中国制造业分布的地理变迁与驱动因素   总被引：7，自引：1，他引：6  

石敏俊  杨晶  龙文  魏也华 《地理研究》2013,32(9):1708-1720

近年来中国制造业分布格局呈现出新的动向。以2004-2005年为转折点,以食品轻纺行业为主的部分制造业部门开始从沿海省份向中西部省份转移,北京、天津、上海、浙江、广东、福建等省份的产业份额明显下降,安徽、江西、湖南、河南、四川等中西部省份的产业份额趋于增加。在地市尺度上,制造业分布变化呈现出"西进北上"的特点,具体表现为产业份额从沿海发达城市转向沿海省份内部发展相对滞后的地市、以及中西部省份内部产业基础较好且本地市场规模较大的地市。中部地区的重点开发区域已成为承接产业转移的重要载体。沿海地区劳动力、土地等要素成本上升导致要素成本的区域差异不断扩大,与此同时中西部地区市场邻近和供给邻近逐步得到改善。沿海地区和中西部地区之间要素成本差异的扩大和贸易成本差异的缩小,使得贸易成本和要素成本的均衡关系发生逆转性变化,这是驱动中国产业分布地理变迁的核心因素。  相似文献   

Transient electromagnetic modelling of an isolated wire loop over a conductive medium     

Marina G. Persova  Yuri G. Soloveichik  Georgy M. Trigubovich  Denis V. Vagin  Petr A. Domnikov 《Geophysical Prospecting》2014,62(5):1193-1201

A large closed wire loop is generally used in field experiments for testing airborne electrical exploration equipment. Thus, methods are required for the precise calculation of an electromagnetic response in the presence of a closed wire loop. We develop a fast and precise scheme for calculating the transient response for such a closed loop laid out at the surface of a horizontally layered conductive ground. Our scheme is based on the relationship between the magnetic flux flowing through a closed loop and the current induced in it. The developed scheme is compared with 2D and 3D finite‐element modelling for several positions of an airborne electromagnetic system flying over a closed loop. We also study the coupling effect between the current flowing in the closed loop and the current flowing in the horizontally layered conductive medium. The result shows that for the central position of the transmitter, the difference between axisymmetrical finite‐element modelling and our scheme is less than 1%. Moreover, for the non‐coaxial transmitter–receiver–loop system, the solution obtained by our scheme is in good agreement with full 3D finite‐element modelling, and our total simulation time is substantially lower: 1 minute versus 120 hours.  相似文献   

Stratigraphy, chemistry, and eruptive dynamics of the 12.4 ka plinian eruption of Apoyeque volcano, Managua, Nicaragua     

Denis Ramón Avellán  José Luis Macías  Giovanni Sosa-Ceballos  Gema Velásquez 《Bulletin of Volcanology》2014,76(2):1-19

Apoyeque volcano, located 9 km northwest of Managua city, erupted explosively at 12.4 ka. The Plinian eruption deposited a widespread pumice fall deposit known as the Upper Apoyeque Tephra (UAq). The UAq is massive, reversely graded, and consists of white juvenile pumice (~78 vol.%), a variety of cognate lithics and accidental altered lithics. The whole-rock pumice composition is rhyodacitic (SiO₂?=?66.9–68.5 wt.%) with a mineral paragenesis of plagioclase, orthopyroxene, clinopyroxene, amphibole, titanomagnetite, and ilmenite in a rhyolitic glass groundmass (SiO₂?=?74.4?±?0.6 wt.%). The deposit’s dispersal axis is to the south, with the deposit covering a minimum area of 877 km² within the 50 cm isopach and has a total volume of 3 km³ (dense rock equivalent, 1.15 km³). The eruption column reached a maximum height of ca.28 km. The eruption ejected a total mass of 3?×?10¹² kg at an average rate of 2?×?10⁸ kg/s, and based on available models, we infer duration of almost 4 h. Petrographic and geochemical characteristics suggest that the eruption was triggered by magma mixing.  相似文献   

Thermodynamical constraints on the crystallization of a deep magma-ocean on Earth     

Denis Andrault 《Comptes Rendus Geoscience》2019,351(2-3):221-228

It has been argued that the crystallization of the magma ocean (MO) after the Moon-forming impact led to the formation of a basal magma ocean (BMO). We search which primordial conditions of pressure, temperature and chemical composition could be compatible with such scenario, based on thermodynamical constraints. The major requirement is an early formation of a viscous layer (VL) of mantle material (i.e. bridgmanite (Bg)) at mid lower-mantle depth, which could insulate thermally and chemically the BMO from the rest of the mantle. To produce such VL, Bg grains should be: (i) neutrally buoyant at mid lower-mantle depths, (ii) sufficiently abundant to produce an efficient insulating layer, and (iii) aggregated to the boundary layer from above and below. The first and the second require a large amount of MO crystallization, up to more than 45%, even in the most favorable case of all Fe partitioning into the melt. The latter is very questionable because the Bg grains have a very small settling velocity. We also investigate different scenarios of MO crystallization to provide constraints on the resulting core temperature. Starting from a fully molten Earth, a temperature as high as ～4725 K could be found at the core–mantle boundary (CMB), if the Bg grains settle early atop the CMB. Such a basal layer of Bg can efficiently decouple from each other the cooling rates of the core and the mantle above the VL. If the settling velocity of Bg grains is too low and/or the MO is too turbulent, such basal VL may not form. In this case, the CMB temperature after MO solidification should stabilize at ～4350 K. At this temperature, enough Bg grains are crystallized to make the mushy mantle viscous at any mantle depth.  相似文献   

Time-resolved,defect-hosted,trace element mobility in deformed Witwatersrand pyrite     

Denis Fougerouse  Steven M. Reddy  Christopher L. Kirkland  David W. Saxey  William D. Rickard  Robert M. Hough 《地学前缘(英文版)》2019,10(1):55-63

The Pb isotopic composition of rocks is widely used to constrain the sources and mobility of melts and hydrothermal fluids in the Earth's crust. In many cases, the Pb isotopic composition appears to represent mixing of multiple Pb reservoirs. However, the nature, scale and mechanisms responsible for isotopic mixing are not well known. Additionally, the trace element composition of sulphide minerals are routinely used in ore deposit research, mineral exploration and environmental studies, though little is known about element mobility in sulphides during metamorphism and deformation. To investigate the mechanisms of trace element mobility in a deformed Witwatersrand pyrite(FeS_2), we have combined electron backscatter diffraction(EBSD) and atom probe microscopy(APM). The results indicate that the pyrite microstructural features record widely different Pb isotopic compositions, covering the entire range of previously published sulphide Pb compositions from the Witwatersrand basin. We show that entangled dislocations record enhanced Pb, Sb, Ni, Tl and Cu composition likely due to entrapment and short-circuit diffusion in dislocation cores. These dislocations preserve the Pb isotopic composition of the pyrite at the time of growth(~3 Ga) and show that dislocation intersections, likely to be common in deforming minerals, limit trace element mobility. In contrast, Pb, As, Ni, Co, Sb and Bi decorate a highangle grain boundary which formed soon after crystallisation by sub-grain rotation recrystallization.Pb isotopic composition within this boundary indicates the addition of externally-derived Pb and trace elements during greenschist metamorphism at ~2 Ga. Our results show that discrete Pb reservoirs are nanometric in scale, and illustrate that grain boundaries may remain open systems for trace element mobility over 1 billion years after their formation.  相似文献   

Source and possible tectonic driver for Jurassic–Cretaceous gold deposits in the West Qinling Orogen,China     

Yafei Wu  Jianwei Li  Katy Evans  Denis Fougerouse  Kirsten Rempel 《地学前缘(英文版)》2019,10(1):107-117

The West Qinling Orogen (WQO) in Central China Orogenic Belt contains numerous metasedimentary rock-hosted gold deposits (>2000 t Au), which mainly formed during two pulses: one previously recognized in the Late Triassic to Early Jurassic (T3–J1) and one only recently identified in the Late Jurassic to Early Cretaceous (J3–K1). Few studies have focused on the origin and geotectonic setting of the J3–K1 gold deposits.Textural relationships, LA-ICP-MS trace element and sulfur isotope compositions of pyrites in hydrothermally altered T3 dykes within the J3–K1 Daqiao deposit were used to constrain relative timing relationships between mineralization and pyrite growth in the dykes, and to characterize the source of ore fluid. These results are integrated with an overview of the regional geodynamic setting, to advance understanding of the tectonic driver for J3–K1 hydrothermal gold systems. Pyrite in breccia- and dyke-hosted gold ores at Daqiao have similar chemical and isotopic compositions and are considered to be representative of J3–K1 gold deposits in WQO. Co/Ni and sulfur isotope ratios suggest that ore fluids were derived from underlying Paleozoic Ni- and Se-rich carbonaceous sedimentary rocks. The geochemical data do not support the involvement of magmatic fluids. However, in the EQO (East Qinling Orogen), J3–K1 deposits are genetically related to magmatism. Gold mineralization in WQO is contemporaneous with magmatic deposits in the EQO and both are mainly controlled by NE- and EW-trending structures produced by changes in plate motion of the Paleo-Pacific plate as it was subducted beneath the Eurasian continent. We therefore infer that the J3–K1 structural regime facilitated the ascent of magma in the EQO and metamorphic fluids in the WQO with consequent differences in the character of contemporaneous ore deposits. If this is correct, then the far-field effects of subduction along the eastern margin of NE Asia extended 1000's of km into the continental interior.  相似文献   

Flow of ultra-hot orogens: A view from the Precambrian, clues for the Phanerozoic   总被引：1，自引：0，他引：1  

Dominique Chardon  Denis Gapais  Florence Cagnard   《Tectonophysics》2009,477(3-4):105

This contribution emphasizes first-order structural and metamorphic characters of Precambrian accretionary orogens to understand the kinematics and thermomechanical state of the continental lithosphere in convergent settings involving massive juvenile magmatism. We define a new class of orogens, called ultra-hot orogens (UHO), in which the weakest type of lithosphere on Earth is deformed. UHO are characterized by (1) distributed shortening and orogen-scale flow combining vertical and horizontal longitudinal advection, under long-lasting convergence, (2) homogeneous thickening by combined downward movements of supracrustal units and three-dimensional mass redistribution in the viscous lower crust, and (3) steady-state, negligible topography and relief leveled by syn-shortening erosion and near-field sedimentation. The flow analysis of UHO provides clues to understanding crustal kinematics beneath high plateaus and suggests that the seismic reflectivity pattern of hot orogens is an image of the layering produced by lateral flow of the lower crust and associated syn-kinematic plutonism.In between the UHO and the modern cold orogens (CO), developed by shortening of lithosphere bearing a stiff upper mantle, two classes of orogens are defined. Hot orogens (HO, representative of Cordilleran and wide mature collisional belts) share flow pattern characteristics with UHO, but involve a less intense magmatic activity and develop high topographies driving their collapse. Mixed-hot orogens (MHO, representative of magmatic arcs and Proterozoic collisional belts) are orogens made of UHO-type juvenile crust and display CO-like structure and kinematics. This classification points to the fundamental link between the presence of a stiff lithospheric mantle and strain localization along major thrusts in convergent settings. A high Moho temperature (> 900 °C), implying thinning of the lithospheric mantle, enhances three-dimensional flow of the lithosphere in response to convergence. Overall, this classification of orogens emphasizes the space and time variability of uppermost mantle temperature in controlling plate interactions and continental growth.  相似文献   

Late Cretaceous porphyry Cu and epithermal Cu–Au association in the Southern Panagyurishte District,Bulgaria: the paired Vlaykov Vruh and Elshitsa deposits     

Kalin Kouzmanov  Robert Moritz  Albrecht von Quadt  Massimo Chiaradia  Irena Peytcheva  Denis Fontignie  Claire Ramboz  Kamen Bogdanov 《Mineralium Deposita》2009,44(6):611-646

Vlaykov Vruh–Elshitsa represents the best example of paired porphyry Cu and epithermal Cu–Au deposits within the Late Cretaceous Apuseni–Banat–Timok–Srednogorie magmatic and metallogenic belt of Eastern Europe. The two deposits are part of the NW trending Panagyurishte magmato-tectonic corridor of central Bulgaria. The deposits were formed along the SW flank of the Elshitsa volcano-intrusive complex and are spatially associated with N110-120-trending hypabyssal and subvolcanic bodies of granodioritic composition. At Elshitsa, more than ten lenticular to columnar massive ore bodies are discordant with respect to the host rock and are structurally controlled. A particular feature of the mineralization is the overprinting of an early stage high-sulfidation mineral assemblage (pyrite ± enargite ± covellite ± goldfieldite) by an intermediate-sulfidation paragenesis with a characteristic Cu–Bi–Te–Pb–Zn signature forming the main economic parts of the ore bodies. The two stages of mineralization produced two compositionally different types of ores—massive pyrite and copper–pyrite bodies. Vlaykov Vruh shares features with typical porphyry Cu systems. Their common geological and structural setting, ore-forming processes, and paragenesis, as well as the observed alteration and geochemical lateral and vertical zonation, allow us to interpret the Elshitsa and Vlaykov Vruh deposits as the deep part of a high-sulfidation epithermal system and its spatially and genetically related porphyry Cu counterpart, respectively. The magmatic–hydrothermal system at Vlaykov Vruh–Elshitsa produced much smaller deposits than similar complexes in the northern part of the Panagyurishte district (Chelopech, Elatsite, Assarel). Magma chemistry and isotopic signature are some of the main differences between the northern and southern parts of the district. Major and trace element geochemistry of the Elshitsa magmatic complex are indicative for the medium- to high-K calc-alkaline character of the magmas. ⁸⁷Sr/⁸⁶Sr_(i) ratios of igneous rocks in the range of 0.70464 to 0.70612 and ¹⁴³Nd/¹⁴⁴Nd_(i) ratios in the range of 0.51241 to 0.51255 indicate mixed crustal–mantle components of the magmas dominated by mantellic signatures. The epsilon Hf composition of magmatic zircons (+6.2 to +9.6) also suggests mixed mantellic–crustal sources of the magmas. However, Pb isotopic signatures of whole rocks (²⁰⁶Pb/²⁰⁴Pb = 18.13–18.64, ²⁰⁷Pb/²⁰⁴Pb = 15.58–15.64, and ²⁰⁸Pb/²⁰⁴Pb = 37.69–38.56) along with common inheritance component detected in magmatic zircons also imply assimilation processes of pre-Variscan and Variscan basement at various scales. U–Pb zircon and rutile dating allowed determination of the timing of porphyry ore formation at Vlaykov Vruh (85.6 ± 0.9 Ma), which immediately followed the crystallization of the subvolcanic dacitic bodies at Elshitsa (86.11 ± 0.23 Ma) and the Elshitsa granite (86.62 ± 0.02 Ma). Strontium isotope analyses of hydrothermal sulfates and carbonates (⁸⁷Sr/⁸⁶Sr = 0.70581–0.70729) suggest large-scale interaction between mineralizing fluids and basement lithologies at Elshitsa–Vlaykov Vruh. Lead isotope compositions of hydrothermal sulfides (²⁰⁶Pb/²⁰⁴Pb = 18.432–18.534, ²⁰⁷Pb/²⁰⁴Pb = 15.608–15.647, and ²⁰⁸Pb/²⁰⁴Pb = 37.497–38.630) allow attribution of ore-formation in the porphyry and epithermal deposits in the Southern Panagyurishte district to a single metallogenic event with a common source of metals.  相似文献   

Editorial     

Hadi Hajibeygi  Jan Dirk Jansen  Olwijn Leeuwenburgh  Denis Voskov 《Computational Geosciences》2017,21(5-6):833-833

  相似文献   

Origin and Extent of Fresh Paleowaters on the Atlantic Continental Shelf, USA   总被引：3，自引：0，他引：3  

by Denis Cohen  Mark Person  Peng Wang  Carl W. Gable  Deborah Hutchinson  ee Marksamer  Brandon Dugan  Henk Kooi  Koos Groen  Daniel Lizarralde  Robert L. Evans  Frederick D. Day-Lewis  John W. Lane Jr. 《Ground water》2010,48(1):143-158

While the existence of relatively fresh groundwater sequestered within permeable, porous sediments beneath the Atlantic continental shelf of North and South America has been known for some time, these waters have never been assessed as a potential resource. This fresh water was likely emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and by elevated recharge in areas overrun by the Laurentide ice sheet at high latitudes. To test this hypothesis, we present results from a high-resolution paleohydrologic model of groundwater flow, heat and solute transport, ice sheet loading, and sea level fluctuations for the continental shelf from New Jersey to Maine over the last 2 million years. Our analysis suggests that the presence of fresh to brackish water within shallow Miocene sands more than 100 km offshore of New Jersey was facilitated by discharge of submarine springs along Baltimore and Hudson Canyons where these shallow aquifers crop out. Recharge rates four times modern levels were computed for portions of New England's continental shelf that were overrun by the Laurentide ice sheet during the last glacial maximum. We estimate the volume of emplaced Pleistocene continental shelf fresh water (less than 1 ppt) to be 1300 km³ in New England. We also present estimates of continental shelf fresh water resources for the U.S. Atlantic eastern seaboard (10⁴ km³) and passive margins globally (3 × 10⁵ km³). The simulation results support the hypothesis that offshore fresh water is a potentially valuable, albeit nonrenewable resource for coastal megacities faced with growing water shortages.  相似文献