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1.
安徽铜陵凤凰山夕卡岩型铜矿床中辉钼矿Re-Os同位素年龄及其地质意义 总被引：5，自引：2，他引：3
铜陵矿集区是我国长江中下游Cu-Au-Fe-Mo成矿带中最重要的有色金属基地之一,凤凰山矿床是铜陵矿集区的重要组成部分,为一个典型的夕卡岩型铜矿床。本文利用Re-Os同位素定年方法对凤凰山铜矿床进行了成矿时代测定,获得了辉钼矿的Re-Os同位素模式年龄范围为139.1±2.4～142.0±2.2Ma,等时线年龄为141.1±1.4Ma,与矿区内石英二长闪长岩和花岗闪长岩SHRIMP锆石U-Pb年龄(144.2±2.3Ma)相吻合,也与铜陵地区其他矿田的成矿时代基本一致,可能为岩石圈减薄事件的成矿响应。 相似文献
2.
The elevated levels of primary productivity associated with eastern boundary currents are driven by nutrient- rich waters upwelled from depth, such that these regions are typically characterised by high rates of nitrate-fuelled phytoplankton growth. Production studies from the southern Benguela upwelling system (SBUS) tend to be biased towards the summer upwelling season, yet winter data are required to compute annual budgets and understand seasonal variability. Net primary production (NPP) and nitrate and ammonium uptake were measured concurrently at six stations in the SBUS in early winter. While euphotic zone NPP was highest at the stations nearest to the coast and declined with distance from the shore, a greater proportion was potentially exportable from open-ocean surface waters, as indicated by the higher specific nitrate uptake rates and f-ratios (ratio of nitrate uptake to total nitrogen consumption) at the stations located off the continental shelf. Near the coast, phytoplankton growth was predominantly supported by ammonium despite the high ambient nitrate concentrations. Along with ammonium concentrations as high as 3.6 µmol l–1, this strongly suggests that nitrate uptake in the inshore SBUS, and by extension carbon drawdown, is inhibited by ammonium, at least in winter, although this has also been hypothesised for the summer. 相似文献
3.
豫西沙沟脉状Ag-Pb-Zn矿床地质特征和成矿流体研究 总被引：6，自引：1，他引：5
豫西沙沟薄脉状Ag-Pb-Zn硫化物矿床位于华北陆块南缘熊耳山地区,主要由多金属硫化物-石英-碳酸盐脉型和石英-碳酸盐-绢云母-多金属硫化物蚀变岩型两种矿化类型组成。主要矿脉的矿物共生序列可以分为成矿前的石英-黄铁矿阶段(Ⅰ)、闪锌矿-石英-方铅矿-少量银矿物阶段(Ⅱ1)、方铅矿-石英-闪锌矿-含铁白云石-银矿物阶段(Ⅱ2)和成矿后的方解石-(石英)阶段(Ⅲ)。对不同阶段的成矿流体研究表明,石英-黄铁矿阶段(Ⅰ)中的含氯化钠子晶三相(LVH)包裹体(Ⅰ1)可能是直接从饱和水的结晶岩浆熔体中出溶形成或是由岩浆流体的减压沸腾形成,显示该区很可能存在岩浆流体端元。多金属硫化物阶段(Ⅱ1Ⅱ2)捕获富液相包裹体(LV型)和个别CO2包裹体(C型),这两个阶段流体包裹体反映了主成矿阶段流体的基本特征,结合包裹体气相和液相成分色谱分析以及包裹体初融温度,认为成矿流体应该为中-低温低盐度含CO2的H2O-NaCl体系。其中,阶段(Ⅱ2)的均一温度(145～288℃,平均为194℃)比阶段(Ⅱ1)的均一温度(185～357℃,平均240℃)低46℃;同时,阶段(Ⅱ2)的盐度(1.91%～10.86%,平均6.38%)较阶段(Ⅱ1)盐度(4.65%～10.11%,平均7.77%)略低。对这一温度和盐度的总体下降趋势的合理解释是大气水的逐渐混入。多金属硫化物阶段(Ⅱ1Ⅱ2)之后的方解石-(石英)阶段普遍为富液相包裹体(LV型),该阶段显著降低的温度(129～208℃,平均165℃)和盐度(1.40%～4.03%,平均2.50%),进一步佐证大气水的不断混入。而且,流体混合可能在引起矿石矿物从热液中沉淀方面起到重要作用。 相似文献
4.
Influence of the oceanic biology on the tropical Pacific climate in a coupled general circulation model 总被引：1，自引：3，他引：1
Matthieu Lengaigne Christophe Menkes Olivier Aumont Thomas Gorgues Laurent Bopp Jean-Michel André Gurvan Madec 《Climate Dynamics》2007,28(5):503-516
The influence of chlorophyll spatial patterns and variability on the tropical Pacific climate is investigated by using a fully
coupled general circulation model (HadOPA) coupled to a state-of-the-art biogeochemical model (PISCES). The simulated chlorophyll
concentrations can feedback onto the ocean by modifying the vertical distribution of radiant heating. This fully interactive
biological-ocean-atmosphere experiment is compared to a reference experiment that uses a constant chlorophyll concentration
(0.06 mg m−3). It is shown that introducing an interactive biology acts to warm the surface eastern equatorial Pacific by about 0.5°C.
Two competing processes are involved in generating this warming: (a) a direct 1-D biological warming process in the top layers
(0–30 m) resulting from strong chlorophyll concentrations in the upwelling region and enhanced by positive dynamical feedbacks
(weaker trade winds, surface currents and upwelling) and (b) a 2-D meridional cooling process which brings cold off-equatorial
anomalies from the subsurface into the equatorial mixed layer through the meridional cells. Sensitivity experiments show that
the climatological horizontal structure of the chlorophyll field in the upper layers is crucial to maintain the eastern Pacific
warming. Concerning the variability, introducing an interactive biology slightly reduces the strength of the seasonal cycle,
with stronger SST warming and chlorophyll concentrations during the upwelling season. In addition, ENSO amplitude is slightly
increased. Similar experiments performed with another coupled general circulation model (IPSL-CM4) exhibit the same behaviour
as in HadOPA, hence showing the robustness of the results. 相似文献
5.
Earth, Moon, and Planets - 相似文献
6.
Mid-Holocene and Last Glacial Maximum climate simulations with the IPSL model—part I: comparing IPSL_CM5A to IPSL_CM4 总被引：1，自引：0，他引：1
Masa Kageyama Pascale Braconnot Laurent Bopp Arnaud Caubel Marie-Alice Foujols Eric Guilyardi Myriam Khodri James Lloyd Fabien Lombard Véronique Mariotti Olivier Marti Tilla Roy Marie-Noëlle Woillez 《Climate Dynamics》2013,40(9-10):2447-2468
The climates of the mid-Holocene (MH), 6,000 years ago, and of the Last Glacial Maximum (LGM), 21,000 years ago, have extensively been simulated, in particular in the framework of the Palaeoclimate Modelling Intercomparion Project. These periods are well documented by paleo-records, which can be used for evaluating model results for climates different from the present one. Here, we present new simulations of the MH and the LGM climates obtained with the IPSL_CM5A model and compare them to our previous results obtained with the IPSL_CM4 model. Compared to IPSL_CM4, IPSL_CM5A includes two new features: the interactive representation of the plant phenology and marine biogeochemistry. But one of the most important differences between these models is the latitudinal resolution and vertical domain of their atmospheric component, which have been improved in IPSL_CM5A and results in a better representation of the mid-latitude jet-streams. The Asian monsoon’s representation is also substantially improved. The global average mean annual temperature simulated for the pre-industrial (PI) period is colder in IPSL_CM5A than in IPSL_CM4 but their climate sensitivity to a CO2 doubling is similar. Here we show that these differences in the simulated PI climate have an impact on the simulated MH and LGM climatic anomalies. The larger cooling response to LGM boundary conditions in IPSL_CM5A appears to be mainly due to differences between the PMIP3 and PMIP2 boundary conditions, as shown by a short wave radiative forcing/feedback analysis based on a simplified perturbation method. It is found that the sensitivity computed from the LGM climate is lower than that computed from 2 × CO2 simulations, confirming previous studies based on different models. For the MH, the Asian monsoon, stronger in the IPSL_CM5A PI simulation, is also more sensitive to the insolation changes. The African monsoon is also further amplified in IPSL_CM5A due to the impact of the interactive phenology. Finally the changes in variability for both models and for MH and LGM are presented taking the example of the El-Niño Southern Oscillation (ENSO), which is very different in the PI simulations. ENSO variability is damped in both model versions at the MH, whereas inconsistent responses are found between the two versions for the LGM. Part 2 of this paper examines whether these differences between IPSL_CM4 and IPSL_CM5A can be distinguished when comparing those results to palaeo-climatic reconstructions and investigates new approaches for model-data comparisons made possible by the inclusion of new components in IPSL_CM5A. 相似文献
7.
Eight-Day Swamp is known to be contaminated with heavy metals, especially mercury. Sediment cores were collected to approximately 32 cm at 17 sites on four transects and analyzed at 1 or 2 cm intervals for seven metals and organic matter. Very high metal levels were found throughout the site. Long and Morgan's "effects range-median" (ER-M) was exceeded in more than 50% of slices for all elements except As. Hg had the highest concentration relative to ER-M; median Hg concentration was 72 times its ER-M. On the marsh plain, all metals showed enrichment at 14-20 cm depth of 10-40X over surficial sediments. 137Cs analysis showed sedimentation rates ranging from 0.33 to 0.50 cm yr(-1) over the last approximately 40 yr. These rates indicate that metal contamination peaks occurred in sediments deposited in the early 1960s. Thus, newer, less contaminated sediments are burying older, more contaminated layers and peak levels of contaminants are becoming less available to benthos. 相似文献
8.
C. R. Olsen N. H. Cutshall I. L. Larsen H. J. Simpson R. M. Trier R. F. Bopp 《Geo-Marine Letters》1984,4(3-4):157-160
The sedimentary distributions of radiocesium and plutonium have been used to determine patterns of fine-particle accumulation, estimate net sediment fluxes from different sources, and develop a fine-particle budget for the Hudson-Raritan estuary. It is proposed that the rates and patterns of fineparticle accumulation reflect a sediment surface in dynamic equilibrium with the wave and current regimes. Rates of accumulation in most estuarine areas appear to equal the rate to sea-level rise or land subsidence. Localized areas, which have not yet attained or are presently out of equilibrium, serve as fine particle traps. 相似文献
9.
—In addition to the near normal-incidence observations within the German DEKORP 2 project in 1984, wide-angle observations have been carried out on a parallel profile across the boundary between the Saxothuringian and Moldanubian crust, approximately 50 km NE of the main transect to control three-dimensional variations. Explosion sources have been used for the entire survey, providing excellent conditions for wide-angle registrations. A velocity model has been derived on the basis of in- and off-line refraction measurements using a kinematic raytracer which was extended to three dimensions by interpolation of 2-D velocity fields between parallel sections. Although prestack-migration of the data led to aliasing effects due to large shot and geophone spacing, stable results were obtained by forming envelopes after single-shot migration. The migrated sections reveal a strongly reflective Moho at about 31 km depth and a steeply (50°) dipping intracrustal reflector, which seems to be related to the border between the two Variscan units. 相似文献
10.
Masa Kageyama Pascale Braconnot Laurent Bopp Véronique Mariotti Tilla Roy Marie-Noëlle Woillez Arnaud Caubel Marie-Alice Foujols Eric Guilyardi Myriam Khodri James Lloyd Fabien Lombard Olivier Marti 《Climate Dynamics》2013,40(9-10):2469-2495
The climates of the mid-Holocene (MH, 6,000 years ago) and the Last Glacial Maximum (LGM, 21,000 years ago) have been extensively documented and as such, have become targets for the evaluation of climate models for climate contexts very different from the present. In Part 1 of the present work, we have studied the MH and LGM simulations performed with the last two versions of the IPSL model: IPSL_CM4, run for the PMIP2/CMIP3 (Coupled Model Intercomparion Project) projects and IPSL_CM5A, run for the most recent PMIP3/CMIP5 projets. We have shown that not only are these models different in their simulations of the PI climate, but also in their simulations of the climatic anomalies for the MH and LGM. In the Part 2 of this paper, we first examine whether palaeo-data can help discriminate between the model performances. This is indeed the case for the African monsoon for the MH or for North America south of the Laurentide ice sheet, the South Atlantic or the southern Indian ocean for the LGM. For the LGM, off-line vegetation modelling appears to offer good opportunities to distinguish climate model results because glacial vegetation proves to be very sensitive to even small differences in LGM climate. For other cases such as the LGM North Atlantic or the LGM equatorial Pacific, the large uncertainty on the SST reconstructions, prevents model discrimination. We have examined the use of other proxy-data for model evaluation, which has become possible with the inclusion of the biogeochemistry morel PISCES in the IPSL_CM5A model. We show a broad agreement of the LGM–PI export production changes with reconstructions. These changes are related to the mixed layer depth in most regions and to sea-ice variations in the high latitudes. We have also modelled foraminifer abundances with the FORAMCLIM model and shown that the changes in foraminifer abundance in the equatorial Pacific are mainly forced by changes in SSTs, hence confirming the SST-foraminifer abundance relationship. Yet, this is not the case in all regions in the North Atlantic, where food availability can have a strong impact of foraminifer abundances. Further work will be needed to exhaustively examine the role of factors other than climate in piloting changes in palaeo-indicators. 相似文献