GRV 051523： A new eucrite     

刘焘  林杨挺  胡森  冯璐 《极地研究(英文版)》2009,20(2):200-208

Grove Mountains (GRV) 051523 is a newly identified eucrite, consisting mainly of coarse-grained pyroxene (62.9 vol%) and plagioclase (34.2 vol%), with less abundant opaque minerals (2.7 vol%), minor silica and tiny FeO-rich olivine (Fa75). Coarse-grained pyroxenes show exsolution of augite lamellae in pigeonite or vice versa. Width of most exsolution lamellae in pyroxenes is 1-3 μm. Opaque minerals are mainly chromite, ilmenite and sulfides. The meteorite was heavily shocked, as indicated by breccias and melt veins. Coarse-grained pyroxenes commonly contain abundant tiny or needle-like chromite inclusions with orientation, probably due to heavy shock events. Pyroxenes in various petrographic occurrences exhibit highly homogeneous compositions, indicating that GRV 051523 experienced intense thermal metamorphism in the parent asteroid 4 Vesta. GRV 051523 is classified as Type 5-6. This new eucrite will have additional constraints on chemical composition, magmatic differentiation, multi-stage shock and thermal history of Vesta.  相似文献   

中国县域网络购物空间格局及其影响因素   总被引：1，自引：0，他引：1  

宋周莺  虞洋  祝巧玲  车姝韵 《地理研究》2019,38(12):2997-3009

基于阿里巴巴县域网络购物数据,分析中国1915个县域的网购格局,并利用地理探测器探讨其影响因素。结果表明：① 县域网购格局整体上以江浙为核心、从东部沿海向内陆扩散,但存在由东部沿海向华北地区延伸的高值条带及内陆散落状的高值区,低值集聚区主要在西南、东北地区。② 县域网购水平的核心影响因素是网商水平、城镇化水平、居民收入,二级影响因素是教育水平、信息化水平、物流发达程度,其他因素的影响较小。③ 不同地区县域网购水平的主要影响因素存在较大差异。除城镇化和受教育水平是所有县域的主要影响因素外,中部地区县域还受收入水平、信息化的影响,西部地区县域还受物流发达程度、经济水平、零售水平的影响,东部地区县域还受网商水平的影响。  相似文献   

The influence of shrimp farms organic waste management on chemical water quality   总被引：1，自引：0，他引：1  

Carlos Augusto Ramos e Silva  Pablo Bezerra Dávalos  Leonel da Silveira Lobo Sternberg  Flavo Elano Soares de Souza  Maria Helena Constantino Spyrides  Paulo Sérgio Lucio 《Estuarine, Coastal and Shelf Science》2010

We evaluated the physical–chemical properties and nutrient concentrations in two shrimp ponds under conventional management, intensive (I-P) and semi-intensive (SI-P), and one under organic management (O-P), three days after loading and before stoking. The mean’s total alkalinity concentrations were 2.26 ± 0.04 mM, 2.28 ± 0.01 mM and 2.59 ± 0.01 mM, respectively for I-P, SI-P and O-P. Bicarbonate and carbonate accounted for 62% and 37% in I-P, 64% and 36% in SI-P and 83–17% in O-P, respectively. Aragonite and calcite were oversaturated around Ω = 5. Mean total phosphate (TP) concentrations were 441.37 ± 92.06 μg/L, 449 ± 48 μg/L and 473.64 ± 84.17 μg/L, under I-P SI-P and O-P management respectively. Following this sequence, NO₃⁻ concentration was 2.98 ± 0.7 μg/L, 1.16 ± 0.16 μg/L and 0.32 ± 0.12 μg/L, under I-P, SI-P and O-P management respectively. Thus, the data suggest that different management of farm organic waste leads to different chemical water quality.  相似文献   

Metamorphic evolution,partial melting and rapid exhumation above an ancient flat slab: insights from the San Emigdio Schist,southern California     

A. D. CHAPMAN  P. I. LUFFI  J. B. SALEEBY  S. PETERSEN 《Journal of Metamorphic Geology》2011,29(6):601-626

The San Emigdio and related Pelona, Orocopia, Rand and Sierra de Salinas schists of southern California were underplated beneath the southern Sierra Nevada batholith and adjacent southern California batholith along a shallow segment of the subducting Farallon plate in Late Cretaceous to early Tertiary time. These subduction accretion assemblages represent a regional, deeply exhumed, shallowly dipping domain from an ancient slab segmentation system and record the complete life cycle of the segmentation process from initial flattening and compression to final extensional collapse. An important unresolved question regarding shallow subduction zones concerns how the thermal structure evolves during the slab flattening process. New field relationships, thermobarometry, thermodynamic modelling and garnet diffusion modelling are presented that speak to this issue and elucidate the tectonics of underplating and exhumation of the San Emigdio Schist. We document an upsection increase in peak temperature (i.e. inverted metamorphism), from 590 to 700 °C, peak pressures ranging from 8.5 to 11.1 kbar, limited partial melting, microstructural evidence for large seismic events, rapid cooling (825–380 °C Myr^?1) from peak conditions and an ‘out and back’P–T path. While inverted metamorphism is a characteristic feature of southern California schists, the presence of partial melt and high temperatures (>650 °C) are restricted to exposures with maximum depositional ages between 80 and 90 Ma. Progressive cooling and tectonic underplating beneath an initially hot upper plate following the onset of shallow subduction provide a working hypothesis explaining high temperatures and partial melting in San Emigdio and Sierra de Salinas schists, inverted metamorphism in the schist as a whole, and the observed P–T trajectory calculated from the San Emigdio body. Lower temperatures in Pelona, Orocopia and Rand schists are likewise explained in the context of this overarching model. These results are consistent with an inferred tectonic evolution from shallow subduction beneath the then recently active Late Cretaceous arc to exhumation by rapid trench‐directed channelized extrusion in the subducted schist.  相似文献   

Metamorphic evolution of sapphirine‐ and orthoamphibole‐cordierite‐bearing gneiss,Okanogan dome,Washington, USA     

D. L. WHITNEY 《Journal of Metamorphic Geology》2011,29(4):425-449

Gneiss domes are commonly cored by quartzofeldspathic rocks that provide little information about the pressure–temperature–fluid history of the domes. Three northern Cordilleran migmatite domes (Thor‐Odin and Valhalla/Passmore, British Columbia, Canada; Okanogan, Washington, USA), however, contain Mg–Al‐rich orthoamphibole‐cordierite gneiss as layers and lenses that record metamorphic conditions and pressure–temperature (P–T) path information not preserved in the host migmatite. These Mg–Al‐rich rocks are therefore a valuable archive of metamorphic conditions during dome evolution, although refractory rocks such as these commonly contain reaction textures that may complicate the calculation of metamorphic conditions. In the Okanogan dome, Mg–Al‐rich layers are part of the Tunk Creek unit, which occurs at the periphery of an underlying migmatite domain. Bulk compositional layers (mm‐ to m‐scale) consist of gedrite‐dominated, hornblende‐dominated and biotite‐bearing layers that contain variable amounts of gedrite, hornblende, anorthite, cordierite, spinel, sapphirine, corundum, kyanite, biotite and/or staurolite. The presence of different compositional layers (some with reaction textures, some without) allows systematic analysis of metamorphic history by a combined petrographic and phase equilibrium analysis. Gedrite‐dominated layers containing relict kyanite preserve evidence of the highest‐P conditions; symplectitic and coronal reaction textures around kyanite indicate decompression at high temperature. Gedrite‐dominated layers lacking these reaction textures contain layers of sapphirine and spinel in apparent textural equilibrium and record a later high‐T–low‐P part of the path. Phase equilibria (pseudosection) analysis for layers that lack reaction textures indicates metamorphic conditions of 720–750 °C at a range of pressures (>8 to <4 kbar) following decompression. Elevated crustal temperatures and concordant structural fabrics in the Tunk Creek unit and underlying migmatite domain suggest that the calculated P–T conditions recorded in Tunk Creek rocks were coeval with anatexis, extension, and dome formation in Palaeocene–Eocene time. In contrast to orthoamphibole‐cordierite gneiss in the other Cordilleran domes, the Tunk Creek unit occurs as a discontinuous km‐scale layer rather than as smaller (m‐scale) pods, is more calcic, and lacks garnet. In addition, kyanite did not transform to sillimanite, and spinel commonly occurs as a blocky matrix phase in addition to vermicules in symplectite. These differences, along with the compositional layering, allow an analysis of bulk composition v. tectonic (P–T path) controls on mineral assemblages and textures. Pseudosection modelling of different layers in the Tunk Creek unit provides a basis for understanding the metamorphic history of these texturally complex, refractory rocks and their host gneiss domes, and other such rocks in similar tectonic settings.  相似文献   

Experimental research on the impact of Corbicula fluminea on DIN exchange at a tidal flat sediment-water interface     

刘杰  陈振楼  许世远  郑祥民 《中国海洋湖沼学报》2007,25(4):434-443

Based on a simulative experiment and a comparison analysis, the effect of bivalve Corbiculafluminea activity on sediment-water exchange of dissolved inorganic nitrogen （DIN） is studied. The areas included three intertidal flat sites of the Changjiang （Yangtze） River estuary in China. The interface exchange flux of ammonium, nitrate and nitrite in the short experiment （6 h） was -46.4-40, -74.8-929.1 and 2.5-14.6 μmol/（m^2·h）, respectively. It was found that the burrowing activities of C. fluminea increased NH4 and NOi release from sediments to overlying water in the short-term experiment. During long-term incubation, NH4 and NOi released in turn from the sediments. At the beginning of incubation, bioturbation by C. fluminea could accelerate NH2 release from sediments 2-17 times in different sites, resulting in stronger nitrification and increased NOi concentrations in the overlying water. Sediment profile analysis post-incubation shows that organic matter mineralization and sediment-water NH4 exchange had been stimulated by C. fluminea bioturbation and bioirrigation during the experiment. Therefore, C. fluminea activities such as excretion, burrowing, irrigation and turbation can effectively alter nitrogen dynamics and accelerate and stimulate nitrogen exchange and cycling at the sediment-water interface.  相似文献   

Chemical degradation characteristics of reinforced concrete reefs in South Korea     

H.S. Kim  C.G. Kim  W.B. Na  J.K. Kim   《Ocean Engineering》2008,35(8-9):738-748

The chemical degradation characteristics of reinforced concrete reefs, which had been fully immersed in Tongyeong waters of South Korea for 18–25 years, were studied. In order to investigate the marine environmental impact on the concrete reefs, environmental factors, for example pH, have been observed between 1997 and 2002. Then, four reinforced concrete reefs recovered from different sites in Tongyeong waters were nondestructively tested. Finally, those test results were analyzed to determine the chemical deterioration. Based on the test results, it is shown that the reinforced concrete reefs have sound chemical properties and their originally estimated service life is secure enough for a further service period in water depths of 28–32 m. A concrete cover depth of 40 mm is recommended for the design of reinforced concrete reefs to achieve safety in marine environments and special events occurring during installation and construction.  相似文献   

Simulation of spatiotemporal dynamics of water fluxes in Germany under climate change     

Shaochun Huang  Valentina Krysanova  Hermann Österle  Fred F. Hattermann 《水文研究》2010,24(23):3289-3306

In most of Europe, an increase in average annual surface temperature of 0·8 °C is observed, and a further increase is projected. Precipitation tends to increase in northern Europe and decrease in southern Europe, with variable trends in central Europe. The climate scenarios for Germany suggest an increase in precipitation in western Germany and a decrease in eastern Germany, and a shift of precipitation from summer to winter. When investigating the effects of climate change, impacts on water resources are among the main concerns. In this study, the first German‐wide impact assessment of water fluxes dynamics under climate change is presented in a spatially and temporally distributed manner using the state‐of‐the‐art regional climate model, Statistical Regional (STAR) model and the semi‐distributed process‐based eco‐hydrological model, soil and water integrated model (SWIM). All large river basins in Germany (lower Rhine, upper Danube, Elbe, Weser and Ems) are included. A special focus of the study was on data availability, homogeneity of data sets, related uncertainty propagation in the model results and scenario‐related uncertainty. After the model calibration and validation (efficiency from 0·6 to 0·9 in 80% of cases) the water flow components were simulated at the hydrotope level, and the spatial distributions were compared with those in the Hydrological Atlas of Germany. The actual evapotransipration is likely to increase in most parts of Germany, while total runoff generation may decrease in south and east regions. The results for the second scenario period 2051–2060 show that water discharge in all six rivers would be 8–30% lower in summer and autumn compared with the reference period, and the strongest decline is expected for the Saale, Danube and Neckar. Higher winter flow is expected in all of these rivers, and the increase is most significant for the Ems (about 18%). However, the uncertainty of impacts, especially in winter and for high water flows, remains high. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Phlogopite and quartz lamellae in diamond‐bearing diopside from marbles of the Kokchetav massif,Kazakhstan: exsolution or replacement reaction?     

L. F. DOBRZHINETSKAYA  R.WIRTH  D. RHEDE  Z. LIU  H. W. GREEN 《Journal of Metamorphic Geology》2009,27(9):607-620

Exsolution lamellae of pyroxene in garnet (grt), coesite in titanite and omphacite from UHPM terranes are widely accepted as products of decompression. However, interpretation of oriented lamellae of phyllosilicates, framework silicates and oxides as a product of decompression of pyroxene is very often under debate. Results are presented here of FIB‐TEM, FEG‐EMP and synchrotron‐assisted infrared (IR) spectroscopy studies of phlogopite (Phlog) and phlogopite + quartz (Qtz) lamellae in diamond‐bearing clinopyroxene (Cpx) from ultra‐high pressure (UHP) marble. These techniques allowed collection of three‐dimensional information from the grain boundaries of both the single (phlogopite), two‐phase lamellae (phlogopite + quartz), and fluid inclusions inside of diamond included in K‐rich Cpx and understanding their relationships and mechanisms of formation. The Cpx grains contain in their cores lamellae‐I, which are represented by topotactically oriented extremely thin lamellae of phlogopite (that generally are two units cell wide but locally can be seen to be somewhat broader) and microdiamond. The core composition is: (Ca_0.94K_0.04Na_0.02) (Al_0.06Fe_0.08Mg_0.88) (Si_1.98Al_0.02)O_6.00. Fluid inclusions rich in K and Si are recognized in the core of the Cpx, having no visible connections to the lamellae‐I. Lamellar‐II inclusions consist of micron‐size single laths of phlogopite and lens‐like quartz or slightly elongated phlogopite + quartz intergrowths; all are situated in the rim zone of the Cpx. The composition of the rim is (Ca_0.95Fe_0.03Na_0.02) (Al_0.05Fe_0.05Mg_0.90)Si₂O₆, and the rim contains more Ca, Mg then the core, with no K there. Such chemical tests support our microstructural observations and conclusion that the phlogopite lamellae‐I are exsolved from the K‐rich Cpx‐precursor during decompression. It is assumed that Cpx‐precursor was also enriched in H₂O, because diamond included in the core of this Cpx contains fluid inclusions. The synchrotron IR spectra of such diamond record the presence of OH^? stretching and H₂O bending motion regions. Lamellar‐II inclusions are interpreted as forming partly because of modification of the lamellae‐I in the presence of fluid enriched in K, Fe and Si during deformation of the host diopside; the latter is probably related to the shallower stage of exhumation of the UHP marble. This study emphasizes that in each case to understand the mechanism of lamellar inclusion formation more detailed studies are needed combining both compositional, structural and three‐dimensional textural features of lamellar inclusions and their host.  相似文献   

Prograde P–T path of medium-pressure granulite facies calc-silicate rocks, Higo metamorphic terrane, central Kyushu, Japan     

K. MAKI  Y. FUKUNAGA  T. NISHIYAMA  Y. MORI 《Journal of Metamorphic Geology》2009,27(2):107-124

This paper reports an occurrence of medium-pressure granulite facies calc-silicate rocks intercalated with pelitic gneisses in the Higo metamorphic terrane, central Kyushu, Japan, which is classified as a low- P /high- T (andalusite-sillimanite type) metamorphic belt. Three equilibrium stages are recognized in the calc-silicate rock based on reaction textures: M1 stage characterized by an assemblage of porphyroblastic garnet + coarse-grained clinopyroxene + plagioclase included in the clinopyroxene; M2 stage by two kinds of breakdown products of garnet, one is plagioclase + coronitic clinopyroxene within garnet and the other is plagioclase + vermicular clinopyroxene surrounding garnet; and M3 stage by amphibole replacing clinopyroxene. The key assemblage in the calc-silicate rock common to M1 and M2 stages is Grt + Cpx + Pl ± Qtz, which constrains the pressure and temperature ( P – T ) conditions for these stages by Fe–Mg exchange reaction and the two univariant net-transfer reactions: 2Grs + Alm + 3Qtz = 3Hd + 3An or 2Grs + Prp + 3Qtz = 3Di + 3An. The P – T conditions for M1 and M2 stages were estimated to be about 8.4 ± 1.9 kbar and 680 ± 122 °C, and 6.7 ± 1.9 to 8.9 ± 2.2 kbar and 700 ± 130 to 820 ± 160 °C, respectively. Estimates are consistent with an isobaric heating P – T path. The high peak temperature conditions at normal crustal depths and the prograde isobaric heating path probably require heat advection due to melt migration during the high- T metamorphism.  相似文献