The Mesozoic granitoid magmatism and metallogeny of the Central Asian and Pacific Belts junction area     

N. P. Romanovsky  Yu. F. Malyshev  M. V. Goroshko  V. G. Gurovich  M. I. Kopylov 《Russian Journal of Pacific Geology》2009,3(4):338-355

Materials pertaining to Mesozoic granitoids in the Central Asian and Pacific Belts junction area and the adjacent platforms are summarized. Maps of the location of massifs, the extensiveness of granitoid magmatism, the manifestations of Mesozoic plumes, and the relief of the asthenosphere surface have been compiled. The locations of the major ore deposits are plotted on the maps. The distribution chart has been constructed for these deposits in the coordinates of the crust and lithosphere. The depth of the occurrence of the sources for large and superlarge gold, tin, polymetallic, molybdenum, tungsten, and uranium deposits has been estimated. Areas showing promise for the discovery of large deposits are defined.  相似文献   

Ordovician ferrosilicic magmas: Experimental evidence for ultrahigh temperatures affecting a metagreywacke source     

A. Castro  A. García-Casco  C. Fernndez  L.G. Corretg  I. Moreno-Ventas  T. Gerya  I. Lw 《Gondwana Research》2009,16(3-4):622-632

Peculiar magmatic rocks were erupted and emplaced at depth at the margin of the Gondwana supercontinent during the Cambro-Ordovician transition. These rocks are characterized by high contents in silica and iron but they do not have equivalents in the high-silica members of the calc-alkaline series. They have particular geochemical signatures, with Al saturation index, ASI > 1, FeO > 2.5 wt.%, MgO > 0.8 wt.% for very low contents in calcium (CaO < 2.0 wt.%), supporting a derivation from near-total melting (> 80 vol.% melt) of metagreywackes. The results from inverse experiments indicate that the most plausible conditions are within the range 1000 °C (excess water) and 1100–1200 °C (subsaturated and dry) at pressures of 1.5 to 2.0 GPa. A tectonic scenario implying melting of subducted sediments within an ascending mantle-wedge plume is suggested for the generation of primary ferrosilicic melts at the Gondwana continental margin during Upper Cambrian to Lower Ordovician times.  相似文献   

The Columbia River plume as cross-shelf exporter and along-coast barrier     

N.S. Banas  P. MacCreadyB.M. Hickey 《Continental Shelf Research》2009

An intensive Lagrangian particle-tracking analysis of the July 2004 upwelling period was conducted in a hindcast model of the US Pacific Northwest coast, in order to determine the effect of the Columbia River plume on the fate of upwelled water. The model, implemented using Regional Ocean Modeling System (ROMS), includes variable wind and atmospheric forcing, variable Columbia river flow, realistic boundary conditions from Navy Coastal Ocean Model (NCOM), and 10 tidal constituents. Model skill has been demonstrated in detail elsewhere [MacCready, P., Banas, N.S., Hickey, B.M., Dever, E.P., Liu, Y., 2008. A model study of tide- and wind-induced mixing in the Columbia River estuary and plume. Continental Shelf Research, this issue, doi:10.1016/j.csr.2008.03.015]. Particles were released in the Columbia estuary, along the Washington coastal wall, and along the model's northern boundary at 48°N. Particles were tracked in three dimensions, using both velocities from ROMS and a vertical random displacement representing turbulent mixing. When 25 h of upwelling flow is looped and particles tracked for 12 d, their trajectories highlight a field of transient eddies and recirculations on scales from 5 to 50 km both north and south of the Columbia. Not all of these features are caused by plume dynamics, but the presence of the plume increases the entrainment of inner-shelf water into them. The cumulative effect of the plume's interaction with these transient features is to increase cross-shelf dispersion: 25% more water is transported laterally past the 100 m isobath when river and estuarine effects are included than when they are omitted. This cross-shelf dispersion also disrupts the southward transport of water along the inner shelf that occurs in the model when the Columbia River is omitted. This second effect—increased retention of upwelled water on the Washington shelf—may be partly responsible for the regional-scale alongcoast gradient in chlorophyll biomass, although variations in shelf width, the Juan de Fuca Eddy to the north, and the intermittency of upwelling-favorable winds are likely also to play important roles.  相似文献   

Perspective on theories of non-Fickian transport in heterogeneous media   总被引：1，自引：0，他引：1  

Shlomo P. Neuman  Daniel M. Tartakovsky 《Advances in water resources》2009

Subsurface fluid flow and solute transport take place in a multiscale heterogeneous environment. Neither these phenomena nor their host environment can be observed or described with certainty at all scales and locations of relevance. The resulting ambiguity has led to alternative conceptualizations of flow and transport and multiple ways of addressing their scale and space–time dependencies. We focus our attention on four approaches that give rise to nonlocal representations of advective and dispersive transport of nonreactive tracers in randomly heterogeneous porous or fractured continua. We compare these approaches theoretically on the basis of their underlying premises and the mathematical forms of the corresponding nonlocal advective–dispersive terms. One of the four approaches describes transport at some reference support scale by a classical (Fickian) advection–dispersion equation (ADE) in which velocity is a spatially (and possibly temporally) correlated random field. The randomness of the velocity, which is given by Darcy’s law, stems from random fluctuations in hydraulic conductivity (and advective porosity though this is often disregarded). Averaging the stochastic ADE over an ensemble of velocity fields results in a space–time-nonlocal representation of mean advective–dispersive flux, an approach we designate as stnADE. A closely related space–time-nonlocal representation of ensemble mean transport is obtained upon averaging the motion of solute particles through a random velocity field within a Lagrangian framework, an approach we designate stnL. The concept of continuous time random walk (CTRW) yields a representation of advective–dispersive flux that is nonlocal in time but local in space. Closely related to the latter are forms of ADE entailing fractional derivatives (fADE) which leads to representations of advective–dispersive flux that are nonlocal in space but local in time; nonlocality in time arises in the context of multirate mass transfer models, which we exclude from consideration in this paper. We describe briefly each of these four nonlocal approaches and offer a perspective on their differences, commonalities, and relative merits as analytical and predictive tools.  相似文献   

Model of the Long Island Sound outflow: Comparison with year-long HF radar and Doppler current observations     

Jenq-Chi Mau  Dong-Ping Wang  David S. Ullman  Daniel L. Codiga 《Continental Shelf Research》2008

A three-dimensional primitive-equation model is used to simulate the Long Island Sound (LIS) outflow for a 1-year (2001) period. The model domain includes LIS and New York Bight (NYB). Tidal and wind forcing are included, and seasonal salinity and temperature variations are assimilated. The model results are validated with the HF radar, moored acoustic Doppler current profiler (ADCP), and ferry-based ADCP observations. The agreement between simulated and observed flow patterns generally is very good. The difference in seasonal mean currents between the model and moored ADCP is about 0.01 m/s; the correlation of dominant velocity fluctuations between the model and HF radar is 0.83; and the difference in mean LIS transport between the model and shipboard ADCP is about 5%. However, the model predicts a prominent tidally generated headland eddy not supported by the HF radar observation. The model sensitivity study indicates that the tides, winds, and ambient coastal front all have important impact on the buoyant outflow. The tides and winds cause stronger vertical mixing, which reduces the surface plume strength. The ambient coastal front, on the other hand, tends to enhance the plume.  相似文献   

The stability of two interacting compositional plumes under the influence of inclined rotation     

I.A. Eltayeb  T.B.A. Elbashir 《地球物理与天体物理流体动力学》2014,108(4):437-462

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The thermal structure of mantle plumes: axisymmetric or triple-junction?     

G. A. Houseman 《Geophysical Journal International》1990,102(1):15-24

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Dynamics of medium-intensity dense water plumes in the Arkona Basin, Western Baltic Sea     

Hans Burchard  Hans Ulrich Lass  Volker Mohrholz  Lars Umlauf  Jürgen Sellschopp  Volker Fiekas  Karsten Bolding  Lars Arneborg 《Ocean Dynamics》2005,55(5-6):391-402

In this study, the dynamics of medium-intensity inflow events over Drogden Sill into the Arkona Sea are investigated. Idealised model simulations carried out with the General Estuarine Transport Model suggest that most of the salt transport during such inflow events occur north of Kriegers Flak, a shoal with less than 20 m water depth surrounded by water depths of more than 40 m. This assumption about the pathway is supported by recent ship-based observations in the Arkona Sea during a medium-intensity inflow event. The propagation of a saline bottom plume could be observed during several days after having passed Drogden Sill. In the area north of Kriegers Flak the plume was about 10 m thick, and propagated with more than 0.5 m s⁻¹ and a salinity of up to 20 psu (with ambient water salinity being 8 psu) eastwards. Although the model simulations were idealised, the structural agreement between the observation and model result was good. The structure and pathways of these medium-intensity inflow events are of specific interest due to the plans for erecting extensive offshore wind farms in the Arkona Sea which may under certain circumstances lead to increased entrainment of ambient water into the bottom plumes.  相似文献   

SeaBeam 3030多波束系统在南海冷泉调查中的应用     

张建兴  宋永东  杜增丰  马小川  栾振东  张鑫  阎军 《海洋科学》2022,46(1):154-162

在冷泉调查研究中,多波束系统因其快速高效、成本较低的特点被广泛应用.本文靶定南海北部陆坡琼东南盆地冷泉发育区,介绍了SeaBeam 3030多波束系统在冷泉发育区中的调查应用实例.通过分析多波束水深数据和水体数据,确定了调查区海底地形地貌以及水体羽状流特征,同时对该冷泉区开展综合调查的必要性进行了初步分析.研究表明,调...  相似文献