排序方式： 共有44条查询结果，搜索用时 15 毫秒
1.
2.
Inna Safonova 《地学前缘(英文版)》2014,5(4):537-552
The paper reviews previous and recently obtained geological, stratigraphic and geochronological data on the Russian-Kazakh Altai orogen, which is located in the western Central Asian Orogenic Belt （CAOB）, between the Kazakhstan and Siberian continental blocks. The Russian-Kazakh Altai is a typical Pacific-type orogen, which represents a collage of oceanic, accretionary, fore-arc, island-arc and continental margin terranes of different ages separated by strike-slip faults and thrusts. Evidence for this comes from key indicative rock associations, such as boninite- and turbidite （graywacke）-bearing volcanogenic-sedimentary units, accreted pelagic chert, oceanic islands and plateaus, MORB-OIB-protolith blueschists. The three major tectonic domains of the Russian-Kazakh Altai are： （1） Altai-Mongolian terrane （AMT）; （2） subduction-accretionary （Rudny Altai, Gorny Altai） and collisional （Kalba-Narym） terranes; （3） Kurai, Charysh-Terekta, North-East, Irtysh and Char suture-shear zones （SSZ）. The evolution of this orogen proceeded in five major stages： （i） late Neoproterozoic-early Paleozoic subduction-accretion in the Paleo-Asian Ocean; （ii） Ordovician-Silurian passive margin; （iii） Devonian-Carboniferous active margin and collision of AMT with the Siberian conti- nent; （iv） late Paleozoic closure of the PAO and coeval collisional magmatism; （v） Mesozoic post-collisional deformation and anarogenic magmatism, which created the modern structural collage of the Russian- Kazakh Altai orogen. The major still unsolved problem of Altai geology is origin of the Altai-Mongolian terrane （continental versus active margin）, age of Altai basement, proportion of juvenile and recycled crust and origin of the middle Paleozoic units of the Gorny Altai and Rudny Altai terranes. 相似文献
3.
Parameter estimation for basin-scale ecosystem-linked population models of large pelagic predators: Application to skipjack tuna 总被引：2，自引：1，他引：1
A Spatial Ecosystem and Population Dynamic Model (SEAPODYM) is used in a data assimilation study aiming to estimate model parameters that describe dynamics of Pacific skipjack tuna population on ocean-based scale. The model based on advection–diffusion–reaction equations explicitly predicts spatial dynamics of large pelagic predators, while taking into account data on several mid-trophic level components, oceanic primary productivity and physical environment. In order to improve its quantitative ability, the model was parameterized through assimilation with commercial fisheries data, and optimization was carried out using maximum likelihood estimation approach. To address the optimization task we implemented an adjoint technique to obtain an exact, analytical evaluation of the likelihood gradient. We conducted a series of computer experiments in order to (i) determine model sensitivity with respect to variable parameters and, hence, investigate their observability; (ii) estimate observable parameters and their errors; and (iii) justify the reliability of the computed solution. Parameters describing recruitment, movement, habitat preferences, natural and fishing mortality of skipjack population were analysed and estimated. Results of the study suggest that SEAPODYM with achieved parameterization scheme can help to investigate the impact of fishing under various management scenarios, and also conduct forecasts of a given species stock and spatial dynamics in a context of environmental and climate changes. 相似文献
4.
5.
Modelling the impact of climate change on Pacific skipjack tuna population and fisheries 总被引：2，自引：0，他引：2
Patrick Lehodey Inna Senina Beatriz Calmettes John Hampton Simon Nicol 《Climatic change》2013,119(1):95-109
IPCC-type climate models have produced simulations of the oceanic environment that can be used to drive models of upper trophic levels to explore the impact of climate change on marine resources. We use the Spatial Ecosystem And Population Dynamics Model (SEAPODYM) to investigate the potential impact of Climate change under IPCC A2 scenario on Pacific skipjack tuna (Katsuwonus pelamis). IPCC-type models are still coarse in resolution and can produce significant anomalies, e.g., in water temperature. These limitations have direct and strong effects when modeling the dynamics of marine species. Therefore, parameter estimation experiments based on assimilation of historical fishing data are necessary to calibrate the model to these conditions before exploring the future scenarios. A new simulation based on corrected temperature fields of the A2 simulation from one climate model (IPSL-CM4) is presented. The corrected fields led to a new parameterization close to the one achieved with more realistic environment from an ocean reanalysis and satellite-derived primary production. Projected changes in skipjack population under simple fishing effort scenarios are presented. The skipjack catch and biomass is predicted to slightly increase in the Western Central Pacific Ocean until 2050 then the biomass stabilizes and starts to decrease after 2060 while the catch reaches a plateau. Both feeding and spawning habitat become progressively more favourable in the eastern Pacific Ocean and also extend to higher latitudes, while the western equatorial warm pool is predicted to become less favorable for skipjack spawning. 相似文献
6.
Pacific superplume-related oceanic basalts hosted by accretionary complexes of Central Asia, Russian Far East and Japan 总被引：5，自引：0，他引：5
I. Yu. Safonova A. Utsunomiya S. Kojima S. Nakae O. Tomurtogoo A.N. Filippov K. Koizumi 《Gondwana Research》2009,16(3-4):587-608
Plume-related oceanic magmatism form oceanic islands, seamounts and plateaus (hereafter “seamounts” or “paleoseamounts”), which are important features in geological history. The accretion of oceanic seamounts to active continental margins significantly contributed to the formation of the continental crust. This paper reviews occurrences of Late Neoproterozoic–Mesozoic seamounts of the Paleo-Asian and Paleo-Pacific oceans, which are hosted by accretionary complexes (ACs) of Russian Altai, East Kazakhstan, Mongolia, Russian Far East and Japan. The paleoseamounts commonly consist of Ti–LREE–Nb-enriched plume-related basalts (OIB-type or intraplate basalts) capped with massive limestone and associated with other units of oceanic plate stratigraphy (OPS): oceanic floor basalts (MORB), pelagic chert, epiclastic slope facies, etc. The paper presents available geochemical data on the plume-related basalts including the first geochemical data on the Middle Paleozoic OIB-type basalts of the Paleo-Asian Ocean hosted by the Ulaanbaatar AC of Mongolia. An emphasis is made for the structural setting of OPS units, specific geochemical features of intraplate basalts, problems of their identification, and distinguishing from magmatic units of a different origin such as MORB, island-arc and back-arc basalts. Finally, we propose a continuous, though periodical, evolution of the Pacific superplume-related magmatism, which can be more reliably proved by studying Middle Paleozoic OPS units hosted by ACs of Mongolia and Tien Shan, and discuss prospects of future studies. 相似文献
7.
The study of clinopyroxenes and melt inclusions provided direct (independent on secondary alteration) information on the petrogenesis
of the island arc complexes of the Chara zone, East Kazakhstan. It was shown that magmatism of this zone evolved from primitive
island-arc systems with boninites to mature island arc with calc-alkaline melts. In terms of trace and rare-earth element
distribution, the melt inclusions in the clinopyroxenes of the Chara zone differ from mid-ocean ridge basalts, being closer
to the island-arc calcalkaline series. Based on inclusion composition, the parental melts of the considered complexes crystallized
within 1150–1190°C with decreasing iron, magnesium, calcium, and sodium contents. Simulation based on melt inclusion data
in clinopyroxenes indicates that the melts contained up to 1 wt % water, which was confirmed by direct ion-microprobe determination
of 0.84 wt % H2O in the inclusions. Calculated liquidus temperatures are consistent with homogenization temperatures of the inclusions. Our
calculations on the basis of inclusion data testify that the primary melts of the studied basaltic series of the Chara zone
were generated from the mantle protolith within temperatures of 1350–1530°C at depths of 50–95 km. Similar parameters are
typical of the generation of the tholeiitic and boninitic island-arc magmas in the modern ocean-continent transition zones
of the Pacific type. In general, the study of clinopyroxenes and melt inclusions suggests that the considered complexes of
the Chara zone were formed with the participation of tholeiitic and calcalkaline volcanogenic systems of basaltic, basaltic
andesite, and, possibly, boninitic composition in the paleogeodynamic setting of evolving ancient island arc. 相似文献
8.
Empirical evidence for both stellar mass black holes (M
•<102
M
⊙) and supermassive black holes (SMBHs, M
•>105
M
⊙) is well established. Moreover, every galaxy with a bulge appears to host a SMBH, whose mass is correlated with the bulge
mass, and even more strongly with the central stellar velocity dispersion σ
c
, the M
•–σ relation. On the other hand, evidence for “intermediate-mass” black holes (IMBHs, with masses in the range 100–105 M
⊙) is relatively sparse, with only a few mass measurements reported in globular clusters (GCs), dwarf galaxies and low-mass
AGNs. We explore the question of whether globular clusters extend the M
•–σ relationship for galaxies to lower black hole masses and find that available data for globular clusters are consistent with
the extrapolation of this relationship. We use this extrapolated M
•–σ relationship to predict the putative black hole masses of those globular clusters where existence of central IMBH was proposed.
We discuss how globular clusters can be used as a constraint on theories making specific predictions for the low-mass end
of the M
•–σ relation. 相似文献
9.
V.A. Simonov I.Yu. Safonova S.V. Kovyazin A.V. Kotlyarov 《Russian Geology and Geophysics》2010,51(5):507-520
The paper presents new data on physico-chemical parameters of the Neoproterozoic–Early Cambrian plume magmatism in the Paleo-Asian Ocean. The data on clinopyroxenes show the plume-related plateaubasalt magmatic systems of the Katun’ paleoseamounts, which interacted with mid-ocean ridge (MOR) magmas. The Kurai paleoseamount consists mainly of plateaubasalt systems, and the Agardag ophiolites represent products of OIB–type “hot-spot” within-plate magmatism. Our study of inclusions showed that the melts of the Katun’ and Kurai paleoseamounts crystallized at lower temperatures (1130–1190 °C) compared to the Agardag ophiolites (1210–1255 °C). The petrochemical analysis of the melt inclusions showed that the Katun’ and Kurai magmatic systems are different from the Mg- and Ti-richer melts of the Agardag ophiolites: the former are similar to the magmas of the Nauru Basin and Ontong Java Plateau (western Pacific), whereas the latter possess geochemical affinities to OIB-type magmatism. The rare-element compositions of the melts of the Katun’ and Kurai paleoseamounts correspond to those of the Ontong Java Plateau and Nauru Basin lavas. The numerically simulated parameters of the Katun’ paleoseamount primary magmas agree with the data on the magmatic systems of the Siberian Platform and Ontong Java Plateau. For the Kurai paleoseamount, the simulated results suggest interaction of deep-seated OIB-type magmatic systems with MOR ones. The Agardag ophiolites were formed in relation to mantle plume activity at the initial stages of paleo-oceanic complexes formation. 相似文献
10.
On Conditions of Phytoplankton Blooms in the Coastal Waters of the North-Western East/Japan Sea 总被引：1，自引：0，他引：1
Seasonal changes of abundance of the main phytoplankton groups of species (diatoms, dinoflagellates, chrysophytes, small flagellates
and cryptophytes) and a set of environmental parameters were investigated in coastal and preestuarine waters of Peter the
Great Bay (East/Japan Sea) in May-October of 1998 and 1999. Three periods of mass development were revealed: spring, summer
and autumn blooms, with successive change of species. The conditions favourable for each group of species were determined.
Driving mechanisms of the succession include nutrients transport through seasonal pycnocline by turbulent mixing, terrestrial
nutrients supply by monsoon floods, nutrients supply by upwellings, and light control by the thickness of upper mixed layer.
Summer succession could be explained by a simple SST-MLD diagram similar to Pingree S-kh diagram with sea surface temperature
as indicator of stratification (S) and mixed layer depth as indicator of light availability (kh). 相似文献