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西藏邦铺超大型钼多金属矿床中矽卡岩铅锌矿体赋存于下二叠统洛巴堆组矽卡岩和大理岩中,矿体呈似层状、透镜状产出,矽卡岩矿物较为发育。为进一步查明矿床矽卡岩矿物种属及矽卡岩类型,剖析矽卡岩形成环境及其与矿化类型之间的关系,基于对矽卡岩矿物系统地显微镜下观测,利用电子探针对矿床主要矽卡岩矿物化学成分进行了系统分析。结果表明,石榴子石端员组分以钙铁榴石为主,含少量锰铝榴石和钙铝榴石;单斜辉石主要为透辉石-钙铁辉石系列,含少量锰钙辉石;似辉石为铁钙蔷薇辉石;角闪石主要为钙质阳起石;绿帘石贫Fe、Mg。矽卡岩矿物组合特征表明,矿床矽卡岩兼具钙矽卡岩和锰质矽卡岩特征;早期矽卡岩形成于较强的氧化环境,成矿岩浆流体亦具有较高氧逸度。邦铺首次发现锰质矽卡岩矿物组合,表明矿区具有银矿找矿潜力,为下一步找矿工作提供了理论支撑。 相似文献
134.
Ken-ichi SHIMOSE Ming XUE Robert D. PALMER Jidong GAO Boon Leng CHEONG David J. BODINE 《大气科学进展》2013,30(2):291-305
Because they are most sensitive to atmospheric moisture content, radar refractivity observations can provide high-resolution information about the highly variable low-level moisture field. In this study, simulated radar refractivity-related phase-change data were created using a radar simulator from realistic highresolution model simulation data for a dryline case. These data were analyzed using the 2DVAR system developed specifically for the phase-change data. Two sets of experiments with the simulated observations were performed, one assuming a uniform target spacing of 250 m and one assuming nonuniform spacing between 250 m to 4 km. Several sources of observation error were considered, and their impacts were examined. They included errors due to ground target position uncertainty, typical random errors associated with radar measurements, and gross error due to phase wrapping. Without any additional information, the 2DVAR system was incapable of dealing with phase-wrapped data directly. When there was no phase wrapping in the data, the 2DVAR produced excellent analyses, even in the presence of both position uncertainty and random radar measurement errors. When a separate pre-processing step was applied to unwrap the phase-wrapped data, quality moisture analyses were again obtained, although the analyses were smoother due to the reduced effective resolution of the observations by interpolation and smoothing involved in the unwrapping procedure. The unwrapping procedure was effective even when significant differences existed between the analyzed state and the state at a reference time. The results affirm the promise of using radar refractivity phase-change measurements for near-surface moisture analysis. 相似文献
135.
2011年11月5日贵州东北部梵净山景区出现强雷电天气,导致34名游客遭遇不同程度的雷击伤害.利用闪电定位资料、天气图、雷达卫星资料、高空资料,对这次雷击事故的雷电特征和雷电天气成因的分析结果表明:1)雷击事故发生时,闪电密度不大,但正闪强度高达259 kA,这在铜仁的冬季属于万分之二的小概率事件.2)高山以及山体上的金属物充当了引雷载体,完全石质结构的山体,因防雷设施不健全,强雷电不能扩散,而产生了直接雷击伤人.3)复杂的大气电场产生球形闪电接地后不能顺利放电,发生爆炸,分解成多个球形闪电,四处飞窜伤人.4)500 hPa波动气流与850 hPa弱切变配合,为对流天气产生提供了条件,但高空要素和相关的对流参数量级较小,不具备强对流产生的条件.5)地形辐合(边界层辐合带)叠加在移入的切变系统上,使风场气旋式切变增强,D(散度)值大幅度降低,ζ(涡度)值大幅度增加,垂直上升运动加强,促成了弱对流向强对流演变;同时辐合线附近冷暖空气交替,使得条件不稳定能量增加,促进暖湿气流加速上升,产生梵净山景区强雷电天气. 相似文献
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Climatic change in Central Asia during MIS 3/2: a case study using biological responses from Lake Baikal 总被引:5,自引:0,他引:5
George E.A. Swann Anson W. Mackay Melanie J. Leng Francois Demory 《Global and Planetary Change》2005,46(1-4):235
A Marine Isotope Stage (MIS) 3/early MIS 2 section from a structural high along the east coast of the North Basin of Lake Baikal was analysed for diatoms, C/N ratios, and organic carbon isotope ratios. Diatoms were present throughout MIS 3 and early MIS 2, with high concentrations of the planktonic taxa Cyclotella sp. c.f. gracilis between 54 and 51.5 kyr BP indicating relatively warm, interstadial, conditions. Following a %TOC inferred climatic cooling between 43.2 and 39.1 kyr BP, evidence of a more muted δ13C(organic) and %TOC inferred climatic warming from c. 39.1–34.7 kyr BP coincides with a period of very high diatom concentrations, indicating high aquatic productivity, at the Buguldeika Saddle in the South Basin of Lake Baikal. No evidence exists for a ‘Kuzmin’ catchment erosional event in the North Basin during MIS 3. This, however, may reflect the location of the coring site away from major riverine inputs. Abrupt climatic cooling at the culmination of both warm phases in the North Basin are associated, on the basis of the palaeomagnetic age-model and correlations to existing sites in Lake Baikal, with the initiation of Heinrich events 5 (c. 50 kyr BP) and 4 (c. 35 kyr BP), respectively, in the North Atlantic. The amount of organic material declines across the MIS 3/MIS 2 transition while constant C/N ratios suggest organic material to be predominantly derived from phytoplankton. An increase in δ13C(organic) at the MIS 3/MIS 2 transition may therefore indicate changes in aquatic productivity, pCO2 or the inorganic carbon pool. 相似文献
137.
Asfawossen Asrat Andy Baker Mohammed Umer Mohammed Melanie J. Leng Peter Van Calsteren Claire Smith 《第四纪科学杂志》2007,22(1):53-63
An annually laminated stalagmite from Southeastern Ethiopia grew for 443±8 yr starting at 5023 yr BP (±160 yr) as determined by lamina‐tuned U‐Th dating. The speleothem shows three growth phases: (1) an initial phase where the stalagmite has a candlestick shape, deposited by relatively slow rate drip water; (2) a middle growth phase where laminae grow on the flanks, suggesting faster drip rates; and (3) a final growth phase where the speleothem becomes narrower owing to a decrease in drip water supply towards the end of deposition. Morphometry, annual growth rate, fluorescence index, and 234U/238U isotope ratio show marked differences between the growth phases, while δ13C and δ18O do not show significant variation, except within the third phase towards the top of the stalagmite, where they have higher values. The study indicates that the multiproxy approach is crucial as the different proxies respond to single climate forcing in different manners. Our results can be widely applied to speleothem studies distinguishing the relative importance of the various proxies in recording cave ‘external’ (climate, hydrology) and cave ‘internal’ (e.g. evaporation) processes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
138.
本文对计算机网络工程的建设过程网络规划、网络设计、网络实施、网络验收等具体过程进行了简要的分析,论述了当今信息时代一个网络工程建设应掌握的基本知识,基本步骤和所应采取的措施。 相似文献
139.