous melts (≥ 3 wt% H₂O). Clinopyroxene in these cumulates has Al₂O₃ contents up to 9 wt% due to the absence of crystallising plagioclase, and is subsequently consumed in a peritectic reaction to form primitive, Al-rich amphibole (Mg# > 73, 12–15 wt% Al₂O₃). The composition of these peritectic amphiboles is distinct from trace element-enriched interstitial amphibole in shallower cumulates. Phenocryst compositions and assemblages in both suites differ markedly from the cumulates. Phenocrysts, therefore, reflect shallow crystallisation and do not record magma differentiation in the deep arc crust.  相似文献   

The latest geodynamics in Asia: Synthesis of data on volcanic evolution,lithosphere motion,and mantle velocities in the Baikal-Mongolian region     

Sergei Rasskazov  Irina Chuvashova 《地学前缘(英文版)》2017,8(4):733-752

From a synthesis of data on volcanic evolution,movement of the lithosphere,and mantle velocities in the Baikal-Mongolian region,we propose a comprehensive model for deep dynamics of Asia that assumes an important role of the Gobi,Baikal,and North Transbaikal transition-layer melting anomalies.This layer was distorted by lower-mantle fluxes at the beginning of the latest geodynamic stage(i.e.in the early late Cretaceous) due to avalanches of slab material that were stagnated beneath the closed fragments of the Solonker,Ural-Mongolian paleoceans and Mongol-Okhotsk Gulf of Paleo-Pacific.At the latest geodynamic stage,Asia was involved in east-southeast movement,and the Pacific plate moved in the opposite direction with subduction under Asia.The weakened upper mantle region of the Gobi melting anomaly provided a counterflow connected with rollback in the Japan Sea area.These dynamics resulted in the formation of the Honshu-Korea flexure of the Pacific slab.A similar weakened upper mantle region of the North Transbaikal melting anomaly was associated with the formation of the Hokkaido-Amur flexure of the Pacific slab,formed due to progressive pull-down of the slab material into the transition layer in the direction of the Pacific plate and Asia convergence.The early—middle Miocene structural reorganization of the mantle processes in Asia resulted in the development of upper mantle low-velocity domains associated with the development of rifts and orogens.We propose that extension at the Baikal Rift was caused by deviator flowing mantle material,initiated under the moving lithosphere in the Baikal melting anomaly.Contraction at the Hangay orogen was created by facilitation of the tectonic stress transfer from the Indo-Asian interaction zone due to the low-viscosity mantle in the Gobi melting anomaly.  相似文献   

Remote mountain lakes of Eastern Siberia: a pattern of ecologically pure non-industrialised water-bodies     

Nina Bondarenko  Natalia Sheveleva  Natalia Rozhkova  Arkadiy Matveev  Vitaliy Samusenok  Alexey Vokin  Anatoliy Yuriev 《Environmental Earth Sciences》2017,76(10):378

A 3-year study of the biota of the remote mountain lakes of Amut, Balan-Tamur, and Yakondykon, situated in the Dzherginsky State Reserve in the Baikalian region of Eastern Siberia, was carried out from 2006 to 2008. Examining the biota of non-modern and non-industrialised mountain lakes allowed us to reveal its background in relation to the species composition of plankton, the main groups of benthos and fishes, production potential, and seasonal dynamics of the ecosystem’s basic links. Our data on pH and biota were compared with the findings of a previous study in 1986 in order to evaluate possible changes associated with probable acidification. We observed that the lakes of the Dzherginsky State Reserve have high species diversity. Despite this, they are classed as oligotrophic water-bodies with regard to the development level of their planktonic and benthic coenoses. These lakes are not polluted by anthropogenic activity and so could be considered as a pattern of ecologically pure water-bodies. It is important to add that high mountain lakes of Pribaikalye presently serve as refuges for species that were widespread during past geological epochs.  相似文献   

Tree wave migration across an elevation gradient in the Altai Mountains,Siberia   总被引：1，自引：1，他引：0  

Viacheslav I. Kharuk  Sergei T. Im  Maria L. Dvinskaya  Kenneth J. Ranson  Il’ya A. Petrov 《山地科学学报》2017,14(3):442-452

The phenomenon of tree waves(hedges and ribbons) formation within the alpine ecotone in Altai Mountains and its response to observed air temperature increase was considered. At the upper limit of tree growth Siberian pine(Pinus sibirica) forms hedges on windward slopes and ribbons on the leeward ones. Hedges were formed by prevailing winds and oriented along winds direction. Ribbons were formed by snow blowing and accumulating on the leeward slope and perpendicular to the prevailing winds, as well as to the elevation gradient. Hedges were always linked with microtopography features, whereas ribbons were not. Trees are migrating upward by waves and new ribbons and hedges are forming at or near tree line, whereas at lower elevations ribbons and hedges are being transformed into closed forests. Time series of high-resolution satellite scenes(from 1968 to 2010) indicated an upslope shift in the position ribbons averaged 155±26 m(or 3.7 m yr~(-1)) and crown closure increased(about 35%–90%). The hedges advance was limited by poor regeneration establishment and was negligible. Regeneration within the ribbon zone was approximately 2.5 times(5060 vs 2120 ha~(-1)) higherthen within the hedges zone. During the last four decades, Siberian pine in both hedges and ribbons strongly increased its growth increment, and recent tree growth rate for 50 year-old trees was about twice higher than those recorded for similarly-aged trees at the beginning of the 20~(th) century. Hedges and ribbons are phenomena that are widespread within the southern and northern Siberian Mountains.  相似文献