Distribution and abundance of pelagic tunicates in the North Yellow Sea     

Pietro Franco  Hongju Chen  Guangxing Liu 《中国海洋大学学报(英文版)》2014,13(5):782-790

In this paper, the distribution patterns and abundance of pelagic tunicates in the North Yellow Sea of China during the period 2006-2007 were analyzed. Zooplankton samples were obtained with vertical towing from bottom to surface using a WP2 plankton net(200 μm mesh size; mouth area: 0.25 m2). Five species belonging to two classes were identified: Oikopleura dioica, O. longicauda and Fritillaria borealis belonging to class Appendicularia; Salpa fusiformis and Doliolum denticulatum of class Thaliacea. O. dioica and O. longicauda were the dominant species, occurring in the samples of all four seasons, with different distribution patterns. Their maximum abundance were 1664.7 ind. m-3(spring) and 1031.7 ind. m-3(spring) respectively. Following Oikopleura spp. were D. denticulatum, which was found only in autumn with an average abundance of 149.6 ind. m-3, and S. fusiformis, which was detected all the year long except for autumn with low abundance(max. abundance 289.4 ind. m-3 in summer). Only a very small amount of F. borealis was detected in summer samples, with an average abundance of 2.7 ind. m-3. The relationship between tunicates abundances and the environmental factors was analyzed using the stepwise regression model for each species. The variation of appendicularian abundance showed a significant correlation with the surface water temperature and with the concentration of Chl-a. No relationship was found between tunicates abundance and salinity, likely due to the slight changes in surface salinity of the studied area during the four seasons. Salps abundance and that of doliolids were significantly correlated to bottom water temperature, indicating that these two species(S. fusiformis and D. denticulatum) migrate vertically in the water column. In particular D. denticulatum, known to be a warm water species, showed not only an important correlation with water temperature, but also a spatial distribution connected to the warm currents in the North Yellow Sea. The occurrence of D. denticulatum represents an interesting result never found in past research work. Water temperature, algal distribution and currents were the most relevant environmental factors influencing the tunicate abundance and distribution in the North Yellow Sea. Further research is needed in order to get more information on the ecology of these organisms and to better understand their role in the ecosystem including the oceanic food web.  相似文献   

Present and future climates of the Greenland ice sheet according to the IPCC AR4 models     

Bruno Franco  Xavier Fettweis  Michel Erpicum  Samuel Nicolay 《Climate Dynamics》2011,36(9-10):1897-1918

The atmosphere?Cocean general circulation models (AOGCMs) used for the IPCC 4th Assessment Report (IPCC AR4) are evaluated for the Greenland ice sheet (GrIS) current climate modelling. The most suited AOGCMs for Greenland climate simulation are then selected on the basis of comparison between the 1970?C1999 outputs of the Climate of the twentieth Century experiment (20C3M) and reanalyses (ECMWF, NCEP/NCAR). This comparison indicates that the representation quality of surface parameters such as temperature and precipitation are highly correlated to the atmospheric circulation (500?hPa geopotential height) and its interannual variability (North Atlantic oscillation). The outputs of the three most suitable AOGCMs for present-day climate simulation are then used to assess the changes estimated by three IPCC greenhouse gas emissions scenarios (SRES) over the GrIS for the 2070?C2099 period. Future atmospheric circulation changes are projected to dampen the zonal flow, enhance the meridional fluxes and therefore provide additional heat and moisture to the GrIS, increasing temperature over the whole ice sheet and precipitation over its northeastern area. We also show that the GrIS surface mass balance anomalies from the SRES A1B scenario amount to ?300?km³/year with respect to the 1970?C1999 period, leading to a global sea-level rise of 5?cm by the end of the 21st century. This work can help to select the boundaries conditions for AOGCMs-based downscaled future projections.  相似文献   

Re-assessing the surface cycling of molybdenum and rhenium     

Christian A. Miller  Bernhard Peucker-Ehrenbrink  Franco Marcantonio 《Geochimica et cosmochimica acta》2011,75(22):7146-7179

We re-evaluate the cycling of molybdenum (Mo) and rhenium (Re) in the near-surface environment. World river average Mo and Re concentrations, initially based on a handful of rivers, are calculated using 38 rivers representing five continents, and 11 of 19 large-scale drainage regions. Our new river concentration estimates are 8.0 nmol kg⁻¹ (Mo), and 16.5 pmol kg⁻¹ (Re, natural + anthropogenic). The linear relationship of dissolved Re and in global rivers (R² = 0.76) indicates labile continental Re is predominantly hosted within sulfide minerals and reduced sediments; it also provides a means of correcting for the anthropogenic contribution of Re to world rivers using independent estimates of anthropogenic sulfate. Approximately 30% of Re in global rivers is anthropogenic, yielding a pre-anthropogenic world river average of 11.2 pmol Re kg⁻¹. The potential for anthropogenic contribution is also seen in the non-negligible Re concentrations in precipitation (0.03-5.9 pmol kg⁻¹), and the nmol kg⁻¹ level Re concentrations of mine waters. The linear Mo- relationship (R² = 0.69) indicates that the predominant source of Mo to rivers is the weathering of pyrite. An anthropogenic Mo correction was not done as anthropogenically-influenced samples do not display the unambiguous metal enrichment observed for Re. Metal concentrations in high temperature hydrothermal fluids from the Manus Basin indicate that calculated end-member fluids (i.e. Mg-free) yield negative Mo and Re concentrations, showing that Mo and Re can be removed more quickly than Mg during recharge. High temperature hydrothermal fluids are unimportant sinks relative to their river sources 0.4% (Mo), and 0.1% (pre-anthropogenic Re). We calculate new seawater response times of 4.4 × 10⁵ yr (τ_Mo) and 1.3 × 10⁵ yr (τ_Re, pre-anthropogenic).  相似文献   

Pyrrhotite Re–Os and SHRIMP zircon U–Pb dating of the Hongqiling Ni–Cu sulfide deposits in Northeast China     

Linsu Lü  Jingwen Mao  Hongbo Li  Franco Pirajno  Zuoheng Zhang  Zhenhua Zhou 《Ore Geology Reviews》2011,43(1):106-119

The Hongqiling (HQL) magmatic Ni–Cu sulfide deposits (Jilin Province, NE China) are located at the southern margin of the eastern Xing'an–Mongolian Orogenic Belt (XMOB) of the eastern Central Asian orogenic belt (CAOB), situated between the Siberian Craton (SC) and the North China Craton (NCC). The HQL ore-bearing mafic–ultramafic intrusions intrude into the metamorphic rocks of the lowermost Huangyingtun Formation of the Hulan Group (HLG), whose lithology is herein identified as a hornblende–zoisite gneiss. SHRIMP zircon U–Pb dating for the HLG, country rock of the HQL deposits, indicated a maximum deposition age of 272.2 ± 4.3 Ma (95% confidence level, MSWD = 2.6, n = 14).Six pyrrhotite samples separated from massive Ni–Cu sulfide ores of the Fujia (No. 7) deposit yielded a Re–Os isotopic isochron age of 208 ± 21 Ma (95% confidence level, MSWD = 2.4, n = 6), indicating that the ore-formation age was Late Triassic. Re–Os isotope analyses showed an initial ¹⁸⁷Os/¹⁸⁸Os ratio of 0.315 ± 0.050. The γ_Os values ranged from + 137 to + 161 with an average of + 151, indicating that its ore-forming materials were mainly derived from mantle with possibly < 30% crustal Os contamination. Large scale magmatic Ni–Cu mineralization in eastern Jilin occurred in post-collisional tectonic setting in the Late Triassic.Our new results suggest that the ages of the Ni–Cu sulfide deposits in the CAOB within China tended to become younger from west to east, as manifested by the Late Caledonian (~ 440 Ma), through the Late Hercynian (300–265 Ma) to the Late Indosinian (225–200 Ma). Such variation could reflect the gradual closure and post-collisional orogeny between the SC and the NCC from west to east.  相似文献   

A tectono-genetic model for porphyry–skarn–stratabound Cu–Au–Mo–Fe and magnetite–apatite deposits along the Middle–Lower Yangtze River Valley, Eastern China     

Jingwen Mao  Guiqing Xie  Chao Duan  Franco Pirajno  Dazio Ishiyama  Yuchuan Chen 《Ore Geology Reviews》2011,43(1):294-314

The Middle–Lower Yangtze River Valley metallogenic belt (YRB), situated along the northern margin of the Yangtze craton, is characterized by porphyry–skarn–stratabound Cu–Au–Mo–Fe deposits in the areas of uplift and magnetite–apatite deposits in Cretaceous fault basins. Following detailed field investigations and a review of published data, we recognize two episodes of magmatism and mineralization in the YRB: 1) 156–137 Ma high-K calc-alkaline granitoids associated with 148–135 Ma porphyry–skarn–stratabound Cu–Au–Mo–Fe deposits and 2) 135–123 Ma shoshonitic series, associated with 134.9–122.9 Ma magnetite–apatite deposits. A-type granitoids and associated alkaline volcanic have a small age range from 126.5 to 124.8 Ma and are temporally, spatially and genetically associated with the second episode. The geodynamic history of the YRB did not experience the Paleozoic to Mesozoic lithospheric thickening that took place in the North China craton. This process is inferred to be linked to partial melting of the delaminated lower crust at high pressures, resulting in the development of C-type adakitic rocks. The petrochemical and Sr/Nd isotopic data show that both the shoshonitic series and A-type granitoids are quite different from adakites, with only some of the K-calc-alkaline granitoids having adakitic signatures. Previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono-thermal evolution from 150 to 100 Ma.All data obtained for the Middle–Lower Yangtze River region consistently show that the Tan–Lu regional strike-slip fault zone, initiated at 233 ± 6 to 225 ± 6 Ma from the collision between the North China and Yangtze cratons and was reactivated at ca. 160 Ma. The Tan–Lu fault was caused by the oblique subduction of the Izanagi plate, which along the YRB the low-angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks. The high-K calc-alkaline granitoids magmas were derived from melting of the subducted slab, with some input of crustal material. These magmas were emplaced at the intersections between NE- and EW-trending faults and formed porphyry–skarn–stratabound Cu–Au–Mo–Fe deposits between 156 and 137 Ma. After 135 Ma the subducted plate changed its direction of motion to northeast, now running parallel to the Eurasian continental margin, and leading to large-scale continental extension. The shoshonitic series and subsequent A-type granitoids magmatism and the development of magnetite–apatite ores in the YRB, took place in both fault basins and NE-trending rifts between 135 and 124 Ma.  相似文献   

The Crati Submarine Fan, Ionian Sea     

Franco Ricci Lucchi  Albina Colella  Gianni Gabbianelli  Sergio Rossi  William R. Normark 《Geo-Marine Letters》1984,3(2-4):71-77

The Crati Fan is located in the tectonically active submerged extension of the Apennines chain and foretrough. The small fan system is growing in a relatively shallow (200 to 450 m), elongate nearshore basin receiving abundant input from the Crati River. The fan is characterized by a short, steep, channelized section (inner or upper fan) and a smooth, slightly bulging distal section (outer or lower fan). The numerous subparallel channels head in the shelf or littoral zone and do not form branching distributary patterns. Sand and mud depositional lobes of the outer fan stretch over more than 60% of fan length. Margin setting represents fan and/or source area  相似文献   

On the infrared void in the Lupus dark clouds     

G. A. P.Franco 《Monthly notices of the Royal Astronomical Society》2002,331(2):474-482

Strömgren uvbyβ photometry observations obtained for 205 stars in the general direction of a void in the IRAS 100-μm emission from the Lupus dark cloud complex are presented and analysed. The colour excess versus distance diagram confirms the existence of a region depleted from interstellar material, which is also seen in the ROSAT soft X-ray background emission map. The distance to the surrounding material is estimated as being within the interval from 60 to 100 pc. This result is in disagreement with previous distance estimates to the supposed supernova that has been suggested as responsible for clearing the region from dust. As an alternative, the data presented support the suggestion that the void may have been produced by the detachment of material from the interface between Loop I and the Local Bubble as a consequence of hydromagnetic instabilities. Moreover, the distribution of colour excess as a function of distance supports a value of ∼150 pc as the most probable distance to the dark cloud known as Lupus 1.  相似文献   

Analysis of the impulsive phase of a solar flare at submillimeter wavelengths     

Raulin  Jean Pierre  Makhmutov  Vladimir S.  Kaufmann  Pierre  Pacini  Alessandra Abe  Lüthi  Thomas  Hudson  Hugh S.  Gary  Dale E. 《Solar physics》2004,223(1-2):181-199

We present a report on the strong X5.3 solar flare which occurred on 25 August 2001, producing high-level γ-ray activity, nuclear lines and a dramatic long-duration white-light continuum. The bulk of millimeter radio fluxes reached a peak of ∼100 000 solar flux units at 89.4 GHz, and a few thousands of solar flux units were detected in the submillimeter range during the impulsive phase. In this paper we focus on and discuss (i) the implications inferred from high frequency radio observations during the impulsive phase; (ii) the dynamics of the low corona active region during the impulsive phase. In particular we found that 4–5 × 10³⁶ accelerated (>20 keV) electrons s⁻¹ radiating in a 1000–1100 G region, are needed to explain the millimeter to submillimeter-wave emissions. We present evidence that the magnetic field in the active region was very dynamic, and that strong non-thermal processes were triggered by the appearance of new, compact, low-lying (few thousand kilometers) loop systems, suggesting the acceleration site(s) were also located in the low solar atmosphere.  相似文献   

Analysis of the impulsive phase of a solar flare at submillimeter wavelengths     

Jean Pierre Raulin  Vladimir S. Makhmutov  Pierre Kaufmann  Alessandra Abe Pacini  Thomas Lüthi  Hugh S. Hudson  Dale E. Gary 《Solar physics》2004,223(1):181-199

  相似文献   

Partial melting of ultrahigh-pressure metamorphic rocks at convergent continental margins: Evidences,melt compositions and physical effects   总被引：2，自引：0，他引：2  

Liang-Peng Deng  Yi-Can Liu  Xiao-Feng Gu  Chiara Groppo  Franco Rolfo 《地学前缘(英文版)》2018,9(4):1229-1242

Ultrahigh-pressure(UHP) metamorphic rocks are distinctive products of crustal deep subduction,and are mainly exposed in continental subduction-collision terranes. UHP slices of continental crust are usually involved in multistage exhumation and partial melting, which has obvious influence on the rheological features of the rocks, and thus significantly affect the dynamic behavior of subducted slices. Moreover,partial melting of UHP rocks have significant influence on element mobility and related isotope behavior within continental subduction zones, which is in turn crucial to chemical differentiation of the continental crust and to crust-mantle interaction.Partial melting can occur before, during or after the peak metamorphism of UHP rocks. Post-peak decompression melting has been better constrained by remelting experiments; however, because of multiple stages of decompression, retrogression and deformation, evidence of former melts in UHP rocks is often erased. Field evidence is among the most reliable criteria to infer partial melting. Glass and nanogranitoid inclusions are generally considered conclusive petrographic evidence. The residual assemblages after melt extraction are also significant to indicate partial melting in some cases. Besides field and petrographic evidence, bulk-rock and zircon trace-element geochemical features are also effective tools for recognizing partial melting of UHP rocks. Phase equilibrium modeling is an important petrological tool that is becoming more and more popular in P-T estimation of the evolution of metamorphic rocks; by taking into account the activity model of silicate melt, it can predict when partial melting occurred if the P-T path of a given rock is provided.UHP silicate melt is commonly leucogranitic and peraluminous in composition with high SiO_2,low MgO, FeO, MnO, TiO_2 and CaO, and variable K_2 O and Na_2 O contents. Mineralogy of nanogranites found in UHP rocks mainly consists of plagioclase + K-feldspar + quartz, plagioclase being commonly albite-rich.Trace element pattern of the melt is characterized by significant enrichment of large ion lithophile elements(LILE), depletion of heavy rare earth elements(HREE) and high field strength elements(HFSE),indicating garnet and rutile stability in the residual assemblage. In eclogites, significant Mg-isotope fractionation occurs between garnet and phengite; therefore, Mg isotopes may become an effective indicator for partial melting of eclogites.  相似文献